Third mandibular molar: development as an indicator of chronological age in a European population.

Assessing biological age in the youth nearby legal age has always represented a stimulating issue for the Italian forensic scientist as far as he deals with matter of imputability and legal or illegal immigration of uncertain age subjects. Since any method of evaluation should of course be accurate, not invasive, reproducible and, as possible, easily exploitable, radiological investigation of age dependent features is the most appropriate instrument to the purpose. Dental development is slower and delayed compared with skeletal bone one, occurring according to a known, regular pattern from whose evaluation a biological age can be assessed with a reasonably restricted span for a certain radiological image. This is the assumption which inspired since 1941 (Schour e Massler) so many anthropologists and forensic and clinic odontologist in investigating biological age by the study of radiological dental morphology. Demirjian and Goldstein [New systems for dental maturity based on seven and four teeth, Ann. Hum. Biol. 3 (1976) 411-421] obtained no differences between two groups of subjects whose age was extimated by the evaluation of 14 teeth in one case and 7 teeth in another, the last being greatly simpler. Afterwards, Thorson (1991), Mincer et al. [The A.B.F.O. study of third molar development and its use as estimator of chronological age, J. Forensic Sci. 38 (1993) 379], Solari and Abramovitc [The accuracy and precision of third molar development as an indicator of chronological age in Hispanic, J. Forensic Sci. (3) (2002) 531-535] and then Prieto Carrero [Evaluation of Chronological Age Based on Third Molar Development in the Spanish Population, Atti del XIX Congresso IALM, Milano, 2003], developed a method based on the evaluation of the radiological development of the alone third molar, according to Demirjian's schematic definitions of crown and root formation. Eight stages of development of the third molar are defined from the time of mineralization appearance of the cusp tips up to complete closing of the apexes. In order to achieve grater precision in discriminating stages F and G, Solari added two stages (F1 and G1), determining 10 stages of maturation of root and crown. Prieto tested the accuracy and precision of this method by the evaluation of about 1300 orthopantomographs of juveniles and young Spanish adults of known age, divided for gender. We analyzed a total of 400 orthopantograms of young Spanish dental patients to evaluate the chronology of the right mandibular third molar development and to assess its correlation with the biological age of the tested. Biological age is attributed with a maximum standard deviation of 2.47 from the mean in the eight stages outline. The greatest limit of the method seems to be the operator experience in determining the dental stage of development. We think that age data coming from such evaluation method should be clearly explained to the magistrate in their true statistical significance and limits