Dental maturity was measured as a continuous function of age by using Demirjian's method. A second objective was to compare the accuracy of age determination by Demirjian's method, polynomial regression (13,22,23), and the modification of Demirjian's method by including the third molar. Demirjian's method is based on eight calcification stages that represent the crown and root calcification to the apex closure for the seven left permanent mandibular teeth. A score is given for each stage, and the sum of the scores provides an estimate of the subject's dental maturity. The overall maturity score may then be converted into a dental age by using available tables and percentile curves. Demirjian's seven-teeth method had a high accuracy but poor reliability. Adding the third molar increased the possibility of prediction until 18 years old, but the mean accuracy decreased after more or less 8 months due to the high variability of the third molar. The polynomial functions provided a high reliability and the same accuracy as the Demirjian eight-teeth method. The polynomial functions (age as a function of score) are suitable methods in forensic science, since reliability is the most important factor; legal authorities need to know children's age in order to determine the application of the law within the parameters of age. 8 figures, 8 tables, and 28 references