Radix entomolaris in permanent mandibular first molars: case reports and literature review.

This article presents three cases involving permanent mandibular first molars with unusual root morphology. While the permanent mandibular first molar normally has two roots (one mesial and one distal), an additional root sometimes is found distolingually; this condition is known as radix entomolaris (RE). This article also reviews the literature concerning the morphology, prevalence, etiology, classification, diagnosis, and significance of RE.