The orthopantomogram, an aid in diagnosis of temporomandibular joint problems. I. The factor of vertical magnification.

As an orthopantomogram provides bilateral information, it seems to be an efficient tool for screening for arthropathy of craniomandibular disorders. An experimental model was designed and constructed to resemble a human mandible. By changing the position of the model in the horizontal plane of the orthopantomograph, nine different images were analysed for changes of vertical magnifications. Emphasis was put on large parts of the mandible like the condyle. In positions that had been altered less than 10 mm from the originally centred position of the mandible in the orthopantomograph, vertical differences between the left and right sides were less than 6%. Observed condylar asymmetries within a 6% difference might, therefore, be due to technical failures.