Correlation of Mandibular Incisor Inclination to Marginal Bone Levels and Cortical Bone Thickness in Different Skeletal Patterns: A Retrospective, Cone Beam Computed Tomography Study

Abstract

Introduction: Biologic factors, such as the cortical bone thickness and supporting bone as well as biomechanical factors, such as proclined teeth are closely interrelated. These factors often determine the potential deleterious effects of orthodontic treatment, such as gingival recession, dehiscence, fenestration, and external root resorption. The alveolar bone thickness and bone levels vary in different facial patterns and here in this study, we are finding if there is any correlation of these to tooth inclinations. Aims and objectives: To assess the influence of mandibular incisor inclination on cortical bone thickness and alveolar bone levels in different skeletal patterns. Materials and methods: Thirty cone beam computed tomography (CBCT) scans and lateral cephalograms of pretreatment patients were analyzed with different skeletal patterns (10 each) for their alveolar bone height, alveolar bone thickness, and cortical bone thickness at mid root level and mandibular incisor inclination. Inclination and thickness were compared among the three groups and were correlated. Results: Although there are wide variations, cortical bone thickness at mid root level in vertical, horizontal, and average growth pattern lingually and labially were 2.3 ± 0.29 mm, 2.4 ± 0.42, 2.2 ± 0.39, and 0.69 ± 0.12, 0.65 ± 0.23, and 0.59 ± 0.37 respectively, and these values were not statistically significant. The vertical alveolar bone height did not hold any significance in our study. The incisor–mandibular plane angle (IMPA) for evaluating growth patterns was found to be significant. Clinical significance: The inclination of the mandibular incisors is an important diagnostic consideration and has to be kept in mind during treatment planning. Excessive proclination of the incisors can lead to dehiscence, fenestration, as well as recession. Therefore, it becomes important to know the thickness of the bone as well as the marginal bone level to help us to use appropriate biomechanics. Conclusion: The mandibular incisor inclination and growth pattern of the patient appear to have no significant impact on the alveolar bone levels and cortical bone thickness. However, studies with a larger sample size and with high-dose CBCT are warranted.