Evaluation of changes in enamel thickness after orthodontic treatment depending on the force applied to remove orthodontic brackets: OCT analysis and universal testing machine

Abstract

Background. Adhesive materials used in orthodontics have contributed to the broadening of treatment options with fixed braces. The adhesive materials physically and chemically bond to the enamel surface and orthodontic bracket base, which, apart from offering advantages, also entails the risk of enamel damage when removing these materials from the tissue surface after the treatment is complete. Objectives. The objective of this study was to assess how the bond strength of adhesive materials affects enamel thickness after removing brackets and whether the type of bonding system affects the amount of adhesive strength of the discussed materials. Material and methods. The tests were carried out on 2 groups of 40 bovine teeth in each group. In the 1st group, the classical orthophosphoric acid and the Transbond Plus self-etching primer (SEP) were used. In the 2nd group, the Transbond XT SEP was applied. In both groups, Transbond XT Light Cure Adhesive was used. The same metal orthodontic brackets were attached to the enamel surface. Optical Coherence Tomography (OCT) scans were made before and after removing brackets, which enabled tissue thickness measurements. The bond strength was evaluated using a universal testing machine. Parametric tests were performed on all obtained variables. Student’s t-tests for independent samples and analysis of correlation with Pearson’s r were carried out. Results. The bond strength between the orthodontic bracket and enamel is statistically significantly different in the 1st group and the 2nd group, and is higher in the 2nd group. Conclusions. There are no significant differences in enamel thickness depending on the bonding system type and there is no correlation between the enamel thickness and the bond strength of orthodontic brackets to the enamel.