Evaluation of Partially Edentulous Arch in Ancient Japanese

Objectives: Dentition continuously proceeds to an edentulous condition over time. When examining a partially edentulous arch, it is necessary to capture a continuously condition without interruption. The causes of tooth loss include caries, periodontal disease, bruxism, and others, though it is difficult to determine the cause of lost teeth in ancient people.

Methods: Skulls dating from the end to last of the Jomon period (4500–2800BP) were examined to determine remaining teeth and occlusal support areas, and caries. Cummer's classification was used to evaluate remaining occlusal support areas, for which each dentition was divided into 3 blocks; anterior tooth area, and left and right posterior tooth areas, then the presence or absence of the examined parameters in 6 blocks of the upper and lower jaws were presented as a table divided into 64 patterns.

Results: In 78 skulls without destruction of the maxilla or mandible, evidence of partially edentulous arch was seen in 28. In those with a partially edentulous arch, a missing lower anterior tooth area was most often seen (n=14). In skulls missing posterior tooth areas, 1 was missing only the upper area, 1 only the lower area, and 3 both areas. Caries occurrence was noted in 53.6% and 26.0% with a partially edentulous and non-edentulous arch, respectively.
Conclusions: Only 35.9% of the examined Jomon skulls had a partially edentulous arch, in which the rate of caries was significantly higher. Therefore, caries was considered to be a major cause of tooth loss in these people. In addition, no difference between the upper and lower missing posterior tooth areas was observed. In contrast, in modern people, a tendency to lose upper jaw teeth more often has been reported.