Maxillary molar distalization or mandibular enhancement: a cephalometric comparison of comprehensive orthodontic treatment including the pendulum and the Herbst appliances

Abstract

Several methods of Class II treatment that do not rely on significant patient compliance have become popular during the last decade, including several versions of the Herbst appliance and the pendulum or Pendex molar-distalization appliances. Yet, these 2 general approaches theoretically have opposite treatment effects, one presumably enhancing mandibular growth, and the other moving the maxillary teeth posteriorly. This study examined the treatment effects produced by 2 types of the Herbst appliance (acrylic splint and stainless-steel crown) followed by fixed appliances, and the pendulum appliance followed by fixed appliances. For each of the 3 treatment groups, lateral cephalograms were analyzed before the start of treatment (T1) and after the second phase of treatment (T2). Patients were matched according to age and sex. The comprehensive treatment time for the pendulum group was 31.6 months, and the acrylic and crowned Herbst groups were treated for 29.5 months and 28.0 months, respectively. Overall from T1 to T2, there were no statistically significant differences in mandibular growth among the 3 groups. Skeletal changes accounted for a larger portion of molar correction in the Herbst treatment groups than in the pendulum group. Patients in the pendulum group had an increase in the mandibular plane angle. Conversely, the mandibular plane angle in patients treated with either Herbst appliance closed slightly from T1 to T2. At T2, the chin points (pogonion) of patients in both Herbst groups, however, were located slightly more anteriorly than were the chin points of the pendulum patients. It is likely that the slight downward and backward rotation of the mandible occurring during treatment in the pendulum patients accounted for much of this difference. The treatment effects produced by the 2 types of Herbst appliance were similar at T2, in spite of their differences in design. It is important not to generalize the findings of this comparison beyond the appliance systems evaluated. The 2 general approaches we evaluated involved a substantial dentoalveolar component in the treatment of Class II malocclusion. A comparison of a molar-distalizing appliance such as the pendulum with other types of functional appliances might yield differing results.