Khosronejad Aria, Navabi Manijeh, Sakhdari Shirin, Rakhshan Vahid
Dentist, Tehran, Iran.
Department of Dental Anatomy and Morphology, Islamic Azad University, Tehran, Iran.
Dent Res J (Isfahan). 2017 Mar-Apr;14(2):143-149.
Third molar development is the only available tool for estimating the age of individuals after puberty. Since this tooth has very high interethnic variability, formulas calculated to estimate the age from its development stages cannot be generalized to other populations and should be adjusted for each region. Therefore, this study was conducted to evaluate this method in a sample of Tehran individuals for the first time, and also to compare the development of third molars across sexes and arches, and to estimate cutoff developmental stages for legal minor/major identification.
A total of 150 dental patients aged between 15 and 25 years old were prospectively enrolled, and their Demirjian stages were recorded. The associations between chronological age and Demirjian stages were evaluated. Dental formation was compared between sexes and jaws. Cutoff stages were determined to identify legal minor/major cases (above or below 18 years old). Age estimation formula was found for this population.
Of the 150 included patients, 56 were males. The difference between the ages of males and females at each given developmental stage was nonsignificant ( > 0.05), except for the H stage. Age difference between same stage teeth of the maxilla and mandible was nonsignificant. Each of the G and H stages was significantly above 18 years old ( < 0.001). Furthermore, E and F stages were below 18 years old ( < 0.001). All the correlations between Demirjian stages and age were above 90% (all < 0.001). Third molar development was positively affected by the chronological age ( = 0.000) and being maxillary ( = 0.000) but not sex ( = 0.113). Regression formula for age estimation was: age = 6.52+ (0.64 × sex) + (0.32 × arch) + (1.86 × Demirjian stage).
Development of third molar might complete after the age 22. Iranian individuals with third molars at the G and H stages are likely above 18 while those at E and F are likely below 18. Pace of molar development differs for jaws, but intergender differences are open to further investigations.
第三磨牙发育情况是青春期后估计个体年龄的唯一可用工具。由于该牙齿在不同种族间存在很大差异，根据其发育阶段计算的年龄估计公式不能推广到其他人群，而应针对每个地区进行调整。因此，本研究首次在德黑兰个体样本中评估该方法，同时比较第三磨牙在不同性别和牙弓的发育情况，并估计用于合法认定未成年人/成年人的发育阶段临界值。
前瞻性纳入150名年龄在15至25岁之间的牙科患者，记录其德米尔jian分期。评估实际年龄与德米尔jian分期之间的关联。比较不同性别和颌骨的牙齿发育情况。确定用于识别合法未成年人/成年人案例（18岁以上或以下）的临界阶段。为该人群找到年龄估计公式。
在纳入的150名患者中，56名是男性。除H期外，在每个给定发育阶段，男性和女性的年龄差异均无统计学意义（P>0.05）。上颌和下颌同一阶段牙齿的年龄差异无统计学意义。G期和H期均显著高于18岁（P<0.001）。此外，E期和F期低于18岁（P<0.001）。德米尔jian分期与年龄之间的所有相关性均高于90%（均P<0.001）。第三磨牙发育受到实际年龄（P=0.000）和上颌情况（P=0.000）的正向影响，但不受性别影响（P=0.113）。年龄估计回归公式为：年龄 = 6.52 +（0.64×性别）+（0.32×牙弓）+（1.86×德米尔jian分期）。
第三磨牙的发育可能在22岁后完成。处于G期和H期的伊朗第三磨牙个体可能超过18岁，而处于E期和F期的可能低于18岁。磨牙发育速度在颌骨间有所不同，但性别差异有待进一步研究。
