Evaluation of the correlation between degree of conversion and shear bond strength in four contemporary orthodontic adhesives: an in vitro study

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Shear Bond Strength (SBS) and Degree of Conversion (DC) are two fundamental properties governing the performance of orthodontic adhesives. This study aimed to evaluate the relationship between DC and SBS in four contemporary orthodontic adhesives, including conventional and no-primer systems. Methods Sixty sound human premolars were randomly allocated into four groups (n = 15). Metal brackets were bonded using one of four adhesives: Transbond XT (conventional), Brace Paste (conventional), Orthocem (no-primer), or GC Orthoconnect (no-primer). Then specimens were stored for 24 hours and subjected to 3,000 thermal cycles. SBS was measured using a universal testing machine. The DC of residual adhesive was determined using Fourier-Transform Infrared (FTIR) Spectroscopy on a subset of ten specimens per group. The Adhesive Remnant Index (ARI) was assessed using stereomicroscopy. Data were analyzed using ANOVA, Tukey’s HSD test, Pearson's correlation, and Fisher's exact test (p < 0.05). Results Statistically significant differences were observed among the groups for both mean SBS (p < 0.001) and mean DC (p = 0.007). GC Orthoconnect exhibited the highest SBS (23.66 ± 5.77 MPa), while Orthocem showed the lowest (10.95 ± 3.31 MPa). Conversely, Orthocem demonstrated the highest DC (79.0 ± 13.8%), whereas Transbond XT had the lowest (58.7 ± 9.9%). Pearson's correlation test revealed no statistically significant correlation between SBS and DC for any of the tested adhesives (p > 0.05). ARI score distributions also differed significantly among the groups (p < 0.001). Conclusions All four adhesives provided clinically acceptable bond strength, and the adhesive remnant was greater in the 3-step groups. However, a higher degree of polymerization did not lead to superior shear bond strength. This finding indicates that the clinical performance of orthodontic adhesives is governed by a complex interplay of various factors beyond the bulk property of DC. Furthermore, composites with a two-step system can be a good clinical alternative for orthodontic treatments due to their adequate bond strength. Shear Bond Strength Degree of Conversion Orthodontic Adhesives FTIR Spectroscopy Dental Composite In Vitro Study Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Background The efficacy and efficiency of fixed orthodontic therapy are fundamentally reliant on the stability and durability of the bond between orthodontic brackets and the enamel surface ( 1 – 3 ).Bond failure is a common clinical complication that can prolong treatment duration, increase chair-side time, and impose additional costs( 4 ). Therefore, achieving an adequate bond strength is a primary objective( 5 ). The clinically accepted range for shear bond strength (SBS), established by Reynolds to be between 6 and 8 MPa, is considered optimal to withstand masticatory forces without risking enamel damage during debonding( 6 ). The evolution of dental materials has led to various orthodontic adhesive systems, broadly classified into conventional and simplified systems. Conventional three-step systems, such as Transbond XT and Brace Paste, involve sequential application of an acid etchant, a primer, and a resin composite( 7 ). While clinically successful, this method is technique-sensitive, particularly to moisture contamination(11 − 8). To address this, simplified "no-primer" or self-adhering composites, such as Orthocem and GC Orthoconnect, have emerged (14 − 12). These systems incorporate acidic functional monomers into the composite paste, eliminating the separate primer step to streamline the clinical workflow and reduce potential procedural errors.(19 − 15). The performance of these resin-based adhesives is dictated by several key material properties. The Degree of Conversion (DC) is a fundamental measure of polymerization efficiency, representing the percentage of monomer double bonds (C = C) converted into single bonds (C − C) to form a polymer network( 20 ). Insufficient DC can compromise mechanical properties and raise biocompatibility concerns due to the potential leaching of unreacted monomers(24 − 21). Shear Bond Strength (SBS), conversely, is a direct measure of the adhesive's mechanical performance at the bond interface( 25 , 26 ) ( 7 ). A logical assumption is that a more completely polymerized resin (higher DC) would result in higher mechanical strength (higher SBS). However, the literature examining this direct relationship in orthodontic adhesives is limited and presents conflicting findings. Some studies suggest a positive correlation, while others find no significant association, indicating a more complex interplay( 27 , 28 ). Therefore, the objective of this in vitro study was to evaluate and compare the SBS and DC of four commercially available orthodontic adhesives, representing both conventional and no-primer systems. The null hypothesis was that there is no significant correlation between shear bond strength and degree of conversion in the tested adhesives. Materials and methods Study design and specimen preparation This in vitro laboratory investigation was conducted after receiving approval from the research ethics committee of Alborz University of Medical Sciences. A total of 60 sound human premolar teeth, extracted for orthodontic purposes, were collected. Teeth with intact buccal enamel, free from caries, cracks, or restorations, were included. The teeth were cleaned and stored in a 0.1% thymol solution for two weeks for disinfection. Prior to bonding, the buccal surface of each tooth was polished for 20 seconds with a non-fluoridated, oil-free pumice slurry, then rinsed and dried. The 60 teeth were randomly allocated into four experimental groups (n = 15). Materials and bonding procedures Four orthodontic adhesive systems were evaluated: Group A : Transbond XT (3M Unitek, Monrovia, CA, USA) – Conventional. Group B : Brace Paste (American Orthodontics, Sheboygan, WI, USA) – Conventional. Group C : Orthocem (FGM Dental Group, Joinville, SC, Brazil) – No-primer. Group D : GC Orthoconnect (GC Corporation, Tokyo, Japan) – No-primer. Stainless steel premolar brackets (MBT prescription, 0.022-inch slot, Mini-Master Series, American Orthodontics) were used for all specimens. All bonding procedures were performed by a single operator according to manufacturers' instructions, using a light-curing unit (Woodpecker LED.D, Guilin, China). Groups A (Transbond XT) and B (Brace Paste) : Enamel was etched with 37% phosphoric acid for 15 seconds, rinsed, and dried. A thin layer of the respective primer was applied. The composite paste was applied to the bracket base, positioned, and light-cured for 20 seconds (Transbond XT) or 10 seconds (Brace Paste). Groups C (Orthocem) and D (GC Orthoconnect) : Enamel was etched with 37% phosphoric acid for 30 seconds, rinsed, and dried. No primer was used. The composite paste was applied to the bracket base, positioned, and light-cured for 20 seconds (10 seconds mesially and 10 seconds distally). Artificial aging All bonded specimens were stored for 24 hours in an incubator at 37°C. Subsequently, they were subjected to 3,000 thermal cycles in a thermocycling machine (Vafaei C-300, Iran) between water baths at 5°C and 55°C, with a 30-second dwell time. Shear bond strength (SBS) testing Each tooth was mounted in a block of self-curing acrylic resin. SBS testing was performed using a universal testing machine (UTM, Model 2050, Zwick/Roell, Ulm, Germany). A shear force was applied at the bracket-enamel interface at a crosshead speed of 0.5 mm/min until failure (Fig. 1 ). SBS was calculated in Megapascals (MPa) using the formula: SBS(MPa) = Force(N)/BracketBaseArea(mm2). Adhesive remnant index (ARI) assessment After debonding, the enamel surface was examined under a stereomicroscope (Nikon SMZ800, Japan) at 10x magnification. The Adhesive Remnant Index (ARI) was scored by a single, blinded evaluator on a scale of 0 to 3, where 0 indicates no adhesive remaining on the tooth and 3 indicates 100% of the adhesive remaining . Degree of conversion (DC) analysis Due to material retrieval challenges, the sample size for DC analysis was ten specimens per group (n = 10). Residual composite was scraped from the bracket bases, pulverized, ...and analyzed using a Fourier-Transform Infrared (FTIR) spectrometer (Nicolet iS10, Thermo Fisher Scientific, Waltham, MA, USA) (Fig. 2 ). The percentage of DC was calculated by comparing the absorbance peak intensity of the aliphatic C = C bond (1635 cm⁻¹) against the stable aromatic C...C bond (1608 cm⁻¹) as an internal standard, using the following formula : $$\:\text{DC\%=100×}\left[\text{1-}\frac{{\text{R}}_{\text{polymerized}}}{{\text{R}}_{\text{unpolymerized}}}\right]$$ Statistical analysis Data were analyzed using SPSS software (Version 27, IBM Corp.). Normality was confirmed with the Kolmogorov-Smirnov test. One-way ANOVA and Tukey’s HSD post-hoc test were used to compare mean SBS and DC values. Pearson's correlation coefficient was used to assess the relationship between SBS and DC. Fisher's exact test was used for ARI scores. The level of statistical significance was set at α = 0.05. Results All results reported are based on the subset of specimens (n = 10 per group) used for both SBS and DC measurements for consistency in the correlation analysis. Shear bond strength (SBS) One-way ANOVA revealed a statistically significant difference in mean SBS values among the four groups (p < 0.001). The descriptive statistics are presented in Table 1 . The GC Orthoconnect group showed the highest mean SBS (23.66 ± 5.77 MPa), while the Orthocem group showed the lowest (10.95 ± 3.31 MPa). Table 1 Descriptive statistics for shear bond strength (SBS) and degree of conversion (DC) (n = 10 per group). Adhesive Group Mean, SD SBS(MPa) Min (SBS) Max (SBS) Mean,SD DC (%) Min (DC) Max (DC) Transbond XT 16.77 ± 3.20 11.46 21.85 58.7 ± 9.9 49 76 Brace Paste 11.98 ± 2.97 8.91 17.13 69.1 ± 7.8 53 77 Orthocem 10.95 ± 3.31 5.43 15.55 79.0 ± 13.8 55 95 GC Orthoconnect 23.66 ± 5.77 14.41 33.95 67.9 ± 15.0 54 94 Tukey's post-hoc test (Table 2 ) showed that GC Orthoconnect had a significantly higher SBS than all other groups (p < 0.01). The mean SBS of Transbond XT was significantly higher than Brace Paste (p = 0.05) and Orthocem (p = 0.012). No significant difference was found between Brace Paste and Orthocem (p = 0.93). The distribution of SBS values is visualized in Fig. 3 and Fig. 4 . Table 2 Results of pairwise comparisons (Tukey's HSD) for SBS and DC. Comparison Mean Difference (SBS) p-value (SBS) Mean Difference (DC) p-value (DC) Transbond XT vs. Brace Paste 4.79 0.050 -10.4 0.23 Transbond XT vs. Orthocem 5.82 0.012 -20.3 0.003 Transbond XT vs. GC Orthoconnect -6.88 0.002 -9.2 0.33 Brace Paste vs. Orthocem 1.03 0.930 -9.9 0.27 Brace Paste vs. GC Orthoconnect -11.67 < 0.001 1.2 0.99 Orthocem vs. GC Orthoconnect -12.70 < 0.001 11.1 0.18 Degree of conversion (DC) A statistically significant difference was also found in mean DC among the groups (p = 0.007), with descriptive statistics shown in Table 1 . The Orthocem group yielded the highest mean DC (79.0 ± 13.8%), while the Transbond XT group had the lowest (58.7 ± 9.9%). Pairwise comparisons (Table 2 ) indicated the only statistically significant difference was between Orthocem and Transbond XT (p = 0.003). The mean DC values are visualized in Fig. 5 . Correlation between SBS and DC Pearson correlation analysis found no statistically significant linear relationship between SBS and DC for any of the four adhesive groups tested (p > 0.05 for all groups), as detailed in Table 3 . Table 3 Pearson correlation analysis between shear bond strength (SBS) and degree of conversion (DC). Adhesive Group Pearson Correlation Coefficient (R) p-value Interpretation Transbond XT 0.51 0.13 Not Significant Brace Paste 0.47 0.16 Not Significant Orthocem 0.49 0.14 Not Significant GC Orthoconnect 0.39 0.26 Not Significant Adhesive remnant index (ARI) Fisher's exact test revealed a statistically significant difference in the distribution of ARI scores among the groups (p < 0.001). The conventional systems, Brace Paste and Transbond XT, predominantly exhibited higher ARI scores (scores 2 and 3), indicating failure at the bracket-adhesive interface. In contrast, the Orthocem group showed a higher frequency of lower scores (scores 0 and 1), suggesting failure at the adhesive-enamel interface( 11 ). The detailed distribution is shown in Table 4 and visualized in Fig. 6 . Table 4 Frequency distribution of adhesive remnant index (ARI) scores (n = 10 per group). Adhesive Group ARI Score 0 (n, %) ARI Score 1 (n, %) ARI Score 2 (n, %) ARI Score 3 (n, %) Transbond XT 0 (0%) 3 (30%) 4 (40%) 3 (30%) Brace Paste 0 (0%) 0 (0%) 4 (40%) 6 (60%) Orthocem 1 (10%) 9 (90%) 0 (0%) 0 (0%) GC Orthoconnect 0 (0%) 3 (30%) 6 (60%) 1 (10%) Discussion One of the reasons for the success of fixed orthodontic treatment is the bond strength of orthodontic brackets to tooth enamel. Weaker bond strength can lead to repeated failures of the enamel-bracket bond ( 29 ), while higher bond strength can cause damage to the tooth surface during the debonding procedure. The bond strength of orthodontic brackets to teeth must be given serious consideration, as their detachment can delay the treatment process and impose additional costs on the patient ( 4 ). A successful bond of brackets to enamel depends on several factors, such as the method of tooth preparation, the cross-sectional area of the brackets, and the type of composite used ( 30 ). Thus, the type of composite used also affects the bond strength, as it can either increase or decrease it. For various types of composites, the more complete the polymerization, the higher the mechanical properties ( 31 ). This study evaluated the correlation between the degree of conversion and shear bond strength of four types of orthodontic adhesives with two different protocols. The "clinically desirable" shear bond strength range was traditionally defined by Reynolds as being between 6 and 8 megapascals (MPa) ( 6 ). This range is considered an optimal balance that both prevents premature bond failure and minimizes the risk of enamel damage during debonding. In the present study, all four adhesive groups tested showed a mean bond strength much higher than this minimum threshold, with the lowest value for Orthocem and the highest for GC Orthoconnect. The study by Sharma et al. (2014) reported similar results ( 5 ). They compared the shear bond strength and adhesive remnant index of four different orthodontic composites. Their method used the conventional etching technique with 37% phosphoric acid for 30 seconds and a crosshead speed of 1 mm/min. The mean shear bond strength for Transbond XT was similar to the findings of the present study for this composite. Similarly, the study by Lon et al. in 2018 reported comparable results ( 32 ). Their method used 45 permanent bovine incisors, and the composites studied were Transbond XT and Orthobond. Their results showed that the mean shear bond strength for the Transbond XT adhesive was very close to that of the present study. The study by Esmaeili et al. in 2023 also had results consistent with the present study ( 33 ). They evaluated the effect of a universal bonding agent on the shear bond strength of OrthoCem and GC Ortho Connect. Their results showed that the mean SBS for Orthocem was very close to our findings, and the mean SBS for GC Ortho Connect without a universal bonding agent was reported to be very high, which is consistent with our results. The study by Scribante et al. in 2013 also had results consistent with the present study ( 18 ). Their results showed that the mean shear bond strength for the Transbond XT adhesive with "anchor pylons" bracket bases was very close to the value reported for this composite in our study. However, the same study reported two different values for Orthocem depending on the bracket base type, both of which differ from the results of the present study. The reasons for this difference could be the crosshead speed (1 mm/min vs. 0.5 mm/min in our study) and the type of bracket used. Furthermore, the results of the study by Perković et al. in 2023 were not consistent with the present study ( 11 ). They found that the bond strength of Transbond XT was slightly higher than GC Orthoconnect, with no statistically significant difference between the two groups. In contrast, our study found the bond strength of GC Orthoconnect to be much higher than Transbond XT. The reason for this difference could be the lack of oral environment simulation or thermocycling in their study. In this study, the Adhesive Remnant Index (ARI) was also examined. Higher ARI scores are more desirable, indicating more adhesive remaining on the enamel and reducing the risk of damage during the debonding process. The results showed that the highest amount of remaining adhesive was for Brace Paste composite (Group B) and the lowest was for Orthocem composite (Group C). The results of the present study were similar to the findings of Lon et al. in 2018 ( 32 ), who found that the amount of remaining adhesive for Transbond XT (a three-step system) was significantly higher than for Orthocem (a two-step system). The results were also similar to the study by Shalini et al. in 2023 ( 34 ), which showed that conventional three-step systems (Transbond XT and Brace Paste) had a higher amount of remaining adhesive. However, the results of the study by Sharma et al. in 2014 were contrary to the present study ( 5 ), as they reported that 15% of the Transbond XT group had ARI scores of 0, which was not observed in our study. This difference could be due to the use of different models of debonding machines. Furthermore, the results of the study by Perković et al. in 2023 were not consistent with the present study ( 11 ). They found no significant difference in ARI between Transbond XT and GC Ortho connect, with most samples in both groups having a score of 1. This is in contrast to our study, where a significant difference was observed between the groups. The durability of the bracket-to-enamel bond is heavily influenced by the quality of the polymerization process, which is quantitatively evaluated by the "Degree of Conversion" (DC). DC values in dental composites are typically reported in the range of 40% to 80% ( 21 ). In this study, the DC of four orthodontic composites was evaluated using FTIR. The statistical findings indicate that Orthocem showed a higher degree of conversion, while the DC of Transbond XT was lower than the other study groups. The DC of Brace Paste and GC Orthoconnect was in a similar functional range between these two. The results obtained in this research were largely similar to the study by Louis et al. in 2023 ( 35 ), who reported a similar DC for TransBond XT and attributed it to its chemical composition. The results were also similar to the research by Wichai et al. in 2018 ( 36 ), where the DC of Transbond XT after 24 hours was similar to our findings. Also, in the research by Perkovic et al. in 2023, the results were similar to ours ( 11 ), as they found that GC OrthoConnect had a significantly higher DC than Transbond XT. However, the results obtained in this research are contrary to the study by Ibrahim et al. in 2023 ( 37 ), who reported a different DC for Transbond XT. The reason for this difference could be variations in methodology, such as the distance of the light source during curing. One of the most important findings of this research was the absence of a statistically significant correlation between shear bond strength (SBS) and degree of conversion (DC) in all four adhesive groups studied. This finding contradicts the fundamental principle in materials science that a resin with more complete polymerization (higher DC) should exhibit superior mechanical properties. This indicates that the relationship between these two variables is more complex than a simple linear relationship. The results of the study by Perkovic et al. in 2023 for Transbond XT are consistent with the findings of the present study ( 11 ). Their study found a moderate positive correlation for GC Ortho Connect, while for Transbond XT, almost no significant correlation was observed. The study by Ibrahim et al. in 2023 was also consistent with our results ( 37 ). They found a positive and significant correlation for three other adhesives, but for Transbond XT, the correlation was positive but not significant. However, the results of the study by Masood et al. were not consistent with our results ( 38 ). They concluded that the observed increase in bond strength with longer curing times could be explained by the simultaneous increase in the degree of conversion, which implicitly suggests a positive relationship. The main reason for the difference in results could be due to different analytical approaches. The present study directly evaluated the statistical correlation between SBS and DC values for each sample, whereas the study by Masood et al. compared the mean SBS and DC between different groups based on curing time. Conclusions Within the limitations of this in vitro study, the following conclusions can be drawn: All four tested orthodontic adhesives provided shear bond strengths adequate for clinical use. Significant differences were observed in both SBS and DC among the materials, with GC Orthoconnect showing the highest bond strength and Orthocem the highest degree of conversion. No statistically significant correlation was found between the degree of conversion and shear bond strength for any of the tested adhesives. This result suggests that for contemporary orthodontic adhesives, high shear bond strength is not solely dependent on achieving a high degree of conversion. Clinical performance is determined by a more complex interplay of factors, including chemical composition and its ability to form a robust interface with etched enamel. Abbreviations ARI Adhesive Remnant Index DC Degree of Conversion FTIR Fourier-Transform Infrared SBS Shear Bond Strength UTM Universal Testing Machine Declarations Ethics approval and consent to participate This study was approved by the research ethics committee of Alborz University of Medical Sciences. All teeth were collected after patients provided informed consent for their use in research, in accordance with the Declaration of Helsinki. Consent for publication Not applicable. Competing interests The authors declare that they have no competing interests. Funding This research received no external funding. Author Contribution N.S.D. conducted the research, collected and analyzed the data, and wrote the manuscript. M.M. and M.E. supervised the project and contributed to the study design. M.S. provided advisory support. S.E. performed the statistical analysis. All authors read and approved the final manuscript. Acknowledgement The author would like to thank the Clinical Research Development Unit of Alborz University of Medical Sciences. Availability of data and materials The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. References Huang Z-M, Gopal R, Fujihara K, Ramakrishna S, Loh P, Foong W, et al. 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Correlation between shear bond strength and degree of conversion of four orthodontic adhesives. Erbil Dent J (EDJ). 2023;6(2):151–9. Masood TM, Abbassy MA, Bakry AS, Matar NY, Hassan AH. Fourier-transform infrared spectroscopy/attenuated total reflectance analysis for the degree of conversion and shear bond strength of Transbond XT adhesive system. Clinical, cosmetic and investigational dentistry. 2018:275–80. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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. 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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-7754985","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":534118507,"identity":"13454b94-3a35-400a-aaaa-8053f72bb667","order_by":0,"name":"Manijeh Mohammadian¹","email":"","orcid":"","institution":"Iran University of Medical Sciences","correspondingAuthor":false,"prefix":"","firstName":"Manijeh","middleName":"","lastName":"Mohammadian¹","suffix":""},{"id":534118508,"identity":"e49cf52f-b709-4394-a2a9-362c066cbec2","order_by":1,"name":"Nadia Sohrabi Derakhshan²","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABA0lEQVRIiWNgGAWjYHACgwMMbECKh4eBGUjJAVkkajEmSgsDspbEBkJazNkPbzzwo8wmn7/n7OHPBTV30jccP3vwwQcGOzndBuxaLHvSCg72nEuznHG2L016xrFnuRvO5CUbzmBINjY7gMsjOQYHeNsOGzCc5zFj5mE7nLvhQI6ZNA/DgcRtuLScf2Nw8G/bfwP58zzGn3n+HU4HihDQciPH4DBv2wEDg7M9BtJA6xKAIoS0PCs4LHMu2cDwzBkzad6+w4Yzb7wxNpxhgMcv55M3f3xTZmcgdyYH6LBvh+X5zucYPvhQYSeHSwsmUACrNCBWOQjIN5CiehSMglEwCkYCAAAhGWSG4BqGhgAAAABJRU5ErkJggg==","orcid":"","institution":"Alborz University of Medical Sciences","correspondingAuthor":true,"prefix":"","firstName":"Nadia","middleName":"Sohrabi","lastName":"Derakhshan²","suffix":""},{"id":534118509,"identity":"d433407e-c2c3-4db3-b026-e2842711a9b1","order_by":2,"name":"Masoumeh Esmaeili³","email":"","orcid":"","institution":"Alborz University of Medical 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14:58:22","extension":"xml","order_by":18,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":96652,"visible":true,"origin":"","legend":"","description":"","filename":"d99016a6435a4819ae1cf7cdb77fca1a1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/4ae223315836c82c6d1096e2.xml"},{"id":94461076,"identity":"fe87b5f6-974e-4f2e-a0b9-e7c0ac704900","added_by":"auto","created_at":"2025-10-27 14:58:45","extension":"html","order_by":19,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":107406,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/d43ce8f422ac537f9ff31f0b.html"},{"id":94461449,"identity":"c72dd8e5-4eff-4e97-bd78-bbd48494ee15","added_by":"auto","created_at":"2025-10-27 14:59:33","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":24020,"visible":true,"origin":"","legend":"\u003cp\u003eA mounted specimen positioned in the universal testing machine (UTM) for shear bond strength\u003c/p\u003e","description":"","filename":"Picture1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/f2ff5282712062c780143cea.jpg"},{"id":94461121,"identity":"6c81e939-5450-4e15-9d11-e3112977b290","added_by":"auto","created_at":"2025-10-27 14:58:54","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":72822,"visible":true,"origin":"","legend":"\u003cp\u003eThe Fourier-Transform Infrared (FT-IR) spectrometer used for the degree of conversion analysis.\u003c/p\u003e","description":"","filename":"Picture2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/198826d2e1667c439646b6f6.jpg"},{"id":94461233,"identity":"0dcc6b3b-5a2b-4333-be13-77f017a8b360","added_by":"auto","created_at":"2025-10-27 14:59:05","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":51977,"visible":true,"origin":"","legend":"\u003cp\u003eBox plot comparison of shear bond strength (MPa) for the four adhesive groups.\u003c/p\u003e","description":"","filename":"Picture3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/4cd2924a10b8e9a495d4a375.jpg"},{"id":94461016,"identity":"e2994ab5-f20c-40ad-9ef0-a929f5736f2d","added_by":"auto","created_at":"2025-10-27 14:58:37","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":51841,"visible":true,"origin":"","legend":"\u003cp\u003eBar chart showing the mean shear bond strength (MPa) with standard deviation for each adhesive group.\u003c/p\u003e","description":"","filename":"Picture4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/624a4a297e38d8110f091188.jpg"},{"id":94461122,"identity":"732b549a-912e-4353-9df5-e862687f3da7","added_by":"auto","created_at":"2025-10-27 14:58:54","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":56420,"visible":true,"origin":"","legend":"\u003cp\u003eBar chart showing the mean degree of conversion (%) with standard deviation for each adhesive group.\u003c/p\u003e","description":"","filename":"Picture5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/046d0c2206698fc8f78fadc1.jpg"},{"id":94460869,"identity":"4f813487-e8ad-4bbe-b85a-df52df078ea0","added_by":"auto","created_at":"2025-10-27 14:58:00","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":60317,"visible":true,"origin":"","legend":"\u003cp\u003eStacked bar chart illustrating the frequency distribution of Adhesive Remnant Index (ARI) scores for each adhesive group.\u003c/p\u003e","description":"","filename":"Picture6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/d00d8d3524c62cb4b7c3cd35.jpg"},{"id":105044072,"identity":"68001534-3222-4429-9048-ce87c4ec6df0","added_by":"auto","created_at":"2026-03-20 08:27:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1078271,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7754985/v1/7c86f3e3-5f4c-4ca3-b83a-46d47484ef35.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluation of the correlation between degree of conversion and shear bond strength in four contemporary orthodontic adhesives: an in vitro study","fulltext":[{"header":"Background","content":"\u003cp\u003eThe efficacy and efficiency of fixed orthodontic therapy are fundamentally reliant on the stability and durability of the bond between orthodontic brackets and the enamel surface (\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e).Bond failure is a common clinical complication that can prolong treatment duration, increase chair-side time, and impose additional costs(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Therefore, achieving an adequate bond strength is a primary objective(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). The clinically accepted range for shear bond strength (SBS), established by Reynolds to be between 6 and 8 MPa, is considered optimal to withstand masticatory forces without risking enamel damage during debonding(\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe evolution of dental materials has led to various orthodontic adhesive systems, broadly classified into conventional and simplified systems. Conventional three-step systems, such as Transbond XT and Brace Paste, involve sequential application of an acid etchant, a primer, and a resin composite(\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e). While clinically successful, this method is technique-sensitive, particularly to moisture contamination(11\u0026thinsp;\u0026minus;\u0026thinsp;8). To address this, simplified \"no-primer\" or self-adhering composites, such as Orthocem and GC Orthoconnect, have emerged (14\u0026thinsp;\u0026minus;\u0026thinsp;12). These systems incorporate acidic functional monomers into the composite paste, eliminating the separate primer step to streamline the clinical workflow and reduce potential procedural errors.(19\u0026thinsp;\u0026minus;\u0026thinsp;15).\u003c/p\u003e\u003cp\u003eThe performance of these resin-based adhesives is dictated by several key material properties. The Degree of Conversion (DC) is a fundamental measure of polymerization efficiency, representing the percentage of monomer double bonds (C\u0026thinsp;=\u0026thinsp;C) converted into single bonds (C\u0026thinsp;\u0026minus;\u0026thinsp;C) to form a polymer network(\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e). Insufficient DC can compromise mechanical properties and raise biocompatibility concerns due to the potential leaching of unreacted monomers(24\u0026thinsp;\u0026minus;\u0026thinsp;21). Shear Bond Strength (SBS), conversely, is a direct measure of the adhesive's mechanical performance at the bond interface(\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e) (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eA logical assumption is that a more completely polymerized resin (higher DC) would result in higher mechanical strength (higher SBS). However, the literature examining this direct relationship in orthodontic adhesives is limited and presents conflicting findings. Some studies suggest a positive correlation, while others find no significant association, indicating a more complex interplay(\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eTherefore, the objective of this \u003cem\u003ein vitro\u003c/em\u003e study was to evaluate and compare the SBS and DC of four commercially available orthodontic adhesives, representing both conventional and no-primer systems. The null hypothesis was that there is no significant correlation between shear bond strength and degree of conversion in the tested adhesives.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003eStudy design and specimen preparation\u003c/p\u003e\u003cp\u003eThis in vitro laboratory investigation was conducted after receiving approval from the research ethics committee of Alborz University of Medical Sciences. A total of 60 sound human premolar teeth, extracted for orthodontic purposes, were collected. Teeth with intact buccal enamel, free from caries, cracks, or restorations, were included. The teeth were cleaned and stored in a 0.1% thymol solution for two weeks for disinfection.\u003c/p\u003e\u003cp\u003ePrior to bonding, the buccal surface of each tooth was polished for 20 seconds with a non-fluoridated, oil-free pumice slurry, then rinsed and dried. The 60 teeth were randomly allocated into four experimental groups (n\u0026thinsp;=\u0026thinsp;15).\u003c/p\u003e\u003cp\u003eMaterials and bonding procedures\u003c/p\u003e\u003cp\u003eFour orthodontic adhesive systems were evaluated:\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eGroup A\u003c/b\u003e: Transbond XT (3M Unitek, Monrovia, CA, USA) \u0026ndash; Conventional.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eGroup B\u003c/b\u003e: Brace Paste (American Orthodontics, Sheboygan, WI, USA) \u0026ndash; Conventional.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eGroup C\u003c/b\u003e: Orthocem (FGM Dental Group, Joinville, SC, Brazil) \u0026ndash; No-primer.\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eGroup D\u003c/b\u003e: GC Orthoconnect (GC Corporation, Tokyo, Japan) \u0026ndash; No-primer.\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eStainless steel premolar brackets (MBT prescription, 0.022-inch slot, Mini-Master Series, American Orthodontics) were used for all specimens. All bonding procedures were performed by a single operator according to manufacturers' instructions, using a light-curing unit (Woodpecker LED.D, Guilin, China).\u003c/p\u003e\u003cp\u003e\u003cul\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eGroups A (Transbond XT) and B (Brace Paste)\u003c/b\u003e: Enamel was etched with 37% phosphoric acid for 15 seconds, rinsed, and dried. A thin layer of the respective primer was applied. The composite paste was applied to the bracket base, positioned, and light-cured for 20 seconds (Transbond XT) or 10 seconds (Brace Paste).\u003c/p\u003e\u003c/li\u003e\u003cli\u003e\u003cp\u003e\u003cb\u003eGroups C (Orthocem) and D (GC Orthoconnect)\u003c/b\u003e: Enamel was etched with 37% phosphoric acid for 30 seconds, rinsed, and dried. No primer was used. The composite paste was applied to the bracket base, positioned, and light-cured for 20 seconds (10 seconds mesially and 10 seconds distally).\u003c/p\u003e\u003c/li\u003e\u003c/ul\u003e\u003c/p\u003e\u003cp\u003eArtificial aging\u003c/p\u003e\u003cp\u003eAll bonded specimens were stored for 24 hours in an incubator at 37\u0026deg;C. Subsequently, they were subjected to 3,000 thermal cycles in a thermocycling machine (Vafaei C-300, Iran) between water baths at 5\u0026deg;C and 55\u0026deg;C, with a 30-second dwell time.\u003c/p\u003e\u003cp\u003eShear bond strength (SBS) testing\u003c/p\u003e\u003cp\u003eEach tooth was mounted in a block of self-curing acrylic resin. SBS testing was performed using a universal testing machine (UTM, Model 2050, Zwick/Roell, Ulm, Germany). A shear force was applied at the bracket-enamel interface at a crosshead speed of 0.5 mm/min until failure (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). SBS was calculated in Megapascals (MPa) using the formula: SBS(MPa)\u0026thinsp;=\u0026thinsp;Force(N)/BracketBaseArea(mm2).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAdhesive remnant index (ARI) assessment\u003c/p\u003e\u003cp\u003eAfter debonding, the enamel surface was examined under a stereomicroscope (Nikon SMZ800, Japan) at 10x magnification. The Adhesive Remnant Index (ARI) was scored by a single, blinded evaluator on a scale of 0 to 3, where 0 indicates no adhesive remaining on the tooth and 3 indicates 100% of the adhesive remaining .\u003c/p\u003e\u003cp\u003eDegree of conversion (DC) analysis\u003c/p\u003e\u003cp\u003eDue to material retrieval challenges, the sample size for DC analysis was ten specimens per group (n\u0026thinsp;=\u0026thinsp;10). Residual composite was scraped from the bracket bases, pulverized, ...and analyzed using a Fourier-Transform Infrared (FTIR) spectrometer (Nicolet iS10, Thermo Fisher Scientific, Waltham, MA, USA) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe percentage of DC was calculated by comparing the absorbance peak intensity of the aliphatic C\u0026thinsp;=\u0026thinsp;C bond (1635 cm⁻\u0026sup1;) against the stable aromatic C...C bond (1608 cm⁻\u0026sup1;) as an internal standard, using the following formula :\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\text{DC\\%=100\u0026times;}\\left[\\text{1-}\\frac{{\\text{R}}_{\\text{polymerized}}}{{\\text{R}}_{\\text{unpolymerized}}}\\right]$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eStatistical analysis\u003c/h2\u003e\u003cp\u003eData were analyzed using SPSS software (Version 27, IBM Corp.). Normality was confirmed with the Kolmogorov-Smirnov test. One-way ANOVA and Tukey\u0026rsquo;s HSD post-hoc test were used to compare mean SBS and DC values. Pearson's correlation coefficient was used to assess the relationship between SBS and DC. Fisher's exact test was used for ARI scores. The level of statistical significance was set at α\u0026thinsp;=\u0026thinsp;0.05.\u003c/p\u003e\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eAll results reported are based on the subset of specimens (n\u0026thinsp;=\u0026thinsp;10 per group) used for both SBS and DC measurements for consistency in the correlation analysis.\u003c/p\u003e\u003cp\u003eShear bond strength (SBS)\u003c/p\u003e\u003cp\u003eOne-way ANOVA revealed a statistically significant difference in mean SBS values among the four groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The descriptive statistics are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The GC Orthoconnect group showed the highest mean SBS (23.66\u0026thinsp;\u0026plusmn;\u0026thinsp;5.77 MPa), while the Orthocem group showed the lowest (10.95\u0026thinsp;\u0026plusmn;\u0026thinsp;3.31 MPa).\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 statistics for shear bond strength (SBS) and degree of conversion (DC) (n\u0026thinsp;=\u0026thinsp;10 per group).\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAdhesive Group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean, SD SBS(MPa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMin (SBS)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMax (SBS)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMean,SD DC (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eMin (DC)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eMax (DC)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransbond XT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e16.77\u0026thinsp;\u0026plusmn;\u0026thinsp;3.20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e11.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e21.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e\u003cp\u003e58.7\u0026thinsp;\u0026plusmn;\u0026thinsp;9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e76\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBrace Paste\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e11.98\u0026thinsp;\u0026plusmn;\u0026thinsp;2.97\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8.91\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e17.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e\u003cp\u003e69.1\u0026thinsp;\u0026plusmn;\u0026thinsp;7.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e77\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrthocem\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e10.95\u0026thinsp;\u0026plusmn;\u0026thinsp;3.31\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e15.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e\u003cp\u003e79.0\u0026thinsp;\u0026plusmn;\u0026thinsp;13.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e95\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGC Orthoconnect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e\u003cp\u003e23.66\u0026thinsp;\u0026plusmn;\u0026thinsp;5.77\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e33.95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e\u003cp\u003e67.9\u0026thinsp;\u0026plusmn;\u0026thinsp;15.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e94\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\u003eTukey's post-hoc test (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) showed that GC Orthoconnect had a significantly higher SBS than all other groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01). The mean SBS of Transbond XT was significantly higher than Brace Paste (p\u0026thinsp;=\u0026thinsp;0.05) and Orthocem (p\u0026thinsp;=\u0026thinsp;0.012). No significant difference was found between Brace Paste and Orthocem (p\u0026thinsp;=\u0026thinsp;0.93). The distribution of SBS values is visualized in Fig.\u0026nbsp;3 and Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eResults of pairwise comparisons (Tukey's HSD) for SBS and DC.\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=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eComparison\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMean Difference (SBS)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ep-value (SBS)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean Difference (DC)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ep-value (DC)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransbond XT vs. Brace Paste\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e4.79\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.050\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-10.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.23\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransbond XT vs. Orthocem\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.012\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-20.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.003\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransbond XT vs. GC Orthoconnect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-6.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-9.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.33\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBrace Paste vs. Orthocem\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.930\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e-9.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.27\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBrace Paste vs. GC Orthoconnect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-11.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.99\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrthocem vs. GC Orthoconnect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e-12.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e11.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e0.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDegree of conversion (DC)\u003c/p\u003e\u003cp\u003eA statistically significant difference was also found in mean DC among the groups (p\u0026thinsp;=\u0026thinsp;0.007), with descriptive statistics shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The Orthocem group yielded the highest mean DC (79.0\u0026thinsp;\u0026plusmn;\u0026thinsp;13.8%), while the Transbond XT group had the lowest (58.7\u0026thinsp;\u0026plusmn;\u0026thinsp;9.9%). Pairwise comparisons (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) indicated the only statistically significant difference was between Orthocem and Transbond XT (p\u0026thinsp;=\u0026thinsp;0.003). The mean DC values are visualized in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCorrelation between SBS and DC\u003c/p\u003e\u003cp\u003ePearson correlation analysis found no statistically significant linear relationship between SBS and DC for any of the four adhesive groups tested (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05 for all groups), as detailed in 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\u003ePearson correlation analysis between shear bond strength (SBS) and degree of conversion (DC).\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=\"char\" char=\".\" 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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAdhesive Group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePearson Correlation Coefficient (R)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eInterpretation\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransbond XT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNot Significant\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBrace Paste\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNot Significant\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrthocem\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNot Significant\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGC Orthoconnect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.26\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNot Significant\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eAdhesive remnant index (ARI)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFisher's exact test revealed a statistically significant difference in the distribution of ARI scores among the groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). The conventional systems, Brace Paste and Transbond XT, predominantly exhibited higher ARI scores (scores 2 and 3), indicating failure at the bracket-adhesive interface. In contrast, the Orthocem group showed a higher frequency of lower scores (scores 0 and 1), suggesting failure at the adhesive-enamel interface(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). The detailed distribution is shown in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and visualized in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFrequency distribution of adhesive remnant index (ARI) scores (n\u0026thinsp;=\u0026thinsp;10 per group).\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=\"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\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAdhesive Group\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eARI Score 0 (n, %)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eARI Score 1 (n, %)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eARI Score 2 (n, %)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eARI Score 3 (n, %)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTransbond XT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (30%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4 (40%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e3 (30%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBrace Paste\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e4 (40%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e6 (60%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOrthocem\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1 (10%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e9 (90%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGC Orthoconnect\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e0 (0%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3 (30%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e6 (60%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e1 (10%)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOne of the reasons for the success of fixed orthodontic treatment is the bond strength of orthodontic brackets to tooth enamel. Weaker bond strength can lead to repeated failures of the enamel-bracket bond (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e), while higher bond strength can cause damage to the tooth surface during the debonding procedure. The bond strength of orthodontic brackets to teeth must be given serious consideration, as their detachment can delay the treatment process and impose additional costs on the patient (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). A successful bond of brackets to enamel depends on several factors, such as the method of tooth preparation, the cross-sectional area of the brackets, and the type of composite used (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e). Thus, the type of composite used also affects the bond strength, as it can either increase or decrease it. For various types of composites, the more complete the polymerization, the higher the mechanical properties (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e). This study evaluated the correlation between the degree of conversion and shear bond strength of four types of orthodontic adhesives with two different protocols.\u003c/p\u003e\u003cp\u003eThe \"clinically desirable\" shear bond strength range was traditionally defined by Reynolds as being between 6 and 8 megapascals (MPa) (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e). This range is considered an optimal balance that both prevents premature bond failure and minimizes the risk of enamel damage during debonding. In the present study, all four adhesive groups tested showed a mean bond strength much higher than this minimum threshold, with the lowest value for Orthocem and the highest for GC Orthoconnect.\u003c/p\u003e\u003cp\u003eThe study by Sharma et al. (2014) reported similar results (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). They compared the shear bond strength and adhesive remnant index of four different orthodontic composites. Their method used the conventional etching technique with 37% phosphoric acid for 30 seconds and a crosshead speed of 1 mm/min. The mean shear bond strength for Transbond XT was similar to the findings of the present study for this composite. Similarly, the study by Lon et al. in 2018 reported comparable results (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e). Their method used 45 permanent bovine incisors, and the composites studied were Transbond XT and Orthobond. Their results showed that the mean shear bond strength for the Transbond XT adhesive was very close to that of the present study. The study by Esmaeili et al. in 2023 also had results consistent with the present study (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). They evaluated the effect of a universal bonding agent on the shear bond strength of OrthoCem and GC Ortho Connect. Their results showed that the mean SBS for Orthocem was very close to our findings, and the mean SBS for GC Ortho Connect without a universal bonding agent was reported to be very high, which is consistent with our results. The study by Scribante et al. in 2013 also had results consistent with the present study (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). Their results showed that the mean shear bond strength for the Transbond XT adhesive with \"anchor pylons\" bracket bases was very close to the value reported for this composite in our study.\u003c/p\u003e\u003cp\u003eHowever, the same study reported two different values for Orthocem depending on the bracket base type, both of which differ from the results of the present study. The reasons for this difference could be the crosshead speed (1 mm/min vs. 0.5 mm/min in our study) and the type of bracket used. Furthermore, the results of the study by Perković et al. in 2023 were not consistent with the present study (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). They found that the bond strength of Transbond XT was slightly higher than GC Orthoconnect, with no statistically significant difference between the two groups. In contrast, our study found the bond strength of GC Orthoconnect to be much higher than Transbond XT. The reason for this difference could be the lack of oral environment simulation or thermocycling in their study.\u003c/p\u003e\u003cp\u003eIn this study, the Adhesive Remnant Index (ARI) was also examined. Higher ARI scores are more desirable, indicating more adhesive remaining on the enamel and reducing the risk of damage during the debonding process. The results showed that the highest amount of remaining adhesive was for Brace Paste composite (Group B) and the lowest was for Orthocem composite (Group C). The results of the present study were similar to the findings of Lon et al. in 2018 (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e), who found that the amount of remaining adhesive for Transbond XT (a three-step system) was significantly higher than for Orthocem (a two-step system). The results were also similar to the study by Shalini et al. in 2023 (\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e), which showed that conventional three-step systems (Transbond XT and Brace Paste) had a higher amount of remaining adhesive. However, the results of the study by Sharma et al. in 2014 were contrary to the present study (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e), as they reported that 15% of the Transbond XT group had ARI scores of 0, which was not observed in our study. This difference could be due to the use of different models of debonding machines. Furthermore, the results of the study by Perković et al. in 2023 were not consistent with the present study (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). They found no significant difference in ARI between Transbond XT and GC Ortho connect, with most samples in both groups having a score of 1. This is in contrast to our study, where a significant difference was observed between the groups.\u003c/p\u003e\u003cp\u003eThe durability of the bracket-to-enamel bond is heavily influenced by the quality of the polymerization process, which is quantitatively evaluated by the \"Degree of Conversion\" (DC). DC values in dental composites are typically reported in the range of 40% to 80% (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). In this study, the DC of four orthodontic composites was evaluated using FTIR. The statistical findings indicate that Orthocem showed a higher degree of conversion, while the DC of Transbond XT was lower than the other study groups. The DC of Brace Paste and GC Orthoconnect was in a similar functional range between these two. The results obtained in this research were largely similar to the study by Louis et al. in 2023 (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e), who reported a similar DC for TransBond XT and attributed it to its chemical composition. The results were also similar to the research by Wichai et al. in 2018 (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e), where the DC of Transbond XT after 24 hours was similar to our findings. Also, in the research by Perkovic et al. in 2023, the results were similar to ours (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e), as they found that GC OrthoConnect had a significantly higher DC than Transbond XT. However, the results obtained in this research are contrary to the study by Ibrahim et al. in 2023 (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e), who reported a different DC for Transbond XT. The reason for this difference could be variations in methodology, such as the distance of the light source during curing.\u003c/p\u003e\u003cp\u003eOne of the most important findings of this research was the absence of a statistically significant correlation between shear bond strength (SBS) and degree of conversion (DC) in all four adhesive groups studied. This finding contradicts the fundamental principle in materials science that a resin with more complete polymerization (higher DC) should exhibit superior mechanical properties. This indicates that the relationship between these two variables is more complex than a simple linear relationship. The results of the study by Perkovic et al. in 2023 for Transbond XT are consistent with the findings of the present study (\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). Their study found a moderate positive correlation for GC Ortho Connect, while for Transbond XT, almost no significant correlation was observed. The study by Ibrahim et al. in 2023 was also consistent with our results (\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e). They found a positive and significant correlation for three other adhesives, but for Transbond XT, the correlation was positive but not significant. However, the results of the study by Masood et al. were not consistent with our results (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). They concluded that the observed increase in bond strength with longer curing times could be explained by the simultaneous increase in the degree of conversion, which implicitly suggests a positive relationship. The main reason for the difference in results could be due to different analytical approaches. The present study directly evaluated the statistical correlation between SBS and DC values for each sample, whereas the study by Masood et al. compared the mean SBS and DC between different groups based on curing time.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eWithin the limitations of this \u003cem\u003ein vitro\u003c/em\u003e study, the following conclusions can be drawn:\u003c/p\u003e\u003cp\u003e\u003col\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eAll four tested orthodontic adhesives provided shear bond strengths adequate for clinical use.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eSignificant differences were observed in both SBS and DC among the materials, with GC Orthoconnect showing the highest bond strength and Orthocem the highest degree of conversion.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eNo statistically significant correlation was found between the degree of conversion and shear bond strength for any of the tested adhesives.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003cspan\u003e\u003cli\u003e\u003cp\u003eThis result suggests that for contemporary orthodontic adhesives, high shear bond strength is not solely dependent on achieving a high degree of conversion. Clinical performance is determined by a more complex interplay of factors, including chemical composition and its ability to form a robust interface with etched enamel.\u003c/p\u003e\u003c/li\u003e\u003c/span\u003e\u003c/ol\u003e\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eARI\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eAdhesive Remnant Index\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eDC\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eDegree of Conversion\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eFTIR\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eFourier-Transform Infrared\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eSBS\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eShear Bond Strength\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eUTM\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eUniversal Testing Machine\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003cp\u003eThis study was approved by the research ethics committee of Alborz University of Medical Sciences. All teeth were collected after patients provided informed consent for their use in research, in accordance with the Declaration of Helsinki.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003cp\u003eNot applicable.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003ch2\u003eCompeting interests\u003c/h2\u003e\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis research received no external funding.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eN.S.D. conducted the research, collected and analyzed the data, and wrote the manuscript. M.M. and M.E. supervised the project and contributed to the study design. M.S. provided advisory support. S.E. performed the statistical analysis. All authors read and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe author would like to thank the Clinical Research Development Unit of Alborz University of Medical Sciences.\u003c/p\u003e\u003ch2\u003eAvailability of data and materials\u003c/h2\u003e\u003cp\u003eThe datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cdiv class=\"Heading\"\u003e\u003cli\u003e\u003cspan\u003eHuang Z-M, Gopal R, Fujihara K, Ramakrishna S, Loh P, Foong W, et al. Fabrication of a new composite orthodontic archwire and validation by a bridging micromechanics model. Biomaterials. 2003;24(17):2941\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShaw W, Addy M, Ray C. Dental and social effects of malocclusion and effectiveness of orthodontic treatment: a review. Commun Dent Oral Epidemiol. 1980;8(1):36\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eChristou T, Betlej A, Aswad N, Ogdon D, Kau CH. Clinical effectiveness of orthodontic treatment on smile esthetics: a systematic review. Clin Cosmet Invest dentistry. 2019:89\u0026ndash;101.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBrightman LJ, Terezhalmy GT, Greenwell H, Jacobs M, Enlow DH. The effects of a 0.12% chlorhexidine gluconate mouthrinse on orthodontic patients aged 11 through 17 with established gingivitis. Am J Orthod Dentofac Orthop. 1991;100(4):324\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSharma S, Tandon P, Nagar A, Singh GP, Singh A, Chugh VK. A comparison of shear bond strength of orthodontic brackets bonded with four different orthodontic adhesives. J orthodontic Sci. 2014;3(2):29\u0026ndash;33.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eReynolds I, Von Fraunhofer J. Direct bonding of orthodontic brackets\u0026mdash;a comparative study of adhesives. Br J Orthod. 1976;3(3):143\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDadgar S, Armin M, Namdar P, Yazdani Charati J, Koohi Z. Shear bond strength of metallic and ceramic brackets bonded with two-step and three-step light cure adhesives. J Mazandaran Univ Med Sci. 2020;30(183):53\u0026ndash;61.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCarstensen W. The effects of different phosphoric acid concentrations on surface enamel. Angle Orthod. 1992;62(1):51\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBates D, Retief D, Jamison HC, Denys F. Effects of acid etch parameters on enamel topography and composite resin-enamel bond strength. Pediatr Dent. 1982;4(2):106\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBishara SE, Soliman MM, Oonsombat C, Laffoon JF, Ajlouni R. The effect of variation in mesh-base design on the shear bond strength of orthodontic brackets. Angle Orthod. 2004;74(3):400\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePerković V, Šimunović Aničić M, Lughi V, Pozzan L, Meštrović S, Turco G. Correlation of shear bond strength and degree of conversion in conventional and self-adhesive systems used in orthodontic bonding procedures. Biomedicines. 2023;11(5):1252.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eOk U, Aksakalli S, Eren E, Kechagia N. Single-component orthodontic adhesives: comparison of the clinical and in vitro performance. Clin Oral Invest. 2021;25:3987\u0026ndash;99.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eElkalza AR, Mostafa D. Laboratory evaluation of shear bond strength of three different bonding systems for orthodontic brackets. Egypt Orthodontic J. 2018;53(June 2018):55\u0026ndash;60.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSamadi F, RahmatiKamel M, Arash V, Khafri S, Abolghasemzadeh F. Scanning electron microscope and shear bond strength analysis of Biofix and Orthocem two-step fluoridated orthodontic adhesives on human enamel. Casp J Dent Res. 2019;8(2):16\u0026ndash;24.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eJoseph R, Ahmed N, Bhat KRR. Evaluation of shear bond strength of a primer incorporated orthodontic composite resin: an in-vitro study. Cureus. 2022;14(4).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBilen HB, \u0026Ccedil;okakoğlu S. Effects of one-step orthodontic adhesive on microleakage and bracket bond strength: An in vitro comparative study. Int Orthod. 2020;18(2):366\u0026ndash;73.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBahrami S, Azarbayejani S, Kazemian M. Comparative evaluation of shear bond strength and debonding properties of GC Ortho Connect composite and Transbond XT composite. Australasian Orthodontic J. 2023;39(1):35\u0026ndash;41.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eScribante A, Sfondrini MF, Fraticelli D, Daina P, Tamagnone A, Gandini P. The influence of no-primer adhesives and anchor pylons bracket bases on shear bond strength of orthodontic brackets. Biomed Res Int. 2013;2013(1):315023.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBecker S. An In Vitro Comparison of Shear Bond Strength Between Two Orthodontic Light-Curable Adhesive Pastes. West Virginia University; 2021.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRahiotis C, editor. editor Degree of cure and monomer leaching from orthodontic adhesive resins: In vitro and in vivo evidence. Seminars in Orthodontics. Elsevier; 2010.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003e\u0026Ccedil;\u0026ouml;rek\u0026ccedil;i B, Malko\u0026ccedil; S, \u0026Ouml;zt\u0026uuml;rk B, G\u0026uuml;nd\u0026uuml;z B, Toy E. Polymerization capacity of orthodontic composites analyzed by Fourier transform infrared spectroscopy. Am J Orthod Dentofac Orthop. 2011;139(4):e299\u0026ndash;304.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eThompson L, Miller E, Bowles W. Materials science: leaching of unpolymerized materials from orthodontic bonding resin. J Dent Res. 1982;61(8):989\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlrahlah A, Silikas N, Watts D. Post-cure depth of cure of bulk fill dental resin-composites. Dent Mater. 2014;30(2):149\u0026ndash;54.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eUysal T, Basciftci FA, Sener Y, Botsali MS, Demir A. Conventional and high intensity halogen light effects on water sorption and microhardness of orthodontic adhesives. Angle Orthod. 2008;78(1):134\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAlvarez D, Barmak AB, Rossouw PE, Michelogiannakis D. Comparison of shear bond strength of orthodontic brackets bonded to human teeth with and without fluorotic enamel: A systematic review and meta-analysis of experimental in vitro studies. Orthod Craniofac Res. 2023;26(2):141\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFonseca-Silva T, Otoni RP, Magalh\u0026atilde;es AAM, Ramos GM, Gomes TR, Rego TM, et al. Comparative analysis of shear bond strength of steel and ceramic orthodontic brackets bonded with six different orthodontic adhesives. Int J Odontostom. 2020;14(4):658\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHenbest N. Orthodontic bracket bond strength and resin composite adhesive degree of conversion associated with type of curing unit and total energy. University of Missouri-Kansas City; 2013.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePonikvar MJ. Effect of delayed polymerization time and bracket manipulation on orthodontic bracket bonding. University of Missouri-Kansas City; 2014.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRead M, O'Brien K. A clinical trial of an indirect bonding technique with a visible light-cured adhesive. Am J Orthod Dentofac Orthop. 1990;98(3):259\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGange P. The evolution of bonding in orthodontics. Am J Orthod Dentofac Orthop. 2015;147(4):S56\u0026ndash;63.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNewman GV. Epoxy adhesives for orthodontic attachments: progress report. Am J Orthod. 1965;51(12):901\u0026ndash;12.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLon LFS, Knop LAH, Shintcovsk RL, Guariza Filho O, Raveli DB. Shear bond strength of three different bonding systems for orthodontic brackets. Brazilian J Oral Sci. 2018;17:e18138\u0026ndash;e.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEsmaily M, Mohammadian M, Faghfourian N. Evaluation of the effects of the universal bond on the shear bond strength of orthodontic brackets bonded with 2 types of composites containing primers. Iran J Orthod. 2023;18(1):1\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShalini S, Jha A, Kashyap P, Gupta P, Rajbhoj S, Bhandari S. A Comparison of the Shear Bond Strength of Orthodontic Brackets Bonded With Different Orthodontic Adhesives. Cureus. 2023;15(5).\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLouis C, Shetty P, Siddharth R, Quadras DD, Mandolil GS, Rai EA. Comparison of the Degree of Conversion of Orthodontic Adhesive when Cured with Different Curing Lights. Kerala Dent J. 2023;46(3):84\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWichai W, Nimcharoensuk K, Anuwongnukroh N, Dechkunakorn S, Roongrujimek P. Degree of conversion of three light-cured orthodontic adhesives. Key Eng Mater. 2018;777:577\u0026ndash;81.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eIbrahim HT, Hassan BA. Correlation between shear bond strength and degree of conversion of four orthodontic adhesives. Erbil Dent J (EDJ). 2023;6(2):151\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMasood TM, Abbassy MA, Bakry AS, Matar NY, Hassan AH. Fourier-transform infrared spectroscopy/attenuated total reflectance analysis for the degree of conversion and shear bond strength of Transbond XT adhesive system. Clinical, cosmetic and investigational dentistry. 2018:275\u0026ndash;80.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Shear Bond Strength, Degree of Conversion, Orthodontic Adhesives, FTIR Spectroscopy, Dental Composite, In Vitro Study","lastPublishedDoi":"10.21203/rs.3.rs-7754985/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7754985/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e\u003cp\u003eThe success of fixed orthodontic treatment is critically dependent on the mechanical integrity of the bracket-enamel bond. Shear Bond Strength (SBS) and Degree of Conversion (DC) are two fundamental properties governing the performance of orthodontic adhesives. This study aimed to evaluate the relationship between DC and SBS in four contemporary orthodontic adhesives, including conventional and no-primer systems.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e\u003cp\u003eSixty sound human premolars were randomly allocated into four groups (n\u0026thinsp;=\u0026thinsp;15). Metal brackets were bonded using one of four adhesives: Transbond XT (conventional), Brace Paste (conventional), Orthocem (no-primer), or GC Orthoconnect (no-primer). Then specimens were stored for 24 hours and subjected to 3,000 thermal cycles. SBS was measured using a universal testing machine. The DC of residual adhesive was determined using Fourier-Transform Infrared (FTIR) Spectroscopy on a subset of ten specimens per group. The Adhesive Remnant Index (ARI) was assessed using stereomicroscopy. Data were analyzed using ANOVA, Tukey\u0026rsquo;s HSD test, Pearson's correlation, and Fisher's exact test (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e\u003cp\u003eStatistically significant differences were observed among the groups for both mean SBS (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) and mean DC (p\u0026thinsp;=\u0026thinsp;0.007). GC Orthoconnect exhibited the highest SBS (23.66\u0026thinsp;\u0026plusmn;\u0026thinsp;5.77 MPa), while Orthocem showed the lowest (10.95\u0026thinsp;\u0026plusmn;\u0026thinsp;3.31 MPa). Conversely, Orthocem demonstrated the highest DC (79.0\u0026thinsp;\u0026plusmn;\u0026thinsp;13.8%), whereas Transbond XT had the lowest (58.7\u0026thinsp;\u0026plusmn;\u0026thinsp;9.9%). Pearson's correlation test revealed no statistically significant correlation between SBS and DC for any of the tested adhesives (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). ARI score distributions also differed significantly among the groups (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e\u003cp\u003eAll four adhesives provided clinically acceptable bond strength, and the adhesive remnant was greater in the 3-step groups. However, a higher degree of polymerization did not lead to superior shear bond strength. This finding indicates that the clinical performance of orthodontic adhesives is governed by a complex interplay of various factors beyond the bulk property of DC. Furthermore, composites with a two-step system can be a good clinical alternative for orthodontic treatments due to their adequate bond strength.\u003c/p\u003e","manuscriptTitle":"Evaluation of the correlation between degree of conversion and shear bond strength in four contemporary orthodontic adhesives: an in vitro study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-27 12:18:02","doi":"10.21203/rs.3.rs-7754985/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a0331da6-17ef-47c8-98de-2bc4d767f48d","owner":[],"postedDate":"October 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-20T08:26:27+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-27 12:18:02","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7754985","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7754985","identity":"rs-7754985","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}