Genetic, Epigenetic and Environmental Influences on Human Tooth Size, Shape and Number


Studies of twins are helping to unravel the roles of genetic, epigenetic and environmental influences on human tooth size, shape and number. There is a relatively strong genetic contribution to variation in these dental phenotypes but comparisons between monozygotic cotwins are also highlighting the roles of environmental and epigenetic factors. Furthermore, by viewing the dentition as a complex adaptive system, with multiple interacting components, a clearer picture is emerging of how common dental anomalies develop and are associated with one another. This article concentrates on providing a synthesis of relevant findings and concepts about variation in the human dentition at a phenotypic level. We focus on patterning within the dentition and dental asymmetry, as well as emphasising the importance of assessing the magnitude of errors when measuring or scoring dental features. We also provide links to several articles published in the Encyclopedia of Life Sciences that cover the molecular aspects of dental development.

Key Concepts:

  • There are distinct patterns of variation within the human dentition that conform to ‘morphogenetic fields’.

  • Patterns of phenotypic variation correspond with the relative amount of time that each tooth germ spends in the soft tissue phase before mineralisation.

  • A unifying aetiological model, incorporating thresholds, serves to explain the relationships between tooth size, shape and number in males and females.

  • Tooth size variation shows a relatively strong genetic component but epigenetic and environmental factors can also contribute to phenotypic variation.

  • Interrelationships exist between dental crown size and morphological dental features, such as the Carabelli trait.

  • Discordance in the expression of missing or extra teeth between monozygotic cotwins indicates involvement of epigenetic influences on dental development.

  • Studies of dizygotic opposite sex twins indicate that hormonal influences in utero can influence dental development.

  • The magnitude of fluctuating dental asymmetry reflects the effects of epigenetic and environmental influences during development.

  • Dental development is a multilevel process involving interacting genetic, epigenetic and environmental factors over an extended period.

  • The dentition fulfils the characteristics of a complex adaptive system.

Keywords: dental development; twins; genetic; epigenetic; environment; complexity; teeth; phenotypes

Figure 1.

Model for unifying aetiology of anomalies of tooth size, shape and number, developed from Brook . The male and female curves have the same shapes but the thresholds for missing teeth or extra teeth, together with abnormal tooth shape, are placed asymmetrically in the tails of the distributions.

Figure 2.

Similar expression of the Carabelli trait on the primary second molars and permanent first molars of both members of a pair of MZ twins.

Figure 3.

Multilevels of tooth development.



Alvesalo L (2009) Human sex chromosomes in oral and craniofacial growth. Archives of Oral Biology 54S: S18–S24.

Apps MVB, Hughes TE and Townsend GC (2004) The effect of birthweight on tooth‐size variability in twins. Twin Research 7: 415–420.

Brook AH (1984) A unifying aetiological explanation for anomalies of tooth number and size. Archives of Oral Biology 29: 373–378.

Brook AH (1995) Dental anomalies and periodontal disease. In: Berkovitz BK, Moxham BJ and Newmann HN (eds) Periodontal Ligament in Health and Disease, 2nd edn, pp. 279–292. London: Mosby.

Brook AH (2009) Multilevel complex interactions between genetic, epigenetic and environmental factors in the aetiology of anomalies of dental development. Archives of Oral Biology 54S: S3–S17.

Brook AH, Elcock C, Aggarwal DL et al. (2009a) Tooth dimensions in hypodontia with a known PAX9 mutation. Archives of Oral Biology 54S: S57–S62.

Brook AH, Griffin RC, Townsend G et al. (2009b) Variability and patterning in permanent tooth size of four human ethnic groups. Archives of Oral Biology 54S: S79–S85.

Butler PM (1939) Studies of the mammalian dentition. Differentiation of the post‐canine dentition. Proceedings of the Zoological Society of London, Series B 109: 1–36.

Butler PM (2001) What happened to the field theory. In: Brook A (ed.) Dental Morphology, pp. 3–12. Sheffield: Sheffield Academic Press Ltd.

Dahlberg AA (1945) The changing dentition of man. Journal of the American Dental Association 32: 676–690.

Dahlberg AA (1951) The dentition of the American Indian. In: Laughlin WS (ed.) The Physical Anthropology of the American Indian, pp. 138–176. New York: Viking Fund Inc.

Dempsey PJ and Townsend GC (2001) Genetic and environmental contributions to variation in human tooth size. Heredity 86: 685–693.

Fearne JM and Brook AH (1993) Small primary tooth‐crown size in low birthweight children. Early Human Development 33: 81–90.

Keene HJ (1982) The morphogenetic triangle: a new conceptual tool for application to problems in dental morphogenesis. American Journal of Physical Anthropology 59: 281–287.

Kieser JA (1990) Human Adult Odontometrics. The Study of Variation in Adult Tooth Size. Cambridge: Cambridge University Press.

Kitamura H (1989) Embryology of the Mouth and Related Structures. Tokyo: Maruzen Co Ltd.

Kjaer I (1998) Neuro‐osteology. Critical Reviews in Oral Biology and Medicine 9: 224–244.

Kondo S and Townsend G (2006) Associations between Carabelli trait and cusp areas in human permanent maxillary first molars. American Journal of Physical Anthropology 129: 196–203.

Mitsiadis TA and Smith MM (2006) How do genes make teeth to order through development? Journal of Experimental Zoology 306B: 177–182.

Osborn JW (1978) Morphogenetic gradients: fields versus clones. In: Butler PM and Joysey KA (eds) Development, Function and Evolution of Teeth, pp. 171–201. London: Academic Press.

Ribeiro DC, Brook AH, Hughes TE, Sampson WJ and Townsend GC (2013) Intrauterine hormone effects on tooth dimensions. Journal of Dental Research 92: 425–431.

Sharpe PT (1995) Homeobox genes and orofacial development. Connective Tissue Research 32: 17–25.

Skinner MM, Wood BA, Boesch C et al. (2008) Dental trait expression at the enamel‐dentine junction of lower molars in extant and fossil hominoids. Journal of Human Evolution 54: 173–186.

Townsend G, Harris E, Lesot H, Clauss F and Brook A (2009a) Morphogenetic fields within the human dentition: A new, clinically relevant synthesis of an old concept. Archives of Oral Biology 54S: S34–S44.

Townsend G, Hughes T, Luciano M, Bockmann M and Brook A (2009b) Genetic and environmental influences on human dental variation: A critical evaluation of studies involving twins. Archives of Oral Biology 54S: S45–S51.

Townsend GC (1983) Fluctuating dental asymmetry in Down's syndrome. Australian Dental Journal 28: 39–44.

Townsend GC and Martin NG (1992) Fitting genetic models to Carabelli trait data in South Australian twins. Journal of Dental Research 71: 403–409.

Townsend GC, Richards L, Hughes T et al. (2005) Epigenetic influences may explain dental differences in monozygotic twin pairs. Australian Dental Journal 50: 95–100.

Turner CG, Nichol CR and Scott GR (1991) Scoring procedures for key morphological traits of the permanent dentition: The Arizona State University Dental Anthropology System. In: Kelley MA and Larsen CS (eds) Advances in Dental Anthropology, pp. 13–31. New York: Wiley‐Liss.

Further Reading

Bailleul‐Forestier I, Molla M, Verloes A et al. (2008) The genetic basis of inherited anomalies of the teeth. Part 1: clinical and molecular aspects of non‐syndromic dental disorders. European Journal of Medical Genetics 51: 273–291.

Bell JT and Saffery R (2012) The value of twins in epigenetic epidemiology. International Journal of Epidemiology 41: 140–150.

Cai J, Cho S‐W, Kim J‐Y et al. (2007) Patterning the size and number of tooth and its cusps. Developmental Biology 304: 499–507.

Cobourne MT and Sharpe PT (2013) Diseases of the tooth: the genetic and molecular basis of inherited anomalies affecting the dentition. WIREs Development Biology 2: 183–212.

Harris EF (2008) Interpreting heritability estimates in the orthodontic literature. Seminars in Orthodontics 14: 125–134.

Harris EF and Smith RN (2009) Accounting for measurement error: a critical but often overlooked process. Archives of Oral Biology 54S: S107–S117.

Jernvall J and Jung HS (2000) Genotype, phenotype and developmental biology of molar tooth characteristics. Yearbook of Physical Anthropology 43: 171–190.

Kangas AT, Evans AR, Thesleff I and Jernvall J (2004) Non independence of mammalian dental characters. Nature 432: 211–214.

Primozic J, Farcnik F and Ovsenik M (2012) Places in the dental arch that show a greater variability in tooth number, shape and position – a prevalence study. Archives of Oral Biology 57: 744–748.

Townsend G, Kanazawa E and Takayama H (2012) New Directions in Dental Anthropology: Paradigms, Methodologies and Outcomes. Adelaide: University of Adelaide Press.

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Townsend, Grant C, and Brook, Alan H(Jun 2013) Genetic, Epigenetic and Environmental Influences on Human Tooth Size, Shape and Number. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0024858]