Sixth and seventh cusp on lower molar teeth of Malawians in East-Central Africa.

Abstract

The expressions of both sixth cusp (C6) and seventh cusp (C7) among the Malawians in East-Central Africa are described and compared with those of other African, Mongoloid, and Caucasoid populations. The subjects consisted of 99 males and 95 females. Scoring was performed using dental hard stone casts according to Turner's standard plaques. A sexual dimorphism in the occurrence of each trait was found to be not significant by chi-square test. The frequency of C6 in Malawians is remarkably lower than that in Mongoloid populations, and is located at the low range of frequency of C6 in the Caucasoid racial variation. On the other hand, C7 was observed more frequently in Malawian samples than in Mongoloid and Caucasoid populations. This tendency is in accordance with findings by Hellman on West African Negroes and by Hanihara on Bantu and American Negroes. Therefore, it is likely that C7 should be one of the components of the “Negroid dental complex”. In general, the Malawians were similar to other African groups with the exception of the Teso in the occurrence of both traits. Concerning the frequency order between first and second lower molars in the Malawians, C6 and C7 appeared more often in first lower molars than in second lower molars. These results concerning C6 seriously question the validity of the “field concept” in relation to the human dentition.