|Year : 2019 | Volume
| Issue : 1 | Page : 28-32
Enamel surface roughness evaluation after debonding ceramic brackets: Use of burs and abrasive systems for resin removal
Andréa Matinez Gobbi1, Alânia Agassis do Nascimento Dalla Valle2, Rodrigo De Carvalho Varella2, Jurandir Antonio Barbosa1, Roberta Tarkany Basting1
1 Department of Dental Materials and Restorative Dentistry, São Leopoldo Mandic Research Institute, Campinas, São Paulo, Brazil
2 IMED Dental School, Passo Fundo, RS, Brazil
|Date of Web Publication||27-Feb-2019|
Dr. Roberta Tarkany Basting
Faculdade São Leopoldo Mandic, Instituto De Pesquisas São Leopoldo Mandic, Área De Dentística, Rua José Rocha Junqueira, 13. Bairro Swift, Campinas, São Paulo
Source of Support: None, Conflict of Interest: None
Aim: This in vitro study aimed to evaluate enamel surface roughness after using burs and abrasive systems to remove residual resin after ceramic bracket debonding. Materials and Methods: Ceramic brackets (Abzil/3M) were bonded to the proximal surfaces of 40 sound premolars using an orthodontic bonding agent (Transbond XT/3M). After 30 days, brackets were debonded. All surfaces were classified according to adhesive remnant index, and then distributed into four groups (n = 10) for the finishing procedures: (G1) Komet H22GK bur at high speed, (G2) Komet H379AGK bur at low speed, (G3) Orthometric CF375R bur at high speed, (G4) Orthometric CB27 bur at low speed. All surfaces were polished using fine sandpaper and felt discs with diamond polishing paste (Diamond Excel/FGM). Enamel roughness was measured with a roughness meter in sequential mode at baseline (before bonding); after rest residual removal and polishing. Multiple comparisons were made using the Tukey–Kramer Test, with a significance level of 5%. Results: Analysis with mixed models for repeated measures, and the Tukey–Kramer test showed no significant difference in mean roughness values between groups (P = 0.6168) at each evaluation time. After finishing, the mean roughness values did not differ significantly from baseline values (P = 0.5565). After polishing, roughness values were significantly lower than in all other times (P < 0.0001) for all groups. Conclusions: Different burs used at high or low speed provided roughness values similar to those of sound enamel. However, polishing produced lower roughness values on enamel submitted to finishing only, also when compared with sound enamel.
Keywords: Dental enamel, orthodontics, resin cements
|How to cite this article:|
Gobbi AM, Valle AD, Varella RD, Barbosa JA, Basting RT. Enamel surface roughness evaluation after debonding ceramic brackets: Use of burs and abrasive systems for resin removal. J Int Oral Health 2019;11:28-32
|How to cite this URL:|
Gobbi AM, Valle AD, Varella RD, Barbosa JA, Basting RT. Enamel surface roughness evaluation after debonding ceramic brackets: Use of burs and abrasive systems for resin removal. J Int Oral Health [serial online] 2019 [cited 2020 Aug 5];11:28-32. Available from: http://www.jioh.org/text.asp?2019/11/1/28/253142
| Introduction|| |
The quest for a safe method to remove adhesive resin after bracket debonding has enabled the investigation of various instruments and procedures that allow better preservation of the enamel structure. Manual instruments such as bracket removing pliers have been used, as well as rotary instruments that use burs and finishing systems.,,,,, However, the incorrect or careless use of these procedures may lead to iatrogenic damage,,, resulting in changes in surface roughness, presence of microfissures and fractures, scratches, and depressions.,,,,,
The higher degree of enamel roughness reduces its brightness and reflectiveness; this may compromise the esthetic appearance of teeth and increase the risks of tooth staining and biofilm retention.,,,,,,, Furthermore, the presence of bonding material after bracket removal also contributes to biofilm accumulation that may lead to staining of this material and cause problems related to dental esthetics.
Although there is no consensus in the literature, one of the most common methods for removing adhesive remnants recommend the use of a low-speed tungsten carbide bur.,, However, some studies indicate the use of the tungsten carbide bus in a high-speed rotation. Subsequent polishing with instruments impregnated with abrasive diamond particles and aluminum oxide discs has also been used.,,,,,,,,,,,, The use of a bur followed by the use of finishing and polishing systems appear to be adequate for resin removal, and studies have verified that the sequential use of polishing procedures is superior than the application of a single procedure with regard to enamel surface roughness.,,,,,,
Among the burs for resin removal, those that have a conical or cylindrical shape and inactive tips may be indicated, because they remove the resin remnants more uniformly that pear- or oval-shaped burs. Pont et al. have emphasized the importance of using inactive tips, because they minimize gingival injuries; in addition, they have a safety bevel in transition from the head of the bur to its long axis, which eliminates the risk of making marks on the enamel. Aluminum oxide, polyester, and silicone rubber discs, followed by felt disks with diamond paste, are considered the best polishing systems because they improve the enamel surface smoothness and leave a flatter and more regular surface.,,
Considering that after orthodontic bracket removal, it would be important to use adequate burs and abrasives to remove the resin remnants, the question of whether the burs and abrasives used in this study were really adequate for removing orthodontic adhesive and restoring the initial surface smoothness of enamel should be evaluated. Thus, the aim of this in vitro study was to evaluate the enamel roughness after removal of the residual resin used for ceramic bracket bonding, with the use of composite removal by means of bur and abrasive systems, at different time intervals of evaluation (after finishing and after polishing). The null hypotheses to be tested were that there were no differences in enamel roughness after removal of the residual resin (1) by means of different removal systems, and (2) after finishing and after polishing removal systems.
| Materials and Methods|| |
This study was approved by the Ethics Committee (CAAE no. 64860317.8.0000.5374). For this study, 40 human premolars extracted for orthodontic purposes were used and were randomly distributed among the experimental groups (n = 10). The sample size was sufficient for this experimental design, as the G * Power software indicated an effect size higher than 0.80 for the variables “time intervals of evaluation,” “removal systems,” and the interaction for a 5% level of significance. A high-effect size for the variable “time intervals of evaluation” (f = 0.46) and for the interaction “time intervals of evaluation” × “removal systems” (f = 0.25) were also observed.
About 100 teeth were initially selected; the inclusion and exclusion criteria were applied by observing the coronal tooth surfaces under a stereoscopic lens at 40× magnification until an adequate number of teeth was obtained. According to the inclusion criteria for this initial stage, sound teeth with flat proximal (mesial or distal) surfaces were selected, on which the bracket bonding procedures would be performed. The teeth were stored in physiological solution for time interval of 2 months until they were used for bracket bonding.
The teeth were positioned with the flattest proximal surface (mesial or distal) selected, perpendicular to the horizontal plane, with the aid of a dental delineator (Steel ruler, Trident, Londrina, Paraná, Brazil). The roots were embedded in 4.5 cm Polyvinyl Chloride tubes with the use of colorless self-polymerizing acrylic resin (Jet Clássico, Campo Limpo Paulista, SP, Brazil).
The initial enamel surface roughness values were evaluated. For this purpose, an area measuring 3.5 mm × 2.5 mm was demarcated in the most central and flattest region of the selected proximal surface, with the use of graphite, to enable to evaluations, and bracket bonding procedures to be performed in the same areas. For the roughness evaluations, a portable roughness meter (Suftest SJ-210, Mitutoyo, Suzano, SP, Brazil) was used, and the mean roughness values (Ra) was obtained with application of a static load of 5 N and speed of 0.5 mm/s. A sequential cutoff point of 0.08 μm (micrometers) was used. In the delimited area, three measurements were made in different positions (vertical, horizontal, and transverse) to obtain the arithmetic mean value of the measurements obtained. At this time, another inclusion criterion was applied to the sample, thereby selecting the teeth with similar initial surface roughness values (mean = 0.23 μm and standard deviation = 0.04 μm), thus obtaining the 50 selected teeth.
Esthetic ceramic brackets (Abzil Transcend, 3M, São José do Rio Preto SP, Brazil) for mandibular central incisors were bonded to the selected teeth. The enamel was etched with 37% phosphoric acid (Condac 37, FGM, Joinville, SC Brazil) for 20 s, followed by washing for 30 s and drying with a triple syringe for 5 s. Adhesive (Primer Transbond XT, 3M Unitek, Monrovia, CA, USA) was applied to the enamel surface with a disposable brush for 5 s. The bracket was fixed with the use of a Bracket Holder Tweezer (Quinelato, Schobell, Rio Claro, São Paulo, Brazil) to apply the resin (Transbond XT, 3M Unitek Monrovia, CA, USA) on the bracket base, which was positioned against the proximal surface of the tooth; and excess resin was removed with an exploratory probe. Light activation was performed for 40 s with the use of a LED light activator appliance (Valo, Ultradent, Salt Lake, USA) with light intensity of 1000 mW/cm2, by applying the light on the bracket. Afterward, the teeth were individually stored in 20 mL of artificial saliva (pH 7; 1.5 mM of calcium, 0.9 mM of phosphorous, 0.15 M potassium chloride, and 0.02 M tris buffer) at 37° C for 30 days. The artificial saliva solution used was the type proposed by Featherstone et al. and modified by Serra and Cury.
The brackets were removed with bracket removing pliers type (QO.346.00, Quinelato, Rio Claro, São Paulo, Brazil), by positioning the bases of the pliers on the mesial and distal portions of the bracket and applying negative pressure to remove it.
To evaluate the adhesive remnant index (ARI), a stereoscopic lens (EK3ST, CQA Comercial Química Americana Ltda, Americana, São Paulo, Brazil) at ×40 magnification were used. The ARI was evaluated according to Artun and Bergland classification criteria: score 0-no adhesive left on enamel; score 1%–<50% of the adhesive left on enamel; score 2-over 50% of the adhesive left on enamel; and score 3%–100% of the adhesive left on enamel.
Only the teeth with ARI classified with score 3 were used to continue with the adhesive remnant removal procedures, by selecting 40 teeth for the study. The teeth were randomly distributed among the groups for performing the residual resin removal procedures according to the different systems [Table 1] and [Figure 1]:
|Figure 1: Finishing burs and polishing system (a) Komet H22GK high-speed bur; (b) Komet H379AGK low-speed bur; (c) Orthometric CF375R high-speed bur; (d) Orthometric CB27 low-speed bur; (e) Polishing disc-fine grained diamond pro (f) Felt disc used with diamond polishing paste Diamond Excel; (g) Mandrel|
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- Komet high-speed bur: The use of Komet H22GK high-speed bur followed by use of fine diamond pro abrasive disc and felt disc with diamond polishing paste
- Komet low-speed bur: The use of Komet H379AGK low-speed bur followed by use of fine diamond pro abrasive disc and felt disc with diamond polishing paste
- Orthometric high-speed bur: The use of Orthometric CR 375R high-speed bur followed by use of fine diamond pro abrasive disc and then felt disc with diamond polishing paste
- Orthometric low-speed bur: The use of Orthometric CB27 low-speed bur followed by use of fine diamond pro abrasive disc and then felt disc with diamond polishing paste.
For residual resin removal, each tooth received a specific bur, and the resin was completely removed, as confirmed by visual inspection. For this purpose, light manual force was applied with the bur rotating from the vestibular to the palatal portion of the resin remnant, until all the adhesive remnant was completely removed, as observed after visual inspection.
All the groups were submitted to polishing with fine grain abrasive discs (Diamond Pro, FGM, Joinville, SC, Brazil). The disc was coupled to a low-speed mandrel, and the disc was applied in the vestibular-palatal direction of the residual resin area for 40 s, on each surface. Washing was performed for 20 s and drying, proceeding with the use of the felt disc (Diamond Flex, FGM, Joinville, SC, Brazil) and diamond polishing paste (Dentscare, FGM, Joinville, SC, Brazil) in the same direction, at low speed for 40 s. The abrasive and felt discs were changed after each sample.
The teeth were evaluated again with regard to ARI and were classified with ARI equal to zero. The surface roughness analysis of the enamel surface was also performed again as previously described.
The data obtained were tabulated into an Excel spreadsheet according to each group. Exploratory data analysis indicated the removal of two outliers; this was followed by the application of the methodology of mixed models for repeated measures (Proc Mixed). The multiple comparisons were made using the Tukey–Kramer Test, considering the level of significance of 5%. All the analyses were performed with SAS (SAS Cary Institute Cary, NC, USA, Release 9.2.2010).
| Results|| |
There was no significant interaction between the factors “removal systems” and “time intervals of evaluation” (P = 0.6168). There was no significant difference in mean roughness values between removal systems (P = 0.5565) in the same time interval. The mean roughness values in the time interval after finishing did not differ significantly from those of the baseline. In the time interval after polishing, the roughness values were significantly lower than those in the other time intervals (P = 0.0001) in all the groups [Table 2].
|Table 2: Mean (standard deviation) of roughness (μm) considering group and time|
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| Discussion|| |
The results of this study showed that no differences on enamel roughness after the use of different removal systems. Thus, the first null hypothesis was accepted, namely, that there are no differences in enamel roughness regardless of the removal system used. However, there were significant differences in enamel roughness among baseline values, after the use of finishing burs and polishing abrasives, thus rejecting the second null hypothesis that there were no differences in enamel roughness after removal of the residual resin after finishing and after polishing removal systems.
During the procedure of debonding ceramic brackets from the tooth surface, authors have recognized that the larger the quantity of adhesive present, the lower would be the probability of deleterious enamel fractures occurring.,,, However, there is concern about changes in the enamel surface resulting from resin removal by means of agents that wear out the material, which may lead to the removal of the most superficial enamel layer.,
At baseline, all the groups presented the same roughness values for standardizing the sample. Preoteasa et al. studied healthy enamel surfaces on all the tooth surfaces (proximal, vestibular, and palatine) and found horizontal and vertical fissures on all of them, with the presence of perikymata and prisms in all directions, so that the proximal surfaces selected in the present study did not make any differences relative to the clinical applicability of the study since the bonding procedures are effected on the vestibular or lingual surfaces of patients' teeth.
After bracket debonding, authors have verified that the resin remnant remained adhered to the enamel surface.,,,, In the present study, samples that presented score 3 were selected, indicating the occurrence of cohesive fractures in resin, with these being considered ideal from the point of view of preserving the enamel.,, Nevertheless, procedures are required to perform their complete removal.
However, one of the limitations of this study was that it was not evaluated the depth of wear on enamel – which could indicate the real quantity of enamel loss resulting from the finishing and polishing procedures, which should be considered in the further studies.
Diverse protocols and instruments have been evaluated with the purpose of minimizing damage caused by the tooth enamel finishing and polishing procedures,,,, among them, the tungsten carbonate burs are the best known for resin remnant removal.,,,,,,, The use of multiple blade burs for finishing was pointed out by some authors as a safe method for removing resin. In the present study, irrespective of being used at high or low speed, the roughness values were similar among the finishing protocols by the composition and shape of the inactive points (conical at high and cylindrical at low speed), and by the moderate pressure used by the operator, without differences when compared with the baseline values. Thus, the use of these burs themselves made it possible to obtain enamel surface smoothness similar to that existent before bracket bonding, without the need for any other system of finishing or polishing. This allowed removal of the resin residues from the enamel in a shorter period, in addition, to enabling the orthodontist to select the type of speed to use according to his/her experience and practicality.
After performing the finishing procedure, subsequent polishing of the surface is recommended to obtain enamel surface smoothness and brightness, using aluminum oxide discs and polishing points.,,,,,,, In the present study, the authors observed that the use of polishing instruments led to a reduction in the surface roughness values, promoting greater surface smoothness, and without differences among the systems associated with finishing. This may have occurred because the same polishing system was used for all the samples, and therefore, no differences among the groups were expected. However, the surface smoothness values were lower in the initial time interval (baseline) in agreement with the majority of authors.,,,,,,,,,,, By obtaining greater smoothness of this surface, this could also result in less biofilm accumulation, with the possibility of providing the enamel with more brightness.
According to the results obtained, the authors could suggest that the finishing and polishing systems evaluate may be used by orthodontists to promote the achievement of smooth enamel surfaces after removing the brackets. The use of the burs and polishing system for removing the resin remnants of bracket bonding promoted adequate surface roughness properties. Future research may rely on the evaluation of enamel wear provided by these different removal systems since this study only evaluated the enamel roughness without considering the enamel loss provided by the removal systems.
| Conclusions|| |
The different burs used at high or low speed produced roughness values similar to those of healthy enamel. Although there were no differences between enamel roughness values before and after finishing with burs, the use of polishing discs made it possible to obtain enamel surfaces with lower roughness values.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]