Bias in superimposition of lateral cephalograms in anterior openbite patients

Abstract

Introduction Anterior open bite malocclusion can be treated non-surgically using fixed appliances, clear aligners, or TADs. Proponents of clear aligners and TADs often attribute bite closure to molar intrusion and counterclockwise rotation of the mandibular plane. These changes may be supported by superimpositions. However, the process of creating a superimposition is subjective, and therefore may be influenced by practitioner bias. Methods The initial and final lateral cephalograms from 30 adult anterior openbite patients were used in this study. Ten of these patients were treated with fixed appliances, 10 with clear aligners, and 10 with temporary anchorage devices (TADs). We asked six orthodontic graduate students and six orthodontic practitioners to complete superimpositions using these radiographs in three separate sessions. In the first session, the raters were told that all patients received treatment with fixed appliances only. In the second session, the raters were told that all patients were treated with clear aligners only, and at the third session, they were told all patients were treated with fixed appliances and TADs. Superimpositions were performed using Dolphin software, and each superimposition was saved as a PDF image. Change in the mandibular plane was the primary outcome and was assessed categorically (closed, no change, opened). Cephalometric values were measured and used to investigate the dental and skeletal changes associated with treatment. Results Although the raters demonstrated a slight tendency toward the mandibular plane closing or staying the same when told the treatment was clear aligners or TADs, these differences were not statistically significant. A high degree of intra- and inter- rater variability in the mandibular plane change was present from all 3 superimposition sessions. The measurements from the lateral cephs showed significant changes for overbite and for incisor vertical and angular movements. Almost no change was observed in anterior facial height, mandibular plane angle, or vertical movement of the 1st molars. Conclusions A significant amount of superimposition bias was not observed in this study. However, there was considerable intra- and inter-rater reliability. This suggests that the same initial and final cephs may be interpreted very differently, based on the subjective superimposition of the raters.