Facial profile changes with various orthodontic premolar extraction sequences during growth.
The Visual Treatment Objective (VTO) is an extremely valuable tool in the process of working out the treatment plan for the individual. This is especially true for the inexperienced operator. Often it becomes clear that extractions are indicated, but there remains uncertainty as to which teeth should be chosen for extractions to give the best results. As it is necessary to express the expected change in profile due to growth of the nose and also of the chin, VTO construction is helpful in determining the extraction decision. Clinical experience and research projects have indicated that the use of mean values has definite limitations when constructing a VTO for an individual. The primary objective of this investigation was to provide formulae by means of which anteroposterior changes in the facial profile of growing individuals for whom four premolar extraction treatment is proposed can be predicted with a greater measure of certainty. The records of 248 growing Caucasian orthodontic patients (120 males and 128 females) were selected and divided into Group 44 (four first premolar extractions), Group 45 (upper first premolar and lower second premolar extractions) and Group 55 (four second premolar extractions). Formulae are presented for the prediction of the amount of incisor retraction, anteroposterior nose growth and for chin growth. The formulae were derived by regression of incisor retraction, anteroposterior nose growth and chin growth on various predictors, and could be used in the construction of VTO's for selected cases.