The radiographic incidence of multiple roots and canals in human mandibular premolars.

The aim of this study was to investigate the incidence in mandibular premolars of multiple roots and root canals that could be demonstrated radiographically. The images of mandibular premolar teeth as seen on intraoral full-mouth radiographic surveys (547) taken with the paralleling technique were examined. In 99 patients (18.1%) there was at least one premolar tooth with either divided canals or roots. First premolars were involved in 15.7% of patients, and second premolars in 7%.