Short-term effects of the activator in skeletal class II division 1 patients with different vertical skeletal pattern. A retrospective study.

The aim of this retrospective study was to analyse the effectiveness of Andresen appliance in inducing an increased mandibular dimension and, above all, to test the "null" hypotesis that the patients' vertical skelettofacial morfology could influence this increase using the Ricketts' method of VERT. Cephalometric records of 42 skeletal class II patients treated at the Orthodontic Department of Catania University were randomly selected. The sample was divided for vertical facial patterns, according to the facial classification method of Ricketts (VERT), into three groups: brachyfacial, mesiofacial and dolicofacial. Ten landmarks were located on the lateral cephalometric radiographs; growth in the horizontal-sagittal direction and in the vertical direction was evaluated using the measurements of total mandibular length (Co-Gn, Co-Pg, Ar-Pg, Ar-Gn), mandibular sagittal position (SNB, ANB) and mandibular ramus height (S-Go, Ar-Go, Co-Go). The intragroup comparisons were made using two tailed t-tests, while the intergroup comparisons were analyzed statistically using the Kruskal-Wallis test. The cephalometric values before (T0) and after (T1) treatment showed significant changes for the majority of the cephalometric variables in each group. Our findings demonstrated a statistically significant greater increase of mandibular dimension in the brachyfacial group, while similar results were found for mesiofacial and dolichofacial groups. The "null" hypothesis, that the skeletal pattern of subjects could influence the increase of mandibular dimension after Andresen treatment, had to be accepted: the brachyfacial patients showed a greater anterior mandibular displacement when compared to mesiofacial or dolichofacial group.