Influence of the cephalometric characteristics on the occlusal success rate of Class II malocclusions treated with nonextraction or with two maxillary premolar extraction protocols.

Aim: To compare the initial cephalometric characteristics of complete Class II malocclusions treated with nonextraction or with two maxillary premolar extractions and to verify their degree of influence on the occlusal success rate.

Methods: A sample of 84 records from patients with complete Class II malocclusions was divided into two groups. Group 1 consisted of 31 patients treated with nonextraction at an initial mean age of 12.95 years, while group 2 included 53 patients treated with two maxillary premolar extractions at an initial mean age of 13.3 years. Initial and final occlusal statuses were evaluated on dental casts with Grainger's Treatment Priority Index (TPI); the initial cephalometric characteristics were obtained on the pretreatment cephalograms. The initial cephalometric characteristics of the groups were compared by t test. A multiple linear regression analysis was used to evaluate the influence of all variables in the percentage of TPI reduction.

Results: The pretreatment cephalometric characteristics of the two maxillary premolar extraction cases were a greater vertical growth pattern, greater max illary and mandibular incisor protrusion, greater maxillary incisor and molar dentoalveolar heights, and greater upper and lower lip protrusion than the nonextraction group. However, the regression analysis demonstrated that only the extraction protocol was significantly associated with the occlusal success rate in the groups.

Conclusions: It was concluded that the initial cephalometric characteristics of the groups did not influence the occlusal success rate of the two treatment protocols investigated.