Impact of malpositioning on panoramic radiography in implant dentistry.

OBJECTIVES: The widely used panoramic radiography as a special kind of tomography underlies intrinsic procedural restrictions such as poor definition, inconsistent magnification, geometric distortion and spatial depositioning of objects situated outside the focal trough. This results in a non-anatomic display of the radiographed anatomic structures. Individual mandibular angle and width of the jaws, adjustment of the focal trough, jaw incongruence as well as patient positioning increase the inconsistency in display of the radiographed objects. This study precisely evaluated the quantitative impact of object malpositioning on the display in panoramic radiography. MATERIALS AND METHODS: A special dental implant model was highly accurate three dimensionally malpositioned and panoramic radiographs were taken. Automated image analysis was performed to exclude subjective assessment error. RESULTS: Precise and retraceable object deposition of up to 5 mm or 5° resulted in relevant deposition of objects and significant changes in object size and inter-object distances in the panoramic image. Unidirectional malpositioning lead to multiple errors in display. CONCLUSIONS: The extent of malpositioning-related display errors additionally to the known physicotechnical insufficiencies of the panoramic radiography demonstrates its limitations in precisely interpreting spatial relationships. CLINICAL RELEVANCE: Measurements within the panoramic radiography must not claim reliability. For a single object securely positioned in the focal trough and perpendicular to the central X-ray beam, measurements may be trustworthy on clinical scale. Once sterical relationships to other structures are evaluated, reliability must be questioned.