Quantitative and subjective analysis of temporomandibular joint radiographs

The lateral oblique transcranial radiograph of the temporomandibular joint is commonly used in dentistry. Changes in horizontal angulation of the x-ray beam can produce changes in radiographic condylar position. This study used quantitative and subjective methods to assess and rank changes in radiographic condylar position as a function of known horizontal x-ray beam changes. Six dry skulls were positioned in a craniostat device where known angulations could be measured. Nine sequential transcranial temporomandibular joint radiographs were made of each joint and five of these 12 sets were randomly selected for analyses. The quantitative method involved film digitization, computer calculations, and expressed condylar position as a ratio between posterior and anterior joint space distributions. Eight observers viewed the same films and ranked radiographic condylar position from anterior to posterior. The two methods agreed with known rankings 81.8% of the time. Subjective rankings were more variable than quantitative rankings. Intraobserver differences were insignificant and the observers were consistent among themselves as a group.