Intrauterine Hormone Effects on Tooth Dimensions

The human dentition is a complex adaptive system that is influenced by genetic, epigenetic, and environmental factors. Within this system, is sexual dimorphism related to the growth promotion of the Y chromosome, or to hormonal influences, or both? This study is the first to investigate both primary and permanent tooth sizes in females from opposite-sex dizygotic (DZOS) twin pairs compared with females from dizygotic same-sex (DZSS) and monozygotic (MZ) twin pairs to indicate the influence of intrauterine male hormone, including the initial testosterone surge, on dental development. Serial dental models of the primary, mixed, and permanent dentitions of 134 females from DZOS, DZSS, and MZ twins were examined. Mesiodistal, buccolingual, crown height, and intercuspal dimensions of all primary teeth and selected permanent teeth were determined by image analysis. Univariate and multivariate analyses showed statistically significantly larger crown size in DZOS females in both dentitions, with the crown height dimensions displaying the greatest increase in size. These findings strongly support the Twin Testosterone Transfer (TTT) hypothesis. We propose that the growth-promoting effects of the Y chromosome and intrauterine male hormone levels influence different tooth dimensions and contribute differentially to the sexual dimorphism of human teeth.

[1]  Dorret I Boomsma,et al.  Does having a twin brother make for a bigger brain? , 2009, European journal of endocrinology.

[2]  G. Townsend,et al.  Intercuspal Distances of Maxillary Pre-molar Teeth in Australian Aboriginals , 1985, Journal of dental research.

[3]  S. Berenbaum,et al.  Prenatal sex hormone effects on child and adult sex-typed behavior: methods and findings , 2005, Neuroscience & Biobehavioral Reviews.

[4]  G. Townsend,et al.  Increased tooth crown size in females with twin brothers: Evidence for hormonal diffusion between human twins in utero , 1999, American journal of human biology : the official journal of the Human Biology Council.

[5]  L. Alvesalo,et al.  Human sex chromosomes in oral and craniofacial growth. , 2009, Archives of oral biology.

[6]  D. Guatelli‐Steinberg,et al.  Dental crown size and sex hormone concentrations: another look at the development of sexual dimorphism. , 2008, American journal of physical anthropology.

[7]  G. Townsend,et al.  Strong Genetic Control of Emergence of Human Primary Incisors , 2007, Journal of dental research.

[8]  E. Miller,et al.  Analysis of the effect of hormones on opposite-sex twin attitudes. , 1995, Acta geneticae medicae et gemellologiae.

[9]  G. Townsend,et al.  Genetic, environmental and epigenetic influences on variation in human tooth number, size and shape , 2011, Odontology.

[10]  E. Miller.  Prenatal sex hormone transfer: A reason to study opposite-sex twins , 1994 .

[11]  M. Maybery,et al.  Sex-specific associations between umbilical cord blood testosterone levels and language delay in early childhood. , 2012, Journal of Child Psychology and Psychiatry and Allied Disciplines.

[12]  D. Ribeiro.  Increased tooth crown size in females from opposite-sex dizygotic twins : a possible intrauterine hormonal influence on dental development. , 2012 .

[13]  M. Maybery,et al.  Evaluating the twin testosterone transfer hypothesis: A review of the empirical evidence , 2011, Hormones and Behavior.

[14]  A. Brook,et al.  Multilevel complex interactions between genetic, epigenetic and environmental factors in the aetiology of anomalies of dental development , 2009, Archives of oral biology.

[15]  M. Dean,et al.  Variation in modern human enamel formation times. , 2006, Journal of human evolution.

[16]  R. N. Smith,et al.  A three-dimensional comparison of the modifying effects of familial genetic contribution in Turner syndrome. , 2009, Frontiers of oral biology.

[17]  H. Lesot,et al.  Epithelial histogenesis during tooth development. , 2009, Archives of oral biology.

[18]  J. Winter,et al.  Studies on human sexual development. II. Fetal and maternal serum gonadotropin and sex steroid concentrations. , 1974, The Journal of clinical endocrinology and metabolism.

[19]  J. Winter,et al.  Studies on human sexual development. I. Fetal gonadal and adrenal sex steroids. , 1973, The Journal of clinical endocrinology and metabolism.

[20]  Gunnar Dahlberg.  Statistical Methods for Medical and Biological Students. , 1941 .

[21]  S. Baron-Cohen,et al.  Fetal testosterone and sex differences. , 2006, Early human development.

[22]  Alan Brook,et al.  New Directions in Dental Anthropology: Modelling the complexity of the dentition , 2012 .