Abstract On the assumption that the degree of variation in a morphological characters is related to its adaptive or functional significance, it was examined, utilizing fluctuating asymmetry and the coefficient of varation, whether there are any differences in adaptive or functional significance between deciduous teeth and the corresponding permanent teeth. Pitman’s tests objectively show that the maxillary lateral permanent incisor is particularly variable, and its precursor, the maxillary lateral deciduous incisor, is as stable as the maxillary central deciduous incisor. This stability in size of the maxillary lateral deciduous incisor suggests that the battery of deciduous incisors has some important function which is not shapred with the permanent incisors but is required for the infant period during which only the deciduous incisors are present.

Key Words: deciduous teeth, permanent teeth, lateral incisor, fluctuating asymmetry, functional difference