The effect of bucco-lingual root angulation on the mesio-distal image perception for panoramic images

The purpose of this study was to assess the effect of buccolingual root orientation on the perception of mesiodistal root angulation and parallelism for panoramic images. A phantom was constructed so that the tooth buccolingual orientation of eight different teeth could be easily modified. The true mesiodistal and buccolingual tooth angulations relative to an orthodontic archwire were calculated with a tri-dimensional coordinate measuring machine. The panoramic films were scanned and digitized with custom-designed software to determine the image mesiodistal angulations. The results of this study revealed that almost all the image angles for each tooth had at least one angle measurement that was statistically different from the other mesiodistal angles with different buccolingual orientations. The roots with buccal root orientations were projected more distally than they were in reality and roots lingually positioned were projected more mesially. This phenomenon was more pronounced in the maxilla than the mandible. The largest root parallelism differences for adjacent teeth occurred between the upper canine and first premolar followed by the mandibular canine/premolar area. Buccolingual orientation changes do not seem to affect the root parallelism expression on the incisor area.