Hard tissue characteristics of patients with bimaxillary protrusion

Abstract

Bimaxillary protrusion (BP) is a common developmental condition amongst the South African Black population characterized by proclined incisors with resultant procumbency of the lips. The aim of this study was to perform a cephalometric radiographic analysis of the pre-treatment dental and skeletal structures in a sample of Black South Africans in order to identify the characteristic features of BP in this race group and compare them to norms. Records of 67 South African Black patients divided into 28 males and 39 females with a mean age of 17.8 years, clinically diagnosed with BP were included in the study. Cephalometric parameters were hand traced on lateral cephalometric radiographs and measurements recorded for evaluation and comparison to norm values used for this population group to determine the features that both males and females present with. Characteristic pre-treatment dental features of the sample included maxillary incisors that were proclined and protruded with resultant decreased interincisal angle, mandibular incisors which were favourably positioned. Skeletal features included retrognathic jaws (maxilla to a greater degree) resulting in a mild to moderate Class III skeletal pattern but with females exhibiting a smaller ANB angle indicating a greater tendency for a Class III skeletal pattern. The skeletal growth pattern was vertically directed with an average anterior facial height ratio. The findings indicate that most BP patients in this South African Black population presented with dentoalveolar protrusion, retrognathic jaws and a mild to moderate skeletal Class III pattern