Influence of horizontal condylar angle and x-ray projection angle on the appearance of the condyle on lateral temporomandibular joint panoramic radiographs.

Aims: This study used dried human mandibles and aimed to assess the effect of different horizontal condylar angle and the effect of different beam angles from three different units in the depiction of medial, central and lateral parts of the condyle on panoramic and lateral temporomandibular joint (TMJ) panoramic images.

Methods: Standard panoramic and lateral TMJ panoramic images of four dried human mandibles with horizontal condylar angles of 5, 8,10, 15, 17 and 20 degrees were analysed. The different parts of the condyle were represented by radiopaque markers. The standard panoramic and lateral TMJ panoramic images of the four mandibles were acquired from three panoramic radiography models with different x-ray beam angle. The images were analysed for the position of these radiopaque markers.

Results: Standard panoramic images demonstrated almost similar images of the condyles in the three panoramic models. The lateral TMJ panoramic images demonstrated the medial pole anterior to the lateral pole when the x-ray projection angle was more than the horizontal condylar angle; superimposition of medial and lateral poles when the x-ray projection angle was equal to horizontal condylar angle; and lateral pole anterior to medial pole when the x-ray projection angle was less than beam projection angle.

Conclusion: This study demonstrated that apart from other factors, the depiction of the mandibular condyle on lateral TMJ panoramic radiographs depends on the horizontal condylar angle, and the x-ray beam angle, which differs among different manufacturers. Therefore these limitations have to be considered when interpreting the integrity of the mandibular condyle on lateral TMJ panoramic radiographs.