A Preliminary Study on Inherited Tooth Morphology Characters of Japanese and Chinese Young Adults

Abstract

A comparative study on inherited tooth morphology characters, in particular the incidence of Carabelli tubercles in the maxillary dentition, was conducted on standardized stone casts obtained from 240 Japanese (124 males (male) and 116 females (females)) and 160 Chinese (74 male, 86 female) young adults. The following results were obtained: 1) No significant differences in the incidence of Carabelli tubercles according to sex or body height were found between the two groups. 2) However, significant differences in the incidence of Carabelli tubercles according to sex were found in both groups. The tubercles occurred more frequently in males. 3) Significant differences between the bilateral and unilateral occurrence of Carabelli tubercles were observed in both the Japanese (p < 0.05) and Chinese (p < 0.01) groups; Carabelli tubercles on upper first molars were always bilateral. 4) The highest incidence of Carabelli tubercles was found in individuals with a body height of 166 approximately 175 cm in both groups, and a significant difference (p < 0.05) between the 156 approximately 165 cm and 166 approximately 175 cm groups was particularly evident in the Japanese adults. The authors postulate that bilateral occurrence of Carabelli tubercles was originally an inherited character in the molar region, but that the character was inhibited during the process of evolution of the masticatory system and regression of the molar dentition.

The Tubercule Carabeli in a Moroccan Population

“…According to our study, sexual dimorphism regarding the frequency and expression of the Carabelli tuber is absent, which is consistent with several studies such as that of Scott, Castro (1989), Tsai, et al, who reported no significant difference between the sexes [8][9][10][11][12][13][14][15][16][17][18][19]. Another Malaysian study has confirmed that there is no sexual dimorphism in the occurrence of the tuber [10].…”

“…Another Malaysian study has confirmed that there is no sexual dimorphism in the occurrence of the tuber [10]. In Nepal, a study has shown that the sex parameter has no implication in the expression of the TC [11].…”

Variation in Dental Crown Morphology in Malaysian Populations

“…The distal accessory ridge was found more often in Jahai males, which is consistent with Scott (1977) who studied the frequencies and degrees of expression of the distal accessory ridge in seven ethnic groups in the United States of America. Carabelli trait in Malaysian Chinese was more common in males, a similar result to that reported in Japanese and Chinese samples (Iwai-Liao et al, 1996), Southern Chinese (Hsu et al, 1999), Australian Aborigines (Townsend and Brown, 1981) and Indian Jats (Kaul and Prakash, 1981). In contrast, Hanihara (1977), Turner and Hanihara (1977), Scott (1980), Manabe et al (1992) and Rusmah (1992) did not find any sexual dimorphism in the occurrence of this trait.…”

“…The frequencies of Carabelli trait found in this study were generally high when compared with other published material for Mongoloid populations (Rusmah, 1992;Iwai-Liao et al, 1996;Hsu et al, 1999). Only one article about Wainwright Eskimos by Hershey (1979) provides figures that approximate those obtained for Carabelli trait in this study.…”

“…Scott and Turner (1997) have concluded that dental morphological traits are suitable for population characterization due to their low sexual dimorphism and strong symmetry, and several researchers have found no evidence of significant sexual dimorphism for various dental traits (Garn et al, 1966b;Bang and Hasund, 1971;Bang and Hasund, 1972;Hanihara, 1977;Turner and Hanihara, 1977;Turner and Scott, 1977;Hershey, 1979;Scott, 1980;Hassanali, 1982;Mayhall et al, 1982;Kieser, 1984;Thomas et al, 1986;Townsend et al, 1986;Haeussler et al, 1989;Townsend et al, 1990;Manabe et al, 1992;Rusmah, 1992;Kannappan and Swaminathan, 1998). Other researchers, however, have noted higher frequencies for certain features in males (Rothhammer et al, 1968;Escobar et al, 1977;Scott, 1977;Townsend and Brown, 1981;Iwai-Liao et al, 1996;Hsu et al, 1997) and occasionally in females (Harris and Bailit, 1980). Several studies have indicated that dental traits tend to be expressed symmetrically (Baume and Crawford, 1979;Harris and Bailit, 1980;Noss et al, 1983b;Townsend et al, 1990) while others have reported evidence of asymmetry (Meredith and Hixon, 1954;Mayhall and Saunders, 1986;Moskona et al, 1996).…”