Vertical changes following orthodontic extraction treatment in skeletal open bite subjects

The purpose of this investigation was to assess the vertical changes occurring in skeletal open bite patients treated orthodontically with different extraction patterns. The study was conducted using lateral cephalometric radiographs taken before and after treatment. Fifteen patients who had an anterior open bite (AOB) only were treated with first premolar extractions (Group E4). Seventeen patients with an AOB extending to the posterior teeth were grouped according to the extractions: extraction of second premolars (Group E5) and first molars (Group E6). Cephalometric data were analysed according to the 'two-factor experiment with a repeated measure on one factor' model. The treatment group factor had three levels, E4, E5, and E6, and the time factor two levels, pre- and post-treatment. The differences between the pre- and post-treatment periods were statistically significant for all the cephalometric variables (P < 0.001, P < 0.0001), except for ANS-Me/Na-Me. The time and group interaction were found to be statistically significant for the variables where the time factor is important, such as SN-GoGn angle, SGn-NBa angle, ANS-Me dimension, Na-Me dimension, forward movement of the maxillary and mandibular molars, and the distance to the mandibular plane of the lower molars. The severity of vertical dysplasia did not change in group E4. Generally, however, within the appropriate indications, extraction of the second premolars or the first molars led to a closing rotation of the mandible in subjects with a skeletal AOB extending to the posterior teeth.