Influence of different final irrigation protocols for removal of photosensitizer activaded by ultrasonic device on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement

Influence of different final irrigation protocols for removal of photosensitizer activaded by ultrasonic device on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement | 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 Influence of different final irrigation protocols for removal of photosensitizer activaded by ultrasonic device on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement Vitor Hugo Sanches Menchik, Anna Vithoria Da Costa Longhi, Matheus Albino Souza, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7934333/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 02 Mar, 2026 Read the published version in Lasers in Medical Science → Version 1 posted 10 You are reading this latest preprint version Abstract Introduction the role of endodontic treatment is to eliminate microorganisms without compromising adjacent tissues and adhesion. The aim of present study was to evaluate the influence of final irrigation protocols for removal of photosensitizer activaded by ultrasonic device(US) on the bond strength(BS) of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement to root dentin. Methods one hundred single-rooted teeth were used. After coronal sectioning, 50 roots were used to assess the bond strength of filling material and 50 to assess the bond strength of restorative material. After sample preparation and photodynamic therapy protocol with US, the roots were randomly divided into five groups (n = 10), according to irrigation protocol for photosensitizer removal: G1(negative control)–distilled water + US;G2–17% EDTA;G3–17% GA;G4 − 17% EDTA + US;G5–17% GA + US. Then, the roots were filled with gutta-percha/Bio-C bioceramic sealer in the first evaluation, and fiber glass posts/Rely-X U200 self-adhesive cement in the second evaluation. In both, the roots were sectioned to obtain 1 mm thick dentin discs containing the filling/restorative material, and the push-out test was performed. Failure patterns were observed under optical microscope. Specific statistical analysis was performed in both evaluations(α 5%). Results in both evaluations, BS was significantly higher in groups 4(17% EDTA + US) and 5(17% GA + US) when compared to all other groups(p 0.05), with a predominance of cohesive failure in all groups. Conclusion the association of US with EDTA and GA for photosensitizer removal improved the BS of filling/restorative material to root dentin. bond strength EDTA glycolic acid photodynamic therapy ultrasonic activation INTRODUCTION The photodynamic therapy (PDT) represents an auxiliary decontamination resource in the endodontic field, involving the ability of a photosensitizer to absorb light-energy and to react with oxygen, generating reactive oxygen species. It adheres and penetrates the bacterial cell wall, precipitating the cytoplasmic content and inducing damage to the DNA of the bacterial cell [ 1 ]. On the other hand, ultrasonic activation (US) has also contributed to greater decontamination in the endodontic treatment, due to the increase in temperature and hydrostatic pressure of the irrigant agents which are used into the root canals [ 2 ]. Considering the microbial etiology of pulp and periapical pathologies, the use of these resources has been recommended to assist conventional chemical-mechanical preparation in the decontamination of root canals [ 1 , 2 ]. According to Ghinzelli et al. [ 3 ], the use of US over the photosensitizer of PDT resulted in higher elimination of bacteria from the root canal space. However, it may compromise the preservation of the cleanliness of the root dentin surface, taking into account the subsequent filling and restoration of the endodontically treated tooth. The photosensitizers presents hydrophilic nature, low molecular weight, and high viscosity. It creates a chemical smear layer that strongly adheres to the canal walls and dentinal tubules [ 4 ], reducing the bond strength of filling and restorative materials [ 5 , 6 ]. In addition, the US can induce greater impulse and impregnation of the photosensitizer to the canal walls, further compromising adhesion. Therefore, the use of final irrigation protocols should be considered when photodynamic therapy is performed. The ethylenediaminetetraacetic acid (EDTA) and glycolic acid (GA) are final irrigants with ability to remove the smear layer [ 7 , 8 ]. The US of these final irrigants contributes for higher smear layer removal [ 9 ]. Thus, the association of EDTA and GA with US could represent an alternative for photosensitizer removal after PDT, in order to provide satisfactory adhesion of filling/restorative materials. Recent research has demonstrated scientific evidences for the use of bioceramic sealers as filling materials. Among other properties, it demonstrates adequate bond strength to dentin [ 10 ]. At the same time, the use of self-adhesive resin cement has been recommended to promote better bond strength of glass fiber posts (GFP) to the root dentin, when the coronal portion presents extensive loss [ 11 ]. However, there are no studies in the literature revealing the effectiveness of final irrigation protocols for photosensitizer removal, when the photosensitizer was activated by US. Moreover, the influence of theses protocols in the bond strength of bioceramic sealers and self-adhesive resin cements is not well elucidated. The aim of present study is to evaluate the influence of of different final irrigation protocols for removal of photosensitizer activaded by ultrasonic device on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement to root dentin. The hypotheses of the present study were that US of the tested final irrigants provides effective removal of photosensitizer, (i) improving the bond strength of filling and (ii) restorative materials to root dentin. MATERIAL AND METHODS This study was appreciated and approved by the local Ethics Commission. Sample collection and preparation One hundred single-rooted extracted human teeth were used in the present study. All teeth were obtained from the Biobank of the School of Dentistry of the University of Passo Fundo (Passo Fundo, RS, Brazil). Dental crowns were sectioned with a rotary diamond disc (#911H, Brasseler, Savannah, GA, United States) so that all roots retained a length of 15 mm. The root length of 15 mm was measured with a ruler, a mark was made on each root in the measurement of 15 mm and the cut was performed at this length, standardizing the length of all roots. After this, 50 roots were prepared by single operator, using the same protocol for pulp tissue removal and standardization of the root canal diameter. The working length (WL) was established by introducing a K-file #10 (Dentsply-Maillefer, Ballaigues, Switzerland) into the canal until its tip was visualized at the apical foramen. From this measurement, 1 mm was subtracted to obtain the WL. Each tooth was fixed in a portable lathe machine, in order to maintain the tooth secured during the root canal preparation. The roots were enlarged to WL using the ProTaper system (Dentsply- Maillefer), following the sequence S1 to F3. Distilled water (DW) (Natupharma, Passo Fundo, RS, Brazil) was used as irrigant solution and renewed at each instrument change. The ProTaper files (Dentsply-Maillefer) were used in a 16:1 gear reduction handpiece powered by a torque-controlled electric motor (X-Smart Plus - Dentsply-Maillefer, Ballaigues, Switzerland) at a constant rotation speed of 300 rpm in a crown-down manner according to the manufacturer’s instructions, by using a gentle in-and-out digital motion. The remaining 50 roots were flared at their coronal and middle thirds using Gates Glidden drills no. 2, 3 and 4 to a depth of 10 mm, after chemo-mechanical preparation, in order to provide adequate space for cementation of GFP. The Gates Glidden drills were used in a low speed handpiece powered by micro electric motor at a constant rotation speed of 10.000 rpm in a crown-down manner, by using a gentle in-and-out digital motion. All root canals were then filled with 17% EDTA (Biodinâmica, Ibiporã, PR, Brazil), and all roots were put into 10 mL plastic vials containing 17% EDTA, such that there were ten samples per vial, so that the roots remained completely covered by the solution. Each plastic vial was inserted into an ultrasonic cleaning machine (Bio Free, Gnatus, Ribeirão Preto, SP, Brazil) for one minute in order to remove the smear layer formed by root canal preparation. After that, the root canals were irrigated with 5mL of DW and dried with absorbent paper points (Tanari, Manacapuru, AM, Brazil). PDT protocol with US The 100 specimens were embedded in epoxy resin (Silaex, São Paulo, SP, Brazil), to facilitate PDT protocol. The root canals were filled with 0.01% (0.1 mg/mL) methylene blue (Chimio Lux DMC, São Carlos, SP, Brazil) until extravasation to the root canal entrance. The photosensitizer was retained in the root canal for 5 min, as pre-irradiation time. Then, US was performed using an ultrasonic device (Nac Plus Ultrasonics, Adiel, Ribeirão Preto, SP, Brazil). The stainless-steel E1 irrisonic endodontic tip (Helse Ultrasonic, Santa Rosa de Viterbo, SP, Brazil) was inserted 1 mm short of the WL and activated for 1 min. Scale power 1 for endodontics (25% power) was used to promote US. After that, a low intensity laser (Therapy XT® DMC, São Carlos, SP, Brazil) was used at 100mW power and continuous emission in the red part of the spectrum (660–690 nm wavelength), with an intra-canal optical fiber of 600 µm diameter, attached at 2 mm short of the working length. The root canals were irradiated for 90 s, with 9 J of total dose delivery and 320 J/cm2 of energy density, remaining the intra-canal fiber in static position, as recommended by the manufacturer. Then, all roots were irrigated with 5 mL of DW, followed by the aspiration of root canals. Classification of treatment protocols According to experimental tests, 50 specimens were used for evaluation of bond strength of filling material and the remaining 50 specimens were used for evaluation of bond strength of restorative material. In both evaluations, the 50 specimens were randomly divided into five groups (n = 10), according to the final irrigation protocol for photosensitizer removal: G1 – DW + US; G2–17% EDTA; G3–17% GA; G4–17% EDTA + US; G5–17% GA + US. The DW, 17% EDTA and 17% were obtained by compounding pharmacy (Natupharma, Passo Fundo, RS, Brazil). In the groups without US, the root canals were completely filled with the tested solution until extravasation to the root canal entrance. Then, the tested solution remained in contact with root canal walls for a period of 1 min. After that, irrigation with 5 mL of DW was performed, thereby concluding the procedure for photosensitizer removal. In the groups with US, the root canals were completely filled with the tested solution until extravasation to the root canal entrance. Then, US was performed using an ultrasonic device (Nac Plus Ultrasonics, Adiel, Ribeirão Preto, SP, Brazil). The stainless-steel E1 irrisonic endodontic tip (Helse Ultrasonic, Santa Rosa de Viterbo, SP, Brazil) was inserted 1 mm short of the WL and activated for 1 min. Scale power 1 for endodontics (25% power) was used to promote US. Every effort was made to minimise contact of the tip with the root canal walls and promote the agitation of the tested final irrigant. After this, irrigation with 5 mL of DW was performed, thereby concluding the procedure for photosensitizer removal. All root canals were dried with aspiration cannula and absorbent paper points (Tanari, Manacapuru, AM, Brazil) in both evaluations. Root canal filling In the first evaluation (bond strength of the filling material), the 10 specimens of each one of five groups were filled by the lateral compaction technique using gutta-percha points (Dentsply-Maillefer) and Bio-C bioceramic sealer (Angelus, Londrina, PR, Brazil). The sealer was applied along the root canal walls using the insertion point of bioceramic sealer. The gutta-percha ProTaper master cone #F3 (Dentsply-Maillefer) was lightly coated with the bioceramic sealer and inserted to the WL. Then, XF gutta-percha accessory points (Dentsply-Maillefe) were introduced into the root canals with the aid of finger spreaders (Dentsply Maillefer, Ballaigues, Switzerland). The gutta-percha accessory points were used until the finger spreader did not penetrate more than 5 millimeters into the root canal. Then, the excess of filling material was removed by cutting with a #2 heated plugger (SS White Duflex, Rio de Janeiro, RJ, Brazil). The root canal entrance was sealed with temporary restorative material (Vidrion R - SS White, Rio de Janeiro, RJ, Brazil). In the second evaluation (bond strength of the restorative material), the 10 specimens of each one of five groups were filled with GFP (Angelus, Londrina, PR, Brazil) and Rely-X U200 self-adhesive cement (3M ESPE, St. Paul, MN, USA). The GFP no. 1 (Angelus) was cleaned with 35% phosphoric acid for 30 s, rinsed for 30 s and gently air-dried. The silane application (3M ESPE) was performed for 1 min, followed by Single-Bond adhesive application (3M ESPE) and light polymerization for 40 s with a halogen light source with a power of 600 mV/cm 2 (Optilux, Demetron Res. Corp, Danbury CT, USA). The Single-Bond adhesive (3M ESPE) was applied in root dentin walls using microbrushes, air-dried for 5 s, and light polymerized for 40 s. Subsequently, Rely-X U200 self-adhesive cement (3M ESPE) was mixed and injected into the root canal of the 10 samples of each group with a suitable Centryx syringe and Acudosse needle (DFL, Rio de Janeiro, RJ, Brazil). The GFP was then covered with the same cement and positioned within the root canal at a 10 mm level, and held under digital pressure for 20 s. After this period, excess cement was removed. The cement was then polymerized using a 600 mW/cm 2 halogen light source (Optilux) for 30 s on each face (buccal, palatal, mesial, distal and occlusal). All procedures and parameters from this section were based in the manufacturer’s instruction. Evaluation on bond strength After the filling procedures, all specimens were stored at 37°C and 95% humidity for 21 days. Subsequently, the roots were sectioned transversely from the root canal entrance into 1 mm thick discs in a metallographic cutter with a diamond disk, at a speed of 350 rpm under cooling. The first disc was discarded, and the next five root discs were selected from each sample, totaling 50 specimens per subgroup (n = 5×10 = 50). Each disc was subjected to the push-out test on a mechanical testing machine (Emic DL 2000, São José dos Pinhais, PR, Brazil) at a speed of 1 mm/min using a stainless steel cylindrical plunger of 0.8 mm dia- meter. The plunger tip was positioned so that it only contacted the filling material. The push-out force was applied in an apico-coronal direction until bond failure occurred, which was manifested by extrusion of the filling material and a sudden drop along the load deflection. The force required to displace the material from the root canal was recorded in Newtons (N) and calculated in megapascals (MPa). After the push-out test, each disc was immediately transported in an Eppendorf tube containing DW to the optical microscope site, in order to calculate the bond strength and evaluate the failure patterns. Each disc was removed from the Eppendorf tube with a tweezer, dried with absorbent paper and positioned in the center of optical microscopy (Zeiss, São Paulo, SP, Brazil), at 50× magnification. The bond strength calculation and the failure pattern evaluation were based on a previous study by Dias et al [ 13 ]. The bond strength (δ) in megapascals was calculated using the formula δ = F/A, in which F is the force (N) used by the test machine and A is the area. To calculate the area, the following equation was applied: A = 2πr × h, in which π is the constant value 3.14, r is the radius of the intra-radicular space, and h is the height (mm). The radius of the intra-radicular space of each disc was measured under optical microscopy, with the aid of a software which provided this mensuration. The height of each disc was measured by using a digital pachymeter. Furthermore, the failure patterns were observed in each disc under optical microscopy (Zeiss, São Paulo, SP, Brazil) at 50× magnification. The classification was established as follows: 1: adhesive, between the dentin and the filling/restorative material, absence of filling/restorative material on the dentin walls of the root canal; 2: cohesive, failure of the filling/restorative material, presence of filling/restorative material on the dentin walls of the root canal; and 3: mixed, both failures (1 and 2) could be observed. All procedures and parameters from this section were based in previous study of Dias et al. [ 12 ]. Statistical analysis The normal distribution of results was confirmed by the Kolmogorov–Smirnov test (p = 0.4015). Bond strength was evaluated using a one-way analysis of variance (ANOVA), followed by the Tukey post-hoc test, enabling a quantitative analysis of these data. The failure mode distribution among the groups was evaluated using the chi-squared test, enabling a descriptive analysis of these data. All tests were set at a 5% level of significance. Data were analyzed using Stat Plus AnalystSoft Inc. version 6.0 (Vancouver, BC, Canada). RESULTS The mean and standard deviation of bond strength of the filling and restorative material to the root canal dentin after tested protocols are presented in Tables 1 and 2 , respectively. In both evaluations, the bond strength was significantly higher in groups 4 (17% EDTA + US) and 5 (17% GA) when compared to all other groups (p 0.05). In addition, it was not revealed statistically significant differences in failure patterns among the groups (p > 0.05), with a higher predominance of cohesive failure in all groups of both evaluations. Table 1 Mean (standard deviation) of bond strength of filling material to root canal dentin (MPa) and percentage of pattern of failure (%) after tested final irrigation protocols. Group n Push Out Bond Strength Failure mode Adhesive Mixed Cohesive 1. DW + US a 30 4.62 (2.51) 10.00 33.33 56.67 2. EDTA b 30 16.10 (4.42) 10.00 23.33 66.67 3. GA b 30 20.61 (5.13) 13.34 33.32 53.34 4. EDTA + US c 30 29.95 (3.23) 16.67 33.33 50.00 5. GA + US c 30 33.35 (3.96) 26.67 19.99 53.34 * Different superscript lowercase letters indicate, in the column, statistically significant differences (p < 0.05). ** DW, distilled water; US, ultrasonic activation; EDTA, Ethylenediaminetetraacetic acid; GA, glycolic acid. A média (desvio padrão) da resistência de união do material obturador à dentina radicular e o percentual dos padrões de falha após os protocolos de irrigação final testados estão expressos na Tabela 1. De acordo com os resultados obtidos, pode-se observar que a resistência de união foi significativamente maior nos grupos 4 (ETDA + US) e 5 (GA + US) quando comparados aos demais grupos (p 0,05). Em relação ao percentual dos padrões de falha, não foi revelada diferença estatisticamente significante entre os grupos testados (p > 0,05), havendo predomínio de falha coesiva em todos os grupos, seguido pela falha mista e, por fim, falha adesiva. Table 2 Mean (standard deviation) of bond strength of restorative material to root canal dentin (MPa) and percentage of pattern of failure (%) of tested final irrigation protocols. Group n Push Out Bond Strength Failure mode Adhesive Mixed Cohesive 1. DW + US a 30 4.90 (1.83) 6.67 39.99 53.34 2. EDTA b 30 21.43 (3.99) 10.00 26.66 63.34 3. GA b 30 22.55 (4.41) 6.67 33.33 50.00 4. EDTA + US c 30 30.95 (3.74) 10.00 40.00 50.00 5. GA + US c 30 33.70 (3.02) 10.00 36.66 53.34 * Different superscript lowercase letters indicate, in the column, statistically significant differences (p < 0.05). ** DW, distilled water; US, ultrasonic activation; EDTA, Ethylenediaminetetraacetic acid; GA, glycolic acid. A média (desvio padrão) da resistência de união do material restaurador à dentina radicular e o percentual dos padrões de falha após os protocolos de irrigação final testados estão expressos na Tabela 2. De acordo com os resultados obtidos, pode-se observar que a resistência de união foi significativamente maior nos grupos 4 (ETDA + US) e 5 (GA + US) quando comparados aos demais grupos (p 0,05). Em relação ao percentual dos padrões de falha, não foi revelada diferença estatisticamente significante entre os grupos testados (p > 0,05), havendo predomínio de falha coesiva em todos os grupos, seguido pela falha mista e, por fim, falha adesiva. DISCUSSION The association of PDT and US represents an auxiliary resource to provide microbial reduction from the root canal system [ 3 ]. Although this benefit, there is a possibility that US may contribute to an even greater impregnation of the photosensitizer on the root dentin, which can reduce the BS of filling and restorative materials to root denin. It is possible because the photosensitizer adheres strongly to the root canal walls and acts as a chemical smear layer [ 4 ]. Moreover, the association of US provide agitation of the photosensitizer, propelling this substance to the root canal walls and the depth of the dentinal tubules, which can further increase this impregnation. Considering that the conventional PDT protocol forms a chemical smear layer that compromises the adhesion of filling and restorative material [ 5 , 6 ], the present study was carried out to evaluate whether the US of the photosensitizer reduces the BS of the tested materials, even after the use of the tested final irrigation protocols. The literature reveals that the association of 17% EDTA with US for 1 minute results in effective removal of the photosensitizer from the root canal walls, as this irrigation protocol increases the bond strength of the filling/restorative materials to the root dentin [ 5 , 6 ]. For these reasons, this irrigation protocol and contact time were used as a parameter in the present study. Furthermore, the present study proposes the use of 17% GA as a final irrigant, making a comparison with the 17% EDTA solution. According to Cecchin et al. [ 13 ], GA was tested as a surface pretreatment agent for dental restorative applications, presenting effective results in the enamel etching and dentin surfaces. At the same time, GA revealed effectiveness for smear layer removal [ 8 ]. Thus, GA was chosen to be tested in the present study, with and without US, evaluating its ability to promote the removal of the chemical smear layer formed by the US of the photosensitizer, and consequently increase the bond strength of the tested materials to root dentin. The intracanal decontamination protocols performed prior to root canal filling or adhesive cementation of intraradicular posts must provide ideal conditions for BS to root dentin. It ensures effective adhesion to the root canal walls, minimizing marginal infiltration and the risk of root fracture, contributing to the longevity of endodontic ally treated teeth [ 14 ]. Considering that BS corresponds to the force required to displace the filling or restorative material adhered to the root dentin, the push-out test has been recommended over time to evaluate this mechanical property. It consists of applying a force to the filling/restorative material through a cross-section of the root until this material is displaced. The displacement force is uniform and simulates clinical reality, it can be performed in different thirds of the root canal, it has high reproducibility, and provides a larger tested adhesion area when compared to other tests, such as microtensile and shear tests [ 12 , 15 ]. For these reasons, the push-out test was used in the present study to evaluate the bond strength of the tested materials. The Bio-C bioceramic sealer is bioactive and releases calcium ions, providing sealing ability through stable chemical bonding, tag-like penetration into the depth of dentinal tubules, and biomineralization stimulation [ 9 , 10 ]. In your turn, the Rely-X U200 self-adhesive resin cement provides recognized micromechanical and chemical retention to root dentin [ 17 ]. Considering that the US of photosensitizer may impregnate root dentin and interfere with the adhesion of filling and restorative materials, the choice of endodontic sealer and adhesive cement for GFP plays a key role at this stage of endodontic treatment. Due to previously described properties, the Bio-C bioceramic sealer with gutta-percha and Rely-X U200 with GFP were tested in the present study after the root dentin was subjected to PDT associated with US, as well as after the tested final irrigation protocols for photosensitizer removal. According to results of present study, the bond strength was significantly higher in groups 2 (17% EDTA) and 3 (17% GA) when compared to control group. This is in agreement with the results of previous studies, where the use of final irrigants with ability for removal of smear layer after PDT protocol induced an increase in the bond strength of filling/restorative materials to root dentin [ 5 , 6 ]. At the same time, the literature reveals that irrigation with inert solution is not enough for photosensitizer removal, remaining a chemical smear layer in the root canal walls [ 4 ]. It highlights the importance of introduction of final irrigation techniques in the step-by-step of PDT protocol. Nowadays, it is not recommended. The EDTA acts by demineralization of superficial dentin and decalcifing the root dentin [ 7 ]. The GA acts by acidic demineralization and indirect organic dissolution [ 8 ]. Therefore, both alternatives present ability for effective photosensitizer removal from root canals, helping to improve the BS to root dentin. The association of US with 17% EDTA and 17% GA resulted in the highest BS values for filling and restorative materials to root dentin, with basis in the results of present study. It confirms the first and second hypothesis of present study. The US acts through the principle of hydrodynamic turbulence, increasing the temperature and hydrostatic pressure of the irrigant agent inserted into the root canal. Then, bubbles and cavitations are generated, and the irrigant agent is propelled more effectively against the root canal walls. It increases its cleaning potential and penetration into the depth of the dentinal tubules [ 18 ]. Similar results were observed in previous studies, also revealing that US promotes higher photosensitizer removal when compared with the isolated use of final irrigants with chelating properties, such as EDTA and QMix [ 5 , 6 ]. According to van der Sluis et al. [ 2 ], the US represents a more effective supplement for cleaning the root canal system and root canal walls, when compared with traditional syringe irrigation. Therefore, the association of US with final irrigants must be considered an essential step into the PDT protocol, considering the findings of the literature and the results of present study. The cohesive failure occurs within the filling or restorative material itself and not at the sealer-dentin or cement-dentin interface. After the push-out test in both evaluations, it was possible to observe a higher predominance of cohesive failure in all groups of present study. The Bio-C bioceramic sealer releases calcium and hydroxyl ions, which react with dentin phosphate and form hydroxyapatite at the sealer-dentin interface, creating micromechanical retention. This bioceramic sealer also exhibits volumetric expansion that fills microspaces and increases marginal adaptation [ 1 , 10 , 16 , 19 ]. In your turn, Rely-X U200 self-adhesive resin cement releases acidic monomers that demineralize and infiltrate the dentin substrate, providing micromechanical retention. At the same time, the reaction between the phosphoric acid monomers of the cement and hydroxyapatite of the dentin substrate provides chemical retention [ 17 , 20 ]. All these mechanisms help to explain the high adhesion provided by the tested bioceramic endodontic sealer and self-adhesive resin cement, as well as the found results of failure pattern in the present study. Despite the fact that there is no statistically significant difference between ETDA and GA in the removal of the US-activated photosensitizer, as well as the fact that there is similarity in the potential for removing the smear layer formed by the instrumentation between the two final irrigants, GA presents some advantages in relation to EDTA. The GA presents low cytotoxicity and does not induce severe damages to the mechanical properties of the dentin, even when activated by US, contrary to what is observed when EDTA is used, bringing deleterious effects in this sense [ 8 , 21 ]. This study suggests the use of GA and US as part of the PDT protocol, ensuring effective photosensitizer removal from the root canal walls. Therefore, US of the photosensitizer can be performed to enhance the antimicrobial action of PDT without compromising the adhesion of the filling/restorative material to the root dentin. CONCLUSIONS Despite the limitations of the present study, it can be concluded that the association of US with 17% EDTA and 17% GA for US-activated photosensitizer removal improved the BS of gutta-percha/bioceramic sealer and fiber glass posts/self-adhesive cement to root dentin. Declarations Compliance with Ethical Standards Conflict of Interest : All authors claim no conflicts of interest, no financial affiliation (e.g., employment, direct payment, stock holdings, retainers, consultantships, patent licensing arrangements, or honoraria) or involvement with any commercial organization with a direct financial interest in the subject or materials discussed in this manuscript, nor have any such arrangements existed in the past three years. Any other potential conflict of interest is disclosed. Ethical Approval : All applicable international, national, and/or institutional guidelines were followed. Informed consent : Not applicable. Funding: The work did not receive financial support. Author Contribution V.H.S.M., A.V.C.L., A.T., B.A.B., M.E.K., M.D., and K.E.B.M. performed all the methodology and experimental tests.J.P.D.C. and Y.D.B. prepared the statistical analysis and tables.M.A.S. and A.V.C.L. wrote the main manuscript text.M.A.S. supervised all experimental tests.All authors reviewed the manuscript. References Manoil D, Parga A, Hellesen C, Khawaji A, Brundin M, Durual S, Özenci V, Fang H, Belibasakis GN (2022) Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy. J Photochem Photobiol B 234:112547 van der Sluis LW, Versluis M, Wu MK, Wesselink PR (2007) Passive ultrasonic irrigation of the root canal: a review of the literature. Int Endod J 40:415–426 Ghinzelli GC, Souza MA, Cecchin D, Farina AP, de Figueiredo JAP (2014) Influence of ultrasonic activation on photodynamic therapy over root canal system infected with Enterococcus faecalis–an in vitro study. 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Photodiagnosis Photodyn Ther 26:224–228 Deari S, Mohn D, Zehnder M (2019) Dentine decalcification and smear layer removal by different ethylenediaminetetraacetic acid and 1-hydroxyethane-1,1-diphosphonic acid species. Int Endod J 52:237–243 Bello YD, Porsch HF, Farina AP, Souza MA, Silva EJNL, Bedran-Russo AK, Cecchin D (2019) Glycolic acid as the final irrigant in endodontics: Mechanical and cytotoxic effects. Mater Sci Eng C Mater Biol Appl 100:323–329 Souza MA, Bischoff KF, Ricci R, Bischoff LF, Reuter E, Gomes NDS, Hofstetter MG, Dos Santos EW, Weissheimer T, Só MVR, da Rosa RA, de Figueiredo JAP, Palhano HS, Bello YD (2024) Glycolic acid and ultrasonic activation: Effects on smear layer removal, dentin penetration, dentin structure and bond strength of the root dentin filling material. J Clin Exp Dent 16:e1269–e1277 Vivan RR, Guerreiro-Tanomaru JM, Bosso-Martelo R, Costa BC, Duarte MA, Tanomaru-Filho M (2016) Push-out bond strength of root-end filling materials. Braz Dent J 27:332–335 Soares CJ, Pereira JC, Valdivia AD, Novais VR, Meneses MS (2012) Influence of resin cement and post configuration on bond strength to root dentine. Int Endod J 45:136–145 Dias KC, Soares CJ, Steier L, Versiani MA, Rached-Júnior FJ, Pécora JD, Silva-Sousa YT, de Sousa-Neto MD (2014) Influence of drying protocol with isopropyl alcohol on the bond strength of resin-based sealers to the root dentin. J Endod 40:1454–1458 Cecchin D, Farina AP, Vidal CMP, Bedran-Russo AK (2018) A novel enamel and dentin etching protocol using α-hydroxy gly- colic acid: surface property, etching pattern, and bond strength studies. Oper Dent 43:101–110 Chandra N, Ghonem H (2001) Interfacial mechanics of push-out tests: theory and experiments, Comp. Part A. Appl Sci Manuf 32:575–584 Goracci C, Tavares AU, Fabianelli A, Monticelli F, Raffaelli O, Cardoso PC, Tay F, Ferrari M (2004) The adhesion between fiber posts and root canal walls: comparison between microtensile and push-out bond strength measurements. Eur J Oral Sci 112:353–361 Inada RN, Queiroz MB, Lopes CS, Silva EC, Torres FF, Silva GF et al (2023) Biocompatibility, bioactive potential, porosity, and interface analysis calcium silicate repair cements in a dentin tube model. Clin Oral Investig 27:3839–3853 Pisani-Proenca J, Erhardt MC, Amaral R, Valandro LF, Bottino MA, Salmeron RDC (2011) Influence of different surface conditioning protocols on microtensile bond strength of self-adhesive resin cements to dentin. J Prosthet Dent 105:227–235 Castagna F, Rizzon P, Rosa RA, Santini MF, Barreto MS, Duarte MA, Só MVR (2013) Effect of passive ultrasonic instrumentation as a final irrigation protocol on debris and smear layer removal–a SEM analysis. Microsc Res Tech 76:496–502 Creazzo G, de Barros Ciribelli Alves BM, de Assis HC, Villamayor KGG, de Sousa-Neto MD, Mazzi-Chaves JF, Lopes-Olhê FC (2025) Bond Strength and adhesive interface quality of new pre-mixed bioceramic root canal sealer. Microsc Res Tech 88:1989–2000 Pinto C, França F, Basting RT, Turssi CP, Amaral F (2024) Evaluation of bond strength of three glass fiber post-systems cemented to large root canals. Oper Dent 49:222–230 Souza MA, Ricci R, Bischoff KF, Reuter E, Ferreira ER, Dallepiane FG, Quevedo LM, Pereira LHB, Bischoff LF, Hofstetter MG, Brammer MP, Bernardes NM, Bervian J (2023) Effectiveness of ultrasonic activation over glycolic acid on microhardness, cohesive strength, flexural strength, and fracture resistance of the root dentin. Clin Oral Investig 27:1659–1664 Additional Declarations No competing interests reported. Supplementary Files 2Table1OK.docx 3Table2OK.docx Cite Share Download PDF Status: Published Journal Publication published 02 Mar, 2026 Read the published version in Lasers in Medical Science → Version 1 posted Editorial decision: Revision requested 05 Jan, 2026 Reviews received at journal 18 Dec, 2025 Reviews received at journal 10 Dec, 2025 Reviewers agreed at journal 09 Dec, 2025 Reviewers agreed at journal 09 Dec, 2025 Reviewers agreed at journal 08 Dec, 2025 Reviewers invited by journal 08 Dec, 2025 Editor assigned by journal 05 Dec, 2025 Submission checks completed at journal 27 Oct, 2025 First submitted to journal 23 Oct, 2025 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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cement","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eThe photodynamic therapy (PDT) represents an auxiliary decontamination resource in the endodontic field, involving the ability of a photosensitizer to absorb light-energy and to react with oxygen, generating reactive oxygen species. It adheres and penetrates the bacterial cell wall, precipitating the cytoplasmic content and inducing damage to the DNA of the bacterial cell [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. On the other hand, ultrasonic activation (US) has also contributed to greater decontamination in the endodontic treatment, due to the increase in temperature and hydrostatic pressure of the irrigant agents which are used into the root canals [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Considering the microbial etiology of pulp and periapical pathologies, the use of these resources has been recommended to assist conventional chemical-mechanical preparation in the decontamination of root canals [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAccording to Ghinzelli et al. [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], the use of US over the photosensitizer of PDT resulted in higher elimination of bacteria from the root canal space. However, it may compromise the preservation of the cleanliness of the root dentin surface, taking into account the subsequent filling and restoration of the endodontically treated tooth. The photosensitizers presents hydrophilic nature, low molecular weight, and high viscosity. It creates a chemical smear layer that strongly adheres to the canal walls and dentinal tubules [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], reducing the bond strength of filling and restorative materials [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In addition, the US can induce greater impulse and impregnation of the photosensitizer to the canal walls, further compromising adhesion. Therefore, the use of final irrigation protocols should be considered when photodynamic therapy is performed.\u003c/p\u003e\u003cp\u003eThe ethylenediaminetetraacetic acid (EDTA) and glycolic acid (GA) are final irrigants with ability to remove the smear layer [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The US of these final irrigants contributes for higher smear layer removal [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Thus, the association of EDTA and GA with US could represent an alternative for photosensitizer removal after PDT, in order to provide satisfactory adhesion of filling/restorative materials. Recent research has demonstrated scientific evidences for the use of bioceramic sealers as filling materials. Among other properties, it demonstrates adequate bond strength to dentin [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. At the same time, the use of self-adhesive resin cement has been recommended to promote better bond strength of glass fiber posts (GFP) to the root dentin, when the coronal portion presents extensive loss [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. However, there are no studies in the literature revealing the effectiveness of final irrigation protocols for photosensitizer removal, when the photosensitizer was activated by US. Moreover, the influence of theses protocols in the bond strength of bioceramic sealers and self-adhesive resin cements is not well elucidated.\u003c/p\u003e\u003cp\u003eThe aim of present study is to evaluate the influence of of different final irrigation protocols for removal of photosensitizer activaded by ultrasonic device on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement to root dentin. The hypotheses of the present study were that US of the tested final irrigants provides effective removal of photosensitizer, (i) improving the bond strength of filling and (ii) restorative materials to root dentin.\u003c/p\u003e"},{"header":"MATERIAL AND METHODS","content":"\u003cp\u003eThis study was appreciated and approved by the local Ethics Commission.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eSample collection and preparation\u003c/h2\u003e\u003cp\u003eOne hundred single-rooted extracted human teeth were used in the present study. All teeth were obtained from the Biobank of the School of Dentistry of the University of Passo Fundo (Passo Fundo, RS, Brazil). Dental crowns were sectioned with a rotary diamond disc (#911H, Brasseler, Savannah, GA, United States) so that all roots retained a length of 15 mm. The root length of 15 mm was measured with a ruler, a mark was made on each root in the measurement of 15 mm and the cut was performed at this length, standardizing the length of all roots.\u003c/p\u003e\u003cp\u003eAfter this, 50 roots were prepared by single operator, using the same protocol for pulp tissue removal and standardization of the root canal diameter. The working length (WL) was established by introducing a K-file #10 (Dentsply-Maillefer, Ballaigues, Switzerland) into the canal until its tip was visualized at the apical foramen. From this measurement, 1 mm was subtracted to obtain the WL. Each tooth was fixed in a portable lathe machine, in order to maintain the tooth secured during the root canal preparation. The roots were enlarged to WL using the ProTaper system (Dentsply- Maillefer), following the sequence S1 to F3. Distilled water (DW) (Natupharma, Passo Fundo, RS, Brazil) was used as irrigant solution and renewed at each instrument change. The ProTaper files (Dentsply-Maillefer) were used in a 16:1 gear reduction handpiece powered by a torque-controlled electric motor (X-Smart Plus - Dentsply-Maillefer, Ballaigues, Switzerland) at a constant rotation speed of 300 rpm in a crown-down manner according to the manufacturer\u0026rsquo;s instructions, by using a gentle in-and-out digital motion.\u003c/p\u003e\u003cp\u003eThe remaining 50 roots were flared at their coronal and middle thirds using Gates Glidden drills no. 2, 3 and 4 to a depth of 10 mm, after chemo-mechanical preparation, in order to provide adequate space for cementation of GFP. The Gates Glidden drills were used in a low speed handpiece powered by micro electric motor at a constant rotation speed of 10.000 rpm in a crown-down manner, by using a gentle in-and-out digital motion.\u003c/p\u003e\u003cp\u003eAll root canals were then filled with 17% EDTA (Biodin\u0026acirc;mica, Ibipor\u0026atilde;, PR, Brazil), and all roots were put into 10 mL plastic vials containing 17% EDTA, such that there were ten samples per vial, so that the roots remained completely covered by the solution. Each plastic vial was inserted into an ultrasonic cleaning machine (Bio Free, Gnatus, Ribeir\u0026atilde;o Preto, SP, Brazil) for one minute in order to remove the smear layer formed by root canal preparation. After that, the root canals were irrigated with 5mL of DW and dried with absorbent paper points (Tanari, Manacapuru, AM, Brazil).\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003ePDT protocol with US\u003c/h3\u003e\n\u003cp\u003eThe 100 specimens were embedded in epoxy resin (Silaex, S\u0026atilde;o Paulo, SP, Brazil), to facilitate PDT protocol. The root canals were filled with 0.01% (0.1 mg/mL) methylene blue (Chimio Lux DMC, S\u0026atilde;o Carlos, SP, Brazil) until extravasation to the root canal entrance. The photosensitizer was retained in the root canal for 5 min, as pre-irradiation time. Then, US was performed using an ultrasonic device (Nac Plus Ultrasonics, Adiel, Ribeir\u0026atilde;o Preto, SP, Brazil). The stainless-steel E1 irrisonic endodontic tip (Helse Ultrasonic, Santa Rosa de Viterbo, SP, Brazil) was inserted 1 mm short of the WL and activated for 1 min. Scale power 1 for endodontics (25% power) was used to promote US. After that, a low intensity laser (Therapy XT\u0026reg; DMC, S\u0026atilde;o Carlos, SP, Brazil) was used at 100mW power and continuous emission in the red part of the spectrum (660\u0026ndash;690 nm wavelength), with an intra-canal optical fiber of 600 \u0026micro;m diameter, attached at 2 mm short of the working length. The root canals were irradiated for 90 s, with 9 J of total dose delivery and 320 J/cm2 of energy density, remaining the intra-canal fiber in static position, as recommended by the manufacturer. Then, all roots were irrigated with 5 mL of DW, followed by the aspiration of root canals.\u003c/p\u003e\n\u003ch3\u003eClassification of treatment protocols\u003c/h3\u003e\n\u003cp\u003eAccording to experimental tests, 50 specimens were used for evaluation of bond strength of filling material and the remaining 50 specimens were used for evaluation of bond strength of restorative material. In both evaluations, the 50 specimens were randomly divided into five groups (n\u0026thinsp;=\u0026thinsp;10), according to the final irrigation protocol for photosensitizer removal: G1 \u0026ndash; DW\u0026thinsp;+\u0026thinsp;US; G2\u0026ndash;17% EDTA; G3\u0026ndash;17% GA; G4\u0026ndash;17% EDTA\u0026thinsp;+\u0026thinsp;US; G5\u0026ndash;17% GA\u0026thinsp;+\u0026thinsp;US. The DW, 17% EDTA and 17% were obtained by compounding pharmacy (Natupharma, Passo Fundo, RS, Brazil).\u003c/p\u003e\u003cp\u003eIn the groups without US, the root canals were completely filled with the tested solution until extravasation to the root canal entrance. Then, the tested solution remained in contact with root canal walls for a period of 1 min. After that, irrigation with 5 mL of DW was performed, thereby concluding the procedure for photosensitizer removal. In the groups with US, the root canals were completely filled with the tested solution until extravasation to the root canal entrance. Then, US was performed using an ultrasonic device (Nac Plus Ultrasonics, Adiel, Ribeir\u0026atilde;o Preto, SP, Brazil). The stainless-steel E1 irrisonic endodontic tip (Helse Ultrasonic, Santa Rosa de Viterbo, SP, Brazil) was inserted 1 mm short of the WL and activated for 1 min. Scale power 1 for endodontics (25% power) was used to promote US. Every effort was made to minimise contact of the tip with the root canal walls and promote the agitation of the tested final irrigant. After this, irrigation with 5 mL of DW was performed, thereby concluding the procedure for photosensitizer removal.\u003c/p\u003e\u003cp\u003eAll root canals were dried with aspiration cannula and absorbent paper points (Tanari, Manacapuru, AM, Brazil) in both evaluations.\u003c/p\u003e\n\u003ch3\u003eRoot canal filling\u003c/h3\u003e\n\u003cp\u003eIn the first evaluation (bond strength of the filling material), the 10 specimens of each one of five groups were filled by the lateral compaction technique using gutta-percha points (Dentsply-Maillefer) and Bio-C bioceramic sealer (Angelus, Londrina, PR, Brazil). The sealer was applied along the root canal walls using the insertion point of bioceramic sealer. The gutta-percha ProTaper master cone #F3 (Dentsply-Maillefer) was lightly coated with the bioceramic sealer and inserted to the WL. Then, XF gutta-percha accessory points (Dentsply-Maillefe) were introduced into the root canals with the aid of finger spreaders (Dentsply Maillefer, Ballaigues, Switzerland). The gutta-percha accessory points were used until the finger spreader did not penetrate more than 5 millimeters into the root canal. Then, the excess of filling material was removed by cutting with a #2 heated plugger (SS White Duflex, Rio de Janeiro, RJ, Brazil). The root canal entrance was sealed with temporary restorative material (Vidrion R - SS White, Rio de Janeiro, RJ, Brazil).\u003c/p\u003e\u003cp\u003eIn the second evaluation (bond strength of the restorative material), the 10 specimens of each one of five groups were filled with GFP (Angelus, Londrina, PR, Brazil) and Rely-X U200 self-adhesive cement (3M ESPE, St. Paul, MN, USA). The GFP no. 1 (Angelus) was cleaned with 35% phosphoric acid for 30 s, rinsed for 30 s and gently air-dried. The silane application (3M ESPE) was performed for 1 min, followed by Single-Bond adhesive application (3M ESPE) and light polymerization for 40 s with a halogen light source with a power of 600 mV/cm\u003csup\u003e2\u003c/sup\u003e (Optilux, Demetron Res. Corp, Danbury CT, USA). The Single-Bond adhesive (3M ESPE) was applied in root dentin walls using microbrushes, air-dried for 5 s, and light polymerized for 40 s. Subsequently, Rely-X U200 self-adhesive cement (3M ESPE) was mixed and injected into the root canal of the 10 samples of each group with a suitable Centryx syringe and Acudosse needle (DFL, Rio de Janeiro, RJ, Brazil). The GFP was then covered with the same cement and positioned within the root canal at a 10 mm level, and held under digital pressure for 20 s. After this period, excess cement was removed. The cement was then polymerized using a 600 mW/cm\u003csup\u003e2\u003c/sup\u003e halogen light source (Optilux) for 30 s on each face (buccal, palatal, mesial, distal and occlusal).\u003c/p\u003e\u003cp\u003eAll procedures and parameters from this section were based in the manufacturer\u0026rsquo;s instruction.\u003c/p\u003e\n\u003ch3\u003eEvaluation on bond strength\u003c/h3\u003e\n\u003cp\u003eAfter the filling procedures, all specimens were stored at 37\u0026deg;C and 95% humidity for 21 days. Subsequently, the roots were sectioned transversely from the root canal entrance into 1 mm thick discs in a metallographic cutter with a diamond disk, at a speed of 350 rpm under cooling. The first disc was discarded, and the next five root discs were selected from each sample, totaling 50 specimens per subgroup (n\u0026thinsp;=\u0026thinsp;5\u0026times;10\u0026thinsp;=\u0026thinsp;50). Each disc was subjected to the push-out test on a mechanical testing machine (Emic DL 2000, S\u0026atilde;o Jos\u0026eacute; dos Pinhais, PR, Brazil) at a speed of 1 mm/min using a stainless steel cylindrical plunger of 0.8 mm dia- meter. The plunger tip was positioned so that it only contacted the filling material. The push-out force was applied in an apico-coronal direction until bond failure occurred, which was manifested by extrusion of the filling material and a sudden drop along the load deflection. The force required to displace the material from the root canal was recorded in Newtons (N) and calculated in megapascals (MPa).\u003c/p\u003e\u003cp\u003eAfter the push-out test, each disc was immediately transported in an Eppendorf tube containing DW to the optical microscope site, in order to calculate the bond strength and evaluate the failure patterns. Each disc was removed from the Eppendorf tube with a tweezer, dried with absorbent paper and positioned in the center of optical microscopy (Zeiss, S\u0026atilde;o Paulo, SP, Brazil), at 50\u0026times; magnification. The bond strength calculation and the failure pattern evaluation were based on a previous study by Dias et al [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The bond strength (δ) in megapascals was calculated using the formula δ\u0026thinsp;=\u0026thinsp;F/A, in which F is the force (N) used by the test machine and A is the area. To calculate the area, the following equation was applied: A\u0026thinsp;=\u0026thinsp;2πr \u0026times; h, in which π is the constant value 3.14, r is the radius of the intra-radicular space, and h is the height (mm). The radius of the intra-radicular space of each disc was measured under optical microscopy, with the aid of a software which provided this mensuration. The height of each disc was measured by using a digital pachymeter. Furthermore, the failure patterns were observed in each disc under optical microscopy (Zeiss, S\u0026atilde;o Paulo, SP, Brazil) at 50\u0026times; magnification. The classification was established as follows: 1: adhesive, between the dentin and the filling/restorative material, absence of filling/restorative material on the dentin walls of the root canal; 2: cohesive, failure of the filling/restorative material, presence of filling/restorative material on the dentin walls of the root canal; and 3: mixed, both failures (1 and 2) could be observed. All procedures and parameters from this section were based in previous study of Dias et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eThe normal distribution of results was confirmed by the Kolmogorov\u0026ndash;Smirnov test (p\u0026thinsp;=\u0026thinsp;0.4015). Bond strength was evaluated using a one-way analysis of variance (ANOVA), followed by the Tukey post-hoc test, enabling a quantitative analysis of these data. The failure mode distribution among the groups was evaluated using the chi-squared test, enabling a descriptive analysis of these data. All tests were set at a 5% level of significance. Data were analyzed using Stat Plus AnalystSoft Inc. version 6.0 (Vancouver, BC, Canada).\u003c/p\u003e\u003c/div\u003e"},{"header":"RESULTS","content":"\u003cp\u003eThe mean and standard deviation of bond strength of the filling and restorative material to the root canal dentin after tested protocols are presented in Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, respectively. In both evaluations, the bond strength was significantly higher in groups 4 (17% EDTA\u0026thinsp;+\u0026thinsp;US) and 5 (17% GA) when compared to all other groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), whereas there was no statistically significant difference between them (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). In addition, it was not revealed statistically significant differences in failure patterns among the groups (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), with a higher predominance of cohesive failure in all groups of both evaluations.\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\u003eMean (standard deviation) of bond strength of filling material to root canal dentin (MPa) and percentage of pattern of failure (%) after tested final irrigation protocols.\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ePush Out Bond Strength\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e\u003cp\u003eFailure mode\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAdhesive\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMixed\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohesive\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1. DW\u0026thinsp;+\u0026thinsp;US \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.62 (2.51)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e56.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2. EDTA \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e16.10 (4.42)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e23.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e66.67\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3. GA \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20.61 (5.13)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e13.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e53.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4. EDTA\u0026thinsp;+\u0026thinsp;US \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e29.95 (3.23)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e16.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e50.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5. GA\u0026thinsp;+\u0026thinsp;US \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33.35 (3.96)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e26.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e19.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e53.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e* Different superscript lowercase letters indicate, in the column, statistically significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e** DW, distilled water; US, ultrasonic activation; EDTA, Ethylenediaminetetraacetic acid; GA, glycolic acid.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003eA m\u0026eacute;dia (desvio padr\u0026atilde;o) da resist\u0026ecirc;ncia de uni\u0026atilde;o do material obturador \u0026agrave; dentina radicular e o percentual dos padr\u0026otilde;es de falha ap\u0026oacute;s os protocolos de irriga\u0026ccedil;\u0026atilde;o final testados est\u0026atilde;o expressos na Tabela 1. De acordo com os resultados obtidos, pode-se observar que a resist\u0026ecirc;ncia de uni\u0026atilde;o foi significativamente maior nos grupos 4 (ETDA\u0026thinsp;+\u0026thinsp;US) e 5 (GA\u0026thinsp;+\u0026thinsp;US) quando comparados aos demais grupos (p\u0026thinsp;\u0026lt;\u0026thinsp;0,05), sem diferen\u0026ccedil;a estatisticamente significante entre si (p\u0026thinsp;\u0026gt;\u0026thinsp;0,05). Em rela\u0026ccedil;\u0026atilde;o ao percentual dos padr\u0026otilde;es de falha, n\u0026atilde;o foi revelada diferen\u0026ccedil;a estatisticamente significante entre os grupos testados (p\u0026thinsp;\u0026gt;\u0026thinsp;0,05), havendo predom\u0026iacute;nio de falha coesiva em todos os grupos, seguido pela falha mista e, por fim, falha adesiva.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\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\u003eMean (standard deviation) of bond strength of restorative material to root canal dentin (MPa) and percentage of pattern of failure (%) of tested final irrigation protocols.\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=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003en\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ePush Out Bond Strength\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"3\" nameend=\"c6\" namest=\"c4\"\u003e\u003cp\u003eFailure mode\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eAdhesive\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMixed\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eCohesive\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1. DW\u0026thinsp;+\u0026thinsp;US \u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.90 (1.83)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e39.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e53.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2. EDTA \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e21.43 (3.99)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e26.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e63.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3. GA \u003csup\u003eb\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e22.55 (4.41)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e33.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e50.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e4. EDTA\u0026thinsp;+\u0026thinsp;US \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e30.95 (3.74)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e40.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e50.00\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e5. GA\u0026thinsp;+\u0026thinsp;US \u003csup\u003ec\u003c/sup\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e33.70 (3.02)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e10.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e36.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e53.34\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colspan=\"6\" nameend=\"c6\" namest=\"c1\"\u003e\u003cp\u003e* Different superscript lowercase letters indicate, in the column, statistically significant differences (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003cp\u003e** DW, distilled water; US, ultrasonic activation; EDTA, Ethylenediaminetetraacetic acid; GA, glycolic acid.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"6\"\u003eA m\u0026eacute;dia (desvio padr\u0026atilde;o) da resist\u0026ecirc;ncia de uni\u0026atilde;o do material restaurador \u0026agrave; dentina radicular e o percentual dos padr\u0026otilde;es de falha ap\u0026oacute;s os protocolos de irriga\u0026ccedil;\u0026atilde;o final testados est\u0026atilde;o expressos na Tabela 2. De acordo com os resultados obtidos, pode-se observar que a resist\u0026ecirc;ncia de uni\u0026atilde;o foi significativamente maior nos grupos 4 (ETDA\u0026thinsp;+\u0026thinsp;US) e 5 (GA\u0026thinsp;+\u0026thinsp;US) quando comparados aos demais grupos (p\u0026thinsp;\u0026lt;\u0026thinsp;0,05), sem diferen\u0026ccedil;a estatisticamente significante entre si (p\u0026thinsp;\u0026gt;\u0026thinsp;0,05). Em rela\u0026ccedil;\u0026atilde;o ao percentual dos padr\u0026otilde;es de falha, n\u0026atilde;o foi revelada diferen\u0026ccedil;a estatisticamente significante entre os grupos testados (p\u0026thinsp;\u0026gt;\u0026thinsp;0,05), havendo predom\u0026iacute;nio de falha coesiva em todos os grupos, seguido pela falha mista e, por fim, falha adesiva.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThe association of PDT and US represents an auxiliary resource to provide microbial reduction from the root canal system [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Although this benefit, there is a possibility that US may contribute to an even greater impregnation of the photosensitizer on the root dentin, which can reduce the BS of filling and restorative materials to root denin. It is possible because the photosensitizer adheres strongly to the root canal walls and acts as a chemical smear layer [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Moreover, the association of US provide agitation of the photosensitizer, propelling this substance to the root canal walls and the depth of the dentinal tubules, which can further increase this impregnation. Considering that the conventional PDT protocol forms a chemical smear layer that compromises the adhesion of filling and restorative material [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], the present study was carried out to evaluate whether the US of the photosensitizer reduces the BS of the tested materials, even after the use of the tested final irrigation protocols.\u003c/p\u003e\u003cp\u003eThe literature reveals that the association of 17% EDTA with US for 1 minute results in effective removal of the photosensitizer from the root canal walls, as this irrigation protocol increases the bond strength of the filling/restorative materials to the root dentin [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. For these reasons, this irrigation protocol and contact time were used as a parameter in the present study. Furthermore, the present study proposes the use of 17% GA as a final irrigant, making a comparison with the 17% EDTA solution. According to Cecchin et al. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], GA was tested as a surface pretreatment agent for dental restorative applications, presenting effective results in the enamel etching and dentin surfaces. At the same time, GA revealed effectiveness for smear layer removal [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Thus, GA was chosen to be tested in the present study, with and without US, evaluating its ability to promote the removal of the chemical smear layer formed by the US of the photosensitizer, and consequently increase the bond strength of the tested materials to root dentin.\u003c/p\u003e\u003cp\u003eThe intracanal decontamination protocols performed prior to root canal filling or adhesive cementation of intraradicular posts must provide ideal conditions for BS to root dentin. It ensures effective adhesion to the root canal walls, minimizing marginal infiltration and the risk of root fracture, contributing to the longevity of endodontic ally treated teeth [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Considering that BS corresponds to the force required to displace the filling or restorative material adhered to the root dentin, the push-out test has been recommended over time to evaluate this mechanical property. It consists of applying a force to the filling/restorative material through a cross-section of the root until this material is displaced. The displacement force is uniform and simulates clinical reality, it can be performed in different thirds of the root canal, it has high reproducibility, and provides a larger tested adhesion area when compared to other tests, such as microtensile and shear tests [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. For these reasons, the push-out test was used in the present study to evaluate the bond strength of the tested materials.\u003c/p\u003e\u003cp\u003eThe Bio-C bioceramic sealer is bioactive and releases calcium ions, providing sealing ability through stable chemical bonding, tag-like penetration into the depth of dentinal tubules, and biomineralization stimulation [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In your turn, the Rely-X U200 self-adhesive resin cement provides recognized micromechanical and chemical retention to root dentin [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Considering that the US of photosensitizer may impregnate root dentin and interfere with the adhesion of filling and restorative materials, the choice of endodontic sealer and adhesive cement for GFP plays a key role at this stage of endodontic treatment. Due to previously described properties, the Bio-C bioceramic sealer with gutta-percha and Rely-X U200 with GFP were tested in the present study after the root dentin was subjected to PDT associated with US, as well as after the tested final irrigation protocols for photosensitizer removal.\u003c/p\u003e\u003cp\u003eAccording to results of present study, the bond strength was significantly higher in groups 2 (17% EDTA) and 3 (17% GA) when compared to control group. This is in agreement with the results of previous studies, where the use of final irrigants with ability for removal of smear layer after PDT protocol induced an increase in the bond strength of filling/restorative materials to root dentin [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. At the same time, the literature reveals that irrigation with inert solution is not enough for photosensitizer removal, remaining a chemical smear layer in the root canal walls [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. It highlights the importance of introduction of final irrigation techniques in the step-by-step of PDT protocol. Nowadays, it is not recommended. The EDTA acts by demineralization of superficial dentin and decalcifing the root dentin [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The GA acts by acidic demineralization and indirect organic dissolution [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Therefore, both alternatives present ability for effective photosensitizer removal from root canals, helping to improve the BS to root dentin.\u003c/p\u003e\u003cp\u003eThe association of US with 17% EDTA and 17% GA resulted in the highest BS values for filling and restorative materials to root dentin, with basis in the results of present study. It confirms the first and second hypothesis of present study. The US acts through the principle of hydrodynamic turbulence, increasing the temperature and hydrostatic pressure of the irrigant agent inserted into the root canal. Then, bubbles and cavitations are generated, and the irrigant agent is propelled more effectively against the root canal walls. It increases its cleaning potential and penetration into the depth of the dentinal tubules [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Similar results were observed in previous studies, also revealing that US promotes higher photosensitizer removal when compared with the isolated use of final irrigants with chelating properties, such as EDTA and QMix [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. According to van der Sluis et al. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], the US represents a more effective supplement for cleaning the root canal system and root canal walls, when compared with traditional syringe irrigation. Therefore, the association of US with final irrigants must be considered an essential step into the PDT protocol, considering the findings of the literature and the results of present study.\u003c/p\u003e\u003cp\u003eThe cohesive failure occurs within the filling or restorative material itself and not at the sealer-dentin or cement-dentin interface. After the push-out test in both evaluations, it was possible to observe a higher predominance of cohesive failure in all groups of present study. The Bio-C bioceramic sealer releases calcium and hydroxyl ions, which react with dentin phosphate and form hydroxyapatite at the sealer-dentin interface, creating micromechanical retention. This bioceramic sealer also exhibits volumetric expansion that fills microspaces and increases marginal adaptation [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. In your turn, Rely-X U200 self-adhesive resin cement releases acidic monomers that demineralize and infiltrate the dentin substrate, providing micromechanical retention. At the same time, the reaction between the phosphoric acid monomers of the cement and hydroxyapatite of the dentin substrate provides chemical retention [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. All these mechanisms help to explain the high adhesion provided by the tested bioceramic endodontic sealer and self-adhesive resin cement, as well as the found results of failure pattern in the present study.\u003c/p\u003e\u003cp\u003eDespite the fact that there is no statistically significant difference between ETDA and GA in the removal of the US-activated photosensitizer, as well as the fact that there is similarity in the potential for removing the smear layer formed by the instrumentation between the two final irrigants, GA presents some advantages in relation to EDTA. The GA presents low cytotoxicity and does not induce severe damages to the mechanical properties of the dentin, even when activated by US, contrary to what is observed when EDTA is used, bringing deleterious effects in this sense [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. This study suggests the use of GA and US as part of the PDT protocol, ensuring effective photosensitizer removal from the root canal walls. Therefore, US of the photosensitizer can be performed to enhance the antimicrobial action of PDT without compromising the adhesion of the filling/restorative material to the root dentin.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eDespite the limitations of the present study, it can be concluded that the association of US with 17% EDTA and 17% GA for US-activated photosensitizer removal improved the BS of gutta-percha/bioceramic sealer and fiber glass posts/self-adhesive cement to root dentin.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003ch2\u003eCompliance with Ethical Standards\u003c/h2\u003e\u003cp\u003e\u003cb\u003eConflict of Interest\u003c/b\u003e: All authors claim no conflicts of interest, no financial affiliation (e.g., employment, direct payment, stock holdings, retainers, consultantships, patent licensing arrangements, or honoraria) or involvement with any commercial organization with a direct financial interest in the subject or materials discussed in this manuscript, nor have any such arrangements existed in the past three years. Any other potential conflict of interest is disclosed.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e\u003cb\u003eEthical Approval\u003c/b\u003e:\u003c/strong\u003e\u003cp\u003eAll applicable international, national, and/or institutional guidelines were followed.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003e\u003cb\u003eInformed consent\u003c/b\u003e:\u003c/h2\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e\u003cp\u003eThe work did not receive financial support.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eV.H.S.M., A.V.C.L., A.T., B.A.B., M.E.K., M.D., and K.E.B.M. performed all the methodology and experimental tests.J.P.D.C. and Y.D.B. prepared the statistical analysis and tables.M.A.S. and A.V.C.L. wrote the main manuscript text.M.A.S. supervised all experimental tests.All authors reviewed the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eManoil D, Parga A, Hellesen C, Khawaji A, Brundin M, Durual S, \u0026Ouml;zenci V, Fang H, Belibasakis GN (2022) Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy. 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J Prosthet Dent 105:227\u0026ndash;235\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCastagna F, Rizzon P, Rosa RA, Santini MF, Barreto MS, Duarte MA, S\u0026oacute; MVR (2013) Effect of passive ultrasonic instrumentation as a final irrigation protocol on debris and smear layer removal\u0026ndash;a SEM analysis. Microsc Res Tech 76:496\u0026ndash;502\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCreazzo G, de Barros Ciribelli Alves BM, de Assis HC, Villamayor KGG, de Sousa-Neto MD, Mazzi-Chaves JF, Lopes-Olh\u0026ecirc; FC (2025) Bond Strength and adhesive interface quality of new pre-mixed bioceramic root canal sealer. Microsc Res Tech 88:1989\u0026ndash;2000\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePinto C, Fran\u0026ccedil;a F, Basting RT, Turssi CP, Amaral F (2024) Evaluation of bond strength of three glass fiber post-systems cemented to large root canals. Oper Dent 49:222\u0026ndash;230\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSouza MA, Ricci R, Bischoff KF, Reuter E, Ferreira ER, Dallepiane FG, Quevedo LM, Pereira LHB, Bischoff LF, Hofstetter MG, Brammer MP, Bernardes NM, Bervian J (2023) Effectiveness of ultrasonic activation over glycolic acid on microhardness, cohesive strength, flexural strength, and fracture resistance of the root dentin. Clin Oral Investig 27:1659\u0026ndash;1664\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"lasers-in-medical-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"lims","sideBox":"Learn more about [Lasers in Medical Science](https://link.springer.com/journal/10103)","snPcode":"10103","submissionUrl":"https://submission.springernature.com/new-submission/10103/3","title":"Lasers in Medical Science","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"bond strength, EDTA, glycolic acid, photodynamic therapy, ultrasonic activation","lastPublishedDoi":"10.21203/rs.3.rs-7934333/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7934333/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ethe role of endodontic treatment is to eliminate microorganisms without compromising adjacent tissues and adhesion. The aim of present study was to evaluate the influence of final irrigation protocols for removal of photosensitizer activaded by ultrasonic device(US) on the bond strength(BS) of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement to root dentin.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eone hundred single-rooted teeth were used. After coronal sectioning, 50 roots were used to assess the bond strength of filling material and 50 to assess the bond strength of restorative material. After sample preparation and photodynamic therapy protocol with US, the roots were randomly divided into five groups (n = 10), according to irrigation protocol for photosensitizer removal: G1(negative control)–distilled water + US;G2–17% EDTA;G3–17% GA;G4 − 17% EDTA + US;G5–17% GA + US. Then, the roots were filled with gutta-percha/Bio-C bioceramic sealer in the first evaluation, and fiber glass posts/Rely-X U200 self-adhesive cement in the second evaluation. In both, the roots were sectioned to obtain 1 mm thick dentin discs containing the filling/restorative material, and the push-out test was performed. Failure patterns were observed under optical microscope. Specific statistical analysis was performed in both evaluations(α 5%).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ein both evaluations, BS was significantly higher in groups 4(17% EDTA + US) and 5(17% GA + US) when compared to all other groups(p \u0026lt; 0.05). Regarding the failure patterns, no statistically significant difference was found between groups (p \u0026gt; 0.05), with a predominance of cohesive failure in all groups.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ethe association of US with EDTA and GA for photosensitizer removal improved the BS of filling/restorative material to root dentin.\u003c/p\u003e","manuscriptTitle":"Influence of different final irrigation protocols for removal of photosensitizer activaded by ultrasonic device on the bond strength of gutta-percha/bioceramic sealer and fiberglass posts/self-adhesive cement","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-11 13:54:07","doi":"10.21203/rs.3.rs-7934333/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-05T21:39:32+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-18T08:00:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-10T08:26:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"177731499425304942989730805406618785497","date":"2025-12-09T08:54:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"301095591868458702853171543228181175753","date":"2025-12-09T06:44:04+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"96163265076741079269020487498514859580","date":"2025-12-08T15:18:07+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-08T15:02:49+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-05T23:17:38+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-27T12:11:32+00:00","index":"","fulltext":""},{"type":"submitted","content":"Lasers in Medical Science","date":"2025-10-23T17:13:26+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"lasers-in-medical-science","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"lims","sideBox":"Learn more about [Lasers in Medical Science](https://link.springer.com/journal/10103)","snPcode":"10103","submissionUrl":"https://submission.springernature.com/new-submission/10103/3","title":"Lasers in Medical Science","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"b895a67f-fbb9-4f6c-9c6d-ac1c5848b062","owner":[],"postedDate":"December 11th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-03-09T16:15:39+00:00","versionOfRecord":{"articleIdentity":"rs-7934333","link":"https://doi.org/10.1007/s10103-026-04838-z","journal":{"identity":"lasers-in-medical-science","isVorOnly":false,"title":"Lasers in Medical Science"},"publishedOn":"2026-03-02 15:56:58","publishedOnDateReadable":"March 2nd, 2026"},"versionCreatedAt":"2025-12-11 13:54:07","video":"","vorDoi":"10.1007/s10103-026-04838-z","vorDoiUrl":"https://doi.org/10.1007/s10103-026-04838-z","workflowStages":[]},"version":"v1","identity":"rs-7934333","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7934333","identity":"rs-7934333","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}