Impact on perceived root resorption based on the amount of incisal inclination as determined from conventional panoramic radiography

•Incisor external apical root resorption was assessed on panoramic radiographs.•As mandibular anteroposterior incisor angulation changed, teeth appeared shorter.•Shorter teeth were associated with increased external apical root resorption.•Actual impact of root foreshortening caused by imaging limitations is questionable.

IntroductionOur objective was to measure the impact on perceived root resorption based on the amount of anteroposterior incisal inclination as determined in vitro from conventional panoramic radiography.MethodsA rapid prototyping model was created to mimic different maxillary and mandibular incisal anteroposterior inclinations. Two titanium beads were placed on the incisors at the apical and incisal edges. Panoramic radiographs were obtained, with the incisors changing relative inclination by 10° increments. The length was measured from the midpoint of the bead on the incisal edge to the midpoint of the bead on the apical edge. By using a length of wire of known size, this value was compared in all images to correct for image magnification.ResultsChanges to mandibular incisor anteroposterior inclinations, as either a theoretical proclination or retroclination, resulted in an increase of “apparent” root resorption on a panoramic radiograph. When the maxillary incisors were significantly and severely retroclined, they appeared larger than expected. When the maxillary incisors were mildly retroclined, the length was roughly similar to the theoretical model. When the maxillary incisors were mildly proclined, they appeared shorter than expected.ConclusionsThe foreshortening or forelengthening of incisor root lengths because of incisor inclination vs root resorption cannot be reliably evaluated from panoramic images. The proposed theoretical model helps to understand the direction of the changes produced by the magnification factor. More severe scenarios where either the maxillary or the mandibular teeth are outside the focal trough have not been fully evaluated. The clinical impact of these changes is likely to be questionable.