Validity of panoramic radiographs for measuring mandibular asymmetry.

The objective of this study is to evaluate the accuracy of panoramic radiographs for diagnosing vertical asymmetry of the posterior mandible. The first part of the study used a model to evaluate the reproducibility of this particular panoramic machine. The tube traverse did not significantly affect the linear measurements, but the side of the machine where the structure was located produced an average of 2.1% variation in the total height of the mandible. In the second part of the study, the left-right (%) differences were measured on the panoramics and the laminographs of five skulls with lead markers. These differences were compared with the percent difference measured directly on the skull and with each other and suggested that the laminograph could be used as the "gold standard" for measuring posterior vertical mandibular asymmetry. The third part of the study evaluated a patient sample (N = 42). The correlation coefficient between the two types of films was determined to be 0.92 for total height and 0.39 for condyle height. Using the 6% cutoff reported in the literature, the sensitivity of the panoramics to diagnose asymmetry for the total height was determined to be 0.62 and the specificity 1.0. This study suggests that the panoramic radiograph can be used to evaluate vertical posterior mandibular asymmetry, but there will be some underdiagnosis.