Optical coherence tomography as a non-invasive method of enamel thickness diagnosis after orthodontic treatment by 3 different types of brackets

Background. Medical digital imaging is the basis of effective medical diagnosis and is now in the mainstream of a dynamically developing branch of science. Optical coherence tomography (OCT) enables real-time in situ imaging of tissues without the need for biopsy, histological procedures or X-rays. Objectives. The aim of the study was to evaluate the application of OCT in orthodontic diagnostics and clinical practice by assessing the thickness of the enamel before and after orthodontic treatment. Material and methods. A hundred and eighty teeth in this in vitro study were divided into 3 groups of 60 teeth each. In each group (Group 1 - metal brackets, Group 2 - ceramic brackets and Group 3 - composite brackets), the orthodontic brackets were attached to the enamel using the 5th-generation adhesive system. The image of the enamel tissue was captured with a 3D-OCT camera before installing orthodontic brackets and after debonding and mechanical processing. The obtained OCT scans were subjected to expert IT analysis. For the statistical analysis, the Shapiro-Wilk test, the median test, the Mann-Whitney U test, Friedman two-way analysis of variance (ANOVA), Wilcoxon matched pairs signed ranks test, the chi(2) test of independence with Yates's correction, and Fisher's exact test were used. Maxwell's general principle was followed when using this type of test. The level of significance was set at p = 0.05. Results. The thickness of the enamel varied least when metal brackets were used. The changes in enamel thickness in the composite and ceramic bracket groups were not statistically significant. Conclusions. Optical coherence tomography is an effective diagnostic tool to evaluate the thickness of the enamel tissue before and after orthodontic treatment. Changes in the enamel layer thickness after orthodontic treatment are determined by the type of material which the orthodontic bracket is made of.