The chronological age estimation of third molar mineralization of Han population in southwestern China

doi:10.1016/j.jflm.2014.03.004

Journal of Forensic and Legal Medicine

Volume 24, May 2014, Pages 24-27

https://doi.org/10.1016/j.jflm.2014.03.004 Get rights and content

Abstract

The purpose of the study was to estimate the chronology of third molar mineralization in Han population of southwestern China and find its unique characteristics so that it would provide a reference in several legal cases like forensic age estimation. The study used Demirjian's staging method to study 2192 orthopantomograms of 984 male and 1208 female subjects aged between 8 and 25 years. The statistical data was analyzed by Student's t test and ANOVA.

The conclusions of the study are: (1) The chronological mineralization age of third molars of Han population in Southwestern China is similar to the Turkish and the Japanese, was earlier than the Austrian and Han of South China, but later than the Spanish. (2) The mineralization timing of the third molars between two sides in maxilla or mandible has no significant differences in the same gender group. (3) There is no significant difference in mineralization of third molars between male and female, except for tooth 48 in Demirjian's stage E. (4) The mineralization of third molar in maxilla is earlier than mandible.

Introduction

In recent years, applications of forensic age assessments have increased rapidly in various aspects of forensic medicine.¹ Some examples include estimating the age of unknown victims, determining the right or obligation of society, explicit the penalty of criminal liability and assess the age of immigrants when they are unable to produce valid identity documents proving their real age.

14, 16, 18 and especially 18 are important ages in Chinese law for the juveniles. So, age estimation in this age group holds a significant importance in different legal cases. The methods of chronologic age estimation include a physical examination for sexual maturity, hand-wrist X-ray examination, radiographic or CT examination of clavicular epiphyseal cartilage, and dental examination.² The drawback of estimating epiphysis-diaphysis ossification in hand and wrist is that the process is completed around the age of 18 which is quite earlier as compared with third molar development that continues until the early twenties. Moreover, towards the end of human skeletal growth and development, only a few age-dependent features can be evaluated by morphological methods. On this context, the third molar, the last tooth to initiate and complete development is the last available dental morphologic predictor of age.³

The initiation, development and eruption of third molar occur after birth, and are closely related with age. Historically, the third molar was called as ‘wisdom tooth’ because the eruption time of the third molar usually coincided with the mental maturity, nearly around 18 years of age. Presently, individual chronological age is determined by observing the development and maturity of crown and root of the third molar through orthopantomograms.

Several methods have been described for the determination of dental development status from radiographs.4, 5, 6, 7 Most of these are based on a comparison of the radiographic image of development of teeth with standard charts compiled from a large number of persons, usually in a well-defined geographic region.² One widely used method is the one first described by Demirjian et al., in 1973 based on a large number of French–Canadian children.⁴ The method evaluates the development of seven mandibular teeth from a panoramic radiograph and calculates dental age.⁸

In any anthropological analysis, the characteristics of reference population are significant. Influence of genetic, nutritional and geographical factors must be taken into account in benchmarking the development. So, cross-applicability of standards for members of different ethnic groups has been the subject of much discussion.⁹ Until now, several studies have been undertaken in different populations and regions to explore the usefulness of the third molar as a reliable age indicator.10, 11, 12, 13 China is vast in territory, and Han is the largest population in the world. Therefore, to estimate the age by evaluating the radiographic features of third molar mineralization in young Han population of a designated area would be very meaningful for forensic age estimation.

In this study, our objective was to evaluate dental development in a sample of adolescents and young adults of southwestern China, make a comparison with previous studies on other ethnic groups or geographical area and try to find any significant trend.

Section snippets

Materials and methods

The sample consisted of 2192 conventional individual orthopantomograms from southwestern China taken at the Affiliated Hospital of Stomatology of Chongqing Medical University between the year 2008 and 2011. Individuals' age and sex were recorded and all of them belonged to Han ethnic group in southwestern China, were in good health without any chronic diseases and genetic diseases and without any features of malnutrition. Moreover, none of the third molars were absent in these individuals. All

Results

The mean mineralization ages for various stages of third molar mineralization with their standard deviations and standard error are described in Table 2.

Firstly, the difference of chronological age between all the four third molars were tested using the Student's t test and was found that only 48 in the stage E had significant difference in mineralization between male and female (p = 0.045). The comparison of mineralization of third molars with reference to gender group is described in Table 3.

Discussion

Human teeth are one of the markers of growth and development. With differences in ethnicity, living environment and habits, the timings of tooth development and eruption are different. And moreover, the differences between countries or other geographical areas are not constant over age and vary in an unordered way.¹⁰ So, a lot of researches have been done to find the correlation between development of teeth and biological age for different races and regions.10, 11, 12, 13

Many methods have been

Conclusion

In this study, we analyzed the chronological development of third molars of Han population in Southwestern China, and found that the population had its own characteristics as follows:

(1)
The mineralization ages between two sides in maxilla or mandible have no significant difference in the same gender group.
(2)
There is no significant difference in mineralization of third molars between males and females, except 48 in stage E.
(3)
The mineralization of third molar in maxilla is earlier than mandible.

Ethical approval

None.

Funding

None.

Conflict of interest

None declared.

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Forensic age estimation of living subjects is a recurrent request from the judicial authority. Several methods are proposed to estimate age. Initially developed to estimate a bone or dental age for medical purposes, these methods have been transposed to judicial purposes and their use is formalized by recommendations. However, we can question their reliability, applicability, and accuracy, which raise many issues. To understand them, we first reviewed the main methods used for age estimation. Then we carried out an inventory in the French forensic units and studied the reports transmitted to the authority. Finally, we compared these data with the expectations of the authorities and courts. Our results show that there are great disparities of these forensic age estimation: the methods used, and the interpretation of their results are variable. This work sheds light on a heterogeneous reality. A national protocol could define the appropriate examinations, the reference studies, and the way in which the results should be presented.
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This technique differs from other anatomically descriptive staging systems, such as the one proposed by Solari and Abramovitch (2002) – that modified the original scheme of Demirjian, Goldstein, & Tanner (1973). Despite the popularity of Demirjian’s technique and its use in international populations, such as Croatian (Sasso et al., 2015) and Chinese (Qing, Qiu, Gao, & Bhandari, 2014), the original system was not designed for adolescents, but for the classification of the seven mandibular left teeth of children. Adaptations were definitely an improvement, but in the present study, GHK figured as technique of choice.
To test the applicability of “Gleiser and Hunt dental staging system modified by Kohler” (GHK) to assess third molar (3 M) development in a Russian population in order to determine the age of majority.
The sample consisted of 918 panoramic radiographs from Russian females (n = 551) and males (n = 367) within the age interval between 8 and 23 years. On each radiograph, 3 M development was classified based on the GHK technique. Statistics tested the data for normality. Mean age and standard deviation were described for each 3 M position. Ordinal logistic regression tested the performance of the technique to classify individuals below or above the 18-year threshold. Receiver Operating Characteristic (ROC) curves were used.
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The GHK technique was able to describe 3 M development in a Russian population. The statistic model was able to classify individuals below or above the 18-year threshold. However, the outcomes must be carefully interpreted, especially in borderline cases (17−19-year spectrum).
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Two hundred studies on the rate of skeletal maturation and four hundred thirty-nine on the rate of dental maturation were found, covering the period from 1952 and 2020 for a total of ninety-eight countries.
For most of the western and central African countries there are currently no data on the rate of skeletal and dental maturation. The same applies to the countries of the Middle East, as well as the eastern European countries, especially as regard the skeletal development.
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Additionally, age estimation is used to decide specific social responsibilities, such as employment and marriage in cases where a living person has not available birth certificates for different reasons [9]. Chinese law assign limited criminal responsibility for young adolescents older than 14 and younger than 16 years old, while full criminal responsibility is attained at age 16; in civil law instead, from 10 to 18 years old they have partial responsibility and those over 18 years old are considered as having full responsibility [10–13]. On lack of valid identification documents to certify if an individual has reached the age of legal responsibility, various physical indicators can be used for age estimation to confirm a person’s chronological age.
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In the context of the Indian legal system, the assessment of an individual's age is crucial because of increased involvement of children and adolescents in committing crimes.17 Previously, several authors studied the application of DS system and another approach for estimating the age, including the age of majority.20,53–62 For estimating the age of majority, Mincer et al.20 showed the low accuracy if DS was used.
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Original communicationThe chronological age estimation of third molar mineralization of Han population in southwestern China

Abstract

Introduction

Section snippets

Materials and methods

Results

Discussion

Conclusion

Ethical approval

Funding

Conflict of interest

Forensic Sci Int

Forensic Sci Int

Forensic Sci Int

Forensic Sci Int

Forensic Sci Int

Forensic Sci Int

Forensic Sci Int

Forensic Sci Int

A new system of dental age assessment

Hum Biol

Age variation of formation stages for ten permanent teeth

J Dent Res

The formation and the alveolar and clinical eruption of the permanent teeth. An orthopantomographic study

Suom Hammaslaak Toim

Original communication
The chronological age estimation of third molar mineralization of Han population in southwestern China