Evaluation of mandibular anterior alveolus in different skeletal patterns.

Nga Hoang,Snehlata Oberoi,David Hatcher,Gerald Nelson

doi:10.1186/s40510-016-0135-z

Abstract

BackgroundThe boundaries for orthodontic tooth movement are set by the bony support of the dentition. This study compares the mandibular anterior alveolar housing in individuals with low, average, and high mandibular plane angles before orthodontic treatment and measures alveolar bone loss and root resorption after orthodontic treatment.MethodsPretreatment cone-beam computed tomography (CBCT) images of 75 non-growing individuals, 25 in three groups: low-angle (sella-nasion to mandibular plane ≤28°), average-angle (30°–37°), and high-angle (≥39°), were analyzed. Buccolingual bone thickness was measured at the root apex, mid-root, and alveolar crest of the mandibular right central incisor. Pre- and posttreatment CBCT images of 11 low-angle, 20 average-angle, and 27 high-angle patients were compared to determine changes in the alveolus and mandibular incisor root after orthodontic treatment.ResultsThe pretreatment anterior alveolar bone widths were significantly different, wider in low-angle than in average- and high-angle individuals (p value = 0.000). High-angle individuals also had greater posttreatment external root resorption, even though the bony housing changed minimally.ConclusionsNegative sequelae of orthodontic treatment are more frequently found in individuals with high mandibular plane angles and could be linked to their thin pre-existing alveolar housing.

Highlights

The boundaries for orthodontic tooth movement are set by the bony support of the dentition
Aim 1: Difference in bony support of mandibular incisors in low, average, and high-angle adult subjects with no orthodontic treatment Our results indicate that there is a relationship between the thickness of the mandibular symphysis at the apex of the lower incisor and mandibular plane angle
The following conclusions were derived from the comparison of alveolar bone support of the mandibular right central incisor in subjects with different vertical skeletal patterns: 1. Total alveolar buccolingual bone thickness at the apex of the lower right central incisor is larger in the hypodivergent group compared to that in the normodivergent and hyperdivergent

Summary

Introduction

The boundaries for orthodontic tooth movement are set by the bony support of the dentition. This study compares the mandibular anterior alveolar housing in individuals with low, average, and high mandibular plane angles before orthodontic treatment and measures alveolar bone loss and root resorption after orthodontic treatment. Biologic factors such as the supporting bone and thickness of the cortical plate as well as biomechanical factors are closely related and determine the potential unwanted side effects of orthodontic treatment, such as external root resorption, gingival recession, dehiscence, and fenestration [1,2,3]. The dimensions of the mandibular alveolus appear to limit orthodontic tooth movement Challenging these boundaries may lead to iatrogenic sequelae.

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