Stress and dental asymmetry in a population of Japanese children

We studied the significance of the magnitude of fluctuating dental asymmetry in 489 Japanese children by regression analysis. The search was for the predictability of asymmetry from levels of five factors assumed to be relevant parameters of prenatal stress. The five factors were derived by principal components analysis to simplify the interrelationships between birth weight, gestational age, maternal age, parity, sex, year of birth, socioeconomic status, and F, the coefficient of inbreeding. Only the regression of asymmetry on a factor representing a secular effect related to sex ratio was statistically significant; however, the relationship was too small to be biologically meaningful. The significance of individual asymmetry is thus equivocal, and this is discussed in terms of the meaning of asymmetry vis à vis overall fitness and developmental homeostasis. We conclude that experimental research will be necessary to elucidate not only the determinants of dental asymmetry but the relationship between these determinants and mortality and morbidity.