Predictability of radiographic diagnosis of variations in root canal anatomy in mandibular incisor and premolar teeth.

Four hundred and fifty-five extracted mandibular incisor and 340 extracted mandibular premolar teeth were radiographed to assess the incidence of twin canals as visualized on radiographs taken in the mesio-distal direction. The ability to detect the presence of these twin canals by viewing radiographs taken in the standard bucco-lingual direction was then assessed. Using the guideline that 'disappearance or narrowing infers division' when viewing these radiographs resulted in a failure to diagnose one-third of the twin canals.