Impact of resin composite type on enamel surface damage during rotary instrument removal in aligner therapy: An <i>in vitro</i> study

Objectives: Attachments are composite structures that help clear aligners (CAs) move teeth and must be removed at the end of treatment. Made from various composites, they are sometimes replaced during therapy. This study evaluates enamel damage after removing attachments made from three different composites, aiming to determine whether the type of resin affects the extent of damage caused by rotary instruments. Material and Methods: This in vitro study used 30 extracted teeth, divided into three groups: A (packable composite), B (flowable composite), and C (orthodontic composite). Before bonding (T0), each tooth was duplicated in epoxy resin. Attachments were applied using a consistent protocol, then removed with a tungsten carbide bur. After removal (T1), teeth were finished with sandpaper discs and polished with pumice paste. Impressions were taken to create resin replicas. Enamel damage was assessed using scanning electron microscopy (SEM), and a modified enamel damage index (EDI) was applied. Data were analyzed with a Chi-square test ( P &lt; 0.05). Results: Groups A (packable composite) and C (orthodontic composite) showed a significant difference in enamel damage ( P = 0.0235) at T1. However, there were no significant differences between Group B (flowable composite) and the other groups ( P &gt; 0.05). Conclusion: Attachment removal causes enamel damage, with greater damage observed in the packable composite group compared to the orthodontic composite group. Group A (packable composite) shows a heterogeneous distribution, with a prevalence of EDI 2 (60%) and lower proportions of EDI 1 and EDI 3 (20% each). In Group B (flowable composite), EDI 1 predominates (60%), followed by EDI 2 (40%). Finally, Group C (orthodontic composite) is characterized almost exclusively by EDI 1 values (80%), with a residual proportion of EDI 2 (20%). These results suggest that the type of composite used for attachments influences enamel surface integrity during removal.