Age estimation plays a prime role in forensic identification especially in absence of concerned documents and in unknown dead or living individuals. Its importance is priceless in a country like India where in, on one hand birth records of 10 million children every year go unregistered and on the other hand there is significant rise in involvement of minors in various crimes. Ideal method of age estimation is a constant search for the forensic odontologist. Delivery of justice can be appropriately made if the age is determined accurately and hence the accurate method of age estimation plays a pivotal role in correct justice being done. Literature provides many population specific methods of dental age estimation. Further validation and modification of these models is required in various populations before considering it for legal applications. The present article reviews the most commonly used radiographic methods of age estimation in children and adolescents and their accuracy in general and in Indian population in particular.

Prabhu R, Chatra L, Shenoy P, Prabhu V (2020) Is there a Need for an India Specific Dental Age Estimation Formula for Children and Adolescents? - A Critical Review. Ann Forensic Res Anal 7(1): 1057.

• Forensic odontology
• Dental age
• Age estimation
• Radiographic methods

For any forensic identification and medico – legal purposes, age estimation plays a significant role in narrowing the search possibilities for unidentified dead as well as the living individuals. It helps in delivering justice to a person involved in civil and the criminal legal actions [1]. An individual’s Chronological age (CA) can be obtained from the birth date and confirmed with the birth registration certificates. But unfortunately, birth registration is not followed strictly in various parts of the world. According to the data between 2006 and 2016 recorded by United Nations Children’s Fund (UNICEF) [2], the registered rate of birth for children under 5 in South Asia was 60 per cent and in India [3] it was only 72% which means out of 26 million children born every year, around 10 million children go unregistered.

According to the NCRB (National Crime Records Bureau) [4] report the number of juveniles in conflict with law under the Indian Penal code section showed increase from 17,819 in year 2003 to 31,725 in 2013. There is significant rise in involvement of minors in the crimes such as rapes, kidnapping, and murder. Also higher numbers of children are involved in the age disputes mostly in the domains of child labor and child marriage. Based on the age of an accused, trial or sentencing is conducted in the adult or juvenile justice courts. Hence knowing accurate age of an individual is of prime importance in the field of forensic dental and medical practice [5].

Saunders in 1837 [6] revealed the significance of dentition in age estimation through his research presentation, entitled “Teeth A Test of Age’’. Later in nineteenth century several methods of dental age estimation were proposed. These methods are found to have their own advantages and disadvantages. Ideal method of age estimation is a constant search for the global as well as for an Indian forensic odontologist. Most of the proposed methods are population specific and based on western population which has been studied by Indian researchers in Indian children with various degrees of accuracy. It is considered that the dental development differs in various geographical regions due to the genetic factors and the cultural background [7].

The present article aims to review the most commonly used dental age estimation methods in children and adolescents and their applicability in various populations which will help us to understand the need for India specific formula for dental age estimation.

Need for age estimation

Age estimation is necessary for both dead and the living, civil as well as criminal litigation [8]. Among various dental disciplines, dental age (DA) assessment is essential for orthodontists in treatment planning of the children with malocclusion [9] and pedodontists for identifying the dental maturity of a child to rule out the systemic disturbances [10]. Its importance in bioarchaeology and human anthropology is priceless as it gives significant information regarding ancestors [7]. In forensic dentistry, age estimation is needed for various medico-legal purposes like personal identification, criminal cases and also in cases of various natural disaster victim identifications [11]. Age estimation is also a very important in disclosing the facts about the age frauds in sports [5]. The medical and the dental experts are always called for estimating the age of players involved in age frauds by the Sports Authority of India (SAI) and the Ministry of Youth Affairs. In their report on “National Code against Age Fraud in Sports,” age estimation evaluation includes dental examination and orthopantomogram (OPG) along with other medical and radiological examination [12].

Legal implications of age in India

As per the criminal law under Indian Penal Code, section 82, a child 12 years cannot be adopted, according to Article 24, Prohibition of Employment of Children in Factories, a child <12 years shall not be employed in any factory or mine or any hazardous work places, according to Child Labor Prohibition and Regulation Act 1986, children <14 years are considered as child labors, according to Section 3, Indian Majority Act 1875, 18 years of age is considered as the age of attaining majority, according to The Child Marriage Restraint Act 1929, for boys legally permissible age is 21 years and for girls it is 18 years. According to section 375 Indian Penal Code, the right age of consent to decide the criminality of the offence of rape is 16 years except in Manipur where it is 14 years [13].

Significance of teeth in age estimation

During the growth process, our physiologic systems such as skeletal system and the dentition pass through a series of changes before arriving at maturity. Although the maturity rate of our physiologic system differs from that of the chronologic age in different individuals, a correlation between the two has been observed [14]. Hence when the chronologic age is unknown or disputed, it can be inferred based on various parameters like dentition, skeleton, mental status of an individual, and other physiological factors like change in voice, attainment of height and weight etc [15].

Among all these indicators, dental maturity indicators are considered to be more reliable and the least variable bioindicator for age assessment. This is because of its low variability to the endocrine & nutritional state of the child, high durability, resistant nature to fire, chemicals and putrefaction and unique nature of incremental formation and periodic mineralization [16-18].

Development of teeth begins as early as 4-6 months of embryonic life and continues till 23 years of age. Thus teeth development can be assessed from the radiographs for a long period of time and also during the periods when no eruption takes place i.e from 2 ½ to 6 years and 12 – 18 years of age. Another reason for considering dental development for age assessment especially in the first two decades of life is that it remains unaffected by local factors such as infection or decreased space unlike tooth emergence [18].

Significance of radiographs in dental age estimation

There are various methods of dental age estimation like clinical or visual method, morphological, histological, biochemical and radiological methods. Clinically the age can be estimated by visualizing the emergence of the tooth in the oral cavity and also based on the regressive changes in the teeth like attrition. It is a convenient method but has several limitations as there are various clinical interpretations of emergence such as, piercing of gingival and exposure of the crown, bony emergence through the alveolar bone or attainment of occlusion by the teeth. Secondly the exact timing of emergence also may be missed and lastly the eruption of the teeth is influenced by the local factors like infection, space in the arch and early tooth loss [14,19].

Morphological and histological methods depend upon the microscopic preparation of the extracted teeth. This may lead to ethical, religious and cultural problems. The time needed for these methods is also longer. They require sophisticated laboratory equipment’s, and hence expensive too so these methods may not be acceptable [14,19].

Whereas the radiographic methods of age estimation are simple, rapid, non-invasive, non – destructive and reproducible and hence can be used in living as well as in unknown dead individuals. Dental Radiography includes simple techniques that are used almost daily in dental practice [20].

Radiographic dental age assessment can be done based on the various parameters like prenatal formation of jaw bones, appearance of tooth germs, initiation of mineralization, degree of crown completion, crown eruption, amount of root completion, amount of root resorption of primary teeth, open apices measurement, pulp tooth ratio, secondary dentine formation and development of third molar [21].

Most of these methods are based on either ‘‘Atlas method’’ in which the developmental stages of the teeth are compared to the given standard or ‘‘Scoring method’’ in which the various stages of the teeth are assigned scores and then statistically anaysed [21].

Methods applicable for children and adolescents

There are many methods of dental age estimation based on the radiographic indicators. Methods which are applicable and more commonly used for the children and adolescents [21] are Schour and Masseler method [22], Nolla’s method [23], Moorees, Fanning and Hunt method [24], Demirjian, Goldstein and Tanner method [9], Willems method [25], Chaillet method [26], Acharya’s method [27],Camerier’s method using open apices [28], Modified Camerier’s Indian formula [29] and London atlas method [30].

Schour and Masseler method

Schour and Masseler published an atlas in 1941 which described 21 chronological steps from 4 months to 21 years that described the development of deciduous as well as the permanent teeth [22].

The age was predicted directly by comparing the calcification stages of teeth on radiographs with the standards. It is one of the oldest and the most well-known atlas method. It was popular because of its simplicity [31].

Applicability

Lower accuracy and precision was observed in comparative studies conducted in New Zealand [32] and by AlQahtani SJ on 1506 skeletal remains [33]. Although this method was found to be reliable in a study by Boel T [34]in Indonesia and by George GJ et al [35], in Mangaluru, India, both these studies are based on a smaller sample size. Further studies are needed on a larger sample size in India to check its reliability

Limitations

Although it is a simpler method of age estimation it has several limitations. The materials and method including the information on analysis is not available in the literature. The tooth stages and the eruption levels are not defined and the age range is small [36]. There are no separate charts for the two different genders. Furthermore, the gaps in the sequence of age categories; for example, after 12 years the chart directly refers to 15 years that affects the accuracy of this method. It does not mention the various stages of root development of third molar too [33].

Nolla’s method

In 1960 Nolla [23] developed a method by assessing the development of each maxillary and mandibular tooth. He assessed the mineralization of permanent teeth using a 10 stage formula. A score is assigned to each tooth after a comparative evaluation of a figure found by Nolla with the developing stages of the teeth on the radiograph. A reading of the maxillary and mandibular teeth is obtained and then compared with the Nolla’s table [36]. Here the advantage is that the assessment of age of girls and boys are done separately and it can be assessed without the third molars.

Applicability

Nolla’s method was found to be more suitable as compared to that of Demerjian in a Brazilian study conducted in 2018 [38]. Studies conducted in Spain by Paz Cortés MM in 2019 [39] and Melo M in 2017 [40] in different age groups of 4-14 years and 7-21 years respectively concluded that the Nolla’s method resulted in underestimation of the age in Spanish children. Whereas overestimation of the age was observed using Nolla’s method in Malaysian children of age group 5-15 years [41].

The applicability of Nolla’s method in Indian population is inconsistent as in one of the studies conducted by Mohammed RB [42] among the children of age group of 6-16 years in Andhra Pradesh observed that Nolla’s method overestimated the age whereas another study conducted in Rajasthan by Hegde S [43] showed underestimation of assessed age.

Limitations

With this method the age estimation can be done only up to 16 years.

Moorees, Fanning and Hunt method

Moorrees, Fanning and Hunt in 1963 [24] published the charts representing various developmental stages of the deciduous and permanent teeth. The method is based on the radiographic survey of a North American population with age range from 6 months upto the development of the mandibular third molar [24]. The charts indicates an average age with two standard deviations and illustrates 14 stages of mineralization and the mean age for the corresponding stage for developing single and multirooted permanent teeth. This method is very simple to apply and also the only standard method that is based on the analysis of data for both the sets of dentition from the same series of children. It provides separate charts for males and females. It is one of the methods recommended by the American Society of Forensic Odontology (ASFO) for age estimation in sub-adult individuals [44].

Applicability

Underestimation of the age has been reported when assessed by Moorees, Fanning and Hunt method in studies conducted at various places like USA [45], Vanezuala [46], South Africa [47] and in Hubli, karnataka- India [48].

Limitations

Underestimation of the age in most of the studies

Demirjian, Goldstein and Tanner method

It is the most widely used method in various countries proposed by Demirjian Goldstein and Tanner9 in 1973. It is based on the developmental stages of seven left mandibular permanent teeth of 2928 French - Canadian subjects (1446 boys and 1482 girls). The approach is similar to the one used for studying the skeletal maturity by Tanner- Whitehouse [49,50]. The same method was later updated by Demirjian and Goldstein in 1976 [5] in which they added two more methods based on four teeth.

The original study [9] proposed 8 stages of tooth development and included teeth from mandibular central incisor to second molar. The detailed description of all the stages is mentioned very clearly in the literature [9].These stages indicate dental maturity of each tooth on a scale of 0–100 on percentile charts. The total maturity scores (S) is then converted into dental age by referring the standard table or by substituting the scores in the regression formula separately for males and females, given by the author [9,20,37].

The method allows the use of opposing side tooth if the concerned tooth is absent and the readings of the central incisor if the first molar is missing [9].

Applicability

It is the most preferred method for dental age estimation in children and adolescents. Descriptions with the radiographic illustrations have been described in detail. It is relatively simple and more précised. But significant overestimation of the age was observed when the method was tested in North Germany [51], Egypt [52] and Brazillian children and adolescents [53]

A meta-analysis by Esan TA in 2018 [54] included 18 published studies comparing Demerjian’s method with that of Willems also observed significant overestimation (p<0.05) of the chronological age with Demirjian’s method compared to the Willems method.

Utility of Demirjian’s method remains unclear in Omanian children [55] since in some age groups it overestimated whereas in some it showed underestimation. In a comparative study in Kosova by Kelmendi J 2018, better accuracy was observed with Demerjian’s four teeth methods than 7 teeth methods.

When the applicability of Demerjian’s method with respect to the Indian population is considered, it is observed that there was overestimation and significant difference between the chronological age and dental age in Mumbai [56,57] and Udaipur studies [58,59]. A meta analysis by Prasad in 2019 [60] that included 20 Indian studies also observed consistent overestimation of the age with Demirjian’s method in Indian population, irrespective of the gender.

Limitations

Literature shows that in most of the studies it overestimates the age. Secondly there in no inclusion of the developing third molar in the survey and it requires presence of the mandibular teeth [20].

Revised Demerjian’s methods

• Willems method

Since a significant overestimation of age was observed with Demirjian’s formula on Belgian Caucasian children, Willems et al [25], modified the dental scores based on Demerjian’s scores and proposed a modified method for dental age estimation for children of both the genders.

Applicability

A meta analysis by Sehrawat JS [61] and Esan TA [54] which included 15 and 18 published studies respectively showed overestimation of children’s’ age with Willem’s method but to a lesser extent than the Demirjian method.

In Indian children, the comparative studies [60] found that Willem’s method underestimates the age but it is more accurate than Demerjian’s method. So the studies concluded that there is a need of population-specific formula for better accuracy of determination of age rather than using a universal method that is developed on other populations

Limitations

Overestimation of age in various population.

• Chaillet method (Demerjian 8 teeth method)

The original Demirjian’s method could be used only till 16 years of age representing the completion of the root of second molar. Due to the unpredictability of anatomy, formation and eruption of the third molar it was excluded from the survey [9].

But the only radiographic parameter which can be used for determination of the age from 16 to 23 years is the third molar [62]. Hence in the late adolescence, inclusion of the third molar helps in providing the information on likelihood of the person to be of 18 years of age [63].

Based on this fact and existing limitations of the original Demirjian’s method [9] the third molar was incorporated in a modification by Chaillet and Demirjian in 2001 [26]. Two additional stages of non-formation of tooth (Stage “0”) and crypt development (Stage “1”) were also added in the modified formula. Developmental stages of the teeth were assigned numerals from 0-9 and multiple regression formula was developed [26].

Applicability

Age assessed was underestimated using Chaillet or Demerjian 8 teeth method in Nepalese population [63] and also was found to be not suitable for Kosovar [56] and Tibetan young adults [64]. Indian studies [42,65]too found underestimation of the age using this formula.

Limitations

Underestimation of age in various population.

• Acharya’s method

In 2010 Acharya [27] proposed a revised method using Demirjian’s 8 teeth scores based on archives of 547 radiographs (348 females, 199 males) aged 7-25 years from an institution in Karnataka. He derived an Indian specific formula that is separate for males and females using regression analysis.

Applicability

According to Acharya [27], the regression equations derived yielded better accuracy with Mean absolute error (MAE) of 0.87 years than the original Chaillet and Demerjian method in the study population.

When Acharya’s formula for evaluated for its accuracy in Odisha population [66,67] of 522 children and adolescent of age group 5-18 years and another study among 106 children and young adults belonging to the age group of 7-23 years, it was found that the MAE was more than 2 years and 1.3 years respectively which showed lower accuracy .

Similar lower accuracy results were also found in comparative studies carried out in Bhivaram, AP [68] and in Telangana [69] wherein there was overestimation of the age using Acharya’s method. Acharya’s formula of dental age estimation was found to be more effective in a Chennai comparative study [70] in 100 subjects of age group of 5-24 years.

Limitations

Lower accuracy has been found with Acharya’s model [27] when studied in various Indian populations. The study was based on the data availed retrospectively from only one institution so there could be a bias in the selection of sample so whether the model can be generalized to the entire population is questionable. Secondly the study [27] is based on French Canadian weighted scores. The use of population specific maturity scores would have improved the age predictions of the study population.

Cameriere method of age estimation using open apices

Demerjian’s method which is the most commonly used method worldwide is based on the progressive sequence of teeth development which are then coded and scored. These maturity scores serve as a function of age within the acceptable error limits. Hence it is believed that this method is basically designed to study the deviation of dental maturity i.e. whether it is advanced or delayed from normal in an individual with known age [71]. Secondly recent studies have also shown that there is a change in the growth trend of the current generation demanding for formulation of a newer method of dental age assessment [72].

In 2006 [28] a new concept of dental age assessment was proposed by Cameriere et al. in children. It is based on the measurement of open apices of seven mandibular teeth on radiographs of 455 Italian Caucasian children.

By measuring the ratio of the width between the open apices to that of the length of the teeth with open apex, and the number of teeth with closed apices, they derived a regression model using variables like gender, sum of the normalised open apices, number of teeth with closed apex and measurements of mandibular left 2nd pre molar which showed the best fit.

Applicability

A study by Cameriere R [73] carried out in 2,652 European Caucasian healthy children (1,382 boys, 1,270 girls) belonging to a heterogenous group aged between 4 and 16 years found residual error rate to be less than 1 year and no statistical significant difference was found between chronological age and the estimated age in the countries studied. Hence it concluded that a single regression equation could be used for all the Caucasian samples.

In a comparative study in 2008 [74] it was found that Cameriere’s method was more accurate than Demerjian and Willem’s method in Italian, Spain and Croatian children. Cameriere’s method was also found to be accurate and more suitable in Mexican children [75].

But when the same formula was checked for its accuracy in Saudi Arabian [76], South African [77], Brazilian [78], North German [79], North China [80] and in Indian children [69,81], it showed underestimation of the assessed age highlighting the significant role of geography, nutrition, and genetics in the different regions in children’s growth.

Whereas in two Indian pilot studies which were carried out to evaluate the accuracy of Cameriere’s method in Kerala [82] and in Mangalorean children [83] significant correlation was found between the chronological age and the estimated age.

Findings of these studies open a scope for a research on a larger sample size to further confirm its reliability in Indian population.

Limitations

Age estimation with this method is possible till the age of 15 years as it is based on 7 teeth and the apices of the roots of second molar closes by this age.

• Camerier’s modified formula for India

When it was studied that Camerier’s method results in underestimation of the age in Haryana population [81], Balwant Rai in 2010 [29], reported a new model for Indian children based on Camerier’s method. In this study the author included the sample subjects belonging to the age of 3-15 years and tried to include the sample from North, Center and South Indian states to represent it as an Indian population.

Applicability

In a comparative study carried out in 60 children of west Godavari district [84] belonging to the age group of 9-14 years, no significant difference was obtained between the chronological age and the estimated age using modified Cameriere’s formula than the Cameriere’s and Demerjian’s method. Significant correlation was found between the chronological age and the age assessed by modified Cameriere’s method in Davangere study [85]. But both these studies are carried out in a smaller sample size. Further studies are essential on a larger sample size to confirm the reliability of modified Cameriere’s population-specific regression equation.

Limitation

Although Rai B [29] has attempted to give an equation for Indian children, the study neither mentions the clarification on the size of the sample nor the reasoning of selection of the study sample from only few states of the country. So whether we can generalize this equation to the whole population needs to be studied further by considering a larger sample size. There is no separate model for males and females as the author or feels that the dental maturation rate is almost the same in males and females whereas as per the literature [24,86]the dental maturity is far ahead in girls than in boys.

London Atlas method

In 2010 a wide-ranging atlas of tooth development stages was developed by AlQahtani et al. [30] based on Moorrees et al.’s [24] and Bengston’s [87] tooth Developmental stages. The atlas was based on the examination of mixed Bangladeshi and white British individuals of age ranging from 28 weeks intrauterine to 23 years.

The London Atlas [30] assessed deciduous as well as permanent dentition. The atlas is easy to visualize and recognize all the tooth development stages as it represents clear pictures of each stage of the teeth development with its clear description. After the first year of life, assignment of age with a range of one year has been presented in the atlas. So it is easier to use and less time consuming too.

This method when further tested by AlQahtani et al in 2014 [33] along with Schour and massler and Ubelaker charts in Bangladeshi and white British sample, authors obtained good accuracy measures for all the age groups with London atlas.

In a Thai study [88] a maximum of 1.3 years of discrepancy was found when the chronological age was compared to that of the estimated age with London Atlas method. A discrepancy of lower than 2 years was observed in a Brazilian study [89] with overestimation in some groups and underestimation in some.

In a comparative study carried out in Saudi Arabia [90] London atlas method consistently underestimated the age but no significant difference was observed between the chronological and the estimated age. London atlas method infect was found to be more accurate than Cameriere’s method. A study conducted in Germany [91] on comparison of London Atlas method with that of Willem’s and Demirjian’s observed that a combination of London atlas and Willem’s method gives more precise results rather than applying any single method.

London atlas method was found to be accurate in Iranian and Hispanic children whereas low accuracy was observed when evaluated in a modern American population representing multiple ancestry groups [92] and also in New Zealand population [32].In a Portuguese study [93] overestimation of age was found in males. Inaccurate results found in both the genders denote inefficiency of universal charts and stresses on the need for separate charts for each sex. This method is not been tested so far in Indian population.

Limitations

There are no separate charts for males and females. It is a subjective method and hence chances of having observer bias are more. Eruption of the teeth is highly influenced by various local factors. Hence, if the development rate of any tooth is faster or slowed down then the use of this method may not be advisable. Secondly if the teeth are mal-aligned then the considerations of the consolidation of development of the teeth are not addressed in the literature. If multiple teeth match the different age estimates then which teeth to be considered for accurate estimation of the age is also not mentioned in the literature [90,93].

 

Based on the above literature it is observed that the dental maturity is influenced by various factors such as environmental, ethnicity, genetic and socioeconomic which can further lead to difference in the teeth development among the people living in different countries and also among residents within a limited geographical area. Hence one cannot expect to have accurate results when age estimation formulas derived from non Indian population is applied to the Indian population. Although attempt has been made by few Indian researchers to modify these formulas and give Indian specific formula, these studies are based on non Indian maturity scores, smaller sample size, improperly distributed sample and hence these formulas may not be generalized to the entire Indian Population. India is a large country represented by diverse group of population from various socio-economic and ethnic backgrounds. Considering this fact and the existing lacunae in the literature the author recommends a further research in developing Indian maturity scores which will help in invention of more accurate scoring based formula of age estimation for Indian population.

Age estimation is required most of the time for delivering justice to an individual either in civil or criminal litigations. Hence the method adopted should always be of more accuracy and have less error rates.

Hence the above evidence suggests that India needs a population specific formula for dental age estimation in children and adolescents based on a systematically designed study by considering a larger sample size represented by various regions of the country which will result in a better accuracy, minimal error rates and can be generalized to the whole population.

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