The aims of this study were to describe maturity data of permanent tooth formation from a large sample and to adapt these for estimating age, to compare mean age dental formation stages between ethnic groups and sexes. This was a retrospective, cross-sectional study of 1,050 panoramic radiographs of healthy dental patients in London aged 2 to 22. Similar numbers of each sex and ethnic group (White and Bangladeshi) were selected for each year of age. Permanent mandibular teeth were scored using 14 stages described by Moorrees and co-workers in 1963 plus crypt stage. Mean age of each tooth stage (age when 50% of sample had reached/ passed each stage) was calculated using probit regression for males and females by ethnic group for each stage. Data were combined where no significant difference between mean age for groups was observed. Average age 'within a stage' was also calculated for each tooth stage. No ethnic difference was noted in mean age. Canine root stages and third molar apex stages were significantly different between the sexes. The average age of most stages was considerably later than that given by Moorrees and co-workers. Accuracy of age estimation on a separate test sample of radiographs was considerably more accurate using these new data. These results provide an accurate method to estimate age from developing permanent mandibular teeth. The lack of ethnic difference in dental maturity of individual teeth, suggest that these findings might be appropriate to accurately estimate age for other groups.