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Advisory Committee Chair

Nada Souccar

Advisory Committee Members

Andre Ferreira

Christos Vlachos

Amjad Javed

Chin-Chuan Fu

Document Type

Thesis

Date of Award

2021

Degree Name by School

Master of Dentistry (MDent) School of Dentistry

Abstract

Objective: The primary objective of this study is to evaluate pre and posttreatment lateral cephalometric radiographs on patients treated with Invisalign by the same orthodontist where lower incisor intrusion was prescribed and to determine the amount of true lower incisor intrusion achieved during treatment. Methods: This retrospective case series study included 48 patients with an overbite exceeding 2mm, who were treated with Invisalign clear aligner therapy, and whose Clincheck treatment plan included lower incisor intrusion. The mean age of the study group was 27 years with 14 (29%) of the subjects being male and 35 (71%) being female. The mean treatment time was 13.77 months. Patients were consecutively treated by the same private practice orthodontist using the same treatment protocols. Pretreatment and posttreatment lateral cephalograms were analyzed to determine changes due to orthodontic treatment and were compared to the predicted Clincheck movements. Results: A statistically significant change (P<0.05) was seen in 6 of the 15 cephalometric measurements. OB was decreased an average of 0.7mm (±1.0mm), OJ was decreased 0.6mm (±1.5mm), ANB decreased 0.2mm (±1.1mm) the upper molars (U6-PP) were extruded 0.6mm (±1.0mm), the lower molars (L6-MP) were extruded 0.3mm (±0.9mm), and the anterior facial height (AFH) was increased 0.4mm (±1.4mm). No significant difference was found in the distance from the center of resistance of the lower incisor to the mandibular plane (Midpoint Root), which showed an average change of 0.1mm (±1.2mm). Conclusions: The amount of lower incisor intrusion seen in this study did not reflect the efficacy that has been presented in previous studies. Our study did show that Invisalign was predictably able to reduce overbite in patients with a pretreatment deep bite and that this correction occurs primarily due to posterior extrusion, secondarily due to relative intrusion, or a change lower incisor proclination, and tertiarily due to lower incisor intrusion.

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