Student Theses, Dissertations and Capstones

Document Type

Thesis - NSU Access Only

Degree Name

Master of Science (M.S.) in Dentistry

Copyright Statement

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Department

College of Dental Medicine

First Advisor

Thyagaseely Premaraj

Date of original Performance / Presentation

January 2024

Publication Date / Copyright Date

1-1-2024

Abstract

Objectives: To evaluate and compare the lower incisor position, its relationship to the alveolar housing and symphyseal bone relative to the mandibular plane, in patients with untreated skeletal class I and II malocclusions. Methods: Sixty-nine pre-treatment CBCTs of skeletal class I (n = 35) and skeletal class II (n = 34) patients were reviewed. For each patient, the lower incisor to mandibular plane angle was determined by measuring and averaging the angle between tooth #24 (IMPA-24) and #25 (IMPA-25). The inclination of the alveolar housing to the mandibular plane angle was determined by two methods: (1) bisecting the angle from most posterior point of the symphyseal bone, to the most superior part of the inter-crestal bone of lower incisors to the B-point (AH- MPA-1), and (2) bisecting an angle created from the lingual aspect of the alveolar housing at the level of the lower incisor apex, to the lower incisor tip, to the buccal aspect of the alveolar housing at the level of the root apex (AH-MPA-2). The convexity of the alveolar housing to symphyseal bone was also determined by finding the angle formed from the inter-crestal bone, the alveolar width midpoint, and menton. Descriptive statistics and pairwise comparisons using Pearson’s correlation test and paired-t test were calculated. Results: Within both the skeletal class I and class II groups, there was a statistically significant difference between the following: (1) the average IMPA and the AH-MPA-1, and (2) AH-MPA-1and the AH-MPA-2 (p < 0.001). No statistically significant difference was found between the average IMPA and the AH-MPA-2. Between skeletal class I and class II, a statistically significant difference (p < 0.001) was seen with all measurements, with the skeletal class II group having overall higher values of IMPA, AH-MPA-1, and AH-MPA-2. The skeletal class I group had a statistically significant lower symphyseal convexity, indicating a more upright symphysis to the mandibular plane. Conclusions: The class II skeletal pattern had significantly higher IMPA, indicating proclined incisors compared to class I skeletal pattern. The first method to determine alveolar inclination, AH-MPA-1, did not reflect the average IMPA as closely as the second method, AH-MPA-2, likely due to variations that may exist in the morphology of the posterior symphysis. In both skeletal classes, the lower incisor was in harmony with the alveolar housing; significant proclination of alveolar housing was seen in skeletal class II malocclusion. These results show that dentoalveolar compensation exists in untreated skeletal class I and class II patients with the alveolar housing appearing to conform to the inclination of the lower incisor. The convexity of alveolar housing to symphysis (symphyseal convexity) reflected the morphing of alveolar bone along with the proclination of lower incisors relative to the symphyseal bone.

Disciplines

Dentistry

Keywords

alveolar housing; CBCT; Class I; Class II; lower Incisor; symphysis

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