Bias in the superimposition of lateral cephalograms in adult patients with anterior open bite.

Introduction: Anterior open bite malocclusion can be treated nonsurgically using fixed appliances, clear aligners, or temporary anchorage devices (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 may be influenced by practitioner bias.

Methods: The initial and final lateral cephalograms from 30 adult anterior patients with open bite were used in this study. Ten patients were treated with fixed appliances, 10 with clear aligners, and 10 with TADs. We asked 6 orthodontic graduate students and 6 orthodontic practitioners to complete superimpositions using these radiographs in 3 separate sessions. In the first session, the raters were told that all patients only received treatment with fixed appliances. In the second session, the raters were told that all patients were treated with clear aligners only, and in 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 Portable Document Format 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 intrarater and interrater variability in the mandibular plane change was present in all 3 superimposition sessions. The measurements from the lateral cephs showed significant changes for overbite and incisor vertical and angular movements. Almost no change was observed in anterior facial height, mandibular plane angle, or vertical movement of the first molars.

Conclusions: This study did not observe a significant amount of superimposition bias. However, there was considerable intrarater and interrater reliability. This suggests that the same initial and final cephs may be interpreted very differently on the basis of the subjective superimposition of the raters.