Third molar maturity index by measurements of open apices in a Libyan sample of living subjects

Highlights

• Age estimation is fundamental both for forensic and civil reason.

• Measurements of third molar maturity index (I_3M) were performed on the Libyan population.

• Using a cut-off of 0.08, the sensitivity of the test for was higher than 90.5% and the specificity 100%.

• Using a cut-off of 0.08, the sensitivity of the test for was higher than 96.0% and the specificity 100%.

Abstract

In most countries, forensic age estimation in living subjects has become increasingly important in the last few years. In addition, as the age of legal majority ranges from 14 to 18 in many countries, and in Libya it is 18 years, radiographic assessment of the degree of third molar development is essential for forensic age estimation of adolescents and young adults. The aim of this paper is to assess the accuracy of the cut-off value of 0.08, by measurements of third molar index (I_3M), in determining if a subject is adult or not in Libyan population. Digital panoramic radiographs of 307 healthy subjects (163 girls, 144 boys), aged between 14 and 22, were analysed. The I_3M, the age and the sex of the subjects were used as predictive variable for age estimation. Using a cut-off of 0.08, the sensitivity of the test for boys was 90.9% and the specificity 100%. The proportion of correctly classified individuals was 95.1% (95% CI: 91.5–98.7%). The sensitivity for girls was 90.6% and the specificity 100%. The proportion of correctly classified individuals was 94.5% (95% CI: 90.9–98.1%). Estimated post-test probability in boys and girls was 100%. Further analyses, performed using a cut-off of 0.09, do not affect the specificity (100%) while they improve the sensitivity for both boys and girls.

Introduction

In the last few years, age estimation in living individuals has become increasingly common in civil and criminal cases involving young people, irregular immigration and the many issues related to asylum seekers [1], [2], [3], [4].

Estimating the age of living subjects often requires an integrative approach that involves anthropology, medicine, forensic dentistry and radiology [2], [3], [4], [5], [6], [7], [8], [9]. Human identification and aging using dentition has been well established in the forensic field and several methods based on dental changes have been developed [10], [11], [12], [13].

In accordance with the updated recommendations for age estimation in criminal proceedings of the Study Group on Forensic Age Diagnostics, for age estimation, a physical, examination, an X-ray examination of the hand as well as a dental examination should be performed. If the skeletal development of the hand is completed, an additional X-ray examination or CT scan of the clavicles should be carried out. The latest version of these recommendations can be found on the AGFAD (Arbeitsgemeinschaft für Forensische Altersdiagnostik or, in English, Study Group on Forensic Age Diagnostics) website at http://campus.uni-muenster.de/6757.html?&L=1.

The most common dental method for age estimation is the Demirjian Staging System (DSS) [14], [15], [16]. This method identifies eight developmental stages (A–H) based on the evaluation of the mineralization of a selected number of teeth [17], [18], [19]. The score system of Willems et al. [20] is the best adaptation of Demirjian’s method and is the recommended method of choice to assess maturity or estimate age if all seven teeth are available [21].

Toward the end of human skeletal growth and development, only a few age-dependent features (third molar development, the closure of the clavicular epiphysis and the ossification of the long bones’ epiphyses) can be evaluated by morphological methods [22], [23]. Since third molars are still growing at the age of 18, their development has recently been considered the most suitable evidence to assess whether a subject is an adult or not [23], [24].

Cameriere et al. [25] developed a new method based on the correlation between the age of the individual and the normalized measures of the open apices and the height of the third molar. A threshold (cut-off) value of 0.08 was identified and used to discriminate between individuals who are or not 18 years of age or older. Furthermore, in many countries, including Libya, the age of 18 represents the legal majority [26].

The age of criminal responsibility in Africa varies by jurisdiction across the continent. It ranges from age 10 in Sierra Leone, Cameroon and Côte d’Ivoire to age 14 in other countries (e.g. Central African Republic, Somalia, Libya, etc.) [27]. In Libya, according to the article 9, Act No. 17 of 1992, regulating the situation of minors, the age of legal majority is 18 years. During the Gaddafi government, the regular age was 18 but 16 years old women could be married as long the parents consented. In addition, in this country pre-marital sex was illegal. After the 2011 revolution, the age of consent limit was removed and, presently, although sex is not allowed outside of marriage, there is no defined age of consent [28], [29].

In Libya, the need for reliable and accurate age estimation techniques has never been greater than in the last five years, mainly due to armed conflicts within the country. The lack of a validated method for assessing age in Libyan population is fundamental in criminal proceedings relating to irregular immigration and emigration movements at both national and international levels [28].

To date, only one study that has focused on the dental age estimation in Libyan population has been published [30]. No previous works have used also the Cameriere’s method in this human group. In addition, in Africa, no systematic studies have been conducted that could inform us of the maturity parameter variations applicable to its population [31]. Only few studies have been carried out in order to age live individuals who have no record/documentation of their chronological age. Garamendi et al. [32] showed very good results when tried to verify the reliability of combined skeletal and dental methods on a Moroccan origin population. Cavrić et al. [33] analyzed the development of the left mandibular third molar by the third molar maturity index (I_3M), established by Cameriere et al. in 2008 [25], and used it for discriminating between minors and adult black Africans from Gaborone, Botswana. Their results indicated that I_3M may be a useful alternative method in legal and forensic practice to discriminate individuals of black African origin who are around the legal adult age of 18 years in Botswana. Uys et al. [34] studied a sample of 604 black South African children to test the validity of the method described by Demirjian [14]. In 2009, Phillips and van Wyk Kotze [35] analysed the accuracy of two dental methods, Demirjian et al. [14] and Moorrees et al. [36] in a sample of South-African children aged between 3 and 16 years.

The aim of this paper is to assess the accuracy of the threshold value of 0.08, by measurements of third molar maturity index (I_3M), in determining if a subject is 18 years of age or not. For this purpose, a sample of living children and young adults from Tripoli, the capital city where different ethnic groups are represented, was analysed.