Comparison of Enamel Surface Integrity after De-Bracketing as Affected by Seven Different Orthodontic Residual Cement Removal Systems

This study used seven different adhesive removal systems to evaluate and compare enamel surface integrity, heat generation, and time consumed during residual cement removal after de-bracketing. The sample size was 140 human premolars. Teeth were cleaned, mounted, and prepared for orthodontic bracket bonding. Brackets were then debonded using bracket-removing pliers. Teeth were randomly assigned to seven groups based on the residual cement removal system: Group 1: Stainbuster bur, Group 2: Renew diamond bur #129, Group 3: Renew carbide bur, Group 4: OneGloss Complete system, Group 5: Sof-Lex system, Group 6: Enhance Finishing and PoGo Polishing complete kit, and Group 7: Renew friction grip points. The enamel surface was evaluated for roughness before bracketing and after residual cement removal using surface profilometry. The time taken for cement removal was recorded using a digital timer, and heat generation was measured using a laser thermometer before and after cement removal. One-way ANOVA compared the pre- and post-values for enamel surface roughness, temperature, and time consumed. When comparing the difference between the post- and pre-finishing roughness using one-way ANOVA, the Renew diamond bur produced the roughest enamel surface post-removal with a mean of 4.716 μm, while the Sof-Lex recorded the lowest at 0.760 μm. The highest mean temperature was recorded with the Stainbuster bur at 5.545 °C, and the lowest temperature was recorded with the Enhance bur at 2.260 °C. The time for cement removal was the shortest with the Enhance bur at 12.2 s, whereas the time was the longest with the Renew diamond bur at 30.4 s. In conclusion, all the residual cement removal systems used in this clinically simulated study were not able to restore the original enamel surface smoothness. However, the 3M Sof-Lex produced the lowest enamel roughness but with more time consumption and heat generation. When selecting the best residual cement removal system to be used, clinicians should weigh the merits and demerits of each system based on the clinical judgement of the operator.


Introduction
Orthodontists face a strategic challenge following the completion of orthodontic cases treated with fixed appliances.The challenge orthodontists face revolves around the restoration of the enamel surface to its original texture, appearance, smoothness, and condition to match its pre-orthodontic therapy state.A roughened enamel surface not only inhibits grip points [Reliance Orthodontics, Itasca, IL, USA], the Renew Finishing System with a carbide bur [Reliance Orthodontics], and the Renew Finishing System with a diamond bur #129 [Reliance Orthodontics].Consequently, this study aimed to evaluate and compare the integrity of the enamel surface, heat generation, and time consumed during the process of residual cement removal after de-bracketing using seven different contemporary adhesive removal systems to find the most effective and efficient method of removing residual cement.This study's tested null hypothesis postulates that there are no significant variations between the seven different examined adhesive removal systems regarding the quality of enamel surface roughness, the heat generated within the teeth, or the procedure duration timing.

Materials and Methods
This study was conducted in accordance with the Declaration of Helsinki and approved by the Research Ethics Committee of the Research Center, King Saud University (E-21-6414).
Sample collection: Freshly extracted for orthodontic treatment, sound human premolar teeth were collected.
The following inclusion criteria were used during sample collection: caries-free, hypoplastic-defect-free, and restoration-free premolars were included.Fractured or cracked teeth and teeth with morphological abnormalities were excluded.The collected teeth were stored in saline at 7 • C up until the time of testing.
A sample of 140 human premolars (n = 140) was used according to the sample size determination: At alpha = 0.05 with effect (1-b) = 0.9 (power) and size ES = 0.4, the total sample size should be at least 140 and 20 selected randomly for each group.
The teeth were randomly divided into seven groups (n = 20 teeth per group), and each group was assigned to a different finishing system, Table 1.To establish a baseline for the surface roughness data, the teeth were positioned within a vinyl polysiloxane putty mold in preparation for scanning using a scanning electron microscope (SEM) (JSM 6610LV; Jeol, Tokyo, Japan).The SEM parameters employed included 15 kV voltage and a 10 mm working distance.To highlight specific regions of interest on the facial tooth surface, magnifications of 30× were chosen and representative SEM scans were captured in the pre-bracket bonding state; see Figure 1.
Before surface profilometry, the teeth were prepared by submerging them in an ultrasonic cleaner containing distilled water for 15 min to remove any debris.They were then air-dried for 60 s.Subsequently, the samples were placed in the sample stage of a Q150R coating machine (QuorumTech, Laughton, UK) to apply a thin 10 nm gold film onto the sample surface during a 1 min run.A Contour GT-K 3D optical microscope (Bruker, Billerica, MA, USA), utilizing 3D non-contact surface metrology with interferometry, was employed for surface profilometer characterization and measurement.interest on the facial tooth surface, magnifications of 30× were chosen and representative SEM scans were captured in the pre-bracket bonding state; see Figure 1.Before surface profilometry, the teeth were prepared by submerging them in an ultrasonic cleaner containing distilled water for 15 min to remove any debris.They were then air-dried for 60 s.Subsequently, the samples were placed in the sample stage of a Q150R coating machine (QuorumTech, Laughton, UK) to apply a thin 10 nm gold film onto the sample surface during a 1 min run.A Contour GT-K 3D optical microscope (Bruker, Billerica, MA, USA), utilizing 3D non-contact surface metrology with interferometry, was employed for surface profilometer characterization and measurement.
The samples were subjected to vertical scan interferometry using a 5× Michelson magnification lens with a 1 mm × 1 mm field of view, Gaussian regression filter, scan speed of 1×, and thresholding set at 4. The samples were positioned on the stage and manually adjusted to obtain an image on the monitor screen.The microscope was controlled using Vision 64 software (Bruker), which managed the instrument settings, data analysis, and graphical output.The measurement was conducted via vertical scanning interferometry, making use of a broadband (typically white) light source suitable for measuring objects with rough surfaces and adjacent pixel height differences exceeding 135 nm.Each sample underwent three scans at different intervals, and the results were averaged to determine roughness.

Preparation of Teeth for Bracket Bonding
For tooth preparation, a 37% phosphoric acid gel was applied to the buccal enamel surface for 15 s, followed by a constant water rinse for 10 s and a 1 -s drying period using an oil-free air jet.Subsequently, to ensure uniform adhesive distribution, the adhesive (Transbond XT. adhesive, 3M Unitek, Monrovia, CA, USA) was applied to the mid region of the bracket's base (3M Victory Series Low Profile Bracket System), and proper pressure was applied to extrude any excess cement.The excess adhesive was removed from around the bracket using a dental explorer.The Transbond XT. adhesive was light cured on all sides of the bracket using an LED light cure unit for 20 s, as per the manufacturer recommendation.One operator carried out the bonding procedure of all brackets to the dental surfaces for the seven tested premolar groups.
The brackets were ultimately removed using a bracket removal plier (3M Unitek removing pliers).Then, each group was administered for residual cement removal using one of the seven tested residual cement removal systems; see Table 1.
A single individual (an orthodontics specialist) performed the remnant cement removal procedure using each of the seven tested residual cement removal systems to ensure standardization and reduce variability.This procedure was performed over a period of 3 days, and the manufacturer's instructions were strictly adhered to for each cement removal system.The samples were subjected to vertical scan interferometry using a 5× Michelson magnification lens with a 1 mm × 1 mm field of view, Gaussian regression filter, scan speed of 1×, and thresholding set at 4. The samples were positioned on the stage and manually adjusted to obtain an image on the monitor screen.The microscope was controlled using Vision 64 software (Bruker), which managed the instrument settings, data analysis, and graphical output.The measurement was conducted via vertical scanning interferometry, making use of a broadband (typically white) light source suitable for measuring objects with rough surfaces and adjacent pixel height differences exceeding 135 nm.Each sample underwent three scans at different intervals, and the results were averaged to determine roughness.

Preparation of Teeth for Bracket Bonding
For tooth preparation, a 37% phosphoric acid gel was applied to the buccal enamel surface for 15 s, followed by a constant water rinse for 10 s and a 1 -s drying period using an oil-free air jet.Subsequently, to ensure uniform adhesive distribution, the adhesive (Transbond XT. adhesive, 3M Unitek, Monrovia, CA, USA) was applied to the mid region of the bracket's base (3M Victory Series Low Profile Bracket System), and proper pressure was applied to extrude any excess cement.The excess adhesive was removed from around the bracket using a dental explorer.The Transbond XT. adhesive was light cured on all sides of the bracket using an LED light cure unit for 20 s, as per the manufacturer recommendation.One operator carried out the bonding procedure of all brackets to the dental surfaces for the seven tested premolar groups.
The brackets were ultimately removed using a bracket removal plier (3M Unitek removing pliers).Then, each group was administered for residual cement removal using one of the seven tested residual cement removal systems; see Table 1.
A single individual (an orthodontics specialist) performed the remnant cement removal procedure using each of the seven tested residual cement removal systems to ensure standardization and reduce variability.This procedure was performed over a period of 3 days, and the manufacturer's instructions were strictly adhered to for each cement removal system.
The duration of each residual cement removal technique was recorded using a digital timer, and heat generation was measured using a laser thermometer before and after cement removal.The collected data were statistically analyzed.

Surface Roughness Final Measurement (Post-Bracket Debonding)
Post-residual cement removal, enamel roughness measurements were performed in a similar routine to the pre-operative enamel surface roughness measurements and representative SEM scans were captured post-bracket debonding; see Figure 1.

Statistical Analysis
The data were statistically analyzed using the IBM-SPSS software (Version 26.0, 2019).One-way ANOVA compared the pre-and post-residual adhesive removal enamel surface roughness values, pre-and post-residual adhesive removal teeth temperature values, and the time consumed for residual adhesive removal.

Results
No significant difference was found in the baseline roughness between the seven groups (p = 0.201); see Table 2.When comparing the difference between the post-and pre-finishing roughness using one-way ANOVA, the mean value of the Renew diamond bur (4.716 µm) was the highest, followed by the Enhance bur (1.773 µm), the Renew carbide bur (1.585 µm), the Renew finishing points (1.349 µm), the OneGloss system (1.023 µm), Stainbuster (1.005 µm), and the Sof-Lex (0.760 µm), Figure 2, Table 3.
The duration of each residual cement removal technique was recorded using a digital timer, and heat generation was measured using a laser thermometer before and after cement removal.The collected data were statistically analyzed.

Surface Roughness Final Measurement (Post-Bracket Debonding)
Post-residual cement removal, enamel roughness measurements were performed in a similar routine to the pre-operative enamel surface roughness measurements and representative SEM scans were captured post-bracket debonding; see Figure 1.

Statistical Analysis
The data were statistically analyzed using the IBM-SPSS software (Version 26.0, 2019).One-way ANOVA compared the pre-and post-residual adhesive removal enamel surface roughness values, pre-and post-residual adhesive removal teeth temperature values, and the time consumed for residual adhesive removal.

Results
No significant difference was found in the baseline roughness between the seven groups (p = 0.201); see Table 2.When comparing the difference between the post-and pre-finishing roughness using one-way ANOVA, the mean value of the Renew diamond bur (4.716 μm) was the highest, followed by the Enhance bur (1.773 μm), the Renew carbide bur (1.585 μm), the Renew finishing points (1.349 μm), the OneGloss system (1.023 μm), Stainbuster (1.005 μm), and the Sof-Lex (0.760 μm), Figure 2, Table 3.There was a significant difference between the pre-and post-finishing temperature using one-way ANOVA (p < 0.000); see Table 4 There was a significant difference between the pre-and post-finishing temperature using one-way ANOVA (p < 0.000); see Table 4.The mean temperature difference with the Stainbuster (5.545 °C) was the highest, followed by the Renew diamond bur (5.485 °C), the Sof-Lex (5.230 °C), the Renew Finishing Points (3.360 °C), the OneGloss (3.245 °C), the Renew carbide bur (3.115 °C), and the Enhance bur (2.260 °C), Figure 3, Table 5.The Enhance bur took the least amount of working time to remove residual cement (12.2 s), followed by the Renew carbide bur (15.6 s), the OneGloss (17.5 s), the Renew Finishing System Points (19.4 s), the Stainbuster (27.6 s), the Sof-Lex (28.5 s), and the Renew diamond bur (30.4 s), Figure 4, Table 6.The Enhance bur took the least amount of working time to remove residual cement (12.2 s), followed by the Renew carbide bur (15.6 s), the OneGloss (17.5 s), the Renew Finishing System Points (19.4 s), the Stainbuster (27.6 s), the Sof-Lex (28.5 s), and the Renew diamond bur (30.4 s), Figure 4, Table 6.The mean temperature difference with the Stainbuster (5.545 °C) was the highest, followed by the Renew diamond bur (5.485 °C), the Sof-Lex (5.230 °C), the Renew Finishing Points (3.360 °C), the OneGloss (3.245 °C), the Renew carbide bur (3.115 °C), and the Enhance bur (2.260 °C), Figure 3, Table 5.The Enhance bur took the least amount of working time to remove residual cement (12.2 s), followed by the Renew carbide bur (15.6 s), the OneGloss (17.5 s), the Renew Finishing System Points (19.4 s), the Stainbuster (27.6 s), the Sof-Lex (28.5 s), and the Renew diamond bur (30.4 s), Figure 4, Table 6.

Discussion
This study investigated the impact of seven different evidence-based approaches to orthodontic residual cement removal systems on enamel surface after de-bracketing regarding the three variables of enamel surface roughness, temperature of teeth in terms of the heat generated during residual cement removal, and the working time taken for the removal process.The results of this study recorded significant differences between the seven tested residual cement removal systems in terms of the three tested variables: induced enamel surface roughness; heat generation within the tooth during the residual cement removal process; as well as the time taken for completion of the procedure.Accordingly, the tested null hypothesis was rejected.
The responsibility of orthodontists in the selection of an appropriate technique for adhesive removal after bracket debonding with the aim of minimizing iatrogenic damage and scratches on the enamel surface, as well as preservation of enamel surface smoothness, is highlighted in this research [26].Orthodontists are advised to choose a protocol for adhesive remnant removal based on scientific evidence in order to accomplish a conservative and effective outcome post-fixed orthodontic treatment.
Regarding the results of the first tested variable, enamel surface roughness, no significant differences were recorded between the teeth assigned to the seven different tested groups in the original enamel condition before bracket bonding.Similar results were reported by other studies [27,28].Various studies have reported different degrees of enamel loss during the removal of residual adhesive material, ranging from a few micrometers to around 50 µm [28][29][30][31].Enamel thickness is stated to range from 1500 µm to 2000 µm; accordingly, it was reported that enamel loss of around 60 µm is not considered detrimental to the tooth [32].Nonetheless, preserving the fluoride enriched surface layer of enamel is crucial when removing residual composite, due to the fact that the highest concentration of fluoride lies at the surface and decreases immensely after the first 20 µm of enamel thickness [32,33].All of the seven tested residual cement removal systems in this study recorded post-de-bracketing surface roughness values well below the 20 µm range.
This research indicated that the different methods used for the removal of residual adhesive resulted in different degrees of enamel loss; this was in accordance with other studies [34,35].It was observed in this study that all seven tested finishing systems had an effect on the enamel tooth surface, and none of the residual cement removal systems succeeded in maintaining the original shape and smoothness of the enamel surface compared to the enamel condition prior to the de-bracketing condition.The results of this study showed that the post-de-bracketing enamel surface roughness was constantly higher than the pre-de-bracketing roughness in all groups, indicating that no residual cement removal method was fully capable of restoring the enamel surface back to its original state.This was in accordance with several studies that proved that none of their tested remnant cement removal systems restored the enamel surface roughness to the original pretesting status [8,9,18,24,28,31].This could be attributed to the fact that adhesive resin tags are capable of penetrating the enamel up to 50 µm during enamel conditioning and bonding procedures [31].
Significant differences were noticed between the seven tested residual cement removal systems in terms of the surface roughness introduced into the enamel surface.The Sof-Lex system group demonstrated the smoothest post-finishing enamel surface.The Sof-Lex was found to significantly reduce surface roughness, as evidenced by the lowest enamel roughness measurements (2.335 µm), compared to the other tested methods.The Stainbuster system recorded the second lowest enamel roughness measurements (2.599 µm).The OneGloss system recorded the third lowest enamel roughness measurements (2.649 µm).Renew Finishing System Points recorded the fourth lowest enamel roughness measurements (3.299 µm).The Renew carbide bur system recorded the fifth lowest enamel roughness measurements (3.367 µm).The Enhance Finishing and PoGo Polishing system recorded the sixth lowest enamel roughness measurements (3.416 µm), whereas the Renew #129 diamond bur system was found to produce the highest levels of roughness on the enamel surface (4.716 µm), as evidenced by the surface profilometry and scanning electron microscopy (SEM) results.In related context, Bansal et al. [28] suggested that the Sof-Lex system ranked second after the Mylar matrix in terms of smoothing, while Shah et al. [24] reported that the Sof-Lex system also secured the second position, following the Enhance Finishing system.
Concerning the results of the second tested variable, the increase in tooth temperature following adhesive cement remnant removal, it was found that there was a noticeable increase in tooth temperature following the finishing procedure.Similar to the enamel surface roughness results obtained in this study, significant differences were noticed between the seven tested residual cement removal systems in terms of the heat generated during the removal of residual cement and finishing procedures.This is in agreement with other studies that reported increase in tooth temperature due to heat generation during the residual cement removal procedure [31,32,36].The Stainbuster bur system group exhibited the highest degree of heat generation with a difference between the tooth temperature before and after residual cement removal of 5.545 • C. The Renew #129 diamond bur system recorded the second highest degree of heat generation (5.485 • C).The Sof-Lex system group demonstrated the third highest degree of heat generation (5.230 • C).The Renew Finishing system points group displayed the fourth highest degree of heat generation (3.360 • C).The OneGloss system group presented the fifth highest degree of heat generation (3.245 • C), while both the Renew carbide bur and the Enhance Finishing and PoGo Polishing systems recorded the lowest degree of heat generation at 3.115 • C and 2.260 • C, conversely.
Relating to the results of the third tested variable, the working time and efficiency of the seven tested residual cement removal systems, it was reported that the recorded working time of the procedure of the removal of the remaining cement varied across the seven tested systems.This study's results of the different timings recorded for the different residual cement removal systems were in agreement with other studies that reported variations in the residual adhesive removal procedure according to the system used [37,38].The duration of the procedure of removal of the remaining cement was the longest with the Renew #129 diamond bur system requiring 30.40 s for residual cement removal.The Sof-Lex system group reported the second longest operating time (28.55 s).The Stainbuster bur system group recorded the third longest operating time (27.65 s).The Renew Finishing system points group presented the fourth longest operating time (19.40 s).The OneGloss system group showed the fifth longest operating time (17.55 s).The Renew carbide bur group revealed the sixth longest operating time (15.60 s).The Enhance Finishing and PoGo Polishing systems proved to be the least time-consuming, taking only 12.2 s for the whole duration of residual cement removal procedure.
The results of this study align with the current literature, documenting that none of the available residual cement removal techniques can completely remove cement remnants from dental tooth surfaces without causing some enamel damage.
The limitations of this study arise from the in vitro study design that prevents the evaluation of the dentinal reaction and pulpal response to the heat generated during the residual orthodontic adhesive removal.

Conclusions
Within the limitations of this study, all seven orthodontic residual cement removal methods were clinically satisfactory for residual orthodontic adhesive removal.
Nevertheless, none of the evaluated systems were able to completely restore the original enamel surface smoothness.
Yet, all seven orthodontic residual cement removal methods yielded a clinically suitable enamel surface roughness, the greatest range of which was well below the 20 µm range.
The 3M Sof-Lex system exhibited the lowest enamel roughness, but at the expense of being more time-consuming and generating higher heat levels compared to the six other residual cement removal systems.

Table 3 .
. Using ANOVA to compare groups by the average roughness.

Table 4 .
Pre-and post-residual cement removal teeth temperature means.

Table 4 .
Pre-and post-residual cement removal teeth temperature means.

Table 5 .
Using ANOVA to compare groups by the average temperature.

Table 6 .
Using ANOVA to compare groups by the average working time.