The effect of horizontal X-ray beam angulation on the detection of furcation defects of mandibular first molars in intraoral radiography

The aim was to investigate the effect of changes in horizontal X-ray beam angulation in intraoral radiography on the detection accuracy of furcation defects in the mandibular first molar, and to examine the anatomical relationship between the roots and furcation area as a possible cause of changes in detectability. Simulated furcation defects with various depths were created in five mandibular first molars. Intraoral radiographs were taken at various horizontal angulations of the projection beams. The diagnostic accuracies were determined based on receiver operating characteristic analysis. The geometric relationship that might influence the accuracy was investigated through use of a compact cone beam CT in 59 first molar areas. Although the horizontal angulations showing the highest accuracies were shifted mesially, no differences were found between the angles of -10 degrees and 20 degrees . The relationship between the roots and the furcation area was relevant to the range of angulations showing high detectabilities. The angulations traditionally used for detecting proximal caries are also suitable for detecting furcation defects.