Enamel is formed from the ectodermal components. Some variations, such as the shovel-shaped incisor or the Carabelli trait are curiosities in clinical practice, but are very useful to the dental anthropologist in tracing population movements. Shoveling of the incisor is common amongst the Chinese, Japanese, Mongolians, and Eskimo. The Carabelli trait is most common amongst European peoples. Other variations, such as agenesis are useful for analysis at the biochemical and molecular level in understanding the fundamental chemistry involved in tooth formation.
Most dental variations are polygenic, that is controlled by several genes.
With these, we often speak of the degree of expression or penetrance. Disturbances in Size. Generalized microdontia is a rare condition associated with uncommon conditions such as pituitary dwarfism. More often, microdontia is limited to just one or two teeth. Peg-shaped incisors tend to be familial.