Prediction of mandibular growth rotation evaluated from a longitudinal implant sample

The aim of this study was to estimate the possibility of predicting the direction and the amount of growth rotation of the mandible on the basis of morphologic criteria observed on a single profile radiograph at pubertal age. The difficulty in such an analysis is due to the fact that the actual growth rotation cannot be evaluated from radiographs by measurements at outer bony contours subjected to remodeling. The sample consisted of twenty-one persons in whom the actual mandibular growth rotation was determined from metallic implants over a 6-year period at around the time of puberty. Morphologic features from the first profile radiograph could therefore be compared with the observed growth changes over the study period and their predicting values calculated. A total of forty-four morphologic variables were employed and the data were analyzed by multivariate statistical methods. For each person, the variables which, alone and in combination, showed the highest predictive value with respect to total mandibular growth rotation are specified. The four variables which, in combination, gave the best prognostic estimate (86%) of mandibular growth rotation in this sample are (1) mandibular inclination, represented by three alternatives--(a) Index I (proportion between posterior and anterior facial height, (b) lower gonial angle (GOL), (c) inclination of lower border (NSL-ML1); (2) intermolar angle (MOLs-MOLi); (3) shape of lower border (ML1-ML2); and (4) inclination of symphysis (CTL-NSL). The statistical analysis was based on a sample of extreme cases. In children with a more normal growth pattern, these features may be less developed. The concordance between the predicted and the observed growth changes is illustrated graphically for each person.