16 The Open Anthropology Journal, 2010, 3, 16-19 1874-9127/10 2010 Bentham Open Open Access Molar Cusps in Southern Chinese John Y.K. Ling and Ricky W.K. Wong* Orthodontics, University of Hong Kong, Hong Kong Abstract: Aim: To investigate the number of molar cusps of the Southern Chinese and compare these with studies in dif- ferent populations. Materials and Methods: The number of molar cusps of study casts of an unselected sample from a 12 year old Hong Kong Oral Health Survey of 12 year old children (n=459; 295 boys and 164 girls) were studied. Results: For upper first molars, 5-cusp molars were the most prevalent in males (39%) while 4-cusp molars were the most prevalent in females (39%). For lower first molars, 5-cusp molars were the most prevalent in both sexes (63%-72%). For lower second molars, 5-cusp molars were the most prevalent in both sexes (43%-53%). Conclusion: Different from traditionally described, the Southern Chinese has more 5-cusp lower second molars than the 4- cusp ones. Keywords: Molar cusp, Southern Chinese. INTRODUCTION It is generally believed that the numerous morphologic characteristics of the teeth are genetically determined [1, 2]. Detailed description and study of these traits could provide valuable information regarding phylogeny of man and dis- tinctions between races and subraces [1, 3-12]. Features of morphology which closely reflect genetic structure should be examined in determining the evolutionary (phylogenetic) relationships of populations and in establishing taxonomies that reflect these relationships [12]. Although tooth mor- phology may be an indicator of genetic distances between populations, it should be viewed with caution [11]. The study of the number of cusps are not only important in an- thropology, it is also important in the study of dental occlu- sion, orthodontics, restorative dentistry and prosthetic den- tistry. In modern man, the number of cusps of the upper molars is frequently reduced from four to three. The formula for the number of cusps of the upper molar series is changing from 4-4-4 to 4-4-3 and 4-3-3. The trend is more marked in fe- males than in males of all populations that have been stud- ied. In most studies, males generally showed a lesser ten- dency than females to reduction in the number of cusps of the upper molars. The process of reduction occurs through the elimination of the hypocone or distolingual cusp, with a subsequent decrease in the mesiodistal crown diameter and in the occlusal area. Moorrees [1] reported that living Aleut females pos- sessed fewer five-cusped second molars than males, the dif- ference being significant (N.B. small sample size of 36). In *Address correspondence to this author at the 2/F, Orthodontics, Prince Philip Dental Hospital, 34 Hospital Road, Sai Ying Pun, Hong Kong; Tel: 852 28590554; Fax: 852 25593803; E-mail: fyoung@hkucc.hku.hk the Aleuts, the frequency of 4 cusps is 100 % for the first molars, 69 % for the 2nd molars and 31 % for the 3rd mo- lars. There are normally five main cusps on a lower molar. The fifth or disto-buccal cusp is the most variable, which may be absent. If the fifth cusp is present it is often placed lingually, out of line with the other two buccal cusps. The fifth cusp may be divided into two parts by a fissure which runs antero-posteriorly, thus the tooth may have three lingual and three buccal cusps [8]. A total of ten cusps can be theo- retically present on a lower molar tooth. There is a large amount of publications on molar morphology, numbers of molar cusps, origins, and evolution of both cusps and teeth [13]. There are no standards yet available to determine whether a cusp should be recorded as one because of its in- adequate size. Suzuki & Sakai [14] found no significant differences in first and second molar cusp numbers of 392 male and female Japanese. The frequency of cusp 6 on first and second molars [65 and 63 % respectively] from Indian crania was found to be about three times that of Aleuts (21 and 18 %) and Eskimos (22 and 18 %). All three groups (Indian, Aleuts and Eski- mos) showed five or six cusped first lower molars. No four- cusped molars were found. Four-cusped second lower molars occurred most often in the Aleuts [9 %], less in Indians [3 %] and least in the Eskimos [1 %] [15]. Europeans and American Whites have the highest and unique frequency of four-cusped lower first molars (10 %) while the rest of the world's populations that have been sam- pled, which included African and American Negroes, Aus- tralians, Melanesians, Chinese, Japanese, Aini and native Americans, possessed on the average less than 3 % four cus- ped first lower molars [16-18].