Studies on the reduction indices of the deciduous teeth of Chinese living in Taiwan.

The reduction index of deciduous teeth was investigated statistically. Materials used were plaster casts of the deciduous dentition taken from Chinese children living in Taiwan. The reduction indices showed no sexual differences. In the maxillary teeth, reduction indices of the bucco-lingual diameters (BL) had the largest values, followed by those of the mesio-distal diameters (MD), and those of the crown area (AREA) which were the least. In contrast to the maxillary teeth, in the mandibular teeth, the reduction indices of MD and those of BL had nearly the same values although the reduction indices of MD were slightly larger than those of BL in females (p < 0.05). With respect to the difference between the maxilla and the mandible, in deciduous incisors the reduction index of MD in the mandible was larger than that in the maxilla (p < 0.01). While in BL the reverse relation was noted. In the deciduous molars the reduction indices of BL and AREA in the maxilla were larger than those in the mandible (p < 0.01). The reduction indices showed no significant difference among the Mongoloid populations sampled. This result may be explained by the primitiveness of deciduous teeth.