The fourth molar in a mandible found in a Jomon skeleton in Japan

A fourth molar in a mandible occurs very rarely, even in clinical surveys involving a large number of modern people. Having encountered a case with the fourth mandibular molar in a prehistoric skull in Japan, we would like to report on the macroscopic morphology of the case using X-rays, and to discuss the case with reference to literature concerning supernumerary teeth in the molar region.