Root development of the lower third molar and its relation to chronological age

Methods based on radiological, distinguishable stages of tooth formation can be used to estimate chronological age in young persons. The best precision and accuracy of these methods of age estimation is obtained when many teeth are under development and when the individual growth rate is rapid. That is during early years-in childhood. After an age of about 14 years it becomes more difficult since all permanent teeth but the wisdom teeth have completed their development and only these remain to be used for age estimation. The aim of this study was to examine the radiological development of the root of the mandibular third molar and to explore its usefulness in age estimation. Also the differences between two independent observers were studied. The observers classified the development of the mandibular third molars, as seen in a panoramic radiograph, into seven defined stages. The two observers agreed in about 84% of the cases in their registration of the different stages, but a significant difference was found between the observers. The mineralisation of the third molar's root was found to start at the age of 15 years and the root was fully formed at about 20 years. Some minor differences were found between sexes in the time sequence of the mineralisation. The study also shows that there is a rather low precision in the age estimation with the method used. In general, a standard deviation of about 1 to 2 years was found around the mean age of the different developmental stages.