Purpose: The purpose of this study was to compare subjective evaluation of occlusal canting in frontal photographs with objective radiographic measurements to determine the threshold at which a cant is recognized as abnormal.
Patients and methods: Standardized frontal photographs (at rest and smiling) of two groups of orthognathic surgery patients were evaluated. Group 1 consisted of patients with a documented occlusal cant (n = 21), and group 2 consisted of patients with no cant (n = 22). Four untrained and five trained observers independently, and blind to the diagnoses, assessed patient photographs to judge the presence or absence of canting. These subjective results were compared with objective measurements of the angle of the occlusal plane to the true horizontal on each patient's posteroanterior (PA) cephalogram.
Results: The mean occlusal cant was 5.0 degrees +/- 1.6 degrees for group 1 and 1.4 degrees +/- 0.9 degree for group 2. The difference between groups was statistically significant (P < .01). Cants greater than 4 degrees were detected clinically with greater than 90% frequency by both untrained and trained observers.
Conclusions: The results of this study indicate that 4 degrees is the threshold for recognition of an occlusal cant by 90% of observers. This information has significant implications for three-dimensional planning and outcome assessment in orthognathic and craniofacial surgery.