Date of Award

2023

Department

Department of Orthodontics

First Advisor

Jonas Bianchi

First Committee Member

Heesoo Oh

Abstract

Introduction: The objective of this study was to investigate the cephalometric and dental changes observed in nongrowing, deep overbite patients of varying mandibular planes treated with Invisalign® (Align Technology, San Jose, CA). Methods: This retrospective study included 51 patients (27 females and 24 males, aged 33.01 ± 14.74; initial overbite of 4.6 ± 0.83 mm; average treatment period of 1.89 ± 0.85 years; average refinements of 2 ± 1.51). The sample was consecutively treated at the University of the Pacific Resident Orthodontic Clinic and one private practice from 2014-2023. The sample was further divided into 2 groups: patients with an FMA ≥ 20° (Group 1, n = 26; 14 females and 12 males; aged 33.52 ± 14.85) and a hypodivergent FMA <20° (Group 2, n=25; 13 females and 12 males; aged 32.47 ± 14.09). Smart Track materials, bite-turbos, and the G5-G8 interface were used for all patients. The initial (T1) and final (T2) overbite, overjet, inter-canine width, and intermolar width were measured on models using OrthoCAD (v 5.9.1.50). The T1 and T2 curve of Spee was measured on 3Shape (Niels Juels Gade, Copenhagen, Denmark). Lateral cephalometric radiographs at T1 and T2 were traced superimposed, and 37 measurements were analyzed on Dolphin (v 12.0.0.55). Descriptive statistics, paired student t-tests, and Pearson correlation analyses were performed. Results: An average overbite correction of – 1.95 mm (p < 0.001), -1.84 mm (p < 0.001), and -2.05 mm (p < 0.001) were observed for the whole sample, Group 1 and Group 2 respectively. Lower incisor intrusion was reported for the whole sample, Group 1, and Group 2 as - 0.77 mm (p < 0.001), -0.72 mm ((p < 0.5), and -0.82 (p < 0.001). Lower molar extrusion was calculated as 0.3 mm (p < 0.05) in Group 1 and 0.35 mm (p < 0.05) in Group 2. Group 1 did not have a statistically significant change in FMA or LAFH, while Group 2 reported a minimal increase in LAFH on an average of 0.35 mm (p < 0.05). Conclusions: Invisalign® can reduce overbite in patients with deep bite malocclusion and varying vertical skeletal patterns. Correction occurs mainly through lower incisor intrusion, lower incisor proclination, and lower molar extrusion. The effects of deep overbite treatment with Invisalign® are largely dental and do not significantly alter a patient’s FMA or LAFH, regardless of the patient’s vertical skeletal pattern.

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