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Objective To investigate the age-related changes of the mandibular third molar root pulp visibility in individuals in East China, and to explore the feasibility of applying this method to determine whether an individual is 18 years or older. Methods A total of 1 280 oral panoramic images were collected from the 15-30 years old East China population, and the mandibular third molar root pulp visibility in all oral panoramic images was evaluated using OLZE 0-3 four-stage method, and the age distribution of the samples at each stage was analyzed using descriptive statistics. Results Stages 0, 1, 2 and 3 first appeared in 16.88, 19.18, 21.91 and 25.44 years for males and in 17.47, 20.91, 22.01 and 26.01 years for females. In all samples, individuals at stages 1 to 3 were over 18 years old. Conclusion It is feasible to determine whether an individual in East China is 18 years or older based on the mandibular third molar root pulp visibility on oral panoramic images. [ABSTRACT FROM AUTHOR]

Background: Having a reliable and feasible method to estimate whether an individual has reached 16 years of age would greatly benefit forensic analysis. The study of age using dental information has matured recently. In addition, machine learning (ML) is gradually being applied for dental age estimation. Aim: The purpose of this study was to evaluate the development of the third molar using the Demirjian method (Demirjian3M), measure the development index of the third molar (I3M) using the method by Cameriere, and assess the periodontal ligament development of the second molar (PL2M). This study aimed to predict whether Chinese adolescents have reached the age of criminal responsibility (16 years) by combining the above measurements with ML techniques. Subjects & methods: A total of 665 Chinese adolescents aged between 12 and 20 years were recruited for this study. The development of the second and third molars was evaluated by taking orthopantomographs. ML algorithms, including random forests (RF), decision trees (DT), support vector machines (SVM), K-nearest neighbours (KNN), Bernoulli Naive Bayes (BNB), and logistic regression (LR), were used for training and testing to determine the dental age. This is the first study to combine ML with an evaluation of periodontal ligament and tooth development to predict whether individuals are over 16 years of age. Results and conclusions: The study showed that SVM had the highest Bayesian posterior probability at 0.917 and a Youden index of 0.752. This finding provides an important reference for forensic identification, and the combination of traditional methods and ML is expected to improve the accuracy of age determination for this population, which is of substantial significance for criminal litigation. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to determine how the removal of non‐impacted third molars (N‐M3s) affects the periodontal status of neighboring second molars (M2s). Subjects and Methods: The periodontal condition of M2s for which the neighboring N‐M3s were removed (more than 6 months previously) and those with intact N‐M3s was analyzed in a cross‐sectional observation study. In an additional case series, periodontal changes in M2s in response to adjacent N‐M3 removal were observed during a 6‐month follow‐up period. Results: A total of 457 patients with 1,301 M2s were enrolled in this cross‐sectional observational study. Compared to M2s with neighboring N‐M3s, M2s without neighboring N‐M3s (teeth removed more than 6 months previously) exhibited a 0.27‐mm reduction in the average pocket depth (PD) (p <.001) and a 0.38‐fold reduced risk of at least one probing site with PD ≥5 mm (PD5+) (p <.001). Subsequently, a 41‐case follow‐up study showed that 6 months after neighboring N‐M3 extraction, the PD of the M2s decreased by 0.31 mm (p <.001), while the incidence of PD5+ decreased by 21.9% when compared to the parameters detected before tooth extraction (p =.004). Conclusions: Removing N‐M3s was associated with an improved periodontal condition in neighboring M2s. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the age-related changes of the mandibular third molar root pulp visibility in individuals in East China, and to explore the feasibility of applying this method to determine whether an individual is 18 years or older., Methods: A total of 1 280 oral panoramic images were collected from the 15-30 years old East China population, and the mandibular third molar root pulp visibility in all oral panoramic images was evaluated using OLZE 0-3 four-stage method, and the age distribution of the samples at each stage was analyzed using descriptive statistics., Results: Stages 0, 1, 2 and 3 first appeared in 16.88, 19.18, 21.91 and 25.44 years for males and in 17.47, 20.91, 22.01 and 26.01 years for females. In all samples, individuals at stages 1 to 3 were over 18 years old., Conclusions: It is feasible to determine whether an individual in East China is 18 years or older based on the mandibular third molar root pulp visibility on oral panoramic images.

Aspartic acid racemization in teeth has been increasingly used to estimate chronological age with a considerably high accuracy in forensic practice. The Chaoshan population in South China is relatively isolated in geography, and has specific lifestyle and dietary inhibits. It is still unknown whether this method is suitable for this population. The aim of this study was to analyze the relationship between chronological age and the d/l aspartic acid ratio in dentin in the third molar tooth of the Chaoshan population. Fifty-eight non-carious third molar teeth (31 mandibles and 27 maxillae), from 58 living individuals of known age (24 males and 34 females), were retrieved. Dentin was extracted from these teeth. The d- and l-aspartic acids in dentins were separated and detected by high performance liquid chromatography (HPLC). Linear regression was performed between the d/l aspartic acid ratio of dentins and chronological age. Results showed that the correlation coefficient (r) was 0.969, and the mean absolute error (MAE) was 2.19 years, its standard deviation (SD) was ±1.53 years, indicating excellent correlation. There was no significant difference in racemization rates of dentin between sexes (P=0.113, F=2.6), or between mandibles and maxillae (P=0.964, F=0.000). Results indicate that the ratio of the d and l forms of aspartic acid of dentins, in the third molar, is closely correlated with chronological age, special lifestyle do no obviously affect the accuracy of the age estimations by aspartic acid racemization of the dentin in the third molar and that aspartic acid racemization in the third molar dentin can be used as an accurate method to estimate chronological age in the Chaoshan population in South China. [ABSTRACT FROM AUTHOR]

Dental age estimation is of great importance for individual identification in forensic medicine and many other fields of study. Among them, tooth eruption is a parameter developmental morphology that can be determined by clinical examinations or by dental X-rays. The purpose of present research is to study the chronological course of third molars eruption in a Chinese population and compare that with other ethnic population for age estimation. A total of 1135 conventional orthopantomograms from 506 male and 629 female northern Chinese subjects aged between 11 and 26 years were analyzed. The eruption status of the third molars was assessed using the developmental stages described by Olze et al. Results showed that the third molars 18, 28, 38 and 48 in the stage A showed significant younger average age in males than in females. The Olze's stage A could be used as a reference stage to determine whether a male or female northern Chinese is likely to be equal or above age 16, with 99.6-100% and 97.4-98.1% of correct predictions, respectively. The stage D was found to be a useful marker for diagnosing age under 16 years, with 98.9-100% and 100% of correct predictions in males and females, respectively. There were some significant differences of the chronological course of the third molars eruption in different ethnic groups, which indicated that population-specific standards could enhance the accuracy of forensic age estimation based on third molar eruption. [ABSTRACT FROM AUTHOR]

In order to study the chronology of age of third molar mineralization of Han in southern China, Demirjian staging method was used to determine the stage of four third molars (18, 28, 38, 48) mineralization in 3,100 Han in southern China aged 4.1–26.9 years based on radiological evidence from digital orthopantomograms. The mean age of the 3,100 patients was 15.96 ± 4.73 years, including 1,200 male (mean age, 15.32 ± 4.62) and 1,900 female (mean age, 16.35 ± 4.76). Results show that there was no significant difference in mineralization between 18 and 28 and 38 and 48 of male or female. However, significant difference was observed between 28 and 38 of female at stage C; 28 was 0.25 years earlier than 38. In male, at stage G, 38 was 0.61 years earlier than 28, and 48 was 0.62 years earlier than 18. At stages D, E, F, G, and H, male 48 was 0.34, 0.66, 0.72, 1.34, and 0.76 years earlier than that of female, respectively. At stages A, D, E, F, G, and H, male 38 was 0.73, 0.26, 0.56, 0.91, 1.29, and 0.70 years earlier than that of female, respectively. At stages B, E, F, G, and H, the mineralization mean age of male 18 was 0.54, 0.50, 0.76, 0.92, and 0.58 years earlier than that of female, respectively. At stages E, F, G, and H, the mineralization mean age of male 28 was 0.51, 0.76, 0.92, and 0.49 years earlier than that of female, respectively. After reviewing the literature, the chronological mineralization age of 48, at stages D to G, of Han in southern China was 1 to 4.6 years earlier than that of Japanese and 1 to 3 years earlier than that of German. The mean age at stage H of 48 of Han in southern China was similar to Turkish, Black African, Japanese, and German, but was later than Spanish. Finally, the conclusions are: (1) in the same gender group of Han in southern China, the mineralization ages between two sides in upper or lower jaw are very similar, and (2) the chronology mean age and complete time of third molar mineralization of male were earlier than that of female. [ABSTRACT FROM AUTHOR]

Objective To investigate the relationship between the stages of calcification of the third molar and age among children in Chengdu. Methods The study subjects consisted of children between 2009 and 2011 at the Department of Orthodontics, West China Hospital of Stomatology, Sichuan University. Panoramic radiographs were obtained. The stages of calcification of the third molar were analyzed by Demirjian' s method. The development of the third molar between the male and female was evaluated by independent samples t-test analysis. The Spearman rank correlation was applied to analyze the stages of calcification of the third molar and chronological age. Results The development of the third molar of the male was different from that of the female at stage A of calcification of the third molar (P=0.026). The Spearman rank correlation coefficient revealed highly significant relationships between the stages of calcification of the third molar and chronological age of the three groups (male, r=0.808, P=0.000, female, r=0.729, P=0.000; all, r=0.760, P=0.000). Furthermore, the linear regression equations were established as follows: Yall=4.898+2.036X; Ymale=4.987+2.046X; Yfemale=4.8l9+2.036X. Conclusion The stages of calcification of the third molar may be an available indicator in judging chronological age of teenager. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the anatomical variations of the root and root canal configuration of the human third molars., Designs: A total of 130 maxillary and 130 mandibular third molars were collected from a native Chinese population. All teeth were scanned by micro-computed tomography. After 3D reconstruction, the root and canal morphology of each tooth was examined both qualitatively and quantitatively., Results: For maxillary molars, a single fused root (67 cases, 51.5%) and a single root canal system (64 cases, 49.2%) was most common root/canal form; the typical three-rooted molars were detected only in 33 cases (25.4%), and the secondary MB canals were detected only in 9 molars (6.9%). For mandibular molars, 62 teeth were single-rooted (47.7%) and 42 had a single root canal system (32.3%); 20 singled-rooted and 60 double-rooted molars exhibited independent mesial and distal root canal systems (61.5%), and the type 1-1 canal was the most common configuration for mesial (57 cases) and distal (81 cases) root canal systems. C-shaped canals were detected in 11 maxillary and 36 mandibular single-rooted molars. The mean root surface area, root and crown volume of mandibular third molars were significantly higher than the maxillary third molars (P <  0.01)., Conclusion: The root canal system of the third molars may exhibit several anatomic variations. Whereas in most of cases, the degree of the canal differentiation was at a low level, and the canal form was not complicate., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The purpose of the present research is to study the radiographic visibility of the periodontal ligament in third molars from a northern Chinese population to determine if this methodology could be used for the 18-year threshold. A total of 1300 conventional orthopantomograms from 650 males and 650 females of northern Chinese subjects aged between 15 and 40 years were analyzed. The radiographic visibility of the periodontal membrane of fully mineralized third molars was assessed using the stages described by Olze et al. (2010). Stage 0 first appeared at the age of 17.05 years in males and at the age of 18.76 years in females. Stage 1 was first detected at 18.52 years in males and 19.59 years in females. Stage 2 was first achieved by males at the age of 22.33 years and by females at the age of 21.37 years. The earliest appearance of stage 3 was 26.85 years in males and 24.92 years in females. If stage 1 is determined, it is possible to prove that an individual has already attained the age of 18 years. Stages 2 and 3 can be used to determine that a person is over 21 years of age. However, it should also be noted that in 271 cases of tooth 38 and 255 cases of tooth 48, the visibility stage could not be reliably assessed because of fused roots or narrowed furcations. Therefore, this method seems to be of limited value for age estimation in the Chinese population.