A comparison of the effects of 2 mandibular anchorage systems used with a 3-dimensional bimetric maxillary distalizing arch.

The purpose of this study was to compare the effects of 2 mandibular anchorage systems used with a 3-dimensional bimetric maxillary distalizing arch. The Wilson rapid molar distalization appliance for Class II molar correction was used with 26 patients; two groups of 13 patients each were formed. In the first group (9 girls, 4 boys with a mean age 11 years 5 months), mandibular anchorage was gained by a modified lip bumper with a standard lingual arch of 0.9-mm stainless steel. The second group (7 girls, 6 boys, with a mean age of 13 years) had a 0.016 x 0.016-inch utility arch, with a 3-dimensional lingual arch for anchorage. Cephalometric radiographs were taken before and after maxillary first molar distalization. The treatment results showed that the extrusion of the mandibular first molar was statistically significant in both the modified lip bumper and utility arch groups (P < .01 and P <.05, respectively). The incisal edge of the mandibular incisor moved forward significantly in the modified lip bumper and utility arch groups (P < .05 and P < .01, respectively); however, the protrusion in the utility arch group was significantly greater than in the lip bumper group (P <.05). In both groups, significant proclination of the mandibular incisor was observed (P < .01). Comparison of the anchor units showed that there was significantly greater proclination in the utility arch group than in the modified lip bumper group (P < .05). Both anchor units similarly enhanced the mandibular first molar anchorage. However, particularly in the utility group, mandibular incisor anchorage control seemed to be inadequate.