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

Abstract

Abstract 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.