Purpose: To evaluate the presence of furcation canals of permanent mandibular teeth using radiography and a clearing technique. Methods: The sample comprised 344 extracted mandibular molars. The presence of furcation canals was assessed by a single trained observer using magnifying lens (4x) for the dental radiographs and a dental optical microscope (30x) for the cleared specimens. Scanning electron microscopy (SEM) was used to evaluate morphological differences in the pulp chamber floor. Results: Radiographs showed that 9% of the specimens had radiolucent areas, 2% had an image that suggested a canal, and 89% had no abnormal findings. Clearing techniques did not show any accessory canal. SEM images revealed dentin tubules in recently extracted teeth; the other specimens had small areas with dentin tubules. Conclusion: Radiography was not better than the clearing technique to diagnose furcation canals. The clearing technique can provide three-dimensional visualization of the internal tooth anatomy for in vitro studies.