Age estimation is a segment of forensic dentistry and it was first established by Edwin Saunders in 1837 that teeth could be used as an indicator of age in cases like infanticides, fires or even to determine the age of a living person for criminal liability etc. With the help of non-invasive techniques applied by dentists every day like radiography it has now become a source of information for forensic odontologists. Teeth are one of the hardest and the most indestructible substances in the body, they have a highly mineralized structure which can make them ‘resistant to decomposition and generally withstand flames, alkalis and acids’ (Gowri Vijay Reesu, 2015) and can remain unchanged for thousands of years. There are various methods of age estimation for neonates, adolescents and adults these include a) Clinical or visual methods, b) Radiographic method, c) Histological method and d) Physical and chemical analysis.
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Firstly, comparing the skeleton, teeth and chronological age of humans can be a complex topic. As the rate of human development is multifactorial and the changes that occur might not work simultaneously to the changes in progressive age. When assessing skeletal development, it normally comes down to the height, changes in the anatomy of the bone, analysis of ossification and the development of epiphyses of various skeletal structures of bones like femurs and ulnas etc. It does not account for conditions such as malnutrition or a growth human deficiency, etc which can delay the start of puberty or even country of residence which would play a key factor e.g. with Vitamin D level and climate etc.
Age estimation using dentition is grouped into three phases: - Pre/neonatal and early postnatal child, children and adolescents and adults. It can be fairly accurate to estimate the age in early childhood as it is less likely to be affected by hormonal and nutritional changes, that may occur in skeletal development. With the help of histological and radiographic methods, it can detect the very early stages of mineralization. With children and adolescents is normally dependent on the eruption of teeth which can be analysed by visual or radiographic measures and/or looking at tooth calcification. After the age of 20, it can prove to be more challenging to estimate age, as methods used for tooth development like, age benchmarks are no longer applicable. The techniques for dentition age estimation are limited to looking at the degenerative changes in the teeth. ‘Compared with age estimation in children using development of dentition, age estimation with the use of teeth is less accurate' (Markova, 2005)
There are a number of different studies conducted for age estimation, for example, the neonatal line which is present in the enamel and dentin of deciduous teeth and first molars and the incremental line of Retzius, can be used to ‘assess the amount of pre and post-natal enamel formation’ (Shamim T, 2006)and determine the age of death. It can differentiate between still and live births, but it is necessary to have a couple of days of survival in order for the neonatal line to develop and ‘the absence of the neonatal line is not always an indicator of stillbirth'. With Schour and Masseler (Schour I, 1940) using radiology, produced a numerical chart that analysed the development of deciduous and permanent teeth of 4 months to 21 years of age. This method did not consider genders and is not applicable to living individuals. Also ‘mean age range of 2–5 years is put at 6 months and is thus too narrow.’ (Ciapparelli, 1992). Miles assessed the relative wear of the three molars and compared to functional age to produce an age estimate of dental attrition and is still used by bioarchaeologists. The method assumes that there is a constant wear rate for all molar, it does not factor in that diet may change over the years affecting attrition. It also neglects the fact that 3rd molars are absent in 10% of the population and when compared with recent studies. It presents a standard deviation of 2 years, with black South Africans maturing 1-2 years earlier than Germans (Hjern A, 2012). However, Lovejoy et al found the method to be accurate and showed the least bias under ageing. Dermijian, Goldstein and Tanner method estimated age based on the seven teeth development on the left side of the mandible. It’s ‘the most used techniques found according to literature…’ (André Luiz Bérgamo, 2016) due to the scoring system maturity and simplistic conversion of dental age. This method, however, excludes children under the age of 5. There is also a lot of different results when tested on different populations to which some found that it overestimated the age rather than underestimate it (Sasso A, 2013). The Gustafson method looked into histological and morphological changes of teeth and the age was estimated using a formula. However, it is a very time-consuming analysis, requires extensive training and equipment and present a standard error of 3.6 years.
Overall it can be said that age estimation using dentition has been well recognised. There are a variety of methods that all show strengths and weaknesses which makes it challenging to determine which is best, combining methods or performing repetitive measurements may give a better age estimate. It is shown that you cannot give a definitive age as with all the methods they do show standard errors but is good as giving an estimate within a given age bracket.
- André Luiz Bérgamo, C. L. (2016). Dental Age Estimation Methods in Forensic Dentistry. Peertechz Journal of Forensic Science and Technology, 1-4.
- Ciapparelli, L. (1992). The chronology of dental development and age assessment. Practical forensic odontology, 22-42.
- Gowri Vijay Reesu, J. A. (2015). Forensic consideration when dealing with incinerated human dental remains. Journal of Forensic and Legal Medicine, 13-17.
- Hjern A, B.-L. M. (2012). Age assessment of young asylum seekers. Acta Paediatrica, 4-7.
- Markova, R. (2005). Third molar as an age indicator in young individuals . Prague Med Rep , 367-98.
- Sasso A, S. S. (2013). Secular trend in the development of permanent teeth in a population of Istria and the Littoral region of Croatia. Journal of Forensic Science , 673-677.
- Schour I, M. M. (1940). Studies in tooth development: the growth patter of human teeth. J am Dent Assoc., 1778-1793.
- Shamim T, I. V. (2006). Age Estimation: A Dental Approach . Journal of Punjab Academy of Forensic Medicine & Toxicology, 1-3.