Overjet reduction and molar correction in fixed appliance treatment of Class II, Division 1, malocclusions: Sagittal and vertical components

The purpose of this study was to quantitatively evaluate skeletal and denta l changes contributing to Class II correction in patients treated with the Begg technique. The sample consisted of 18 male subjects with Class II, div ision 1, malocclusions treated with fixed appliances (Begg technique, nonex traction) for an average period of 1.3 years (standard deviation, 0.24 year s). Lateral radiographs in habitual occlusion taken at 6 months before the start of treatment, at the start of treatment, and 6, 12, and 18 months aft er the start of treatment were analyzed. During the control period, normal sagittal and vertical growth changes occurred. In the initial treatment per iod (0 to 6 months), the overjet reduction (6.6 mm; P < .001) and the molar correction (2.2 mm; P < .001) were obtained mainly by dental movements. Th e overbite was reduced by 4.1 mm (P < .001). The NSL/ML and NL/ML angles in creased by 1.5 degrees (P < .05) and 1.4 degrees (P < .01), respectively, a nd the anterior lower facial height increased by 3.1 mm (P < .001), During the second period of treatment (6 to 12 months), the molar correction conti nued to improve, and the anterior lower facial height continued to increase . During the third period (12 to 18 months), a small relapse in overjet and overbite was noted, but the anterior lower facial height continued to incr ease. During the total treatment period (0 to 18 months), the overjet reduc tion and molar correction were 5.8 mm (P < .001) and 3.0 mm (P < .001), res pectively. Mandibular growth exceeded maxillary growth by 1.1 mm (P < .01). The overbite correction and the increase in anterior lower facial height w ere 3.0 mm (P < .001) and 5.0 mm (P <.001), respectively. The NSL/ML angle increased 1.0 degrees (P < .05). The conclusions were that the changes cont ributing to the Class II correction were mostly dental. Vertically, the net effects of treatment were an increase in the mandibular plane angle and in lower anterior facial height.