Correct bonding and debonding techniques play an important role in orthodontics. Many factors affect these procedures; the most important among them are the type of adhesive used for bonding, the instruments used for bracket debonding, and the finishing and polishing methods of adhesive resin removal [13].
With evolution of composite resin and adhesive systems, more effective bonding between enamel and resin can be achieved resulting in fewer brackets debonding rate. But, due to this increased adhesion of resin to enamel surface, removal of resin after debonding becomes more troublesome. So, the technique used for residual resin removal plays important role to avoid enamel surface damages, such as enamel cracks, rougher enamel surface, wear of enamel, overheating of the teeth, and pulpal damage [14].
In our study, no statistically significant difference in baseline surface roughness was noted between One gloss group, Enhance system group, Stainbuster group, and Soflex disc and wheels group. On the other hand, finishing instruments affected the surface roughness parameters. Higher roughness values were obtained with use of the Soflex group than other three groups (p < 001).
Our results showed that Soflex disc group created roughest enamel surface in comparison to other three groups. Results were in accordance with the results of Challa et al. [15], who assessed the effectiveness of five resin removal methods including tungsten Carbide burs (TCB), Discs (Sof-Lex), One step system (PoGo), and combination of carbide bur with multistep and one step polishing systems (TCB + Sof-Lex + pogo). Scanning electron microscopic results showed that enamel surface was near to original in samples finished with One step system (PoGo) followed by Sof-Lex dics.
Howell [16] in his study observed that Sof-Lex discs followed by slurry of pumice led to roughest enamel surface. Michele vidor [17] recommended using Enhance finishing tip followed by aluminum oxide polishing rather than Soflex discs as more enamel damage was observed with Soflex system.
Didem Atabek [7] evaluated enamel surface roughness after debonding using Enhance and pogo system, Stainbuster bur, and Soflex discs. Profilometric analysis suggested that smoothest enamel surface was obtained with Enhance system and roughest enamel surface was achieved using Soflex discs.
Brijesh in their in vitro study compared Enhance and Pogo system, One gloss system, and Soflex spiral wheels. Their results suggested that Enhance and Pogo micro polisher were better in creating smoother enamel surface than One gloss system and Soflex discs [18].
In the present study, SEM was used to assess enamel surface configurations. This method cannot provide a quantitative assessment. It is only used as a supportive tool with quantitative assessment methods [19].
SEM micrographs showed that Stainbuster bur seemed to be very efficient way to clean the surface. This qualitative result of smoothest surface achieved with Stainbuster bur agreed with our quantitative result. One gloss system and Soflex discs were the most hazardous techniques to the enamel surface. Enhance and pogo system was less destructive to enamel surface than One Gloss system and Soflex disc and wheels.
In the current study, surface roughness tester was used for assessing enamel surface roughness quantitatively. The surface roughness tester (Insize, ISR-C100) can measure up to 16 different parameters. The tester has a probe position indicator that helps in accurate identification of location. Display window shows roughness values, profile, and curves. The instrument can get connected with printer via Bluetooth [20].
All measured roughness parameters (Ra, Rt, Rz) for Sof-Lex disc and wheels were statistically higher than other finishing and polishing systems employed in this study. While all the roughness values were lowest for stainbuster group indicates smoothest enamel surface among all four groups.
The differences in roughness after finishing and polishing among the techniques also depend on patterns of particle size and their organization within the resin matrix of respective bur/wheel/disc. Aluminum oxide disks have limitations because of their shape, which make them difficult to use efficiently in posterior teeth [21].
Bicakci [22] used high speed burs without water cooling. They noticed heating in the pulp chamber resulting in vascular hyperemia and occasional breakage of odontoblasts was seen. This is a transient reversible condition. Damage of pulp gets repaired within about 20 days. It was recommended to remove most of the residual resin under water cooling and turning the water cooling off during removal of last resin layer, so that it helps in distinguishing between enamel surface and resin remnants, thereby preventing further enamel damage and loss. Therefore, in our study, water cooling was used initially to remove bulk of composite and last layer of resin was removed without water coolant.
Speed of hand piece is one of the important issues while removing adhesive resin with hand piece. A low-speed rotary instrument creates additional vibrations and uncomfortable for patients [23]. Risk of pulpal damage increases with low-speed instrument [24]. It is noted that low-speed instrument created irregular enamel surface but the natural enamel itself also showed slightly repetitive and spiky enamel [23]. It was found that effective adhesive removal was achieved with low-speed burs than high-speed burs due to the fact that both the depth and the area of the residual resin layer were significantly lower after using low-speed burs (p value < 0.05). Bishara et al. [24] observed that enamel loss was less with low-speed burs than high-speed burs. For such reasons, slow speed hand piece was used in our study.
Generation of aerosols is another demerit of residual resin removal with rotary instrument. Jonke E et al. [25] in their study observed that after ceramic bracket debonding and various cleanup methods, aerosols produced during composite grinding can act as endocrinological disruptors.
Debonding and adhesive resin removal techniques are operator-dependent procedures. Thus, the results may probably differ among operators. So as to lessen this inaccuracy, just one operator carried out all the clinical procedures in our study. Results of the current study showed that post clean-up roughness (post polishing roughness) was more than the prebonding enamel roughness (baseline roughness) in all the four groups. This implies that no resin removal method was able to completely restore the enamel surface roughness to its original form [26].
Our study has some limitations and warrant future studies to combat the same. Latest methods such as confocal laser microscopy and atomic force microscopy (AFM) are being used to obtain 3D data of enamel roughness that will help in gaining more clear information regarding the amount of enamel loss caused due to various resin removal methods.
Second limitation of our study is in vitro study. Our study being in vitro, the result of this study cannot be directly applied in clinical situations. Factors such as saliva, oral hygiene, temperature, and pH can also affect our results. Future in vivo studies are required to confirm our results and clinical implementation [27].