Abstract:

BACKGROUND: The diagnosis and treatment of periodontal disease often requires measuring alveolar bone height and root length, but the validity of panoramic radiographs for quantitative measurement is still controversial.
OBJECTIVE: To evaluate the reliability of vertical lineal measurement on panoramic radiographs by means of amendment with reference pins.
METHODS: Permanent teeth of 20 orthodontic cases patients were selected. 5.00 mm steel balls were embedded in molar, premolar and incisor models as the measuring objects, and the reference pins of 10.0 mm length were placed on corresponding position with the ball as the reference standard. Panoramic radiographs of model were taken to measure the vertical diameter of ball images. The measurements were calibrated and corrected using reference pins. The variation between image measurements of steel balls on panoramic radiographs and their true values was compared.
RESULTS AND CONCLUSION: When using single reference or average reference of several pins, the distortion rate of panoramic measurements varied on different regions and different placement of reference pins, more than 5% in some regions. The accuracy of the results could be improved using reference pins which were completely perpendicular to occlusal plane to amend the vertical lineal measurement on panoramic radiographs. Here, all distortion rates were less than 1%, and the amendatory results were independent of calibration methods. Whereas the amendatory results were not satisfactory when using reference pins attached the surface of the alveolar of models.