[A study on the dental traits and crown sizes of Japanese children]

The purpose of this study was to clarify the relationship between crown size and crown form of deciduous teeth. The materials used in this study were 1063 shed or extracted deciduous teeth of Japanese children that were identified according to the individual's name, sex and age. These deciduous teeth were classified as to each developmental stage of the dental traits appearing on the crown, and were measured for the mesiodistal crown diameter and labio (bucco) lingual crown diameter. The results obtained were summarized as follows. 1. Tooth size i. For the upper deciduous teeth, the mean values of the tooth sizes (mesiodistal crown diameter and labio (bucco) lingual crown diameter) decreased in the order of V, IV, III, I and II with the exception of mesiodistal crown diameter in girls which decreased in the order of V, IV, III (which was equal to I in size) and II. For the lower deciduous teeth, the mean values of the tooth sizes (mesiodistal crown diameter and labio (bucco) lingual crown diameter) decreased in the order of V, IV, III, II and I. ii. The coefficients of covariation had a tendency to be larger in deciduous anterior teeth than in deciduous molars and were especially large in upper and lower deciduous lateral incisors in the mesiodistal crown diameter and in lower first deciduous molars, lower deciduous lateral incisors and lower deciduous canines in the labio (bucco) lingual crown diameter. iii. The mean values of tooth size (mesiodistal crown diameter and labio (bucco) lingual crown diameter) had a tendency to be larger in boys than in girls. Sexual size differences were significant in upper deciduous canines (mesiodistal crown diameter and labio (bucco) lingual crown diameter) and lower deciduous second molars (bucco lingual crown diameter). 2. Frequency of dental traits i. Shovel shaped teeth were found in 83.5% of the upper deciduous central incisors, 91.8% of the deciduous lateral incisors, 29.6% of the deciduous canines and 46.1% of the lower deciduous central incisors, 45.5% of the deciduous lateral incisors, 40.7% of the deciduous canines. ii. Crown surface patterns of the upper deciduous molars: Type 3 in the first deciduous molars and type 4 in the second deciduous molars were found much more frequency.(ABSTRACT TRUNCATED AT 400 WORDS)