Effective mandibular and maxillary base length in developing Class III malocclusions with high and low mandibular plane angles.

Introduction Skeletal Class III is one of a complex sagittal interjaw relationship. It is the result of malrelation in sagittal position of one or both jaw bones or disproportionate ratio of their length. Objective This study was carried out to assess the effective mandibular and maxillary bases length in developing Class III malocclusion with high and low mandibular plane angles. Materials and methods Cross-sectional study was carried out on a selected sample of 75 lateral cephalometric radiographs of orthodontic patients of both sexes with age ranged from 6 to 12 years old. They were divided into three equal groups. Group 1: normal ANB and mandibular plane angles as a control group, group 2: skeletal Class III with low mandibular plane angles, and group 3: skeletal Class III with high mandibular plane angles. The sample was collected from patient record files at the clinic of the Orthodontic Department, Faculty of Dentistry, Tanta University, Egypt. Results A statistically significant difference was found in the effective maxillary length between group 1 and group 2 and 3. While effective mandibular length showed no statistically significant differences between the three groups. Conclusion Short maxillary base length is the main etiological factor for skeletal Class III malocclusion. While prominent mandibular base length has minimal effect in development of skeletal Class III malocclusion. [ABSTRACT FROM AUTHOR]