Evaluation of the centroid method of occlusion for studying mandibular and maxillary growth

The aim of this study was to evaluate the centroid method of occlusion for studying mandibular growth and development. This novel technique comparatively expresses the direction of growth of the maxilla and mandible as a single unit. The centroid 'G' was geometrically calculated from the triangle Deltaabc, which comprised the palatal, articulare-gnathion (Ar-Gn), and A-B planes. The plane angles and positional relationship of the centroid with the upper first molar was investigated, focusing on differences between genders and malocclusions. Lateral cephalograms were obtained of 26 males and 51 females with a 'normal' Class I occlusion, 216 females with a Class III incisor relationship, and 230 females, all aged >18 years, with a Class II incisor relationship. Bolton standards and Sakamoto's data were used to determine changes in the angle of the palatal plane to the Ar-Gn plane. Non-significant levels of variation were observed in the angle of the palatal plane to the Ar-Gn plane during the developmental period from childhood to adulthood. Among Class I adult subjects, Deltaabc was similar between genders and the centroid G was located near the occlusal surface of the upper first molar. There was no difference in the area of Deltaabc between malocclusion types. The positional relationship of the centroid G with the upper first molar revealed a shift of the centroid mesially and cervically during the transition from Class III to Class I to Class II. These findings indicate that the centroid method can contribute to orthopaedic diagnosis and the planning of treatment strategies.