Comparative long term post-treatment changes in hyperdivergent Class II Division 1 patients with early cervical...

This was a retrospective study of 45 Class II Division I hyperdivergent patients treated in the mixed dentition with cervical traction and an incisor biteplane. The interjaw or "B" angle (mandibular plane to palatal plane angle) was used to determine hyperdivergency. The treated sample was subdivided into 2 groups reflecting whether the mandibular or palatal plane contributed the greatest amount to the more than 1 standard deviation of the "B" angle from the mean value of the "B" angle present in the 89 untreated Class I controls. Complete records including lateral cephalometric head films were acquired at the start of treatment and 18 to 91 months after discontinuing all retention. Null hypotheses were designed to determine if any significant changes in the "B" angle, mandibular plane angle, or palatal plane angle occurred in the control group or the treated group. Thirty-two angular, linear, and proportional data were accumulated to determine the presence or absence of significant differences. The only significant angular differences found were in the group in which the palatal plane inclination was increased relative to Frankfort Horizontal. In this group, the palatal plane became more nearly parallel to Frankfort Horizontal than in the control group, and showed an increase instead of a decrease in the Y-axis. Proportional and linear data indicated the palatal plane change was a lack of descent of Posterior Nasal Spine while the descent of Anterior Nasal Spine was equal to that of the control group. The increase in the Y-axis was not the result of bite opening, but a lack of mandibular horizontal development as indicated by less of an increase in the Facial Angle. Of the 45 patients, only 4 (9%) required 2 phases of treatment and 1 of those required extraction. Thirty patients (67%) completed treatment with alignment and retraction of the maxillary anterior segment and 11 (24%) had additional alignment of the mandibular anterior segment.