The morphologic basis for the extraction decision in Class II, division 1 malocclusions: a comparative study

Abstract

The purpose of this study was to compare the pretreatment dentofacial characteristics of persons with Class II, Division 1 malocclusions treated with either an extraction or a nonextraction approach. Such comparisons might help identify which parameters influence the extraction decision. Lateral cephalograms were available on 91 Class II, Division 1 cases, 44 were eventually treated with first premolar extractions and 47 were treated nonextraction. Twenty-four landmarks were located and digitized on each cephalogram. From these landmarks, 33 angular and linear dimensions were obtained. The Class II cases were also compared with normal subjects matched for age and sex. Comparisons between the Class II, Division 1 groups and normals indicated that, in general, the Class II, Division 1 malocclusion is associated with a larger overjet, deeper overbite, larger ANB angle, more retrusive mandible, and a convex soft tissue profile. Comparisons between subjects treated with and without extractions indicated that at pretreatment, the extraction groups had significantly larger tooth size-arch length discrepancies in both the maxillary and mandibular arches. In addition, the upper and lower lips in male subjects, and the lower lip in female subjects were significantly more protrusive in the subjects who were eventually treated with four first premolar extractions. These results indicate that in this group of patients, lip protrusion is one of the important parameters on which the extraction decision was based.