Three-Dimensional Analysis of Occlusal Plane Changes After Clear Aligner Therapy: A Retrospective Study.

Objective: The purpose of the present study was to evaluate: (i) occlusal plane (OP) changes after clear aligner therapy (CAT) and (ii) whether such changes correlate with the patient's facial divergence. Materials and Methods: Three-dimensional models of 118 patients (49 males and 59 females; mean ± standard deviation age 22.3 ± 3.4 years) treated with clear aligners were analysed retrospectively. Using CAD-CAM software, it was possible to define three planes: the reference palatine plane (PP), the OP and the reference vertical maxillary plane. The PP and OP meet mesially, identifying an angle (α) in the sagittal view. The intersection of the occlusal and vertical maxillary planes creates two angles in the frontal view: an angle (β) for the right side and an angle (γ) for the left side. Using Autodesk Fusion 360, the angles were investigated before treatment (T0) and after treatment (T1) to calculate the change for each angle Δ(T1-T0). Subsequently, lateral cephalograms were analysed and five measurements were made. Results: One-way analysis of variance (ANOVA), showed a significant difference between hyperdivergent and hypodivergent patients for Δα and Δβ. The post hoc Tukey test showed the following differences: Δα was 3.81° greater in hyperdivergent patients compared with hypodivergent patients, and Δβ was 1.69° greater in hyperdivergent patients compared with hypodivergent patients. Conclusion: Treatment with aligners did not lead to a clinically significant change in the OP. However, when dividing the sample into groups based on craniofacial divergence, OP orientation change differed significantly between the three groups. Clinical Significance: According to the present study, aligners may be a useful therapeutic option for hyperdivergent patients and a less favourable option for hypodivergent patients and patients with occlusal asymmetries, both structural and functional, who may need particular treatment approaches and diagnostic evaluations.