A quantitative comparison of paralleling long-cone and bisection-of-angle periapical radiography.

Quantitative data permit the variability comparison of crown-root ratios computed from periapical films of a single central incisor taken by five technicians using the bisection-of-angle and the paralleling long-cone techniques. The paralleling long-cone technique produces significantly less distortion and is less variable. It is the method of choice for assessing natural root resorption and resorption due to orthodontic therapy.