The Study On The Dental Age Assessment For Shanghai Adolecents Based On The Third Molars

OBJECTIVE:To distinguish adults and minors in Shanghai,the best cut-off stage of Demirjian stage system and the best I_3M cut-off value of third molar maturity index were determined and compared.Using the third molar maturity index to explore the validity of Orthopantomographs（OPGs）and cone beam CT（CBCT）in identifying legal adults.The dental age evaluation provides some experimental theoretical and practical value for forensic dentistry.METHODS:（1）556 OPGs of 14-24-year-old adolescents in Shanghai were included,including 276males and 280 females.Using the Demirjian stage method and the third molar maturity index to evaluate the left mandibular third molar,the best cut-off stage of the legal adult was identified by the Demirjian stage method through probability statistics,the best cut-off value of the legal adult was determined by the third molar maturity index through Youden index.The applicability of Demirjian stage stytem and the third molar maturity index to assess the legal age of 18 was compared in diagnostic performance.（2）440 14-24-year-old adolescents in Shanghai who have OPG and CBCT were included in this study,including 220 males and 220 females.The third molar maturity index was used to measure the left mandibular third molar quantitatively on two kinds of radiologic images.The validity of the third molar maturity index was compared between OPGs and CBCT between adults and minors in Shanghai.RESULTS:Stage H of Demirjian stage system and I_3M=0.08 of third molar maturity index can be used as the best cut-off stage and cut-off value to identify the population in Shanghai,and the third molar maturity index can be more accurate.Compared with OPGs,CBCT can be used to identify the third molar maturity more accurately.CONCLUSION:The third molar maturity index is a useful method to assess if a subject is older than 18years of age or not in Shanghai.