Abstract
The tempo of tooth mineralization is under significant genetic control, and the orderly progression of morphological changesโin concert with the long span during growth in which teeth formโmakes โdental ageโ a useful measure of a person's degree of biological maturity. The third molar is of particular interest because (1) it is the last and most variable tooth to form and (2) it is the only tooth to complete formation after puberty, which has made it attractive in forensic and legal circles as an estimator of adulthood. Age standards are described here for mandibular third molar formation stages in a crossโsectional sample of 4,010 persons (age range: 3โ25 years), with proportionate sample sizes of American blacks and whites and males and females. Formation was scored against the 15โgrade ordinal scheme of Moorrees, and descriptive statistics were computed using proportional hazards survival analysis. Blacks achieved each formation stage significantly ahead of whites, but not in a uniform manner. Instead, there was an enhanced advancement in blacks during crown formation and during late stages of root formation. In both races formation proceeded faster in males, which is unique for the third molar, as prior studies suggest. Sample variance increases with the stage of formation, such that 95% confidence limits span 8 or more years for root formation stages. Consequently, the third molar provides a rough gauge of an individual's chronological age, but the considerable variability precludes any precise estimate, particularly in late adolescence where most forensic interest has focused. Am J Phys Anthropol, 2006. ยฉ 2006 WileyโLiss, Inc.