In vitro study into the influence of X-ray beam angulation on the detection of artificial caries defects on bitewing radiographs

Little is known about the influence of errors in angulation of the X-ray beam on the correct diagnosis of interproximal caries defects from bitewing radiographs. In this study radiographs were made of 10 artificial lesions resembling initial interproximal caries defects in mandibular teeth at different projection angles within a range of +/- 15 degrees in horizontal and in vertical direction and presented in a random order to 25 dentists. The result show that the best angle for lesion detection was site-specific with about a 7 degrees tolerance range. On the average, best detection performance was achieved with horizontal angulation perpendicular to the tooth surfaces, and vertical angulation with a positive or negative tilt of 12-15 degrees relative to the perpendicular. Deviations from the best horizontal angle resulted mainly in loss of sensitivity, while vertical misangulations caused mainly a drop of the specificity. The classification of lesions with an actual depth less than halfway into the enamel is influenced to a larger extent than that of deeper lesions.