Pilot study on calculus removal from orthodontic retainers using different mechanical approaches: an in-vitro investigation of the adhesive strength of fixed retainers

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Pfaff, Ralf Erber, Christoph J. Roser, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8895010/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Introduction Orthodontic fixed retainers are often a predilection site for calculus build-up. However, standardized protocol for professional mechanical plaque removal (PMPR) does not yet exist that takes into account the slight weakening of the adhesive bond. Material and Methods In this in-vitro study, three cleaning protocols were evaluated: Group A: ultrasonic stainless-steel tip (Piezon PS, EMS Dental); Group B: Polyetheretherketone (PEEK) ultrasonic tip (PI Max, EMS Dental); and Group C: sonic cleaning (SiroTip S1, Sirona Dental Systems). These protocols were assigned artificial lower canine-to-canine segments with individual Twistflex retainers bonded (n = 10/group). Following artificial ageing of the adhesive bond, artificial calculus was applied and removed according to the respective cleaning protocol. After repeating twice, adhesive bond strengths were analysed. Results The Kruskal-Wallis test showed that the choice of instrumentation significantly influences the integrity of the adhesive bond (p = 0.036). Post-hoc pairwise comparisons revealed that Group A had significantly higher shear bond strength compared to Group C (p = 0.028). Conclusions This in-vitro study shows that the type of the PMPR system used has a significant influence on the shear bond strength of fixed retainers. Ultrasound-driven stainless-steel scalers appear to be more gentle than sonic-driven devices. Clinical relevance In clinical practice, the accidental debonding of retainer attachments during PMBR is a frequent complication. The present in-vitro study investigates whether specific cleaning modalities can minimize the risk of compromising the adhesive bonding. Specifically, different cleaning modalities (ultrasonic versus sonic) and various tip materials are evaluated and compared. orthodontics retainer calculus ultrasonic sonic Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Following orthodontic treatment, fixed retainers are widely employed to stabilise the treatment results [ 1 ]. Their efficacy in maintaining post-treatment dental alignment is well-accepted [ 2 ]. Although fixed retainers are not considered primary etiological factors for periodontal disease [ 3 – 5 ], they may facilitate plaque and calculus accumulation [ 6 ] thereby increasing the risk of localized gingival inflammation in the absence of a rigorous oral hygiene [ 7 , 8 ]. From a biomechanical perspective, multi-stranded 'Twistflex' retainers currently provide the gold standard for orthodontic retention [ 9 ]. Although the surface area is increased by the stranding of several wires, Twistflex retainers do not exhibit significantly higher calculus accumulation [ 6 , 10 ] regardless of the wire material [ 6 ]. However, a precise fit of the retainer to the dental arch and the lingual tooth surfaces seems to have a positive effect on oral health [ 11 ]. While fixed retainers are essential for stabilizing orthodontic outcomes, they increase the risk of compromising the oral health by increased plaque and calculus accumulation [ 12 ]. Consequently, the results of the recent German Oral Health Study underscores the vital role of professional tooth cleaning PMBR in mitigating these risks in general [ 13 , 14 ]. Currently, approximately 80% of young adults in Germany utilize professional cleaning services [ 13 ]. Given the high prevalence of fixed retainers following orthodontic therapy [ 11 ] and the resulting growth of this patient population, identifying the most effective and safe mechanical debridement methods for PMBR is clinically highly relevant. Mechanical debridement of orthodontic appliances such as brackets appears to have an impact on their shear bond strengths [ 15 , 16 ]. It is therefore plausible that mechanical calculus removal has an influence on adhesive bonding. So far studies investigating the impact of calculus removal around fixed retainers are missing in the literature. Thus, the aim of this in-vitro study was to evaluate the impact of different calculus removal protocols on the adhesive bond strengths of fixed orthodontic retainers. The investigation focuses on two aspects: (I) the influence of the debridement modality, comparing ultrasonic and sonic instrumentation under comparable conditions, and (II) the influence of ultrasonic tip material, comparing stainless steel and carbon-reinforced PEEK tips with identical device settings. Accordingly, the primary outcome was to measure the shear bond strength required to induce debonding of fixed orthodontic retainers following repeated mechanical calculus removal. As a secondary outcome, instrument-related parameters, including tip wear and the incidence of tip fractures, were assessed for further insight into the practical and economic implications of the various systems. Material and methods This in-vitro study was in accordance with the CRIS guidelines for reporting in-vitro studies [ 17 ]. A total of 34 mandibular anterior segment models were constructed to simulate the lower anterior region. Each segment consisted of six CAD/CAM-manufactured artificial teeth (canine to canine), resulting in a total of 204 CAD/CAM-manufactured artificial front and canine teeth made of Trinia (Trinia, Bicon, Boston, USA) according to an established protocol [ 18 , 19 ]. Two canine teeth and the four incisors were inserted into n = 34 3D-printed moulds to simulate the lower front teeth area. The validity of this in-vitro model in simulating physiological tooth mobility has been shown previously [ 18 ]. Fabrication of Retainers The dental arches were scanned using the iTero Lumina (Align Technology, Santa Clara, California, USA) intraoral scanner. Using the Bender 2 (YOAT Corporation, Lynnwood, Washington, USA) bending robot, passively fitting retainers were manufactured individually for each dental arch from Ti5-Twistflex-wires [ 9 ]. The passive fit of each retainer on the respective dental arch was checked prior to adhesive fixation. The adhesive bonds were then artificially aged by thermo-cycling (10.000 thermal cycles between 6.5°C and 60°C (Z005, Zwick Roell, Ulm, Germany), for a duration of approximately 12 days) [ 18 , 20 ]. After the artificial ageing, each adhesive bond was tested with a dental probe by the same examiner each time. Three adhesive joints failed initially. These dental arches were excluded from the trial. One intact dental arch was kept as a spare, which was not needed in this trial. Artificial calculus application and experimental removal Artificial calculus was applied around the intact retainers according to manucfacturer’s instructions (Frasaco A-CK Calculus, frasaco GmbH, Tettnang, Germany) [ 21 , 22 ]. The calculus extended beyond the bonding site and into the approximal spaces. The remaining 30 dental arches were divided into three equal groups. Calculus was removed by a trained practitioner using three cleaning protocols (see Fig. 2 ): Group A: ultrasonic stainless-steel tip (Piezon-Tip, EMS Dental, Nyon, Switzerland) Group B: ultrasonic 30% carbon-reinforced PEEK tip (Pi Max Tip, EMS Dental, Nyon, Switzerland) Group C: sonic cleaning with stainless steel tip (SiroTip S1, Sirona Dental Systems, Bensheim, Germany). The tips of groups A and B were applied with AirFlow Prophylaxis Master One (EMS Dental, Nyon, Switzerland) using the manufacturer’s instructions (water: level 10, power: level 4). The difference between these two groups was therefore only the tip material used. Group C was applied to the treatment unit using the SiroAir L handpiece [ 23 ]. During mechanical calculus removal, water cooling was used for all groups. The various tips were used in accordance with the manufacturer's instructions. The cleaning was considered complete when no more calculus was visible. This check was always carried out by the same person using dental loupes. Subsequently, the adhesion of the bonding sites was checked manually and documented again. The calculus removal was performed twice under the conditions specified. Testing of shear bond strength The shear bond strength of all remaining retainers was tested afterwards using a universal testing machine (Z005, Zwick/Roell, Ulm, Germany) following the ISO/TS 11405:2015 standard (Fig. 3 ). To this end, the test specimen was lowered at a speed of 1 mm/min with a preload of 2 N. In accordance with Roser et al. (2023) [ 9 ], tooth 31 was subjected to an axial load using the universal testing machine until the failure of the adhesive bond was observed . In addition, the wear and tear on the tips and the number of tips used were documented. Peak consumption was measured using a calliper gauge. Outcomes The primary outcome was the shear bond strength required to induce debonding of fixed orthodontic retainers after repeated mechanical calculus removal. For analytical purposes, two predefined comparisons were addressed within this primary outcome: I. a method-related comparison between ultrasonic and sonic instrumentation using stainless steel tips (Group A vs. Group C) II. a material-related comparison between stainless steel and carbon-reinforced PEEK ultrasonic tips operated under identical device settings (Group A vs. Group B). Secondary outcomes included instrument-related parameters, particularly the number of tips used, the occurrence of tip fractures, and cumulative tip consumption (mm). Statistical methods Data analysis was performed using R version 4.5.2 [ 24 ]. The primary outcome—the shear bond strength required to induce debonding of fixed orthodontic retainers after repeated mechanical calculus removal—was summarized using the mean ± standard deviation, median (Q1–Q3), minimum, and maximum, and was graphically displayed using boxplots. Difference in shear bond strength required to induce debonding of fixed orthodontic retainers after repeated mechanical calculus removal between the three cleaning protocol used for calculus removal (Group A: ultrasonic stainless-steel tip (Piezon PS, EMS Dental); Group B: Polyetheretherketone (PEEK) -coated ultrasonic tip (PI Max, EMS Dental); and Group C: sonic cleaning (SiroTip S1, Sirona Dental Systems) was assessed using a Kruskal–Wallis test. Upon statistical significance of the Kruskal-Wallis test, non-parametric post-hoc Nemenyi tests are conducted to assess pairwise differences in required shear bond strength between the three cleaning protocol used for calculus removal. For each post-hoc pairwise comparison, the p-value from the Nemenyi test is reported, along with the estimated Wilcoxon–Mann–Whitney probability of superiority and its corresponding 95% confidence interval. No formal sample size calculation was performed; therefore, p-values should be interpreted descriptively. All statistical tests were conducted at the 5% significance level. Figure 3 : Retainer debonding during shear strength testing following the initial failure of the adhesive interface Results The Kruskal-Wallis test suggests that the cleaning protocol used for calculus removal has a significant impact (p < 0.036) on the shear bond strength of retainers after treatment. Regarding the predefined primary comparison addressing the debridement modality, pairwise post-hoc comparisons using the Nemenyi test revealed that statistically significant higher forces were required to cause bond failures after use of ultrasonic stainless steel (Group A) compared to sonic stainless stell (Group C) (p = 0.028). Moreover, there is an 85% (95%-CI = [0.67, 0.94]) probability that the shear bond strength of retainers is higher for a segment in Group A than in Group C. With regard to the predefined material-related comparison within ultrasonic instrumentation, no statistically significant difference was observed between the ultrasonic stainless-steel (SS) and the ultrasonic PEEK instrumentation (Group A vs. Group B, P = 0.519). However, Group A tends to have a higher shear bond strength of retainers than Group B. For a segment in Group A, there is a 63% (95%-CI = [0.38, 0.83]) probability that the shear bond strength of retainers is higher than for a segment in Group B. Similarly, the Nemenyi test showed no significant difference between ultrasonic PEEK and sonic stainless-steel instrumentation (Group B vs. Group C, p = 0.32) (Fig. 1 ). A segment in Group C only had a 30% (95%-CI [0.14, 0.57]) probability to have a higher shear bond strength of retainers than a segment in Group B (see Tables 1 and 2 ). Table 1 Descriptive description of shear bond strength Group A (ultrasonic SS) Group B (ultrasonic PEEK) Group C (sonic SS) n 10 10 10 Mean (SD) 274.1 (49.5) 236.1 (77.7) 191.31 (52.9) Median (Q1-Q3) 282.5 (212.5–319.4) 225.27 (167.1–307.7) 180.7 (152.1–222.9) Min- Max 203.4–327.4 135.1–344.4 133.6–310.8 Table 2 Pairwise comparisons of shear bond strength at failure (N) between the cleaning protocols using the Nemenyi test. Reported are the p-value of the Nemenyi test, along with the estimated Wilcoxon–Mann–Whitney probability of superiority and its corresponding 95% confidence interval . Comparison: G1 vs G2 Nemenyi p P (G1 > G2) 95% - CI PO 1 Group A Group C 0.028 * 0.85 [0.67, 0.94] PO 2 Group A Group B 0.519 0.63 [0.38, 0.83] Exploratory Group C Group B 0.304 0.32 [0.14, 0.57] Note: PO1 = predefined primary comparison addressing debridement modality (ultrasonic vs. sonic). PO2 = predefined primary comparison addressing tip material within ultrasonic instrumentation (stainless steel vs. PEEK). Exploratory = exploratory comparison between ultrasonic PEEK and sonic stainless steel instrumentation. P means the probability that a shear bond strength value in Group 1 exceed one in Group 2. Instrument durability differed markedly between ultrasonic PEEK and stainless-steel tips Across the 20 treatment cycles per group (comprising 10 retainers, two cycles), a single instrument tip was sufficient for Groups A and C, respectively. In contrast, multiple instruments were required for Group B. In Groups A and C, the stainless-steel tips showed a cumulative length loss of approximately 1 mm. In Group B, a total of 15 carbon-reinforced PEEK tips were consumed. The median cumulative length loss was 5 mm per tip (range: 4-8mm). According to the manufacturer’s instructions, this degree of attrition classified the tips as unusable for further treatment (Table 3 ). Table 3 Instrument-related outcomes across all treatment cycles. Group Instrument type Treatment cycles (n) Tips used (n) Cumulative tip consumption A Ultrasonic, stainless steel 20 1 1 mm B Ultrasonic, PEEK 20 15* median 5 mm (4–8 mm) C Sonic, stainless steel 20 1 1 mm Note: Cumulative tip consumption refers to total length loss per instruments. *Tip not usable after treatment cycle Discussion To the best of our knowledge, this study is the first to examine different professional cleaning protocols for fixed lingual retainers. The primary objective of this study was to isolate the bonding stability of retainers under standardized conditions. Primary endpoint: Impact of Debridement Modalities on Bond Stability of fixed retainers The primary objective of this study was to isolate the bonding stability of retainers the standardized conditions. Our findings indicate that the choice of instrumentation significantly impacts bond integrity. Specifically, a significant difference was observed between the stainless-steel groups Group A (ultrasonic, 24–32 kHz, stainless steel) and Group C (sonic, 6 kHz, stainless steel). Debridement with the former instrumentation demonstrated a significantly lower impact on the retainer bond, preserving higher shear bond strength compared to the latter. This suggests that high-frequency ultrasonic oscillation may preserve adhesive integrity more effectively than low-frequency sonic debridement. While this difference is statistically significant, all investigated protocols yielded bond strengths exceeding the 3 to 18 N range typically required to withstand intraoral forces [ 25 ]. Consequently, all tested modalities can be considered clinically acceptable, although repeated mechanical debridement appears to progressively attenuate the long-term stability of the adhesive bond. Regarding tip material, our data suggest that the composition of ultrasonic tips plays only a minor role in maintaining shear bond strength. No significant differences were observed between Group A (stainless steel) and Group B (carbon-reinforced PEEK) using identical device settings. Both the stainless-steel tip (Piezon PS) and the 30% carbon-reinforced PEEK tip (PI Max) demonstrated a non-destructive interaction with the adhesive bond. Nevertheless, the stainless-steel ultrasonic tip (Group A) exhibited a marginal superiority in bond maintenance. Notably, the PEEK-based ultrasonic instrumentation (Group B) showed no significant difference compared to the sonic-driven stainless-steel instrumentation (Group C). This suggests that the mechanical advantages of ultrasonic oscillation may be partially mitigated by the use of softer, polymer-based tip materials, indicating that the benefits of high-frequency instrumentation are not universal across all material combinations. Previous studies on the use of stainless steel or PEEK ultrasonic instruments have dealt with changes in surface structure. Cleaning implant surfaces with a PEEK tip appears to result in similar or slightly lesser changes to the surface texture [ 26 , 27 ]. Secondary Endpoint: Tip consumption The assessment of cumulative instrument wear revealed that the attrition rate of the carbon-reinforced PEEK tips was significantly higher than that of the conventional stainless-steel tips. Throughout the debridement of twelve retainers over two cycles—all characterized by heavy calculus accumulation—a total of 15 PEEK tips (Group B) were required. Instrument length was monitored continuously during the procedure using the manufacturer’s standardized gauge to ensure functional integrity. Upon reaching the wear limit defined by the manufacturer, the tip was immediately replaced to maintain standardized treatment conditions. The high fracture rate and excessive wear of PEEK tips rendered their routine use economically impractical compared to the more durable stainless-steel tips (Groups A and C), which remained within manufacturer-specified wear limits. Despite the observation of gray residues on the enamel-like substrate [ 26 , 28 , 29 ] and high replacement costs, the carbon-reinforced PEEK system represents a clinically viable, low-noise alternative for patients with high tactile or auditory sensitivity [ 29 – 32 ]. While its bond preservation is comparable to traditional methods, its primary advantage lies in the nature of the debridement process Previous clinical research has established that piezoelectric ultrasonic scaler generally elicit fewer negative emotional responses than magnetostatic systems, largely due to reduced acoustic emissions [ 32 ]. By eliminating metal-on-metal contact, the use of PEEK tips is expected to further enhance patient comfort. This reduced vibration and noise profile may alleviate dental anxiety during professional tooth cleaning, suggesting that the selection of tip material should be guided not only by adhesive integrity but also by the objective of improving the overall patient experience. Methodology While prospective clinical trials offer high external validity, they introduce a multitude of confounding variables. As established by Roser et al. (2023) [ 9 ], this controlled approach eliminates the influence of bruxism and varying masticatory forces. Furthermore, laboratory testing standardizes the adhesive interface. By utilizing accelerated aging and mechanical cycling, this study establishes a reliable baseline of bonding durability, providing a necessary "proof of concept" before advancing to clinical studies As the highest forces on a tooth typically originate from the occlusal surface, axial loading was applied in accordance with the protocol described by Roser et al. [ 9 ] to ensure standardised experimental setting. In order to achieve better standardisation, calculus removal was performed by the same practitioner every time. A particular strength of the present study is the use of individual tooth models [ 19 ] which allowed for physiological tooth movement. This model provides a close approximation of the clinical situation and enable a comprehensive evaluation of the stability of the entire retainer. Furthermore, Roser et al., 2022 demonstrated that the tooth model utilized here exhibits shear bond strengths comparable to those of bovine teeth [ 18 ], which are approved for norm-compliant testing to evaluate shear bond strength (ISO/TS 29022:2013). This approach facilitated an approximation of clinical conditions. Artificial calculus was applied in a physiological pattern surrounding the bonding sites and subsequently removed under standardised conditions by a single practitioner. However, this can also be seen as a limitation due to a lack of generalizability. Furthermore, the wear of the utilized tips used was documented. To the best of our knowledge, there are currently no available studies addressing the wear of power-driven instruments during calculus removal in this experimental context. The present study has several limitations. (I) Due to the laboratory setting, factors like saliva, biofilm presence, or thermal variations could not be assessed. (II) The current protocol may not be directly transferable to other bonding strategies or materials. (III) Assessment of shear bond strength was only unidirectional in our setting, not including multidirectional forces. In the field of periodontology and preventive dentistry, the application of sonic and ultrasonic systems for calculus removal is well-documented [ 30 , 33 – 36 ]. Regarding hard tissue loss following instrumentation, linear oscillating ultrasonic devices appear to perform significantly better than ellipsoidal oscillating sonic instruments [ 34 – 36 ]. This is attributed to the absence of undesirable linear forces in linear vibration. Historically, ultrasonic scalers were reported to yield inferior results compared to sonic scalers regarding surface roughness on tooth structures and composite restorations [ 35 , 37 , 38 ]; however, more recent studies demonstrate comparable or even superior performance [ 39 ]. In accordance, our investigation showed that stainless steel ultrasonic instruments utilizing linear vibration (Piezon principle) resulted in a lower reduction in shear bond strength than instruments in the sonic -driven instruments. No significant differences were found between different tip materials tested. This in-vitro study provides initial evidence that the method of mechanical calculus removal appears to influence the long-term stability of adhesively fixed retainers. Although previous studies have shown that the artificial teeth used here possess adhesive properties comparable to human teeth [ 18 ] and these models can realistically simulate physiological tooth movement realistically [ 19 ], clinical studies are necessary to confirm these findings. Conclusions Within the limitations of the in-vitro design the following conclusions can be drawn: 1. The frequency range utilized for mechanical calculus removal appears to significantly influence the bond stability of Twistflex retainers under mechanical stress; consequently, the use of ultrasonic instrumentation may be preferable for the professional debridement of Twistflex retainers. 2. The material of the ultrasonic tip does not appear to exert a significant effect on bond stability 3. While PEEK tips for ultrasonic-driven devices exhibit significantly higher wear rates and associated costs compared to stainless steel alternatives, they demonstrate comparable outcomes regarding bond stability and may serve as a viable alternative for noise-sensitive patients. Declarations Conflict of interest: The authors declare no conflict of interest. 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Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 20 Feb, 2026 Reviewers invited by journal 19 Feb, 2026 Editor assigned by journal 17 Feb, 2026 Submission checks completed at journal 17 Feb, 2026 First submitted to journal 16 Feb, 2026 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8895010","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":594397585,"identity":"37fdc2f6-8227-463f-8ff1-445ea751275c","order_by":0,"name":"Marie-Therese Heberer","email":"","orcid":"","institution":"Heidelberg University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Marie-Therese","middleName":"","lastName":"Heberer","suffix":""},{"id":594397586,"identity":"08bd962f-24bb-465c-9764-8fcf65649b19","order_by":1,"name":"Max S. Pfaff","email":"","orcid":"","institution":"Heidelberg University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Max","middleName":"S.","lastName":"Pfaff","suffix":""},{"id":594397588,"identity":"7468b70d-ed68-4fc1-80c2-0bb00a02d100","order_by":2,"name":"Ralf Erber","email":"","orcid":"","institution":"Heidelberg University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ralf","middleName":"","lastName":"Erber","suffix":""},{"id":594397589,"identity":"ae4cfcf7-f8f4-4046-92ac-22bfbaeecd81","order_by":3,"name":"Christoph J. Roser","email":"","orcid":"","institution":"Heidelberg University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Christoph","middleName":"J.","lastName":"Roser","suffix":""},{"id":594397590,"identity":"14d74a3b-5597-4c1a-ae48-469a773d3c77","order_by":4,"name":"Sinclair Awounvo","email":"","orcid":"","institution":"Heidelberg University","correspondingAuthor":false,"prefix":"","firstName":"Sinclair","middleName":"","lastName":"Awounvo","suffix":""},{"id":594397591,"identity":"65797003-b56b-4be7-b58c-cc08a02f94b2","order_by":5,"name":"Andreas Zenthöfer","email":"","orcid":"","institution":"Heidelberg University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Andreas","middleName":"","lastName":"Zenthöfer","suffix":""},{"id":594397592,"identity":"3b345cf8-84fc-4aa6-b715-588170afa0f1","order_by":6,"name":"Christopher J. Lux","email":"","orcid":"","institution":"Heidelberg University Hospital","correspondingAuthor":false,"prefix":"","firstName":"Christopher","middleName":"J.","lastName":"Lux","suffix":""},{"id":594397593,"identity":"be38f011-532f-48b5-b3ab-dd33db2148fe","order_by":7,"name":"Valentin Bartha","email":"data:image/png;base64,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","orcid":"","institution":"Heidelberg University Hospital","correspondingAuthor":true,"prefix":"","firstName":"Valentin","middleName":"","lastName":"Bartha","suffix":""}],"badges":[],"createdAt":"2026-02-16 17:08:15","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8895010/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8895010/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103313781,"identity":"f8935127-1671-4ba1-b1f7-d754fa49d0ea","added_by":"auto","created_at":"2026-02-24 10:32:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":61388,"visible":true,"origin":"","legend":"\u003cp\u003eStudy process as a flow chart\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8895010/v1/fbf37cebf6d8ee018ba99152.png"},{"id":104397506,"identity":"235cbe84-6389-464c-83d7-ebfefa680b70","added_by":"auto","created_at":"2026-03-11 11:50:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":526574,"visible":true,"origin":"","legend":"\u003cp\u003eCalculus removal by different cleaning protocols (A: ultrasonic stainless-steel tip, B: ultrasonic 30% carbon-reinforced PEEK tip. C: sonic cleaning with stainless steel tip)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8895010/v1/3c2a0fce2244d04b0ec0e958.png"},{"id":103313783,"identity":"f78e00e8-097f-4ff7-9e3d-de08a653a043","added_by":"auto","created_at":"2026-02-24 10:32:18","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":181126,"visible":true,"origin":"","legend":"\u003cp\u003eRetainer debonding during shear strength testing following the initial failure of the adhesive interface\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8895010/v1/e1e7fb3775c668c1f12f170d.png"},{"id":103313784,"identity":"c78149ae-81af-4319-ba5e-3f40b088c335","added_by":"auto","created_at":"2026-02-24 10:32:18","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":19367,"visible":true,"origin":"","legend":"\u003cp\u003eFigure 3: \u0026nbsp;Box plot representation of the shear bond strength testing following cleaning with three different methods. * statistically significant difference\u003c/p\u003e","description":"","filename":"03.png","url":"https://assets-eu.researchsquare.com/files/rs-8895010/v1/034c1c4eadf511717e72d4d4.png"},{"id":104411652,"identity":"bcc9d77c-51a1-4e18-8813-a07855eab636","added_by":"auto","created_at":"2026-03-11 12:57:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1736768,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8895010/v1/5b691062-ce22-4b60-bde8-4aa2418919de.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Pilot study on calculus removal from orthodontic retainers using different mechanical approaches: an in-vitro investigation of the adhesive strength of fixed retainers","fulltext":[{"header":"Introduction","content":"\u003cp\u003eFollowing orthodontic treatment, fixed retainers are widely employed to stabilise the treatment results [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Their efficacy in maintaining post-treatment dental alignment is well-accepted [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Although fixed retainers are not considered primary etiological factors for periodontal disease [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], they may facilitate plaque and calculus accumulation [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] thereby increasing the risk of localized gingival inflammation in the absence of a rigorous oral hygiene [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFrom a biomechanical perspective, multi-stranded 'Twistflex' retainers currently provide the gold standard for orthodontic retention [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Although the surface area is increased by the stranding of several wires, Twistflex retainers do not exhibit significantly higher calculus accumulation [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] regardless of the wire material [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, a precise fit of the retainer to the dental arch and the lingual tooth surfaces seems to have a positive effect on oral health [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eWhile fixed retainers are essential for stabilizing orthodontic outcomes, they increase the risk of compromising the oral health by increased plaque and calculus accumulation [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Consequently, the results of the recent German Oral Health Study underscores the vital role of professional tooth cleaning PMBR in mitigating these risks in general [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Currently, approximately 80% of young adults in Germany utilize professional cleaning services [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Given the high prevalence of fixed retainers following orthodontic therapy [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e] and the resulting growth of this patient population, identifying the most effective and safe mechanical debridement methods for PMBR is clinically highly relevant.\u003c/p\u003e \u003cp\u003eMechanical debridement of orthodontic appliances such as brackets appears to have an impact on their shear bond strengths [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. It is therefore plausible that mechanical calculus removal has an influence on adhesive bonding. So far studies investigating the impact of calculus removal around fixed retainers are missing in the literature.\u003c/p\u003e \u003cp\u003eThus, the aim of this in-vitro study was to evaluate the impact of different calculus removal protocols on the adhesive bond strengths of fixed orthodontic retainers. The investigation focuses on two aspects: (I) the influence of the debridement modality, comparing ultrasonic and sonic instrumentation under comparable conditions, and (II) the influence of ultrasonic tip material, comparing stainless steel and carbon-reinforced PEEK tips with identical device settings. Accordingly, the primary outcome was to measure the shear bond strength required to induce debonding of fixed orthodontic retainers following repeated mechanical calculus removal. As a secondary outcome, instrument-related parameters, including tip wear and the incidence of tip fractures, were assessed for further insight into the practical and economic implications of the various systems.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cp\u003eThis in-vitro study was in accordance with the CRIS guidelines for reporting in-vitro studies [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e]. A total of 34 mandibular anterior segment models were constructed to simulate the lower anterior region. Each segment consisted of six CAD/CAM-manufactured artificial teeth (canine to canine), resulting in a total of 204 CAD/CAM-manufactured artificial front and canine teeth made of \u003cem\u003eTrinia\u003c/em\u003e (Trinia, Bicon, Boston, USA) according to an established protocol [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e]. Two canine teeth and the four incisors were inserted into n\u0026thinsp;=\u0026thinsp;34 3D-printed moulds to simulate the lower front teeth area. The validity of this in-vitro model in simulating physiological tooth mobility has been shown previously [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\n\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eFabrication of Retainers\u003c/h2\u003e\n \u003cp\u003eThe dental arches were scanned using the \u003cem\u003eiTero Lumina\u003c/em\u003e (Align Technology, Santa Clara, California, USA) intraoral scanner. Using the \u003cem\u003eBender 2\u003c/em\u003e (YOAT Corporation, Lynnwood, Washington, USA) bending robot, passively fitting retainers were manufactured individually for each dental arch from Ti5-Twistflex-wires [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e]. The passive fit of each retainer on the respective dental arch was checked prior to adhesive fixation. The adhesive bonds were then artificially aged by thermo-cycling (10.000 thermal cycles between 6.5\u0026deg;C and 60\u0026deg;C (Z005, Zwick Roell, Ulm, Germany), for a duration of approximately 12 days) [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e20\u003c/span\u003e]. After the artificial ageing, each adhesive bond was tested with a dental probe by the same examiner each time. Three adhesive joints failed initially. These dental arches were excluded from the trial. One intact dental arch was kept as a spare, which was not needed in this trial.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eArtificial calculus application and experimental removal\u003c/h3\u003e\n\u003cp\u003eArtificial calculus was applied around the intact retainers according to manucfacturer\u0026rsquo;s instructions (Frasaco A-CK Calculus, frasaco GmbH, Tettnang, Germany) [\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. The calculus extended beyond the bonding site and into the approximal spaces. The remaining 30 dental arches were divided into three equal groups.\u003c/p\u003e\n\u003cp\u003eCalculus was removed by a trained practitioner using three cleaning protocols (see Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e):\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003e\n \u003cp\u003eGroup A: ultrasonic stainless-steel tip (Piezon-Tip, EMS Dental, Nyon, Switzerland)\u003c/p\u003e\n \u003c/li\u003e\n \u003cli\u003e\n \u003cp\u003eGroup B: ultrasonic 30% carbon-reinforced PEEK tip (Pi Max Tip, EMS Dental, Nyon, Switzerland)\u003c/p\u003e\n \u003c/li\u003e\n \u003cli\u003e\n \u003cp\u003eGroup C: sonic cleaning with stainless steel tip (SiroTip S1, Sirona Dental Systems, Bensheim, Germany).\u003c/p\u003e\n \u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eThe tips of groups A and B were applied with AirFlow Prophylaxis Master One (EMS Dental, Nyon, Switzerland) using the manufacturer\u0026rsquo;s instructions (water: level 10, power: level 4). The difference between these two groups was therefore only the tip material used. Group C was applied to the treatment unit using the SiroAir L handpiece [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e]. During mechanical calculus removal, water cooling was used for all groups. The various tips were used in accordance with the manufacturer\u0026apos;s instructions.\u003c/p\u003e\n\u003cp\u003eThe cleaning was considered complete when no more calculus was visible. This check was always carried out by the same person using dental loupes. Subsequently, the adhesion of the bonding sites was checked manually and documented again. The calculus removal was performed twice under the conditions specified.\u003c/p\u003e\n\u003ch3\u003eTesting of shear bond strength\u003c/h3\u003e\n\u003cp\u003eThe shear bond strength of all remaining retainers was tested afterwards using a universal testing machine (Z005, Zwick/Roell, Ulm, Germany) following the ISO/TS 11405:2015 standard (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). To this end, the test specimen was lowered at a speed of 1 mm/min with a preload of 2 N. In accordance with Roser et al. (2023) [\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e], tooth 31 was subjected to an axial load using the universal testing machine until the failure of the adhesive bond was observed .\u003c/p\u003e\n\u003cp\u003eIn addition, the wear and tear on the tips and the number of tips used were documented. Peak consumption was measured using a calliper gauge.\u003c/p\u003e\n\u003ch3\u003eOutcomes\u003c/h3\u003e\n\u003cp\u003eThe primary outcome was the shear bond strength required to induce debonding of fixed orthodontic retainers after repeated mechanical calculus removal. For analytical purposes, two predefined comparisons were addressed within this primary outcome:\u003c/p\u003e\n\u003cp\u003e\u003cspan\u003e\u003c/span\u003e\u003c/p\u003e\n\u003cp\u003eI. a method-related comparison between ultrasonic and sonic instrumentation using stainless steel tips (Group A vs. Group C)\u003c/p\u003e\u003cspan\u003e\n \u003cp\u003eII. \u0026nbsp;a material-related comparison between stainless steel and carbon-reinforced PEEK ultrasonic tips operated under identical device settings (Group A vs. Group B).\u003c/p\u003e\n\u003c/span\u003e\n\u003cp\u003e\u003c/p\u003e\n\u003cp\u003eSecondary outcomes included instrument-related parameters, particularly the number of tips used, the occurrence of tip fractures, and cumulative tip consumption (mm).\u003c/p\u003e\n\u003ch3\u003eStatistical methods\u003c/h3\u003e\n\u003cp\u003eData analysis was performed using R version 4.5.2 [\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]. The primary outcome\u0026mdash;the shear bond strength required to induce debonding of fixed orthodontic retainers after repeated mechanical calculus removal\u0026mdash;was summarized using the mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation, median (Q1\u0026ndash;Q3), minimum, and maximum, and was graphically displayed using boxplots.\u003c/p\u003e\n\u003cp\u003eDifference in shear bond strength required to induce debonding of fixed orthodontic retainers after repeated mechanical calculus removal between the three cleaning protocol used for calculus removal (Group A: ultrasonic stainless-steel tip (Piezon PS, EMS Dental); Group B: Polyetheretherketone (PEEK) -coated ultrasonic tip (PI Max, EMS Dental); and Group C: sonic cleaning (SiroTip S1, Sirona Dental Systems) was assessed using a Kruskal\u0026ndash;Wallis test. Upon statistical significance of the Kruskal-Wallis test, non-parametric post-hoc Nemenyi tests are conducted to assess pairwise differences in required shear bond strength between the three cleaning protocol used for calculus removal. For each post-hoc pairwise comparison, the p-value from the Nemenyi test is reported, along with the estimated Wilcoxon\u0026ndash;Mann\u0026ndash;Whitney probability of superiority and its corresponding 95% confidence interval. No formal sample size calculation was performed; therefore, p-values should be interpreted descriptively. All statistical tests were conducted at the 5% significance level.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e: Retainer debonding during shear strength testing following the initial failure of the adhesive interface\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThe Kruskal-Wallis test suggests that the cleaning protocol used for calculus removal has a significant impact (p\u0026thinsp;\u0026lt;\u0026thinsp;0.036) on the shear bond strength of retainers after treatment.\u003c/p\u003e \u003cp\u003eRegarding the predefined primary comparison addressing the debridement modality, pairwise post-hoc comparisons using the Nemenyi test revealed that statistically significant higher forces were required to cause bond failures after use of ultrasonic stainless steel (Group A) compared to sonic stainless stell (Group C) (p\u0026thinsp;=\u0026thinsp;0.028). Moreover, there is an 85% (95%-CI = [0.67, 0.94]) probability that the shear bond strength of retainers is higher for a segment in Group A than in Group C.\u003c/p\u003e \u003cp\u003eWith regard to the predefined material-related comparison within ultrasonic instrumentation, no statistically significant difference was observed between the ultrasonic stainless-steel (SS) and the ultrasonic PEEK instrumentation (Group A vs. Group B, P\u0026thinsp;=\u0026thinsp;0.519). However, Group A tends to have a higher shear bond strength of retainers than Group B. For a segment in Group A, there is a 63% (95%-CI = [0.38, 0.83]) probability that the shear bond strength of retainers is higher than for a segment in Group B. Similarly, the Nemenyi test showed no significant difference between ultrasonic PEEK and sonic stainless-steel instrumentation (Group B vs. Group C, p\u0026thinsp;=\u0026thinsp;0.32) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). A segment in Group C only had a 30% (95%-CI [0.14, 0.57]) probability to have a higher shear bond strength of retainers than a segment in Group B (see Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\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\u003eDescriptive description of shear bond strength\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup A (ultrasonic SS)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup B (ultrasonic PEEK)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eGroup C (sonic SS)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003en\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMean (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e274.1 (49.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e236.1 (77.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e191.31 (52.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMedian (Q1-Q3)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e282.5 (212.5\u0026ndash;319.4)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e225.27 (167.1\u0026ndash;307.7)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e180.7 (152.1\u0026ndash;222.9)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMin- Max\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e203.4\u0026ndash;327.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e135.1\u0026ndash;344.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e133.6\u0026ndash;310.8\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 \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\u003ePairwise comparisons of shear bond strength at failure (N) between the cleaning protocols using the Nemenyi test. Reported are the p-value of the Nemenyi test, along with the estimated Wilcoxon\u0026ndash;Mann\u0026ndash;Whitney probability of superiority and its corresponding 95% confidence interval .\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=\"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\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e \u003cp\u003eComparison: G1 vs G2\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNemenyi p\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP (G1\u0026thinsp;\u0026gt;\u0026thinsp;G2)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e95% - CI\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePO 1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e0.028 *\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.85\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e[0.67, 0.94]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePO 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup A\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.519\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.63\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e[0.38, 0.83]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eExploratory\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGroup C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGroup B\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.304\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e[0.14, 0.57]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"6\"\u003e\u003cem\u003eNote: PO1\u0026thinsp;=\u0026thinsp;predefined primary comparison addressing debridement modality (ultrasonic vs. sonic). PO2\u0026thinsp;=\u0026thinsp;predefined primary comparison addressing tip material within ultrasonic instrumentation (stainless steel vs. PEEK). Exploratory\u0026thinsp;=\u0026thinsp;exploratory comparison between ultrasonic PEEK and sonic stainless steel instrumentation. P means the probability that a shear bond strength value in Group 1 exceed one in Group 2.\u003c/em\u003e\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e\n\u003ch3\u003eInstrument durability differed markedly between ultrasonic PEEK and stainless-steel tips\u003c/h3\u003e\n\u003cp\u003eAcross the 20 treatment cycles per group (comprising 10 retainers, two cycles), a single instrument tip was sufficient for Groups A and C, respectively. In contrast, multiple instruments were required for Group B. In Groups A and C, the stainless-steel tips showed a cumulative length loss of approximately 1 mm. In Group B, a total of 15 carbon-reinforced PEEK tips were consumed. The median cumulative length loss was 5 mm per tip (range: 4-8mm). According to the manufacturer\u0026rsquo;s instructions, this degree of attrition classified the tips as unusable for further treatment (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\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\u003eInstrument-related outcomes across all treatment cycles.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\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=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGroup\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eInstrument type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTreatment cycles (n)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eTips used (n)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCumulative tip consumption\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUltrasonic, stainless steel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUltrasonic, PEEK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e15*\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003emedian 5 mm (4\u0026ndash;8 mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSonic, stainless steel\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1 mm\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 \u003cem\u003eNote: Cumulative tip consumption refers to total length loss per instruments. *Tip not usable after treatment cycle\u003c/em\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eTo the best of our knowledge, this study is the first to examine different professional cleaning protocols for fixed lingual retainers. The primary objective of this study was to isolate the bonding stability of retainers under standardized conditions.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e\u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003ePrimary endpoint: Impact of Debridement Modalities on Bond Stability of fixed retainers\u003c/span\u003e\u003c/h2\u003e \u003cp\u003eThe primary objective of this study was to isolate the bonding stability of retainers the standardized conditions. Our findings indicate that the choice of instrumentation significantly impacts bond integrity. Specifically, a significant difference was observed between the stainless-steel groups Group A (ultrasonic, 24\u0026ndash;32 kHz, stainless steel) and Group C (sonic, 6 kHz, stainless steel). Debridement with the former instrumentation demonstrated a significantly lower impact on the retainer bond, preserving higher shear bond strength compared to the latter. This suggests that high-frequency ultrasonic oscillation may preserve adhesive integrity more effectively than low-frequency sonic debridement. While this difference is statistically significant, all investigated protocols yielded bond strengths exceeding the 3 to 18 N range typically required to withstand intraoral forces [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Consequently, all tested modalities can be considered clinically acceptable, although repeated mechanical debridement appears to progressively attenuate the long-term stability of the adhesive bond.\u003c/p\u003e \u003cp\u003eRegarding tip material, our data suggest that the composition of ultrasonic tips plays only a minor role in maintaining shear bond strength. No significant differences were observed between Group A (stainless steel) and Group B (carbon-reinforced PEEK) using identical device settings. Both the stainless-steel tip (Piezon PS) and the 30% carbon-reinforced PEEK tip (PI Max) demonstrated a non-destructive interaction with the adhesive bond. Nevertheless, the stainless-steel ultrasonic tip (Group A) exhibited a marginal superiority in bond maintenance. Notably, the PEEK-based ultrasonic instrumentation (Group B) showed no significant difference compared to the sonic-driven stainless-steel instrumentation (Group C). This suggests that the mechanical advantages of ultrasonic oscillation may be partially mitigated by the use of softer, polymer-based tip materials, indicating that the benefits of high-frequency instrumentation are not universal across all material combinations. Previous studies on the use of stainless steel or PEEK ultrasonic instruments have dealt with changes in surface structure. Cleaning implant surfaces with a PEEK tip appears to result in similar or slightly lesser changes to the surface texture [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eSecondary Endpoint: Tip consumption\u003c/h2\u003e \u003cp\u003eThe assessment of cumulative instrument wear revealed that the attrition rate of the carbon-reinforced PEEK tips was significantly higher than that of the conventional stainless-steel tips. Throughout the debridement of twelve retainers over two cycles\u0026mdash;all characterized by heavy calculus accumulation\u0026mdash;a total of 15 PEEK tips (Group B) were required. Instrument length was monitored continuously during the procedure using the manufacturer\u0026rsquo;s standardized gauge to ensure functional integrity. Upon reaching the wear limit defined by the manufacturer, the tip was immediately replaced to maintain standardized treatment conditions. The high fracture rate and excessive wear of PEEK tips rendered their routine use economically impractical compared to the more durable stainless-steel tips (Groups A and C), which remained within manufacturer-specified wear limits. Despite the observation of gray residues on the enamel-like substrate [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] and high replacement costs, the carbon-reinforced PEEK system represents a clinically viable, low-noise alternative for patients with high tactile or auditory sensitivity [\u003cspan additionalcitationids=\"CR30 CR31\" citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. While its bond preservation is comparable to traditional methods, its primary advantage lies in the nature of the debridement process Previous clinical research has established that piezoelectric ultrasonic scaler generally elicit fewer negative emotional responses than magnetostatic systems, largely due to reduced acoustic emissions [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. By eliminating metal-on-metal contact, the use of PEEK tips is expected to further enhance patient comfort. This reduced vibration and noise profile may alleviate dental anxiety during professional tooth cleaning, suggesting that the selection of tip material should be guided not only by adhesive integrity but also by the objective of improving the overall patient experience.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eMethodology\u003c/h2\u003e \u003cp\u003eWhile prospective clinical trials offer high external validity, they introduce a multitude of confounding variables. As established by Roser et al. (2023) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], this controlled approach eliminates the influence of bruxism and varying masticatory forces. Furthermore, laboratory testing standardizes the adhesive interface. By utilizing accelerated aging and mechanical cycling, this study establishes a reliable baseline of bonding durability, providing a necessary \"proof of concept\" before advancing to clinical studies As the highest forces on a tooth typically originate from the occlusal surface, axial loading was applied in accordance with the protocol described by Roser et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] to ensure standardised experimental setting. In order to achieve better standardisation, calculus removal was performed by the same practitioner every time. A particular strength of the present study is the use of individual tooth models [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] which allowed for physiological tooth movement. This model provides a close approximation of the clinical situation and enable a comprehensive evaluation of the stability of the entire retainer. Furthermore, Roser et al., 2022 demonstrated that the tooth model utilized here exhibits shear bond strengths comparable to those of bovine teeth [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], which are approved for norm-compliant testing to evaluate shear bond strength (ISO/TS 29022:2013). This approach facilitated an approximation of clinical conditions. Artificial calculus was applied in a physiological pattern surrounding the bonding sites and subsequently removed under standardised conditions by a single practitioner. However, this can also be seen as a limitation due to a lack of generalizability. Furthermore, the wear of the utilized tips used was documented. To the best of our knowledge, there are currently no available studies addressing the wear of power-driven instruments during calculus removal in this experimental context.\u003c/p\u003e \u003cp\u003eThe present study has several limitations. (I) Due to the laboratory setting, factors like saliva, biofilm presence, or thermal variations could not be assessed. (II) The current protocol may not be directly transferable to other bonding strategies or materials. (III) Assessment of shear bond strength was only unidirectional in our setting, not including multidirectional forces.\u003c/p\u003e \u003cp\u003eIn the field of periodontology and preventive dentistry, the application of sonic and ultrasonic systems for calculus removal is well-documented [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan additionalcitationids=\"CR34 CR35\" citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Regarding hard tissue loss following instrumentation, linear oscillating ultrasonic devices appear to perform significantly better than ellipsoidal oscillating sonic instruments [\u003cspan additionalcitationids=\"CR35\" citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. This is attributed to the absence of undesirable linear forces in linear vibration.\u003c/p\u003e \u003cp\u003eHistorically, ultrasonic scalers were reported to yield inferior results compared to sonic scalers regarding surface roughness on tooth structures and composite restorations [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]; however, more recent studies demonstrate comparable or even superior performance [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In accordance, our investigation showed that stainless steel ultrasonic instruments utilizing linear vibration (Piezon principle) resulted in a lower reduction in shear bond strength than instruments in the sonic -driven instruments. No significant differences were found between different tip materials tested.\u003c/p\u003e \u003cp\u003eThis \u003cem\u003ein-vitro\u003c/em\u003e study provides initial evidence that the method of mechanical calculus removal appears to influence the long-term stability of adhesively fixed retainers. Although previous studies have shown that the artificial teeth used here possess adhesive properties comparable to human teeth [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] and these models can realistically simulate physiological tooth movement realistically [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], clinical studies are necessary to confirm these findings.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eWithin the limitations of the in-vitro design the following conclusions can be drawn:\u003c/p\u003e\n\u003cp\u003e1. The frequency range utilized for mechanical calculus removal appears to significantly influence the bond stability of Twistflex retainers under mechanical stress; consequently, the use of ultrasonic instrumentation may be preferable for the professional debridement of Twistflex retainers.\u003c/p\u003e\n\u003cp\u003e2. The material of the ultrasonic tip does not appear to exert a significant effect on bond stability\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e3. While PEEK tips for ultrasonic-driven devices exhibit significantly higher wear rates and associated costs compared to stainless steel alternatives, they demonstrate comparable outcomes regarding bond stability and may serve as a viable alternative for noise-sensitive patients.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cu\u003eConflict of interest:\u003c/u\u003e The authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cu\u003eEthics approval:\u003c/u\u003e\u0026nbsp; This article does not contain any studies with human participants or animals performed by any of the authors and is in accordance with the ethical standards of the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBooth, F.A., J.M. Edelman, and W.R. 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Datta, \u003cem\u003eCRIS Guidelines (Checklist for Reporting In-vitro Studies): A concept note on the need for standardized guidelines for improving quality and transparency in reporting in-vitro studies in experimental dental research.\u003c/em\u003e J Conserv Dent, 2014. \u003cstrong\u003e17\u003c/strong\u003e(4): p. 301-4.\u003c/li\u003e\n \u003cli\u003eRoser, C.J., et al., \u003cem\u003eOrthodontic shear bond strength and ultimate load tests of CAD/CAM produced artificial teeth.\u003c/em\u003e Clin Oral Investig, 2022. \u003cstrong\u003e26\u003c/strong\u003e(12): p. 7149-7155.\u003c/li\u003e\n \u003cli\u003eRoser, C.J., et al., \u003cem\u003eA new CAD/CAM tooth mobility simulating model for dental in vitro investigations.\u003c/em\u003e Clinical Oral Investigations, 2023. \u003cstrong\u003e27\u003c/strong\u003e(9): p. 5131-5140.\u003c/li\u003e\n \u003cli\u003eDeurer, N., et al., \u003cem\u003eAbrasion of Pro Seal\u0026reg; and Opal\u0026reg; Seal\u0026trade; by professional tooth cleaning protocols: results from an in vitro study and a randomized controlled trial.\u003c/em\u003e Eur J Orthod, 2020. \u003cstrong\u003e42\u003c/strong\u003e(6): p. 596-604.\u003c/li\u003e\n \u003cli\u003eKayaalti-Yuksek, S., et al., \u003cem\u003eEffect of preclinical training in periodontal instrumentation on undergraduate students\u0026rsquo; anxiety, clinical performance, satisfaction.\u003c/em\u003e BMC Oral Health, 2025. \u003cstrong\u003e25\u003c/strong\u003e(1): p. 1167.\u003c/li\u003e\n \u003cli\u003eGraetz, C., et al., \u003cem\u003eHow to train periodontal endoscopy? 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Smith, \u003cem\u003eHow to use new materials and workflows to restore edentulous patients.\u003c/em\u003e 2019.\u003c/li\u003e\n \u003cli\u003eDrisko, C.L., et al., \u003cem\u003ePosition paper: sonic and ultrasonic scalers in periodontics. Research, Science and Therapy Committee of the American Academy of Periodontology.\u003c/em\u003e J Periodontol, 2000. \u003cstrong\u003e71\u003c/strong\u003e(11): p. 1792-801.\u003c/li\u003e\n \u003cli\u003eYu, J.F., et al., \u003cem\u003eHuman amygdala activation by the sound produced during dental treatment: A fMRI study.\u003c/em\u003e Noise Health, 2015. \u003cstrong\u003e17\u003c/strong\u003e(78): p. 337-42.\u003c/li\u003e\n \u003cli\u003eYou, X., X. Wu, and S. Chen, \u003cem\u003eEffects of a new magnetostrictive ultrasonic scaler and a traditional piezoelectric ultrasonic scaler on root surfaces and patient complaints.\u003c/em\u003e Sci Rep, 2024. \u003cstrong\u003e14\u003c/strong\u003e(1): p. 6601.\u003c/li\u003e\n \u003cli\u003eArabaci, T., Y. Ci\u0026ccedil;ek, and C.F. Canak\u0026ccedil;i, \u003cem\u003eSonic and ultrasonic scalers in periodontal treatment: a review.\u003c/em\u003e Int J Dent Hyg, 2007. \u003cstrong\u003e5\u003c/strong\u003e(1): p. 2-12.\u003c/li\u003e\n \u003cli\u003eJotikasthira, N.E., T. Lie, and K.N. Leknes, \u003cem\u003eComparative in vitro studies of sonic, ultrasonic and reciprocating scaling instruments.\u003c/em\u003e J Clin Periodontol, 1992. \u003cstrong\u003e19\u003c/strong\u003e(8): p. 560-9.\u003c/li\u003e\n \u003cli\u003eSchmidlin, P.R., et al., \u003cem\u003eTooth substance loss resulting from mechanical, sonic and ultrasonic root instrumentation assessed by liquid scintillation.\u003c/em\u003e J Clin Periodontol, 2001. \u003cstrong\u003e28\u003c/strong\u003e(11): p. 1058-66.\u003c/li\u003e\n \u003cli\u003eAbdul Hayei, N.A., et al., \u003cem\u003eInfluence of scaler tip design on root surface roughness, tooth substance loss and patients\u0026apos; pain perception: an in vitro and a randomised clinical trial.\u003c/em\u003e BMC Oral Health, 2021. \u003cstrong\u003e21\u003c/strong\u003e(1): p. 169.\u003c/li\u003e\n \u003cli\u003eLai, Y.L., et al., \u003cem\u003eEffects of sonic and ultrasonic scaling on the surface roughness of tooth-colored restorative materials for cervical lesions.\u003c/em\u003e Oper Dent, 2007. \u003cstrong\u003e32\u003c/strong\u003e(3): p. 273-8.\u003c/li\u003e\n \u003cli\u003eErdilek, D., et al., \u003cem\u003eEffects of ultrasonic and sonic scaling on surfaces of tooth-colored restorative materials: An in vitro study.\u003c/em\u003e Niger J Clin Pract, 2015. \u003cstrong\u003e18\u003c/strong\u003e(4): p. 467-71.\u003c/li\u003e\n \u003cli\u003eGraetz, C., et al., \u003cem\u003eRemoval of simulated biofilm: an evaluation of the effect on root surfaces roughness after scaling.\u003c/em\u003e Clin Oral Investig, 2017. \u003cstrong\u003e21\u003c/strong\u003e(4): p. 1021-1028.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"clinical-oral-investigations","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cloi","sideBox":"Learn more about [Clinical Oral Investigations](http://link.springer.com/journal/784)","snPcode":"784","submissionUrl":"https://submission.nature.com/new-submission/784/3","title":"Clinical Oral Investigations","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"orthodontics, retainer, calculus, ultrasonic, sonic","lastPublishedDoi":"10.21203/rs.3.rs-8895010/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8895010/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\u003eOrthodontic fixed retainers are often a predilection site for calculus build-up. However, standardized protocol for professional mechanical plaque removal (PMPR) does not yet exist that takes into account the slight weakening of the adhesive bond.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterial and Methods\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this in-vitro study, three cleaning protocols were evaluated: Group A: ultrasonic stainless-steel tip (Piezon PS, EMS Dental); Group B: Polyetheretherketone (PEEK) ultrasonic tip (PI Max, EMS Dental); and Group C: sonic cleaning (SiroTip S1, Sirona Dental Systems). These protocols were assigned artificial lower canine-to-canine segments with individual Twistflex retainers bonded (n = 10/group). Following artificial ageing of the adhesive bond, artificial calculus was applied and removed according to the respective cleaning protocol. After repeating twice, adhesive bond strengths were analysed.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe Kruskal-Wallis test showed that the choice of instrumentation significantly influences the integrity of the adhesive bond (p = 0.036). Post-hoc pairwise comparisons revealed that Group A had significantly higher shear bond strength compared to Group C (p = 0.028).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis in-vitro study shows that the type of the PMPR system used has a significant influence on the shear bond strength of fixed retainers. Ultrasound-driven stainless-steel scalers appear to be more gentle than sonic-driven devices.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eClinical relevance\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn clinical practice, the accidental debonding of retainer attachments during PMBR is a frequent complication. The present in-vitro study investigates whether specific cleaning modalities can minimize the risk of compromising the adhesive bonding. Specifically, different cleaning modalities (ultrasonic versus sonic) and various tip materials are evaluated and compared.\u003c/p\u003e","manuscriptTitle":"Pilot study on calculus removal from orthodontic retainers using different mechanical approaches: an in-vitro investigation of the adhesive strength of fixed retainers","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-24 10:32:13","doi":"10.21203/rs.3.rs-8895010/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"287980688547827153855482207161304936903","date":"2026-02-20T10:49:28+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-19T18:24:37+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-18T04:02:01+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-18T03:59:57+00:00","index":"","fulltext":""},{"type":"submitted","content":"Clinical Oral Investigations","date":"2026-02-16T16:54:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"clinical-oral-investigations","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"cloi","sideBox":"Learn more about [Clinical Oral Investigations](http://link.springer.com/journal/784)","snPcode":"784","submissionUrl":"https://submission.nature.com/new-submission/784/3","title":"Clinical Oral Investigations","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"def8a089-5f60-4c56-9421-4f99ca5b46d5","owner":[],"postedDate":"February 24th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-02-24T10:32:14+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-24 10:32:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8895010","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8895010","identity":"rs-8895010","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}