基于下颌第二, 第三磨牙发育建立中国北方人群18周岁评估模型

Objective To establish a linear relationship between age and the development process of the mandibular second, third molars in a northern Chinese population and test its accuracy in inferring whether the subject is over 18 years old. Methods The orthopantograms (OPGs) of 960 northern Chinese people aged between 10.00 to 25.99 years were selected. The gender, birth date, and date of the orthopantograms of each sample were recorded. The development stages of left mandibular second and third molars were divided with Demirjian method. The experimental group(760 individuals) constructed a Logistic regression equation to infer whether the subject is over 18 years old. The validation group (200 individuals) tested the accuracy of the equation. Results When only using third molar, the formula obtained for inferring whether the subject's age is over 18 years is: logit P₁=-18.276+0.494 x₁+2.953 x₃. When combining the second and the third molars, the formula is: logit P₂=-21.045+3.177 x₁+0.619 x₂+ 2.088 x₃. (x₁ stands for gender, male is marked as 1 and female is marked as 2; x₂ and x₃ stand for the development stage of second molar and third molar, respectively). The accuracy rates of this equation in estimating whether ages of subjects from the validation group were over 18 years old for males and females were 88.0%-92.0% and 85.0%-88.0%, respectively. Conclusion The age estimation formulas based on the development of mandibular second and third molars have important value in judging whether the individual is over 18 years old. Meanwhile, the accuracy of age estimation can be improved by combining the development of second and third molars together.