Accuracy of tooth length measurements from periapical radiographs.

This study was undertaken to investigate and assess two radiographic techniques for measuring tooth length. The result of this study demonstrated the inadequacy of determining tooth lengths using radiographs alone without the introduction of instruments into the canal as close as possible to the root apex. Neither of the techniques proved ideal, however, the Paralleling Extension Tube Technique seemed relatively more accurate and reliable than the Bisecting-Angle Technique.