Transverse implications of maxillary premolar extraction in Class III presurgical orthodontic treatment

Introduction: Maxillary premolars are often extracted to resolve incisor proclination in presurgical orthodontic treatment for severe skeletal Class III patients. The aim of this article was to compare arch-width changes and orthodontic tooth movements between maxillary premolar extraction and nonextraction modalities, and to provide an additional indication for presurgical maxillary premolar extraction according to the transverse dental arch characteristics of Class III surgical-orthodontic patients. Methods: Pretreatment and posttreatment dental casts of 55 adult Class III patients (24 nonextraction, 31 extraction) who underwent surgical-orthodontic treatment were collected. The changes in maxillary and mandibular dental arch widths were measured from the canines to the second molars. Orthodontic tooth movement was evaluated with an angulation-and-inclination measuring gauge. Results: Statistical analyses showed that intermaxillary arch congruity was attributed mainly to maxillary arch-width changes. The arch-width changes could be interpreted as the result of inclination changes in both posterior dentitions. For the arch-width change, analysis of covariance (ANCOVA) showed a significant extraction effect: the premolar extraction group's ability to accommodate arch-width change was significantly greater than that of the nonextraction group. Conclusions: The indications for maxillary premolar extraction in Class III presurgical orthodontic treatment might depend in part on the characteristics of the maxillary arch width and posterior teeth inclinations.