Dental traits that characterize size, occlusion, and morphology are complex, multifactorial developmental traits for which the level of familial resemblance is high, but for which the genetic and environmental correlates are not yet understood. Due to methodological limitations, earlier studies assumed a priori that resemblance between relatives is due solely to genetic factors. As a result, a traditional view is held that genes are the major determinants of all dental traits and other factors can be ignored. Animal experimentation, however, has clearly refuted this view. In man, it is only through recently developed path analysis that the causal basis of such traits may be conclusively sorted out as biologic or cultural inheritance. These models, however, require data on common family environment which is a latent variable and cannot be directly measured or observed. Path and structural models derive much of their power from the ability to incorporate such a latent variable in the analysis, where relevant environmental data may be tested for validity as measures of an index of common family environment. Indexed data for dental developmental traits are presently nonexistent, mainly because of difficulties in the presence of environmental heterogeneity of study populations.
The specific aim of this one-year pilot project is to determine the feasibility of unraveling genetic and cultural inheritance of complex dental traits by constructing an environmental index from a unique population with a honogeneous commune type of environment, now available for study together with dental cast records. The data will also permit the identification of nontransmissible common sibling environment and transmissible parent-offspring components. Once the compound genetic and cultural effects are unraveled, genetic mechanisms of transmission, such as major gene effects against a multifactorial background, may then be tested. Otherwise, knowledge concerning genetics of human dental traits will continue to be at a standstill.
