Influence of patient head positioning on measured axial tooth inclination in panoramic radiography

Panoramic radiographs are routinely used to assess the mesiodistal axial inclination of teeth (MDAI) in orthodontic treatment. These radiographs are sensitive to minor deviations from standard head position that result in image distortions. The aim of this study is to measure and quantify the changes in MDAI on panoramic radiograph resulting from changes in patient head position.

The testing devise was a human skull with guide wires placed on the facial surface of the teeth and alveolar process along the long axis of each tooth. Panoramic radiographs were captured digitally with the orientation of the skull in Frankfurt horizontal plane parallel to the floor and with 1 degrees , 2 degrees , 5 degrees , 7 degrees , and 10 degrees both superior and inferior rotations. The mesiodistal tooth angulations were determined using MIPAC software (DentalEye and LEAD Technologies, Inc. 2005).

The more distal the position of the tooth in the arch the greater the change in MDAI with a change in vertical head position. A maximum change of approximately 10 degrees was observed in MDAI of both the maxillary and mandibular molars with a corresponding superior head tilt of 10 degrees. The Mandibular anteriors displayed significant inconsistencies in MDAI with both superior and inferior head tilt. A superior head tilt produced a greater change in mesiodistal angulation than did an inferior head tilt.

Accurately taken panoramic radiographs can serve as a convenient tool for evaluating the MDAI before, during and after orthodontic treatment. Additional radiographs are recommended for the mandibular anteriors.