Outcome of Endodontic Treatment with Heated-Activated Sodium Hypochlorite and Minimal Instrumentation versus Conventional Instrumentation: A Pilot Clinical Trial

Outcome of Endodontic Treatment with Heated-Activated Sodium Hypochlorite and Minimal Instrumentation versus Conventional Instrumentation: A Pilot Clinical Trial | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Outcome of Endodontic Treatment with Heated-Activated Sodium Hypochlorite and Minimal Instrumentation versus Conventional Instrumentation: A Pilot Clinical Trial Fabienne El Jagi, Issam Khalil, Alfred Naaman, Marc Krikor Kaloustian, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8262641/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Aim This pilot clinical trial aims to preliminarily evaluate and compare radiographic healing outcomes of a minimally instrumentation technique using a novel device capable of both heating and activating 5.25% of intracanal sodium hypochlorite (NaOCl) versus conventional reciprocating instrumentation with sonic activation on single rooted teeth with apical periodontitis. Material and Methods Thirty-two single rooted teeth with pre-operative periapical radiolucency and PAI score ≥ 3 were randomly divided into: ( 1 ) Conventional reciprocating instrumentation using Reciproc Blue files and sonic activation, ( 2 ) Minimal instrumentation technique using ProGlider 16.02 to the foramen along with a novel device capable of heating and activating NaOCl. Follow up was scheduled at 3,6 and 12 months and a periapical index (PAI) was recorded at T0, T3, T6 and T12 to evaluate the treatment outcome. Once a PAI score was assigned, each tooth was classified into: healed, healing and diseased, based on loose criteria healed and healing cases were considered successful, while the strict criteria consider only healed cases as successful. Data analysis was performed using IBM SPSS Statistics 27, quantitative data were summarized as means ± SD, qualitative as frequencies (percentages), PAI’s normality was confirmed by Shapiro-Wilk test and Chi-square tested categorical variables; significance set at p < 0.05. Results Both groups had a 100% success rate under loose criteria. Stricter criteria, however, caused a modest decline in the success rate, especially in the Minimal instrumentation group. The Conventional approach had a greater success rate of 93.8%, whereas the Minimal technique demonstrated an 80.0% success rate with no significant difference (p = 0.333). Conclusion Both techniques exhibited predictable outcomes regarding radiographic healing with no significant difference between the two methods. Future studies should employ CBCT analysis and larger sample size to validate long-term efficacy of this novel device. Activation apical periodontitis endodontic outcome heating minimally invasive sodium hypochlorite Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Apical periodontitis (AP) is a chronic disease caused by infection in the root canal system, which triggers inflammation in the periapical tissues, leading to bone resorption and the development of lesion reaction within the periapical tissues ( 1 ).The primary objective in managing chronic apical periodontitis is to eliminate the root canal infection or to significantly reduce the bacterial load to a level that supports the healing of the surrounding tissue ( 2 ). Mechanical instrumentation is the primary technique to decrease bacterial load in an infected root canal system and create space to deliver the irrigant to areas that instrument cannot reach ( 3 ).However, it has several disadvantages, including the production of smear layer and dentine debris ( 4 ) .Furthermore, not all canals walls can be reached by instruments and scientific evidence indicates that depending on the root canal anatomy at least 15% to 20% of the canal walls may remain untouched ( 5 ) highlighting the critical role of chemical agents in cleaning and disinfecting the root canal system ( 6 ). Sodium hypochlorite (NaOCl) is the gold standard irrigation solution due to its antibacterial capacity and its ability to dissolve necrotic tissue and organic components ( 7 ). Then, in order to enhance its propriety numerous articles have focused on activation irrigation strategies using many techniques such as ultrasonic and sonic ( 8 ) .However, according to the current ESE S3-level clinical practice guideline, adjunctive irrigation activation techniques (such as ultrasonic, sonic, or laser systems) have not demonstrate a clinically significant benefit in terms of periapical healing when managing apical periodontitis( 9 ). To further enhance the effectiveness of NaOCl, increasing its temperature has been suggested ( 8 ) .Heating NaOCl reduces the solution’s viscosity, enhance its ability to flow more effectively in narrow canals ( 10 ), improve its capability to dissolve tissue ( 11 ), remove dentin debris ( 7 ), and have superior antimicrobial properties( 8 , 11 ). Since preheated NaOCl rapidly loses its temperature once introduced into the canal, limiting the potential benefits of heating( 12 ), Woodmanstry introduced intracanal heating of NaOCl to sustain theses enhanced properties( 13 ).Yared et al. showed the potential of intracanal heating in killing bacteria in conventional instrumentation canals and in non-instrumented canals ( 14 ). Iandolo et al. found that the use of intracanal heating of NaOCl combined with ultrasonic activation (UA) significantly improved the penetration of irrigant into dentinal tubules comparing to using UA alone( 8 ). Furthermore, Histological analysis confirmed that this technique significantly reduced the amount of residual debris than traditional syringe irrigation with NaOCl ( 8 ). Hence, recent studies have argued whether such irrigation techniques might be used to disinfect non-instrumented and/or minimally tapered root canals ( 15 , 16 ). The concept of Minimally Invasive Endodontics (MIE) entails the treatment and prevention of pulp diseases, while preserving as much as possible the hard tissues of the tooth ( 17 , 18 ) and maintain the strength, integrity, long-term functionality of the treated tooth and aiming to ensure its survival throughout the patient's lifetime ( 17 ). To date, evidence on the outcome of minimally instrumented canals is lacking, despite recommendation to use enhanced irrigation techniques. Similarly, it remains unclear whether combining intracanal heating with activation of NaOCl improves clinical outcomes, even though growing evidence highlights its potential benefits in terms of cleaning efficacy and disinfection ability. The aim of this pilot clinical trial is to preliminarily radiologically evaluate and compare the healing outcome of a minimally instrumentation technique using a novel device capable of both heating and activating 5.25% of NaOCl compared to conventional reciprocating instrumentation with sonic activation on thirty-two single rooted teeth with apical periodontitis. Materials and Methods Study Design The preliminary study was designed as a pilot clinical study, parallel-group, double-blind equivalence clinical trial in which both the participants and the observers were blinded to the treatment assignments. The Institutional Ethics Committee approved the protocol and the informed consent (2023 − 266). The study was registered on www.clinicaltrials.gov databases with number (NCT06461728) and complied with the principles of the Declaration of Helsinki and Good Clinical Practice. This randomized clinical trial was prepared in accordance with the 2020 Preferred Reporting Item for Randomized Trials in Endodontics (PRIVATE) guidelines ( 19 ). This study adheres to the CONSORT guidelines for the reporting of clinical trials. Sample Size The sample size for this pilot clinical study was determined pragmatically to evaluate feasibility and obtain preliminary estimates of treatment effect and variability. The number of cases was selected to allow assessment of recruitment, follow-up, and protocol adherence, while providing sufficient data for planning a future powered trial. The pilot clinical study was conducted according to the principles of the Declaration of Helsinki. A total of 32 periapical lesions (16 per group) were included, accounting for an estimated 20% potential loss to follow-up. This sample size was considered adequate for the exploratory objectives of the pilot phase and to generate effect-size data for subsequent sample size calculations in a larger confirmatory study. Case Selection This pilot clinical trial comprised a series of thirty-two ( 32 ) teeth with apical periodontitis from twenty-four ( 24 ) patients with non-contributory medical history, were recruited at the Postgraduate Endodontics Clinic of The Faculty of Dental Medicine at Saint Joseph University (Beirut, Lebanon). Patients were informed about treatment options, follow-up period desired, as well as the associated benefits and risks, and provided consent for the examination and treatment of their teeth. Case selection were based on the following criteria: single rooted teeth, necrotic pulp and asymptomatic apical periodontitis as confirmed by negative response to cold tests and absence of bleeding on entering the pulp chamber. Briefly, a comprehensive pain, medical and dental history was taken to confirm the absence of symptoms, etiology of disease and potential medical contra-indications to participation. This was followed by a systematic extra- and intra-oral hard and soft tissue examination where the selected tooth was subjected to a focused visual (restorability; restoration presence, type and quality; presence of caries, cracks and fractures), periapical (tenderness to percussion or palpation; presence of sinus or swelling), periodontal (six-point probing depths, mobility) and occlusal (static and dynamic) assessment and teeth with pre-operative periapical radiolucency and PAI score ≥ 3 according to the classification of Ørstavik et al. 1986 ( 20 ). Data Collection Patients were referred to the Postgraduate Endodontics Clinic of The Faculty of Dental Medicine at Saint Joseph University (Beirut-Lebanon), and all those included in this study were asymptomatic at the time of consultation, which allowed for the treatment to be conducted in a single-appointment in all cases. Patients were treated between January 2024, and September 2024, and the teeth were examined clinically and radiographically using PA preoperatively (T0) and at recall (T3, T6, T9 and T12). In order to take standardized radiographs throughout the experiment, pretreatment bite blocks were fabricated using a bite registration material (Kerr Corporation, Romulus, MI, USA) and PA were taken standardized paralleling technique with periapical film (Durr Dental, Bietigheim - Bissingen, Germany) mounted on the customized radiographic stent and connected to the X-ray tube (Kodak RVG6100, Carestream Dental LLC, Atlanta, GA) via an adapter ring. The exposure parameters were 655 KV, 7.5 mA and 0.15 seconds. The radiographs were anonymized, and randomly mixed and three experienced endodontists examined and graded the perioperative radiograph blindly and independently of each patient according to the classification of Ørstavik et al. 1986. All radiographs were digitally scanned, saved in JPEG format and imported into ImageJ software version 1.41 (National Institute of Health, Bethesda, MD, USA). The examiners met as a group to review all scores to enhance inter-rater agreement. Root Canal Treatment Procedures The single operator performed all endodontic procedure under strict aseptic settings and local anesthesia using a dental operating microscope (Leica Microsystems, Wetzlar, Germany) at a x6.4 magnification and over one visit. Teeth were subsequently isolated using rubber and liquid dam. A conservative straight-line access opening was prepared, with removal of all pulp horns and ledges. To preserve tooth structure, orifice openers were not used during the instrumentation process, then the access cavity was performed using sterile round diamond burs (Maillefer, Ballaigues, Switzerland) mounted on a high-speed hand piece, then irrigated with 2 mm of 5.25% NaOCl. the WL was determined with an apex locator at “0.0” reading and was confirmed with PA using a size 10 K file (Dentsply, Maillfer, Ballaigues, Switzerland). Patency was obtained by taking a size 10 K file (Dentsply, Maillfer, Ballaigues, Switzerland) 1 mm past the terminus of the canal. Then a size 15 K file (Dentsply, Maillfer, Ballaigues, Switzerland) was introduced, only root canals with an initial apical size equivalent to 15 K file were selected and roots with larger foramina were excluded. All cases were treated in a single visit by a single endodontic postgrFaduate student that could not be blinded and teeth that required more than one visit were excluded. The included teeth were randomly assigned into two experimental groups (n = 16) by using allocation software ( http://www.randomization.com/ ) according to standardized procedure: Group CRI (conventional reciprocating instrumentation) (n = 16): Each canal was prepared using Reciproc Blue nickel titanium file 25/08 (VDW, Munich, Germany). The instruments were operated using VDW Silver Motor (VDW) in the “RECIPROC ALL” preset program and used to the WL in a slow “in-and-out” pecking motion, with an amplitude of 3mmamplitude limit and a gentle apical pressure was combined with a brushing motion against the lateral canal walls. After three pecking movements, the instrument was removed from the canal ( 21 ). Continuous checking of the canal patency was done using size 10 hand. The canals were irrigated during the preparation procedure with 3ml of 5.25% sodium hypochlorite at room temperature using Irriflex endodontic irrigation needle (Produits Dentaires SA, Vevey, reflexSwitzerland) mounted on a 3 ml syringe (Plastipak, Franklin Lakes, NJ, USA) 2mm of the WL. Once the instrumentation is done, the final irrigation protocol consisted of 3 ml of 17% EDTA, 3 ml of distilled water and 3 ml of 5.25% NaOCl, each for 2 minutes ( 15 ). NaOCl was placed in the canal and activated using the size 25.04 taper tip of a sonic device EndoActivator (Dentsply Tulsa Dental Specialties, Tulsa, OK, USA) at 1-10kHz and the activator tip was placed within 2 mm of the WL. This cycle was repeated three more times, and the canal was rinsed with 3 ml of 5.25% NaOCl at room temperature after each cycle. After the completion of the endodontic procedures, gauging of the apex using K files (Maillefer, Ballaigues, Switzerland) was done and canals were dried with Reciproc R25 paper points (VDW) and Reciproc R25 gutta-percha points (VDW) was lightly coated with AH plus resin-based sealer (Dentsply, DeTrey, Konstanz, Germany) and placed into the canal down to the WL. Excess of gutta-percha was cut at the CEJ with a heat plugger (Fast-Pack pro-obturation system), and the coronal part of the gutta-percha was condensed with gentle pressure using an endodontic plugger (Heat carrier Dentsply, Maillfer, Ballaigues, Switzerland). A periapical radiograph was obtained to assess the quality of root filling and a layer of 1mm of glass ionomer (Fuji II LC Capsules, GC America, Alsip, IL USA) and a final periapical Xray was taken. Teeth were then referred to the Restorative Department for a final restoration and no later than 4 weeks after the completion of endodontic treatment. Group MI (minimal instrumentation) (n = 16): A glide path was established using a size 10 K file (Dentsply, Maillfer, Ballaigues, Switzerland), followed by ProGlider 16.02 to the WL, then the canal was irrigated with 3 ml of 5, 25% of NaOCl at room temperature using Irriflex endodontic needle (Produits Dentaires SA, Vevey, Switzerland) mounted on a 3 ml syringe (Plastipak, Franklin Lakes, NJ, USA) 2mm of the WL. NaOCl was left in the canal and access cavity. The novel device operates at frequency of 280 Hz and the temperature of the tip is 100°C while the temperature of the solution in the canal when it is heated reaches a minimum of 45°C. The prototype needle tip was placed in the canal within 2 mm of the WL, it was moved with small (few mm) in-and out movement, this procedure was repeated three more times and a fresh solution of NaOCl is replaced every time. NaOCl was aspirated from the canal and the access cavity and the final irrigation protocol consisted of 3 ml of 17% EDTA, 3 ml of distilled water and 3 ml of 5.25% NaOCl, each for 2 minutes ( 15 ). After the completion of the endodontic procedures, the canals were dried using sterile paper point (Maillfer, Ballaigues, Switzerland), and the gutta-percha cone 2% tapered size 20 or 25 (Dentsply, Maillfer, Ballaigues, Switzerland) was inserted into the canal to check apical fit using 3 methods: visual, to confirm that the tip reached the full WL; tactile, by feeling “tug-back” sensation and radiographic, to ensure the cone reached to WL, than the chosen gutta-percha cone was lightly coated with AH plus resin-based sealer (Dentsply, DeTrey, Konstanz, Germany) and placed into the canal down to the WL. Excess of gutta-percha was cut at the CEJ with a heat plugger (Fast-Pack pro-obturation system), and the coronal part of the gutta-percha was condensed with gentle pressure using an endodontic plugger (Heat carrier Dentsply, Maillfer, Ballaigues, Switzerland). A periapical radiograph was obtained to assess the quality of root filling and a layer of 1 mm of glass ionomer (Fuji II LC Capsules, GC America, Alsip, IL USA) and a final periapical Xray was taken. Teeth were then referred to the Restorative Department for a final restoration and no later than 4 weeks after the completion of endodontic treatment. Follow-up Patients were followed up periodically every 3-6-9-12 months. Patients were contacted by telephone to recall appointments. During follow-up visit, each patient was evaluated and recorded for the presence of clinical signs (swelling, sinus tract) and/or symptoms: spontaneous or provoked pain, tenderness to percussion/palpation and the quality of coronal restoration. Post-operative standardized radiographs were taken. Preoperative, postoperative and follow-up radiographs were compared in order to evaluate the occurrence of healing and were assigned PAI scores by three blinded endodontists (Figs. 2 and 3 ). In case of disagreement, the highest score is used as the reference. Once a PAI score was assigned, each tooth was classified into the following outcomes groups based on radiographic and clinical evaluation ( 22 ): Healed: The tooth is functional and asymptomatic, with no signs of apical periodontitis (PAI = 1) Healing: The tooth is functional and asymptomatic, with periapical lesions that have reduced in size (PAI > 1) Diseased: The tooth is non-functional and symptomatic, with signs of apical periodontitis (PAI > 1), or asymptomatic but with larger periapical lesions Based on loose criteria, both healed and healing cases were considered successful, while the strict criteria consider only healed cases as successful ( 23 ). Statistical Analysis The data were analyzed using IBM SPSS Statistics for Windows (Version 27). Descriptive statistics were summarized and presented as means ± standard deviations for quantitative variables and as frequencies (percentages) for qualitative variables. The normality of distribution for the PAI quantitative variable was assessed using the Shapiro-Wilk test, and the results were satisfactory (p > 0.05). The box plot figure illustrated the distribution of PAI across the treatment group and within time. The analysis highlights the median, interquartile range (IQR), and potential outliers for each group. The chi-square test was used to compare two categorical variables. Statistical significance was defined as a p-value < 0.05 Results Sample Characteristics Of the thirty-two ( 32 ) teeth initially enrolled, during follow-up, one was excluded after presenting pain on percussion and swelling. CBCT revealed a previously undetected second canal, meeting the study’s exclusion criteria. Both groups had a similar gender distribution (15 males and 16 females): 7 males and 8 females in MI group and 8 males and 8 females in CRI group aged 25–55 years (mean age: 42.3 ± 8.7 years). Dental arch distribution analysis revealed 16 cases in the upper jaw and 15 in the lower jaw. However, there was a significant difference in the distribution between groups (p = 0.049), with MI group containing 66,7% mandibular cases (n = 10) while CRI group containing 68,8% maxillary cases (n = 11) (Table 1 ). Table 1 Baseline Characteristics of Studied Sample (N = 31) Total Minimal Conventional p-value Gender Male Female 15 16 7 8 8 8 0.853 Age 25–33 34–44 45–55 11 7 13 6 2 7 5 5 6 0.491 Jaw Upper Lower 16 15 5 10 11 5 0.049 Treatment Outcome Distribution by Technique Both loose and strict criteria were used to compare the treatment outcomes between CRI and MI (Table 2 and Fig. 4 ). Based on loose criteria both groups had a 100% success rate and neither group saw any treatment failures. Stricter criteria, however, caused a modest decline in the success rate, especially in MI group. The CRI technique had a greater success rate of 93.8%, whereas the MI technique demonstrated an 80.0% success rate with no significant difference (p = 0.333) (Table 2 and Fig. 4 ). Table 2 Treatment Outcome Distribution Per Technique (N = 31) Final treatment outcome Technique P-value Minimal Conventional N (%) N (%) Loose criteria Success 15 (100.0%) 16 (100.0%) Failure 0 (0%) 0 (0%) Strict Criteria Success 12 (80.0%) 15 (93.8%) 0.333 Failure 3 (20.0%) 1 (6.3%) Association Between Age Category and Success Rate The association between age group and the success rate according to strict criteria is presented in Table 3 for the entire sample as well as for each treatment group (MI and CRI). All age groups in the entire sample showed high success rates: 81.8% in the 25–33 age group, 85.7% in the 34–44 age group, and 92.3% in the 45–55 age group. No significant difference between age and treatment success was detected (p = 0.809). MI group's success rates were 83.3% for age 25–33, 50.0% ( 34 – 44 ), and 85.7% ( 45 – 55 ). A p-value of 0.492 further indicated that there was no significant age-related influence. The success rates in the CRI group were high, reaching 80.0% in the 25–33 age group and 100% in the 34–44 and 45–55 age groups; nevertheless, the difference was not statistically significant (p = 0.625). Overall, these results indicated that neither treatment group's success rate under strict criteria was influenced by age category. Table 3 Association Between Age Category and Success Rate Based on Strict Criteria Strict Criteria p-value Success Failure All sample Age category 0.809 25–33 9 (81.8%) 2 (18.2%) 34–44 6 (85.7%) 1 (14.3%) 45–55 12 (92.3%) 1 (7.7%) Minimal 0.492 25–33 5 (83.3%) 1 (16.7%) 34–44 1 (50.0%) 1 (50.0%) 45–55 6 (85.7%) 1 (14.3%) Conventional 0.625 25–33 4 (80.0%) 1 (20.0%) 34–44 5 (100%) 0 (0%) 45–55 6 (100%) 0 (0%) PAI score Over Time and Between Treatment Groups Figure 5 shows how the PAI changed over time in CRI and MI groups. Both groups had high PAI values at baseline, ranging from 3 to 4. Both groups' PAI levels decreased over time, suggesting that healing had improved. At the 3-month point, there was some variability, notably in the MI group, but this variability seemed to decrease and diminish later in follow-ups, especially in the CRI group. By six months, the scores had decreased to about one or two, and they stayed that way for nine and twelve months. At 9 months in CRI group, the error was little to no variation in PAI scores among patients in that group at that time point. According to the bar height, every patient had the same or almost the same PAI score, which was nearly about 1. Overall, both treatment approaches showed comparable and successful decreases in PAI scores over the course of the 12-month period, indicating that they were successful in promoting healing. Discussion To our knowledge, this is the first pilot study to evaluate the efficacy of a minimal instrumentation technique using a novel device capable of both heating and activating 5,25% intracanal sodium hypochlorite compared to conventional reciprocating instrumentation with sonic activation in single rooted teeth with apical periodontitis. The outcomes at 1 year were favorable and comparable in both treatment groups (Table 2 and Fig. 2 ). Under loose criteria, the overall success rate in our MI group (80%) was higher than that reported in a comprehensive systematic review on endodontic outcomes ( 24 ). When strict criteria are applied, the success rate in our pilot clinical study (100%) closely matched the collective weighted success rate by the same authors ( 24 , 25 ). In the past decade, outcome studies have shifted from using terms like healed, healing and diseased to more flexible approach that defines success as strict or loose, alongside failure ( 26 ). Recent findings from a prospective study done by Montero et al. 2025, align with the results of our research in their evaluation of apical periodontitis treatment in 170 molars, they compared the GentleWave ® system (GW) to ultrasonic activation with negative pressure irrigation (UA + NPI) utilizing standardized instrumentation with EdgeFile ® X7 FireWire files (0.04 and 0.06 tapers )over a mean follow-up of 14.9 months, no significant difference were observed between groups under strict criteria success rates were 70.6% (GW) vs 72.9% (UA + NPI); under loose criteria rates were 83.5% (GW) vs 8.1% (UA + NPI). Notably, our study achieved under loose criteria a 100% success rate greater than the rates presented by Montero et al. 2025( 26 ). This difference in the results may be attributed to: the smaller sample size (N = 31), the methodological differences such as the use of new device capable of heating and activating NaOCl in our MI group, which enhances tissue dissolution and antimicrobial efficacy ( 8 ). Under strict criteria, our success rates declined: 93.8% for CRI group vs 80.0% for MI group, as similarly noted by Montero et al’s larger sample, even though the difference remained statistically non-significant ( 26 ). These studies highlight that while success rate may vary based on assessment criteria and procedural difference, neither disinfection method demonstrates superiority, the higher success rate in our study under loose criteria could suggest potential advantages of heating and activating NaOCl paired with minimal instrumentation even though further research with larger sample size is needed. Standardization of the treatment procedure is essential in clinical research to minimize variability and ensure reliable outcomes. Including molars in our study would increase the possibility of bias, as molar treatments are significantly more difficult to standardize due to root canal curvature, anatomic differences of the isthmuses, treatment duration, procedural errors ( 27 ). Therefore, only single-rooted teeth were selected, allowing for greater consistency and reducing potential sources of bias. Additional studies are needed to assess whether comparable outcomes can be achieved in multi-rooted teeth, where irrigation protocols may play an important role in the success of the treatment as well as in cases presenting with more acute clinical signs and symptoms of periapical disease ( 28 ) .In addition, all patients, were successfully contacted at the time of follow-up and confirmed that the treated teeth remained in place, symptom-free, and functional. This minimized the possibility that undetected failures were missed, supporting the use of a per-protocol analysis, an approach commonly applied in most endodontic clinical trials and studies ( 29 , 30 ) As illustrated in Fig. 5 , both treatment protocols demonstrated comparable and significant reductions in PAI scores over 12 months, indicating their success in promoting periapical healing, it is important to note that all lesions included in this study had an initial PAI score ≥ 3. Previous studies have reported that treatment success rates is independent of pre-existing lesion size ( 31 ). Moazami et al. 2011 similarly revealed no correlation between lesion dimensions and treatment success ( 32 ). However, some research suggests smaller lesion may exhibit slightly superior healing rates compared to greater lesions ones ( 33 , 34 ). These results are encouraging, given that larger lesions pose more difficulties in healing ( 35 ), emphasizing their role as interfering variables in outcome assessment ( 36 ). Moreover, factors such as gender and age did not show significant associations with the outcome. To effectively disinfect the root canal, the irrigant must flow and reach the biofilm, where it can mechanically disrupt it and deliver its chemical effect ( 27 ). However, in MI group, this goal of thorough disinfection proves unattainable necessitating the use of heated and activated NaOCl. Increasing the temperature of NaOCl enhances its ability to penetrate narrow canals by reducing viscosity ( 10 ),while simultaneously improving tissue dissolution, debris removal ( 7 ), and antimicrobial properties ( 8 ). The rationale for minimal instrumentation in this group lies in avoiding excessive dentin debris which risks accumulation in non-instrumented regions like isthmuses and fins ( 37 ). This debris accumulation further impedes irrigant contact with the biofilm, making debris removal more difficult than anticipated ( 37 ). Furthermore, both dentin debris and smear layer reduce the effectiveness of root canal medicaments and irrigants ( 38 ). In MI group, a glide path was established using a size 10 k File, followed by ProGlider 16.02 to the WL, without any additional instrumentation or shaping. This approach enabled us to evaluate whether the protocol of irrigation procedure itself can disrupt biofilm. While larger canals allow for more efficient irrigant exchange, they also result in reduced shear stress on the root canal walls ( 39 ). Furthermore, a larger canal may present more surface area for interaction with the irrigant, which could need a greater volume of irrigant or prolonged irrigation time to achieve optimal chemical activity ( 27 ). Larger instruments are inherently less flexible and struggle to remain centered within the canal, especially in curved anatomies. This lack of centering can lead to uneven dentin removal, with excessive cutting on one side of the canal and untouched areas on the opposite wall—ultimately compromising tooth structure without guarantying improved cleanliness( 40 ). Supporting this, Lee et al. demonstrated that while canals prepared to a larger size #40 were cleaner than smaller preparations #20 when using conventional syringe and needle irrigation, this difference disappeared when ultrasonic activation of the irrigant was employed( 41 ).Under activated conditions, even minimally instrumented canals achieved cleanliness comparable to that of larger preparations, in both round and oval canals( 41 ). These findings reinforce the principle that minimal shaping, when combined with advanced irrigant activation techniques such as ultrasonic and heated sodium hypochlorite can preserve dentin integrity without compromising disinfection efficacy. Siqueira et al. demonstrated that un-instrumented root canal walls retain debris ( 42 ). A histological study confirms those findings, particularly in groups where syringe and needle irrigation were used ( 41 ). However, this difference was not observed in groups where the irrigant was ultrasonically activated ( 41 ). In those groups, the size of the canal preparation did not significantly affect cleanliness, highlighting the critical role of irrigation dynamics ( 41 ). Notably, MI group which utilized intracanal heating and activation of NaOCl, achieved similar outcomes to CRI group, despite reduced instrumentation. NaOCl, in concentrations between 0.5% and 8.25%, is the most commonly used irrigant in root canal treatment ( 43 , 44 ). In the present study 5.25% of NaOCl was used, the choice of the EndoActivator as the sonic activation device in CRI group of this study was strategically justified by its ability to balance efficacy with minimal invasiveness while PUI carries risks of unintended dentine removal when the metal tip touches canal walls ( 45 ), the EndoActivator’s flexible polymer tips operate at lower frequencies (1-10KHz), generating controlled hydrodynamic shear stress without aggressive mechanical contact ( 45 ). Furthermore, studies have demonstrated that sonic activation systems achieve comparable biofilm disruption compared to ultrasonic techniques ( 46 ). Sirtes et al. (2005) demonstrated that heating NaOCl, even at low concentrations, improves its ability to dissolve pulp tissue and enhances its antimicrobial effectiveness while preserving its chemical integrity and clinical safety ( 47 ).They also reported that increasing the temperature of sodium hypochlorite from 20°C to 45°C resulted in approximately a 100-fold enhancement in its bactericidal activity against E. faecalis ( 47 ).According to Costigan, in heated sodium hypochlorite solutions, the time required to kill Mycobacterium tuberculosis decreases as temperature rises. At 60°C, bacterial elimination occurs within 30 seconds; at 55°C, within 60 seconds; and at 50°C, within 90 seconds. This illustrates the marked enhancement of antimicrobial efficacy achieved by elevating the irrigant temperature( 48 ). Moreover, an in vitro study evaluating different irrigation protocols concluded that only NaOCl heated inside the canal and combined with ultrasonic activation was able to partially dissolve pulp tissue within lateral canals, highlighting the clinical relevance of heating NaOCl to enhance tissue dissolution ( 49 ). Supporting this, another study assessing antibiofilm activity against E. faecalis found that heating NaOCl combined with irrigant activation produced the greatest reduction in bacterial biofilms, emphasizing that elevated temperature and activation synergistically improve root canal disinfection ( 50 ).Overall, these findings highlight that increasing the temperature of the irrigant significantly enhances its ability to eliminate bacteria and dissolve pulp tissue. Assessing the safety of heating sodium hypochlorite is essential to avoid potential damage to periodontal tissues and bone. Brown et al. (1970) evaluated the thermophysical properties of enamel and dentin and demonstrated that dentin possesses lower thermal diffusivity than enamel, indicating a reduced ability to conduct heat ( 51 ). Consistently, Elhenawy et al. (2025) reported that the apical third of the root exhibited the lowest temperature increase( 52 ). Moreover, most studies have shown that temperature changes on the root surface remain below 10°C, supporting the low risk of damage to periodontal tissues and bone( 53 , 54 ). Erickson et al. highlighted that bone tissue becomes sensitive to heat at approximately 47°C, with greater injury observed at 53°C for 1 minute and exposure to 60°C or more results in irreversible cessation of blood flow and necrosis, persisting without repair for over 100 days( 55 ). Based on these findings, the novel device employed in our study, which heats sodium hypochlorite up to 45°C, can be considered safe. In the present study, AH Plus resin-based sealer was selected as the sealer for obturation of minimally tapered canals, since previous findings have shown that, unlike other sealers, its sealing ability is not adversely affected by greater sealer thickness( 56 ).It has superior dimensional stability, implying minimal shrinkage( 57 ), high bond strength to dentine( 58 ) and to the filling material ( 59 ) and has low solubility( 60 ). In addition, Paula-Silvia et al. concluded that conventional PA may lead to misinterpretation of lesion size changes due to inconsistencies in angulation during follow-up imaging which can impact treatment outcome evaluations ( 61 ). To mitigate this risk, standardized PA radiographs were obtained using pretreatment bite blocks fabricated from bite registration material ensuring consistent orientation across all time points, but the inherent limitations of 2D radiography in capturing volumetric changes remain a problem in the preliminary trial ( 61 ). Therefore, CBCT imaging offers greater accuracy in detection apical periodontitis compared to conventional PA ( 62 ). The recall rate in this study was very high (100%), which can be related that the follow-up period was only 12 months, as recall rates in clinical studies generally decline over time. In a study done by Ørstavik, the recall rates decreased from 71% after the first year to 33% after the fourth year ( 63 ). In previous outcome studies, the median recall rate was 52.7% ( 24 ). One drawback of a short follow-up is that the percentage of teeth with complete resolution of radiolucency may be underestimated because lesions may still be in the healing process ( 24 ). The European Society of Endodontology (ESE) (2006) recommends at least 4 years of follow-up to confirm the complete resolution of apical periodontitis. In addition, a recent study done by Bardini et al., 2023 shows that healing outcomes tends to improve with follow-ups duration more than one year ( 22 ). However, liang et al. demonstrated that during 10–19 months of evaluation, some large lesions could be almost completely resolved, while small radiolucencies showed only minimal decreased, indicating that time was not the primary responsible factor ( 27 ). The strength of the current study is the randomization of the teeth to the different treatment protocols, blinded patients, including only single rooted teeth, and one operator performing the treatments. However, the operator could not be blinded as he/she was informed of the treatment protocol to be performed. Regarding the findings of this study certain limitations must be considered, the most significant is the small sample size (N = 31), which reduces statistical power, increases variability in dental conditions among participants, and raises the risk of overestimating treatment efficacy. Furthermore, while the PAI and PA are widely accepted for outcome assessment, they may lack the diagnostic sensitivity of CBCT in detecting subtle periapical changes. This pilot clinical trial demonstrates that MI with heated and activated 5.25% NaOCl achieves 12-month success rates comparable to CRI in single-rooted teeth with apical periodontitis. The findings support minimally invasive strategies that optimize irrigant dynamics while preserving dentin, offering a promising alternative to traditional protocols. Conclusion Within the limitations of this pilot clinical trial, both conventional reciprocating instrumentation and the minimal instrumentation technique demonstrated comparable effectiveness in promoting healing of apical periodontitis. The minimal instrumentation technique with heating and activated sodium hypochlorite shows potential for enhancing the healing of periapical lesions. The novel device used in this technique presents an intriguing advancement, further large-scale clinical trial with more rigorous and standardized protocols are needed. However, further research should also explore its application in multirooted teeth, where conserving dentinal structure is essential for long-term success and tooth preservation. Abbreviations 2D Two Dimensional 3D Three Dimensional AP Apical Periodontitis CBCT Cone Beam Computed Tomography EDTA EthyleneDiamineTetraacetric Acid GW GentleWave® MIE Minimally Invasive Endodontic NaOCl Sodium Hypochlorite PA Periapical Radiograph PAI Periapical Index PUI Passive Ultrasonic Irrigation SI Sonic Irrigation UA Ultrasonic Activation WL Working Length Declarations ETHICS APPROVAL AND CONSENT TO PARTICIPATE This pilot clinical study obtained ethical approval from the Saint Joseph University of Beirut Ethics Committee (Approval number: 2023-266). All procedures were performed in accordance with the Declaration of Helsinki. All participants provided written informed consent prior to participation. CONSENT FOR PUBLICATION Written informed consent was obtained from all individual study participants DATA AVAILABILITY STATEMENT The data that support the findings of this study are available from the corresponding author upon reasonable request. CONFLICT OF INTEREST STATEMENT The authors deny any conflicts of interest related to this study. FUNDING INFORMATION No source of financial support. AUTHORS’ CONTRIBUTIONS Fabienne El Jagi : Conceptualization, Methodology, Investigation, Writing—original draft preparation. Issam Khalil: Reviewing and Editing. Alfred Naaman: Visualization. Carla Zougheib : Validation. Marc Krikor Kaloustian : Writing—reviewing and editing. Tracy El Feghaly : Formal Analysis. Marie Abboud Mehanna : Data Curation. Roula El Hachem: Supervision, Writing—original draft, Resources, Validation, Conceptualization. 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Outcome of Root Canal Treatment in Dogs Determined by Periapical Radiography and Cone-Beam Computed Tomography Scans. J Endod. 2009 May;35(5):723–6. Schloss T, Sonntag D, Kohli MR, Setzer FC. A Comparison of 2- and 3-dimensional Healing Assessment after Endodontic Surgery Using Cone-beam Computed Tomographic Volumes or Periapical Radiographs. J Endod. 2017 Jul;43(7):1072–9. Ørstavik D. Time‐course and risk analyses of the development and healing of chronic apical periodontitis in man. Int Endod J. 1996 May;29(3):150–5. Additional Declarations No competing interests reported. Supplementary Files CONSORT2025editablechecklist.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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06:05:06","extension":"png","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":4490,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/8e35a2f0f49de417f0b7b37b.png"},{"id":100361874,"identity":"18503bb2-3c4f-46e6-8a25-b9a5e2ee1d63","added_by":"auto","created_at":"2026-01-16 07:45:52","extension":"xml","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":154768,"visible":true,"origin":"","legend":"","description":"","filename":"c82e180151cc464f9e1a398f5d9d1b121structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/886d0e45dfdeadfbbdabc045.xml"},{"id":100010260,"identity":"215ada1a-2dcb-4e6b-bc68-41abe096f5e1","added_by":"auto","created_at":"2026-01-12 06:05:06","extension":"html","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":173442,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/55cd18ea57c441328064483a.html"},{"id":100010243,"identity":"00410513-b3b5-4322-b481-ee6ad6c1ef7a","added_by":"auto","created_at":"2026-01-12 06:05:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":104141,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eFlowchart showing exclusions, allocations, losses and success rates of the study\u003c/em\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/6f738fb86dc6a5f6f414b575.png"},{"id":100010245,"identity":"5cce6c4b-26b7-496f-8485-b31fd5840621","added_by":"auto","created_at":"2026-01-12 06:05:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":129199,"visible":true,"origin":"","legend":"\u003cp\u003eDelimitation of the border of the periapical lesions at T0, T3, T6, T9 andT12 (minimal instrumentation group)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/5838aa15c9859288621cf791.png"},{"id":100010250,"identity":"e04573ce-4df4-45d6-8ea1-adbb99e3b8ab","added_by":"auto","created_at":"2026-01-12 06:05:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":184890,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDelimitation of the border of the periapical lesions atT0, T3, T6, T9 and T12 (conventional reciprocating instrumentation group)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/e8087b510e40775a604aa6ef.png"},{"id":100361629,"identity":"b5113596-4f2a-4ee7-96d5-0159fbf31f5c","added_by":"auto","created_at":"2026-01-16 07:45:23","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":17578,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eSuccess Rate by Group Category and Success Rate Based on Strict and Loose Criteria\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/912f298eeb4bd0bbec7a90af.png"},{"id":100010253,"identity":"0934a4fc-0c6f-49d0-9573-a7de510b1645","added_by":"auto","created_at":"2026-01-12 06:05:05","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":30333,"visible":true,"origin":"","legend":"\u003cp\u003ePAI Score Over Time and Between Treatment Group\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/6aed7a84453de422da200c76.png"},{"id":106185128,"identity":"e8a4d527-a017-40f9-9aef-36ffb5bd7a22","added_by":"auto","created_at":"2026-04-05 15:10:13","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1344480,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/7505d7c7-ffd0-427f-900f-cb074953d682.pdf"},{"id":100361755,"identity":"c72273fe-25ba-4296-bf44-a2a8406dcd3b","added_by":"auto","created_at":"2026-01-16 07:45:41","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":36602,"visible":true,"origin":"","legend":"","description":"","filename":"CONSORT2025editablechecklist.docx","url":"https://assets-eu.researchsquare.com/files/rs-8262641/v1/107864b3b3bbd9505628cf33.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Outcome of Endodontic Treatment with Heated-Activated Sodium Hypochlorite and Minimal Instrumentation versus Conventional Instrumentation: A Pilot Clinical Trial","fulltext":[{"header":"Introduction","content":"\u003cp\u003eApical periodontitis (AP) is a chronic disease caused by infection in the root canal system, which triggers inflammation in the periapical tissues, leading to bone resorption and the development of lesion reaction within the periapical tissues (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e).The primary objective in managing chronic apical periodontitis is to eliminate the root canal infection or to significantly reduce the bacterial load to a level that supports the healing of the surrounding tissue (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMechanical instrumentation is the primary technique to decrease bacterial load in an infected root canal system and create space to deliver the irrigant to areas that instrument cannot reach (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).However, it has several disadvantages, including the production of smear layer and dentine debris (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) .Furthermore, not all canals walls can be reached by instruments and scientific evidence indicates that depending on the root canal anatomy at least 15% to 20% of the canal walls may remain untouched (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) highlighting the critical role of chemical agents in cleaning and disinfecting the root canal system (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSodium hypochlorite (NaOCl) is the gold standard irrigation solution due to its antibacterial capacity and its ability to dissolve necrotic tissue and organic components (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). Then, in order to enhance its propriety numerous articles have focused on activation irrigation strategies using many techniques such as ultrasonic and sonic (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e) .However, according to the current ESE S3-level clinical practice guideline, adjunctive irrigation activation techniques (such as ultrasonic, sonic, or laser systems) have not demonstrate a clinically significant benefit in terms of periapical healing when managing apical periodontitis(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). To further enhance the effectiveness of NaOCl, increasing its temperature has been suggested (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e) .Heating NaOCl reduces the solution\u0026rsquo;s viscosity, enhance its ability to flow more effectively in narrow canals (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e), improve its capability to dissolve tissue (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e), remove dentin debris (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e), and have superior antimicrobial properties(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Since preheated NaOCl rapidly loses its temperature once introduced into the canal, limiting the potential benefits of heating(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e), Woodmanstry introduced intracanal heating of NaOCl to sustain theses enhanced properties(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).Yared et al. showed the potential of intracanal heating in killing bacteria in conventional instrumentation canals and in non-instrumented canals (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIandolo et al. found that the use of intracanal heating of NaOCl combined with ultrasonic activation (UA) significantly improved the penetration of irrigant into dentinal tubules comparing to using UA alone(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Furthermore, Histological analysis confirmed that this technique significantly reduced the amount of residual debris than traditional syringe irrigation with NaOCl (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Hence, recent studies have argued whether such irrigation techniques might be used to disinfect non-instrumented and/or minimally tapered root canals (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe concept of Minimally Invasive Endodontics (MIE) entails the treatment and prevention of pulp diseases, while preserving as much as possible the hard tissues of the tooth (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e) and maintain the strength, integrity, long-term functionality of the treated tooth and aiming to ensure its survival throughout the patient's lifetime (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). To date, evidence on the outcome of minimally instrumented canals is lacking, despite recommendation to use enhanced irrigation techniques. Similarly, it remains unclear whether combining intracanal heating with activation of NaOCl improves clinical outcomes, even though growing evidence highlights its potential benefits in terms of cleaning efficacy and disinfection ability.\u003c/p\u003e \u003cp\u003eThe aim of this pilot clinical trial is to preliminarily radiologically evaluate and compare the healing outcome of a minimally instrumentation technique using a novel device capable of both heating and activating 5.25% of NaOCl compared to conventional reciprocating instrumentation with sonic activation on thirty-two single rooted teeth with apical periodontitis.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eStudy Design\u003c/h2\u003e \u003cp\u003eThe preliminary study was designed as a pilot clinical study, parallel-group, double-blind equivalence clinical trial in which both the participants and the observers were blinded to the treatment assignments. The Institutional Ethics Committee approved the protocol and the informed consent (2023\u0026thinsp;\u0026minus;\u0026thinsp;266). The study was registered on \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e\u003ca href=\"http://www.clinicaltrials.gov\" target=\"_blank\"\u003ewww.clinicaltrials.gov\u003c/a\u003e\u003c/span\u003e\u003cspan address=\"http://www.clinicaltrials.gov\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e databases with number (NCT06461728) and complied with the principles of the Declaration of Helsinki and Good Clinical Practice. This randomized clinical trial was prepared in accordance with the 2020 Preferred Reporting Item for Randomized Trials in Endodontics (PRIVATE) guidelines (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). This study adheres to the CONSORT guidelines for the reporting of clinical trials.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSample Size\u003c/h3\u003e\n\u003cp\u003eThe sample size for this pilot clinical study was determined pragmatically to evaluate feasibility and obtain preliminary estimates of treatment effect and variability. The number of cases was selected to allow assessment of recruitment, follow-up, and protocol adherence, while providing sufficient data for planning a future powered trial. The pilot clinical study was conducted according to the principles of the Declaration of Helsinki.\u003c/p\u003e \u003cp\u003eA total of 32 periapical lesions (16 per group) were included, accounting for an estimated 20% potential loss to follow-up. This sample size was considered adequate for the exploratory objectives of the pilot phase and to generate effect-size data for subsequent sample size calculations in a larger confirmatory study.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eCase Selection\u003c/h3\u003e\n\u003cp\u003eThis pilot clinical trial comprised a series of thirty-two (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e) teeth with apical periodontitis from twenty-four (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e) patients with non-contributory medical history, were recruited at the Postgraduate Endodontics Clinic of The Faculty of Dental Medicine at Saint Joseph University (Beirut, Lebanon). Patients were informed about treatment options, follow-up period desired, as well as the associated benefits and risks, and provided consent for the examination and treatment of their teeth. Case selection were based on the following criteria: single rooted teeth, necrotic pulp and asymptomatic apical periodontitis as confirmed by negative response to cold tests and absence of bleeding on entering the pulp chamber. Briefly, a comprehensive pain, medical and dental history was taken to confirm the absence of symptoms, etiology of disease and potential medical contra-indications to participation. This was followed by a systematic extra- and intra-oral hard and soft tissue examination where the selected tooth was subjected to a focused visual (restorability; restoration presence, type and quality; presence of caries, cracks and fractures), periapical (tenderness to percussion or palpation; presence of sinus or swelling), periodontal (six-point probing depths, mobility) and occlusal (static and dynamic) assessment and teeth with pre-operative periapical radiolucency and PAI score\u0026thinsp;\u0026ge;\u0026thinsp;3 according to the classification of \u0026Oslash;rstavik et al. 1986 (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e).\u003c/p\u003e\n\u003ch3\u003eData Collection\u003c/h3\u003e\n\u003cp\u003ePatients were referred to the Postgraduate Endodontics Clinic of The Faculty of Dental Medicine at Saint Joseph University (Beirut-Lebanon), and all those included in this study were asymptomatic at the time of consultation, which allowed for the treatment to be conducted in a single-appointment in all cases. Patients were treated between January 2024, and September 2024, and the teeth were examined clinically and radiographically using PA preoperatively (T0) and at recall (T3, T6, T9 and T12).\u003c/p\u003e \u003cp\u003e In order to take standardized radiographs throughout the experiment, pretreatment bite blocks were fabricated using a bite registration material (Kerr Corporation, Romulus, MI, USA) and PA were taken standardized paralleling technique with periapical film (Durr Dental, Bietigheim - Bissingen, Germany) mounted on the customized radiographic stent and connected to the X-ray tube (Kodak RVG6100, Carestream Dental LLC, Atlanta, GA) via an adapter ring. The exposure parameters were 655 KV, 7.5 mA and 0.15 seconds. The radiographs were anonymized, and randomly mixed and three experienced endodontists examined and graded the perioperative radiograph blindly and independently of each patient according to the classification of \u0026Oslash;rstavik et al. 1986. All radiographs were digitally scanned, saved in JPEG format and imported into ImageJ software version 1.41 (National Institute of Health, Bethesda, MD, USA). The examiners met as a group to review all scores to enhance inter-rater agreement.\u003c/p\u003e\n\u003ch3\u003eRoot Canal Treatment Procedures\u003c/h3\u003e\n\u003cp\u003eThe single operator performed all endodontic procedure under strict aseptic settings and local anesthesia using a dental operating microscope (Leica Microsystems, Wetzlar, Germany) at a x6.4 magnification and over one visit. Teeth were subsequently isolated using rubber and liquid dam.\u003c/p\u003e \u003cp\u003eA conservative straight-line access opening was prepared, with removal of all pulp horns and ledges. To preserve tooth structure, orifice openers were not used during the instrumentation process, then the access cavity was performed using sterile round diamond burs (Maillefer, Ballaigues, Switzerland) mounted on a high-speed hand piece, then irrigated with 2 mm of 5.25% NaOCl. the WL was determined with an apex locator at \u0026ldquo;0.0\u0026rdquo; reading and was confirmed with PA using a size 10 K file (Dentsply, Maillfer, Ballaigues, Switzerland). Patency was obtained by taking a size 10 K file (Dentsply, Maillfer, Ballaigues, Switzerland) 1 mm past the terminus of the canal.\u003c/p\u003e \u003cp\u003eThen a size 15 K file (Dentsply, Maillfer, Ballaigues, Switzerland) was introduced, only root canals with an initial apical size equivalent to 15 K file were selected and roots with larger foramina were excluded. All cases were treated in a single visit by a single endodontic postgrFaduate student that could not be blinded and teeth that required more than one visit were excluded.\u003c/p\u003e \u003cp\u003eThe included teeth were randomly assigned into two experimental groups (n\u0026thinsp;=\u0026thinsp;16) by using allocation software (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.randomization.com/\u003c/span\u003e\u003cspan address=\"http://www.randomization.com/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) according to standardized procedure:\u003c/p\u003e \u003cp\u003e \u003cb\u003eGroup CRI\u003c/b\u003e (conventional reciprocating instrumentation) (n\u0026thinsp;=\u0026thinsp;16): Each canal was prepared using Reciproc Blue nickel titanium file 25/08 (VDW, Munich, Germany). The instruments were operated using VDW Silver Motor (VDW) in the \u0026ldquo;RECIPROC ALL\u0026rdquo; preset program and used to the WL in a slow \u0026ldquo;in-and-out\u0026rdquo; pecking motion, with an amplitude of 3mmamplitude limit and a gentle apical pressure was combined with a brushing motion against the lateral canal walls. After three pecking movements, the instrument was removed from the canal (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). Continuous checking of the canal patency was done using size 10 hand. The canals were irrigated during the preparation procedure with 3ml of 5.25% sodium hypochlorite at room temperature using Irriflex endodontic irrigation needle (Produits Dentaires SA, Vevey, reflexSwitzerland) mounted on a 3 ml syringe (Plastipak, Franklin Lakes, NJ, USA) 2mm of the WL. Once the instrumentation is done, the final irrigation protocol consisted of 3 ml of 17% EDTA, 3 ml of distilled water and 3 ml of 5.25% NaOCl, each for 2 minutes (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). NaOCl was placed in the canal and activated using the size 25.04 taper tip of a sonic device EndoActivator (Dentsply Tulsa Dental Specialties, Tulsa, OK, USA) at 1-10kHz and the activator tip was placed within 2 mm of the WL. This cycle was repeated three more times, and the canal was rinsed with 3 ml of 5.25% NaOCl at room temperature after each cycle. After the completion of the endodontic procedures, gauging of the apex using K files (Maillefer, Ballaigues, Switzerland) was done and canals were dried with Reciproc R25 paper points (VDW) and Reciproc R25 gutta-percha points (VDW) was lightly coated with AH plus resin-based sealer (Dentsply, DeTrey, Konstanz, Germany) and placed into the canal down to the WL. Excess of gutta-percha was cut at the CEJ with a heat plugger (Fast-Pack pro-obturation system), and the coronal part of the gutta-percha was condensed with gentle pressure using an endodontic plugger (Heat carrier Dentsply, Maillfer, Ballaigues, Switzerland). A periapical radiograph was obtained to assess the quality of root filling and a layer of 1mm of glass ionomer (Fuji II LC Capsules, GC America, Alsip, IL USA) and a final periapical Xray was taken. Teeth were then referred to the Restorative Department for a final restoration and no later than 4 weeks after the completion of endodontic treatment.\u003c/p\u003e \u003cp\u003e \u003cb\u003eGroup MI\u003c/b\u003e (minimal instrumentation) (n\u0026thinsp;=\u0026thinsp;16): A glide path was established using a size 10 K file (Dentsply, Maillfer, Ballaigues, Switzerland), followed by ProGlider 16.02 to the WL, then the canal was irrigated with 3 ml of 5, 25% of NaOCl at room temperature using Irriflex endodontic needle (Produits Dentaires SA, Vevey, Switzerland) mounted on a 3 ml syringe (Plastipak, Franklin Lakes, NJ, USA) 2mm of the WL. NaOCl was left in the canal and access cavity. The novel device operates at frequency of 280 Hz and the temperature of the tip is 100\u0026deg;C while the temperature of the solution in the canal when it is heated reaches a minimum of 45\u0026deg;C. The prototype needle tip was placed in the canal within 2 mm of the WL, it was moved with small (few mm) in-and out movement, this procedure was repeated three more times and a fresh solution of NaOCl is replaced every time. NaOCl was aspirated from the canal and the access cavity and the final irrigation protocol consisted of 3 ml of 17% EDTA, 3 ml of distilled water and 3 ml of 5.25% NaOCl, each for 2 minutes (\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e). After the completion of the endodontic procedures, the canals were dried using sterile paper point (Maillfer, Ballaigues, Switzerland), and the gutta-percha cone 2% tapered size 20 or 25 (Dentsply, Maillfer, Ballaigues, Switzerland) was inserted into the canal to check apical fit using 3 methods: visual, to confirm that the tip reached the full WL; tactile, by feeling \u0026ldquo;tug-back\u0026rdquo; sensation and radiographic, to ensure the cone reached to WL, than the chosen gutta-percha cone was lightly coated with AH plus resin-based sealer (Dentsply, DeTrey, Konstanz, Germany) and placed into the canal down to the WL. Excess of gutta-percha was cut at the CEJ with a heat plugger (Fast-Pack pro-obturation system), and the coronal part of the gutta-percha was condensed with gentle pressure using an endodontic plugger (Heat carrier Dentsply, Maillfer, Ballaigues, Switzerland). A periapical radiograph was obtained to assess the quality of root filling and a layer of 1 mm of glass ionomer (Fuji II LC Capsules, GC America, Alsip, IL USA) and a final periapical Xray was taken. Teeth were then referred to the Restorative Department for a final restoration and no later than 4 weeks after the completion of endodontic treatment.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eFollow-up\u003c/h2\u003e \u003cp\u003ePatients were followed up periodically every 3-6-9-12 months. Patients were contacted by telephone to recall appointments. During follow-up visit, each patient was evaluated and recorded for the presence of clinical signs (swelling, sinus tract) and/or symptoms: spontaneous or provoked pain, tenderness to percussion/palpation and the quality of coronal restoration. Post-operative standardized radiographs were taken. Preoperative, postoperative and follow-up radiographs were compared in order to evaluate the occurrence of healing and were assigned PAI scores by three blinded endodontists (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In case of disagreement, the highest score is used as the reference. Once a PAI score was assigned, each tooth was classified into the following outcomes groups based on radiographic and clinical evaluation (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e):\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eHealed: The tooth is functional and asymptomatic, with no signs of apical periodontitis (PAI\u0026thinsp;=\u0026thinsp;1)\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eHealing: The tooth is functional and asymptomatic, with periapical lesions that have reduced in size (PAI\u0026thinsp;\u0026gt;\u0026thinsp;1)\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eDiseased: The tooth is non-functional and symptomatic, with signs of apical periodontitis (PAI\u0026thinsp;\u0026gt;\u0026thinsp;1), or asymptomatic but with larger periapical lesions\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e \u003cp\u003eBased on loose criteria, both healed and healing cases were considered successful, while the strict criteria consider only healed cases as successful (\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eThe data were analyzed using IBM SPSS Statistics for Windows (Version 27). Descriptive statistics were summarized and presented as means\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviations for quantitative variables and as frequencies (percentages) for qualitative variables. The normality of distribution for the PAI quantitative variable was assessed using the Shapiro-Wilk test, and the results were satisfactory (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). The box plot figure illustrated the distribution of PAI across the treatment group and within time. The analysis highlights the median, interquartile range (IQR), and potential outliers for each group. The chi-square test was used to compare two categorical variables. Statistical significance was defined as a p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eSample Characteristics\u003c/h2\u003e \u003cp\u003eOf the thirty-two (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e) teeth initially enrolled, during follow-up, one was excluded after presenting pain on percussion and swelling. CBCT revealed a previously undetected second canal, meeting the study\u0026rsquo;s exclusion criteria.\u003c/p\u003e \u003cp\u003eBoth groups had a similar gender distribution (15 males and 16 females): 7 males and 8 females in MI group and 8 males and 8 females in CRI group aged 25\u0026ndash;55 years (mean age: 42.3\u0026thinsp;\u0026plusmn;\u0026thinsp;8.7 years). Dental arch distribution analysis revealed 16 cases in the upper jaw and 15 in the lower jaw. However, there was a significant difference in the distribution between groups (p\u0026thinsp;=\u0026thinsp;0.049), with MI group containing 66,7% mandibular cases (n\u0026thinsp;=\u0026thinsp;10) while CRI group containing 68,8% maxillary cases (n\u0026thinsp;=\u0026thinsp;11) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBaseline Characteristics of Studied Sample (N\u0026thinsp;=\u0026thinsp;31)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTotal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMinimal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eConventional\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eGender\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMale\u003c/p\u003e \u003cp\u003eFemale\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15\u003c/p\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e7\u003c/p\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e8\u003c/p\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.853\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25\u0026ndash;33\u003c/p\u003e \u003cp\u003e34\u0026ndash;44\u003c/p\u003e \u003cp\u003e45\u0026ndash;55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e11\u003c/p\u003e \u003cp\u003e7\u003c/p\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.491\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eJaw\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUpper\u003c/p\u003e \u003cp\u003eLower\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e16\u003c/p\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e11\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.049\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eTreatment Outcome Distribution by Technique\u003c/h2\u003e \u003cp\u003eBoth loose and strict criteria were used to compare the treatment outcomes between CRI and MI (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Based on loose criteria both groups had a 100% success rate and neither group saw any treatment failures. Stricter criteria, however, caused a modest decline in the success rate, especially in MI group. The CRI technique had a greater success rate of 93.8%, whereas the MI technique demonstrated an 80.0% success rate with no significant difference (p\u0026thinsp;=\u0026thinsp;0.333) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eTreatment Outcome Distribution Per Technique (N\u0026thinsp;=\u0026thinsp;31)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eFinal treatment outcome\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eTechnique\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\" morerows=\"2\" rowspan=\"3\"\u003e \u003cp\u003eP-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMinimal\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eConventional\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eN (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eN (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLoose criteria\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSuccess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15 (100.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16 (100.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFailure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0 (0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eStrict Criteria\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSuccess\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (80.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15 (93.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003e0.333\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFailure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3 (20.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (6.3%)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eAssociation Between Age Category and Success Rate\u003c/h2\u003e \u003cp\u003eThe association between age group and the success rate according to strict criteria is presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e for the entire sample as well as for each treatment group (MI and CRI). All age groups in the entire sample showed high success rates: 81.8% in the 25\u0026ndash;33 age group, 85.7% in the 34\u0026ndash;44 age group, and 92.3% in the 45\u0026ndash;55 age group. No significant difference between age and treatment success was detected (p\u0026thinsp;=\u0026thinsp;0.809). MI group's success rates were 83.3% for age 25\u0026ndash;33, 50.0% (\u003cspan additionalcitationids=\"CR35 CR36 CR37 CR38 CR39 CR40 CR41 CR42 CR43\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e), and 85.7% (\u003cspan additionalcitationids=\"CR46 CR47 CR48 CR49 CR50 CR51 CR52 CR53 CR54\" citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e). A p-value of 0.492 further indicated that there was no significant age-related influence. The success rates in the CRI group were high, reaching 80.0% in the 25\u0026ndash;33 age group and 100% in the 34\u0026ndash;44 and 45\u0026ndash;55 age groups; nevertheless, the difference was not statistically significant (p\u0026thinsp;=\u0026thinsp;0.625). Overall, these results indicated that neither treatment group's success rate under strict criteria was influenced by age category.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAssociation Between Age Category and Success Rate Based on Strict Criteria\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eStrict Criteria\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSuccess\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAll sample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge category\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.809\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u0026ndash;33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9 (81.8%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2 (18.2%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34\u0026ndash;44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (85.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (14.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e45\u0026ndash;55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (92.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (7.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eMinimal\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.492\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u0026ndash;33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (83.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (16.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34\u0026ndash;44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1 (50.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (50.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e45\u0026ndash;55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (85.7%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (14.3%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eConventional\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.625\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e25\u0026ndash;33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4 (80.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1 (20.0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34\u0026ndash;44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5 (100%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e45\u0026ndash;55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6 (100%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003ePAI score Over Time and Between Treatment Groups\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows how the PAI changed over time in CRI and MI groups. Both groups had high PAI values at baseline, ranging from 3 to 4. Both groups' PAI levels decreased over time, suggesting that healing had improved. At the 3-month point, there was some variability, notably in the MI group, but this variability seemed to decrease and diminish later in follow-ups, especially in the CRI group. By six months, the scores had decreased to about one or two, and they stayed that way for nine and twelve months. At 9 months in CRI group, the error was little to no variation in PAI scores among patients in that group at that time point. According to the bar height, every patient had the same or almost the same PAI score, which was nearly about 1. Overall, both treatment approaches showed comparable and successful decreases in PAI scores over the course of the 12-month period, indicating that they were successful in promoting healing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eTo our knowledge, this is the first pilot study to evaluate the efficacy of a minimal instrumentation technique using a novel device capable of both heating and activating 5,25% intracanal sodium hypochlorite compared to conventional reciprocating instrumentation with sonic activation in single rooted teeth with apical periodontitis.\u003c/p\u003e \u003cp\u003eThe outcomes at 1 year were favorable and comparable in both treatment groups (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Under loose criteria, the overall success rate in our MI group (80%) was higher than that reported in a comprehensive systematic review on endodontic outcomes (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). When strict criteria are applied, the success rate in our pilot clinical study (100%) closely matched the collective weighted success rate by the same authors (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the past decade, outcome studies have shifted from using terms like healed, healing and diseased to more flexible approach that defines success as strict or loose, alongside failure (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). Recent findings from a prospective study done by Montero et al. 2025, align with the results of our research in their evaluation of apical periodontitis treatment in 170 molars, they compared the GentleWave\u003csup\u003e\u0026reg;\u003c/sup\u003e system (GW) to ultrasonic activation with negative pressure irrigation (UA\u0026thinsp;+\u0026thinsp;NPI) utilizing standardized instrumentation with EdgeFile\u003csup\u003e\u0026reg;\u003c/sup\u003e X7 FireWire files (0.04 and 0.06 tapers )over a mean follow-up of 14.9 months, no significant difference were observed between groups under strict criteria success rates were 70.6% (GW) vs 72.9% (UA\u0026thinsp;+\u0026thinsp;NPI); under loose criteria rates were 83.5% (GW) vs 8.1% (UA\u0026thinsp;+\u0026thinsp;NPI). Notably, our study achieved under loose criteria a 100% success rate greater than the rates presented by Montero et al. 2025(\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). This difference in the results may be attributed to: the smaller sample size (N\u0026thinsp;=\u0026thinsp;31), the methodological differences such as the use of new device capable of heating and activating NaOCl in our MI group, which enhances tissue dissolution and antimicrobial efficacy (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Under strict criteria, our success rates declined: 93.8% for CRI group vs 80.0% for MI group, as similarly noted by Montero et al\u0026rsquo;s larger sample, even though the difference remained statistically non-significant (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e). These studies highlight that while success rate may vary based on assessment criteria and procedural difference, neither disinfection method demonstrates superiority, the higher success rate in our study under loose criteria could suggest potential advantages of heating and activating NaOCl paired with minimal instrumentation even though further research with larger sample size is needed.\u003c/p\u003e \u003cp\u003eStandardization of the treatment procedure is essential in clinical research to minimize variability and ensure reliable outcomes. Including molars in our study would increase the possibility of bias, as molar treatments are significantly more difficult to standardize due to root canal curvature, anatomic differences of the isthmuses, treatment duration, procedural errors (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e). Therefore, only single-rooted teeth were selected, allowing for greater consistency and reducing potential sources of bias. Additional studies are needed to assess whether comparable outcomes can be achieved in multi-rooted teeth, where irrigation protocols may play an important role in the success of the treatment as well as in cases presenting with more acute clinical signs and symptoms of periapical disease (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e) .In addition, all patients, were successfully contacted at the time of follow-up and confirmed that the treated teeth remained in place, symptom-free, and functional. This minimized the possibility that undetected failures were missed, supporting the use of a per-protocol analysis, an approach commonly applied in most endodontic clinical trials and studies (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eAs illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, both treatment protocols demonstrated comparable and significant reductions in PAI scores over 12 months, indicating their success in promoting periapical healing, it is important to note that all lesions included in this study had an initial PAI score\u0026thinsp;\u0026ge;\u0026thinsp;3. Previous studies have reported that treatment success rates is independent of pre-existing lesion size (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). Moazami et al. 2011 similarly revealed no correlation between lesion dimensions and treatment success (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e). However, some research suggests smaller lesion may exhibit slightly superior healing rates compared to greater lesions ones (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). These results are encouraging, given that larger lesions pose more difficulties in healing (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e), emphasizing their role as interfering variables in outcome assessment (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e). Moreover, factors such as gender and age did not show significant associations with the outcome.\u003c/p\u003e \u003cp\u003eTo effectively disinfect the root canal, the irrigant must flow and reach the biofilm, where it can mechanically disrupt it and deliver its chemical effect (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e). However, in MI group, this goal of thorough disinfection proves unattainable necessitating the use of heated and activated NaOCl. Increasing the temperature of NaOCl enhances its ability to penetrate narrow canals by reducing viscosity (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e),while simultaneously improving tissue dissolution, debris removal (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e), and antimicrobial properties (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). The rationale for minimal instrumentation in this group lies in avoiding excessive dentin debris which risks accumulation in non-instrumented regions like isthmuses and fins (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). This debris accumulation further impedes irrigant contact with the biofilm, making debris removal more difficult than anticipated (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). Furthermore, both dentin debris and smear layer reduce the effectiveness of root canal medicaments and irrigants (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). In MI group, a glide path was established using a size 10 k File, followed by ProGlider 16.02 to the WL, without any additional instrumentation or shaping. This approach enabled us to evaluate whether the protocol of irrigation procedure itself can disrupt biofilm. While larger canals allow for more efficient irrigant exchange, they also result in reduced shear stress on the root canal walls (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). Furthermore, a larger canal may present more surface area for interaction with the irrigant, which could need a greater volume of irrigant or prolonged irrigation time to achieve optimal chemical activity (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eLarger instruments are inherently less flexible and struggle to remain centered within the canal, especially in curved anatomies. This lack of centering can lead to uneven dentin removal, with excessive cutting on one side of the canal and untouched areas on the opposite wall\u0026mdash;ultimately compromising tooth structure without guarantying improved cleanliness(\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). Supporting this, Lee et al. demonstrated that while canals prepared to a larger size #40 were cleaner than smaller preparations #20 when using conventional syringe and needle irrigation, this difference disappeared when ultrasonic activation of the irrigant was employed(\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e).Under activated conditions, even minimally instrumented canals achieved cleanliness comparable to that of larger preparations, in both round and oval canals(\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). These findings reinforce the principle that minimal shaping, when combined with advanced irrigant activation techniques such as ultrasonic and heated sodium hypochlorite can preserve dentin integrity without compromising disinfection efficacy.\u003c/p\u003e \u003cp\u003eSiqueira et al. demonstrated that un-instrumented root canal walls retain debris (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e). A histological study confirms those findings, particularly in groups where syringe and needle irrigation were used (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). However, this difference was not observed in groups where the irrigant was ultrasonically activated (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). In those groups, the size of the canal preparation did not significantly affect cleanliness, highlighting the critical role of irrigation dynamics (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e). Notably, MI group which utilized intracanal heating and activation of NaOCl, achieved similar outcomes to CRI group, despite reduced instrumentation.\u003c/p\u003e \u003cp\u003eNaOCl, in concentrations between 0.5% and 8.25%, is the most commonly used irrigant in root canal treatment (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e). In the present study 5.25% of NaOCl was used, the choice of the EndoActivator as the sonic activation device in CRI group of this study was strategically justified by its ability to balance efficacy with minimal invasiveness while PUI carries risks of unintended dentine removal when the metal tip touches canal walls (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e), the EndoActivator\u0026rsquo;s flexible polymer tips operate at lower frequencies (1-10KHz), generating controlled hydrodynamic shear stress without aggressive mechanical contact (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e). Furthermore, studies have demonstrated that sonic activation systems achieve comparable biofilm disruption compared to ultrasonic techniques (\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSirtes et al. (2005) demonstrated that heating NaOCl, even at low concentrations, improves its ability to dissolve pulp tissue and enhances its antimicrobial effectiveness while preserving its chemical integrity and clinical safety (\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e).They also reported that increasing the temperature of sodium hypochlorite from 20\u0026deg;C to 45\u0026deg;C resulted in approximately a 100-fold enhancement in its bactericidal activity against \u003cem\u003eE. faecalis\u003c/em\u003e(\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e).According to Costigan, in heated sodium hypochlorite solutions, the time required to kill \u003cem\u003eMycobacterium tuberculosis\u003c/em\u003e decreases as temperature rises. At 60\u0026deg;C, bacterial elimination occurs within 30 seconds; at 55\u0026deg;C, within 60 seconds; and at 50\u0026deg;C, within 90 seconds. This illustrates the marked enhancement of antimicrobial efficacy achieved by elevating the irrigant temperature(\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e). Moreover, an in vitro study evaluating different irrigation protocols concluded that only NaOCl heated inside the canal and combined with ultrasonic activation was able to partially dissolve pulp tissue within lateral canals, highlighting the clinical relevance of heating NaOCl to enhance tissue dissolution (\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e). Supporting this, another study assessing antibiofilm activity against \u003cem\u003eE. faecalis\u003c/em\u003e found that heating NaOCl combined with irrigant activation produced the greatest reduction in bacterial biofilms, emphasizing that elevated temperature and activation synergistically improve root canal disinfection (\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e).Overall, these findings highlight that increasing the temperature of the irrigant significantly enhances its ability to eliminate bacteria and dissolve pulp tissue.\u003c/p\u003e \u003cp\u003eAssessing the safety of heating sodium hypochlorite is essential to avoid potential damage to periodontal tissues and bone. Brown et al. (1970) evaluated the thermophysical properties of enamel and dentin and demonstrated that dentin possesses lower thermal diffusivity than enamel, indicating a reduced ability to conduct heat (\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e). Consistently, Elhenawy et al. (2025) reported that the apical third of the root exhibited the lowest temperature increase(\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e). Moreover, most studies have shown that temperature changes on the root surface remain below 10\u0026deg;C, supporting the low risk of damage to periodontal tissues and bone(\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e, \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e). Erickson et al. highlighted that bone tissue becomes sensitive to heat at approximately 47\u0026deg;C, with greater injury observed at 53\u0026deg;C for 1 minute and exposure to 60\u0026deg;C or more results in irreversible cessation of blood flow and necrosis, persisting without repair for over 100 days(\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e). Based on these findings, the novel device employed in our study, which heats sodium hypochlorite up to 45\u0026deg;C, can be considered safe.\u003c/p\u003e \u003cp\u003eIn the present study, AH Plus resin-based sealer was selected as the sealer for obturation of minimally tapered canals, since previous findings have shown that, unlike other sealers, its sealing ability is not adversely affected by greater sealer thickness(\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e).It has superior dimensional stability, implying minimal shrinkage(\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e), high bond strength to dentine(\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e) and to the filling material (\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e) and has low solubility(\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn addition, Paula-Silvia et al. concluded that conventional PA may lead to misinterpretation of lesion size changes due to inconsistencies in angulation during follow-up imaging which can impact treatment outcome evaluations (\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e). To mitigate this risk, standardized PA radiographs were obtained using pretreatment bite blocks fabricated from bite registration material ensuring consistent orientation across all time points, but the inherent limitations of 2D radiography in capturing volumetric changes remain a problem in the preliminary trial (\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e). Therefore, CBCT imaging offers greater accuracy in detection apical periodontitis compared to conventional PA (\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe recall rate in this study was very high (100%), which can be related that the follow-up period was only 12 months, as recall rates in clinical studies generally decline over time. In a study done by \u0026Oslash;rstavik, the recall rates decreased from 71% after the first year to 33% after the fourth year (\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e). In previous outcome studies, the median recall rate was 52.7% (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). One drawback of a short follow-up is that the percentage of teeth with complete resolution of radiolucency may be underestimated because lesions may still be in the healing process (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). The European Society of Endodontology (ESE) (2006) recommends at least 4 years of follow-up to confirm the complete resolution of apical periodontitis. In addition, a recent study done by Bardini et al., 2023 shows that healing outcomes tends to improve with follow-ups duration more than one year (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e). However, liang et al. demonstrated that during 10\u0026ndash;19 months of evaluation, some large lesions could be almost completely resolved, while small radiolucencies showed only minimal decreased, indicating that time was not the primary responsible factor (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe strength of the current study is the randomization of the teeth to the different treatment protocols, blinded patients, including only single rooted teeth, and one operator performing the treatments. However, the operator could not be blinded as he/she was informed of the treatment protocol to be performed. Regarding the findings of this study certain limitations must be considered, the most significant is the small sample size (N\u0026thinsp;=\u0026thinsp;31), which reduces statistical power, increases variability in dental conditions among participants, and raises the risk of overestimating treatment efficacy. Furthermore, while the PAI and PA are widely accepted for outcome assessment, they may lack the diagnostic sensitivity of CBCT in detecting subtle periapical changes.\u003c/p\u003e \u003cp\u003eThis pilot clinical trial demonstrates that MI with heated and activated 5.25% NaOCl achieves 12-month success rates comparable to CRI in single-rooted teeth with apical periodontitis. The findings support minimally invasive strategies that optimize irrigant dynamics while preserving dentin, offering a promising alternative to traditional protocols.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWithin the limitations of this pilot clinical trial, both conventional reciprocating instrumentation and the minimal instrumentation technique demonstrated comparable effectiveness in promoting healing of apical periodontitis. The minimal instrumentation technique with heating and activated sodium hypochlorite shows potential for enhancing the healing of periapical lesions. The novel device used in this technique presents an intriguing advancement, further large-scale clinical trial with more rigorous and standardized protocols are needed. However, further research should also explore its application in multirooted teeth, where conserving dentinal structure is essential for long-term success and tooth preservation.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e2D\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eTwo Dimensional\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003e3D\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eThree Dimensional\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAP\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eApical Periodontitis\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eCBCT\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eCone Beam Computed Tomography\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eEDTA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eEthyleneDiamineTetraacetric Acid\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eGW\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eGentleWave\u0026reg;\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eMIE\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eMinimally Invasive Endodontic\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eNaOCl\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSodium Hypochlorite\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePeriapical Radiograph\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePAI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePeriapical Index\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003ePUI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003ePassive Ultrasonic Irrigation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSI\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSonic Irrigation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eUA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eUltrasonic Activation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eWL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eWorking Length\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eETHICS APPROVAL AND CONSENT TO PARTICIPATE\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis pilot clinical study obtained ethical approval from the Saint Joseph University of Beirut Ethics Committee (Approval number: 2023-266). All procedures were performed in accordance with the Declaration of Helsinki. All participants provided written informed consent prior to participation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCONSENT FOR PUBLICATION\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWritten informed consent was obtained from all individual study participants\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDATA AVAILABILITY STATEMENT\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCONFLICT OF INTEREST STATEMENT\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors deny any conflicts of interest related to this study.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFUNDING INFORMATION\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo source of financial support.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAUTHORS\u0026rsquo; CONTRIBUTIONS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFabienne El Jagi\u003c/strong\u003e: Conceptualization, Methodology, Investigation, Writing\u0026mdash;original draft preparation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eIssam Khalil:\u0026nbsp;\u003c/strong\u003eReviewing and Editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAlfred Naaman:\u003c/strong\u003e Visualization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCarla Zougheib\u003c/strong\u003e: Validation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMarc Krikor Kaloustian\u003c/strong\u003e: Writing\u0026mdash;reviewing and editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTracy El Feghaly\u003c/strong\u003e: Formal Analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMarie Abboud Mehanna\u003c/strong\u003e: Data Curation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRoula El Hachem:\u003c/strong\u003e Supervision, Writing\u0026mdash;original draft, Resources, Validation, Conceptualization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eACKNOWLEGEMENTS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors received no benefits or support from any organization for the submitted work and have no acknowledgments to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eClinical trial registration\u0026nbsp;\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe study was registered on www.clinicaltrials.gov databases with number (NCT06461728): in 8 July 2024\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRicucci D, Siqueira JF. 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Int Endod J. 2022;55(S4):845\u0026ndash;71. \u003c/li\u003e\n\u003cli\u003eSiqueira JF, P\u0026eacute;rez AR, Marceliano‐Alves MF, Provenzano JC, Silva SG, Pires FR, et al. What happens to unprepared root canal walls: a correlative analysis using micro‐computed tomography and histology/scanning electron microscopy. Int Endod J. 2018 May;51(5):501\u0026ndash;8.\u003c/li\u003e\n\u003cli\u003eCj R. Cleaning and shaping the root canal system. Pathw Pulp. 2010;231\u0026ndash;92. \u003c/li\u003e\n\u003cli\u003eIandolo A, Abdellatif D, Amato M, Pantaleo G, Blasi A, Franco V, et al. Dentinal tubule penetration and root canal cleanliness following ultrasonic activation of intracanal-heated sodium hypochlorite. Aust Endod J. 2020;46(2):204\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eDuncan HF, Kirkevang LL, Peters OA, El-Karim I, Krastl G, Del Fabbro M, et al. Treatment of pulpal and apical disease: The European Society of Endodontology (ESE) S3-level clinical practice guideline. 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Int Arab J Dent. 2024 Nov 1;15(2):46\u0026ndash;53. \u003c/li\u003e\n\u003cli\u003eNagendrababu V, Duncan HF, Bj\u0026oslash;rndal L, Kvist T, Priya E, Jayaraman J, et al. PRIRATE 2020 guidelines for reporting randomized trials in Endodontics: a consensus-based development. Int Endod J. 2020;53(6):764\u0026ndash;73.\u003c/li\u003e\n\u003cli\u003e\u0026Oslash;rstavik D, Kerekes K, Eriksen HM. The periapical index: A scoring system for radiographic assessment of apical periodontitis. Dent Traumatol. 1986;2(1):20\u0026ndash;34. \u003c/li\u003e\n\u003cli\u003eDe-Deus G, Belladonna FG, Zuolo AS, Sim\u0026otilde;es-Carvalho M, Santos CB, Oliveira DS, et al. Effectiveness of Reciproc Blue in removing canal filling material and regaining apical patency. Int Endod J. 2019 Feb;52(2):250\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eBardini G, Bellido MM, Rossi-Fedele G, Casula L, Dettori C, Ideo F, et al. A 4-year follow-up of root canal obturation using a calcium silicate-based sealer and a zinc oxide-eugenol sealer: A randomized clinical trial. Int Endod J. 2025;58(2):193\u0026ndash;208.\u003c/li\u003e\n\u003cli\u003eNg YL, Mann V, Gulabivala K. Outcome of secondary root canal treatment: a systematic review of the literature. Int Endod J. 2008;41(12):1026\u0026ndash;46.\u003c/li\u003e\n\u003cli\u003eNg YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature \u0026ndash; Part 1. Effects of study characteristics on probability of success. Int Endod J. 2007;40(12):921\u0026ndash;39.\u003c/li\u003e\n\u003cli\u003eNg YL, Mann V, Rahbaran S, Lewsey J, Gulabivala K. Outcome of primary root canal treatment: systematic review of the literature \u0026ndash; Part 2. Influence of clinical factors. Int Endod J. 2008;41(1):6\u0026ndash;31.\u003c/li\u003e\n\u003cli\u003eMontero LQ, Basrani B, Ellis DA, Cohenca N. Healing outcomes following the treatment of molars using different root canal disinfection methods: A prospective cohort study. J Endod [Internet]. 2025 Apr 24 [cited 2025 May 3]; Available from: https://www.sciencedirect.com/science/article/pii/S009923992500192X\u003c/li\u003e\n\u003cli\u003eLiang YH, Jiang LM, Jiang L, Chen XB, Liu YY, Tian FC, et al. Radiographic Healing after a Root Canal Treatment Performed in Single-rooted Teeth with and without Ultrasonic Activation of the Irrigant: A Randomized Controlled Trial. J Endod. 2013 Oct;39(10):1218\u0026ndash;25.\u003c/li\u003e\n\u003cli\u003eLaukkanen E, Vehkalahti MM, Kotiranta AK. Radiographic outcome of root canal treatment in general dental practice: tooth type and quality of root filling as prognostic factors. Acta Odontol Scand. 2021 Jan 2;79(1):37\u0026ndash;42.\u003c/li\u003e\n\u003cli\u003eArslan H, Ahmed HMA, Şahin Y, Doğanay Yıldız E, G\u0026uuml;ndoğdu EC, G\u0026uuml;ven Y, et al. Regenerative Endodontic Procedures in Necrotic Mature Teeth with Periapical Radiolucencies: A Preliminary Randomized Clinical Study. J Endod. 2019 Jul 1;45(7):863\u0026ndash;72.\u003c/li\u003e\n\u003cli\u003eSaini A, Nangia D, Sharma S, Kumar V, Chawla A, Logani A, et al. Outcome and associated predictors for nonsurgical management of large cyst-like periapical lesions: A CBCT-based prospective cohort study. Int Endod J. 2023 Feb;56(2):146\u0026ndash;63.\u003c/li\u003e\n\u003cli\u003eBaseri M, Radmand F, Milani AS, Gavgani LF, Salehnia F, Dianat O. The effect of periapical lesion size on the success rate of different endodontic treatments: a systematic review and meta-analysis. Evid Based Dent. 2023 Mar;24(1):43\u0026ndash;43.\u003c/li\u003e\n\u003cli\u003eMoazami F, Sahebi S, Sobhnamayan F, Alipour A. Success Rate of Nonsurgical Endodontic Treatment of Nonvital Teeth with Variable Periradicular Lesions. Iran Endod J. 2011;6(3):119\u0026ndash;24.\u003c/li\u003e\n\u003cli\u003eMarquis VL, Dao T, Farzaneh M, Abitbol S, Friedman S. Treatment Outcome in Endodontics: The Toronto Study. Phase III: Initial Treatment. J Endod. 2006 Apr 1;32(4):299\u0026ndash;306.\u003c/li\u003e\n\u003cli\u003ePeters LB, Wesselink PR. Periapical healing of endodontically treated teeth in one and two visits obturated in the presence or absence of detectable microorganisms. Int Endod J. 2002 Aug;35(8):660\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eChybowski EA, Glickman GN, Patel Y, Fleury A, Solomon E, He J. Clinical Outcome of Non-Surgical Root Canal Treatment Using a Single-cone Technique with Endosequence Bioceramic Sealer: A Retrospective Analysis. J Endod. 2018 Jun 1;44(6):941\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eGulabivala K, Ng YL. Factors that affect the outcomes of root canal treatment and retreatment\u0026mdash;A reframing of the principles. Int Endod J. 2023;56(S2):82\u0026ndash;115.\u003c/li\u003e\n\u003cli\u003eRobinson JP, Lumley PJ, Claridge E, Cooper PR, Grover LM, Williams RL, et al. An analytical Micro CT methodology for quantifying inorganic dentine debris following internal tooth preparation. J Dent. 2012 Nov 1;40(11):999\u0026ndash;1005.\u003c/li\u003e\n\u003cli\u003eHaapasalo M, Qian W, Portenier I, Waltimo T. Effects of Dentin on the Antimicrobial Properties of Endodontic Medicaments. J Endod. 2007 Aug 1;33(8):917\u0026ndash;25.\u003c/li\u003e\n\u003cli\u003eKamburoğlu K, Kili\u0026ccedil; C, \u0026Ouml;zen T, Horasan S. Accuracy of chemically created periapical lesion measurements using limited cone beam computed tomography. Dentomaxillofacial Radiol. 2010 Feb 1;39(2):95\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eIncreased Apical Enlargement Contributes to Excessive Dentin Removal in Curved Root Canals: A Stepwise Microcomputed Tomography Study - ClinicalKey [Internet]. [cited 2025 Jul 27]. Available from: https://ezproxy.usj.edu.lb:2106/#!/content/playContent/1-s2.0-S0099239911010302?returnurl=https:%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0099239911010302%3Fshowall%3Dtrue\u0026amp;referrer=https:%2F%2Fpubmed.ncbi.nlm.nih.gov%2F\u003c/li\u003e\n\u003cli\u003eLee OYS, Khan K, Li KY, Shetty H, Abiad RS, Cheung GSP, et al. Influence of apical preparation size and irrigation technique on root canal debridement: a histological analysis of round and oval root canals. Int Endod J. 2019 Sep;52(9):1366\u0026ndash;76.\u003c/li\u003e\n\u003cli\u003eSiqueira Junior JF, R\u0026ocirc;\u0026ccedil;as IDN, Marceliano-Alves MF, P\u0026eacute;rez AR, Ricucci D. Unprepared root canal surface areas: causes, clinical implications, and therapeutic strategies. Braz Oral Res [Internet]. 2018 Oct 18 [cited 2025 Jun 14];32(suppl 1). Available from: http://www.scielo.br/scielo.php?script=sci_arttext\u0026amp;pid=S1806-83242018000500600\u0026amp;lng=en\u0026amp;tlng=en\u003c/li\u003e\n\u003cli\u003eGazzaneo I, Vieira GCS, P\u0026eacute;rez AR, Alves FRF, Gon\u0026ccedil;alves LS, Mdala I, et al. Root Canal Disinfection by Single- and Multiple-instrument Systems: Effects of Sodium Hypochlorite Volume, Concentration, and Retention Time. J Endod. 2019 Jun;45(6):736\u0026ndash;41.\u003c/li\u003e\n\u003cli\u003eCullen JKT, Wealleans JA, Kirkpatrick TC, Yaccino JM. The Effect of 8.25% Sodium Hypochlorite on Dental Pulp Dissolution and Dentin Flexural Strength and Modulus. J Endod. 2015 Jun 1;41(6):920\u0026ndash;4.\u003c/li\u003e\n\u003cli\u003eHoedke D, Kaulika N, Dommisch H, Schlafer S, Shemesh H, Bitter K. Reduction of dual-species biofilm after sonic- or ultrasonic-activated irrigation protocols: A laboratory study. Int Endod J. 2021;54(12):2219\u0026ndash;28.\u003c/li\u003e\n\u003cli\u003eAbouzaid K, Dhaimy S. Antibacterial Efficacy of Sonic Versus Ultrasonic Irrigation of the Root Canal System: A Systematic Review. Oral Health Dent Sci [Internet]. 2021 Dec 30 [cited 2024 Nov 10];5(5). Available from: http://scivisionpub.com/pdfs/antibacterial-efficacy-of-sonic-versus-ultrasonic-irrigation-of-the-root-canal-system-a-systematic-review-1955.pdf\u003c/li\u003e\n\u003cli\u003eSirtes G, Waltimo T, Schaetzle M, Zehnder M. The Effects of Temperature on Sodium Hypochlorite Short-Term Stability, Pulp Dissolution Capacity, and Antimicrobial Efficacy. J Endod. 2005 Sep 1;31(9):669\u0026ndash;71.\u003c/li\u003e\n\u003cli\u003eCostigan SM. Effectiveness of Hot Hypochlorites of Low Alkalinity in Destroying \u003cem\u003eMycobacterium tuberculosis\u003c/em\u003e. J Bacteriol. 1936 Jul;32(1):57\u0026ndash;63.\u003c/li\u003e\n\u003cli\u003eAmato M, Pantaleo G, Abtellatif D, Blasi A, Gagliani M, Iandolo A. An in vitro evaluation of the degree of pulp tissue dissolution through different root canal irrigation protocols. J Conserv Dent JCD. 2018;21(2):175\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eChoudhury P, Raghu R, Shetty A, Santhosh L, Subhashini R, Nikhitha KL. Antibiofilm activity of sodium hypochlorite against enterococcus faecalis using four irrigant activation protocols. J Conserv Dent Endod. 2024 Jul;27(7):724.\u003c/li\u003e\n\u003cli\u003eBrown WS, Dewey WA, Jacobs HR. Thermal properties of teeth. J Dent Res. 1970;49(4):752\u0026ndash;5.\u003c/li\u003e\n\u003cli\u003eElhenawy AM, Moussa SM, Alnakeeb MA, Genena S. Effect of Different Methods of Heating Sodium Hypochlorite Irrigating Solution on the External Root Surface Temperature. J Endod. 2025 Jun 6;S0099-2399(25)00315-2.\u003c/li\u003e\n\u003cli\u003eSariyilmaz \u0026Ouml;, Sariyilmaz E, Keskin C. Comparative Analysis of Temperature Changes with Preheated and Intracanal Heated Solutions and Ultrasonic Activation in Immature Teeth. J Endod. 2025 Jan 1;51(1):71\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003eSimeone M, Valletta A, Giudice A, Di Lorenzo P, Iandolo A. The activation of irrigation solutions in Endodontics: a perfected technique. G Ital Endodonzia. 2015 Nov 1;29(2):65\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003eEriksson AR, Albrektsson T. Temperature threshold levels for heat-induced bone tissue injury: A vital-microscopic study in the rabbit. J Prosthet Dent. 1983 Jul;50(1):101\u0026ndash;7.\u003c/li\u003e\n\u003cli\u003ePolymicrobial Leakage of Four Root Canal Sealers at Two Different Thicknesses - Journal of Endodontics [Internet]. [cited 2025 Aug 16]. Available from: https://www.jendodon.com/article/S0099-2399(06)00315-3/abstract\u003c/li\u003e\n\u003cli\u003eLee JK, Kwak SW, Ha JH, Lee W, Kim HC. Physicochemical Properties of Epoxy Resin-Based and Bioceramic-Based Root Canal Sealers. Bioinorg Chem Appl. 2017;2017:1\u0026ndash;8.\u003c/li\u003e\n\u003cli\u003eDe-Deus G, Di Giorgi K, Fidel S, Fidel RAS, Paciornik S. Push-out Bond Strength of Resilon/Epiphany and Resilon/Epiphany Self-Etch to Root Dentin. J Endod. 2009 Jul;35(7):1048\u0026ndash;50.\u003c/li\u003e\n\u003cli\u003eLee K, Williams M, Camps J, Pashley D. Adhesion of Endodontic Sealers to Dentin and Gutta-Percha. J Endod. 2002 Oct;28(10):684\u0026ndash;8.\u003c/li\u003e\n\u003cli\u003eSch\u0026auml;fer E, Zandbiglari T. Solubility of root‐canal sealers in water and artificial saliva. Int Endod J. 2003 Oct;36(10):660\u0026ndash;9. \u003c/li\u003e\n\u003cli\u003eGarcia De Paula-Silva FW, Hassan B, Bezerra Da Silva LA, Leonardo MR, Wu MK. Outcome of Root Canal Treatment in Dogs Determined by Periapical Radiography and Cone-Beam Computed Tomography Scans. J Endod. 2009 May;35(5):723\u0026ndash;6.\u003c/li\u003e\n\u003cli\u003eSchloss T, Sonntag D, Kohli MR, Setzer FC. A Comparison of 2- and 3-dimensional Healing Assessment after Endodontic Surgery Using Cone-beam Computed Tomographic Volumes or Periapical Radiographs. J Endod. 2017 Jul;43(7):1072\u0026ndash;9.\u003c/li\u003e\n\u003cli\u003e\u0026Oslash;rstavik D. Time‐course and risk analyses of the development and healing of chronic apical periodontitis in man. Int Endod J. 1996 May;29(3):150\u0026ndash;5.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Activation, apical periodontitis, endodontic outcome, heating, minimally invasive, sodium hypochlorite","lastPublishedDoi":"10.21203/rs.3.rs-8262641/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8262641/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eAim\u003c/h2\u003e \u003cp\u003eThis pilot clinical trial aims to preliminarily evaluate and compare radiographic healing outcomes of a minimally instrumentation technique using a novel device capable of both heating and activating 5.25% of intracanal sodium hypochlorite (NaOCl) versus conventional reciprocating instrumentation with sonic activation on single rooted teeth with apical periodontitis.\u003c/p\u003e\u003ch2\u003eMaterial and Methods\u003c/h2\u003e \u003cp\u003eThirty-two single rooted teeth with pre-operative periapical radiolucency and PAI score\u0026thinsp;\u0026ge;\u0026thinsp;3 were randomly divided into: (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) Conventional reciprocating instrumentation using Reciproc Blue files and sonic activation, (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Minimal instrumentation technique using ProGlider 16.02 to the foramen along with a novel device capable of heating and activating NaOCl. Follow up was scheduled at 3,6 and 12 months and a periapical index (PAI) was recorded at T0, T3, T6 and T12 to evaluate the treatment outcome. Once a PAI score was assigned, each tooth was classified into: healed, healing and diseased, based on loose criteria healed and healing cases were considered successful, while the strict criteria consider only healed cases as successful. Data analysis was performed using IBM SPSS Statistics 27, quantitative data were summarized as means\u0026thinsp;\u0026plusmn;\u0026thinsp;SD, qualitative as frequencies (percentages), PAI\u0026rsquo;s normality was confirmed by Shapiro-Wilk test and Chi-square tested categorical variables; significance set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eBoth groups had a 100% success rate under loose criteria. Stricter criteria, however, caused a modest decline in the success rate, especially in the Minimal instrumentation group. The Conventional approach had a greater success rate of 93.8%, whereas the Minimal technique demonstrated an 80.0% success rate with no significant difference (p\u0026thinsp;=\u0026thinsp;0.333).\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eBoth techniques exhibited predictable outcomes regarding radiographic healing with no significant difference between the two methods. Future studies should employ CBCT analysis and larger sample size to validate long-term efficacy of this novel device.\u003c/p\u003e","manuscriptTitle":"Outcome of Endodontic Treatment with Heated-Activated Sodium Hypochlorite and Minimal Instrumentation versus Conventional Instrumentation: A Pilot Clinical Trial","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 06:05:00","doi":"10.21203/rs.3.rs-8262641/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"b602e202-cb09-4f3f-b8ff-33687fa81ae1","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-05T15:09:38+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-12 06:05:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8262641","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8262641","identity":"rs-8262641","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}