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Anchorage provided during intra-arch distal molar movement: a comparison between the Nance appliance and a fixed frontal bite plane.

The aim of this retrospective study was to evaluate and compare the anchorage provided with the Nance appliance (NA) and the fixed frontal bite plane (FBP) during intra-arch distal molar movement. After a sample size calculation, 20 patients were recruited and randomly selected for each group from patients who fulfilled the following criteria: use of an intra-arch Ni-Ti coil appliance with either NA or FBP to provide anchorage during a six-month molar distalization period, no orthodontic treatment before molar distalization, and first and second maxillary molars in occlusion. The outcome measures assessed were anchorage loss, ie, anterior movement of maxillary central incisors, distal movement of maxillary molars, and bite opening effect. The mean age in the NA group was 14.7 years (SD 1.09) and in the FBP group 15.0 years (SD 0.99). The data revealed that the maxillary central incisors moved anteriorly 1.4 mm in the NA group and 1.9 mm in the FBP group. The difference in anchorage loss was not significant. The mean amount of molar distalization within the maxilla was 1.7 mm in the NA group and 1.8 mm in the FBP group. In both groups, the overbite was significantly reduced and the overbite was decreased significantly more in the FBP group. Because neither the NA nor FBP provided stable anchorage, a second treatment phase is recommended to reverse the anchorage loss after distal molar movement. If molar distalization is planned in deep bite cases, the FBP is the anchorage system of choice.