191 © 2010 The Anthropological Society of Nippon ANTHROPOLOGICAL SCIENCE Vol. 118(3), 191–198, 2010 Enamel thickness in Asian human canines and premolars Robin N.M. FEENEY 1 , John P. ZERMENO 2 , Donald J. REID 3 , Syozi NAKASHIMA 4 , Hiroshi SANO 5 , Armasastra BAHAR 6 , Jean-Jacques HUBLIN 1 , Tanya M. SMITH 1,2 * 1 Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig D-04103, Germany 2 Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA 3 Department of Oral Biology, School of Dental Sciences, Newcastle University, Newcastle upon Tyne NE2 4BW, UK 4 Research and Technology Headquarters, Oral Care Research Laboratories, Odawara 256-0811, Japan 5 Product Development Department, International Division, Lion Corporation, Tokyo 130-8644, Japan 6 Faculty of Dentistry, University of Indonesia, Jakarta 10430, Indonesia Received 6 October 2009; accepted 4 March 2010 Abstract Dental enamel thickness continues to feature prominently in anthropological studies of ape and human evolution, as well as studies of preventative oral care and treatment. Traditional studies of enamel thickness require physical sectioning of teeth for linear and scaled measurements. Recent applications of microtomographic imaging allow scientists to employ larger and more diverse samples, including global samples of recent humans as well as fossil hominin teeth. Unfortunately, little is known about the degree of enamel thickness variation among human populations, particularly across the dentition. This study employed microtomography to virtually image, section, and quantify the average enamel thickness of a sample of clinically extracted Indonesian canine and premolar teeth. This virtual sample was compared to physically sectioned African and European teeth. The results demonstrate that average enamel thickness is similar among human dentitions; no significant differ- ences were detected within tooth positions, which is surprising given developmental differences be- tween European and African canines and premolars. When populations were combined, differences were found in average enamel thickness between maxillary and mandibular premolars, and between canines and premolars within both dental arcades. This finding is potentially due to differences in pre- molar morphology and a trend of increasing enamel thickness distally throughout the dentition. The finding of limited population variation within tooth positions and significant variation between tooth positions is consistent with previous two-dimensional and three-dimensional studies of human molar enamel thickness. Average enamel thickness in canines and premolars does not differ between the sexes in our sample, although male teeth tend to have larger enamel and dentine cross-sectional areas, enamel–dentine junction lengths, and bi-cervical diameters. Males have significantly greater dentine area and enamel–dentine junction length than females for maxillary canines and premolars. The results of this study suggest that enamel thickness values in mixed-populations of humans are appropriate for comparisons with fossil hominins. Key words: average enamel thickness, dental anthropology, human variation, microtomography, human evolution Introduction Enamel thickness has figured prominently in studies of human evolution over the past three decades and is recog- nized as an important morphological difference between thinly enameled African apes and thickly enameled Homo (e.g. Gantt, 1977; Molnar and Gantt, 1977; Martin, 1983, 1985). It has been studied in both extant and extinct primate species to understand taxonomic and phylogenetic relation- ships (e.g. Schwartz, 2000a; Kono, 2004; Smith et al., 2005, 2006, 2008, 2009a; Olejniczak et al., 2008a, b; Suwa et al., 2009) and tooth function (e.g. Macho and Berner, 1993, 1994; Macho, 1994; Schwartz, 2000b). Information on enamel thickness is also valuable for clinical preventative and therapeutic measures (e.g. Stroud et al., 1998; Jarvis, 1990; Rossouw and Tortorella, 2003; Hall et al., 2007). However, little work has been done to quantify variation in enamel thickness across the dentition (but see Smith et al., 2008) or to assess population-specific differences in enamel thickness and distribution in teeth other than molars. Enamel thickness studies from physical sections necessi- tate partial destruction of the crown to view and measure internal structures (e.g. Macho and Berner, 1993, 1994; Macho, 1994; Schwartz, 2000a, b; Grine, 2002, 2005; Smith et al., 2005, 2006, 2008), which often limits sample sizes. Brief Communication * Correspondence to: Tanya M. Smith, Department of Human Evolutionary Biology, Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA. E-mail: tsmith@fas.harvard.edu Published online 1 May 2010 in J-STAGE (www.jstage.jst.go.jp) DOI: 10.1537/ase.091006