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Dental age estimation in fetal and children
Chapter 7
Dental age estimation in fetal and children Sakher AlQahtani College of Dentistry, King Saud University, Riyadh, Saudi Arabia
7.1 Introduction Knowing the age is a basic human right and having it documented is what gives identity to the individual [1]. In the society we live in, date of birth is the epitome of one’s entity, and the time elapsed since then is defined as the chronological age [2]. This age determines when a child enters school, if he/she is entitled to minor’s asylum, when he/she can work as well as incriminating offenders rightfully according to their age and protect them and the people around them. Currently, there are 30% 50% of the 50 million births each year, which are unrecorded [3], which is in the violation of children’s human rights. The age of criminal responsibility can be as young as 7 years in Switzerland and South Africa, to as old as 18 years in Belgium and the United States of America. No finalized government guidelines and/or protocol are in place so far, and no country has got it right. In the absence of documents, or when age is disputed, age estimation is inevitable. The surge of asylum seekers with no documents during the war in Bosnia in the early 1990s was just the beginning of a big movement of refugees seeking shelter in safer countries: people fleeing famine in East Africa, ethnic cleansing in Middle and West Africa, genocides in the Middle East, and oppressive regimes in the near and far East. Minors make up a big bulk of refugees and asylum seekers. Checking their correct age not only benefits the hosting country but also protects the minors from exploitation and ensures they get the support they need. Moreover, countries sometimes need to age their own citizens who were not recorded at birth, got their documents stolen, or those who have been kidnaped at some point. Age assessment is done when there is a serious doubt, and it is the last resource, keeping the best interest of the child as the main priority and Age Estimation. DOI: https://doi.org/10.1016/B978-0-12-814491-6.00007-8 Copyright © 2019 Elsevier Inc. All rights reserved.
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giving the benefit of the doubt. However, law is biased toward social services assessment using Merton Age Compliance Guidelines published in 2003 [4], instead of using ionizing radiation examination which includes assessing physical appearance, the interaction of the individual during the assessment process, social history, family composition, how does the individual respond to authority/instruction, education, independent/self-care skills, health, medical assessment and information from documentation, and other sources. Choosing the right age assessment method relies heavily on the individual in question, in regard to the presence of teeth in the oral cavity or not and whether the subject is alive or not. In the cases of living children, the guidelines for dealing with those cases of age dispute according to the United Nations Convention on the Rights of the Child and the United Kingdom Border Agency are as follows: G
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Nondiscrimination against race, color, sex, language, religion, political or other opinion, national, ethnic or social origin, property, disability, birth, or other status. Best interests of the child in all actions concerning children, whether undertaken by public or private social welfare institutions, courts of law, administrative authorities or legislative bodies, the best interests of the child shall be a primary consideration. Ensure that the child has protection and care as it is necessary for his or her well-being, taking into account the rights and duties of his or her parents, legal guardians, or other individuals legally responsible for him or her, and, to this end, shall take all appropriate legislative and administrative measures. Every child matters, even if he/she is someone, subject to immigration control. Children should have their cases dealt with in a way that minimizes the uncertainty that they may experience. An accompanied or unaccompanied child (over the age of 12), who has his/her age disputed, has his/her own right to be interviewed about the substance of his/her assessment, unless the child is unfit or unable to be interviewed. The assessment should be conducted in the presence of a responsible adult (i.e., a parent, guardian, representative or another adult who has responsibility for the child but is independent of the Secretary of State). The assessor should have specialist training in the age assessment of children and have particular regard to the possibility that the child feels inhibited or alarmed; if the child appears tired or distressed, the assessment will be suspended.
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The assessment process should obtain details about: the child’s identity, country of origin and family, their health and any special needs, and the identity of anyone accompanying the child or acting as his/her responsible adult. Children must be dealt with as a priority in view of their vulnerability.
For general cases of age dispute in the living, the following points should be taken into consideration: G
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A signed, written informed consent must be obtained from the individual or his/her guardian/legal representative, before any examination is undertaken. The informed consent must clearly explain to the individual that the examination is primarily to assess his/her age. However, since the examination would encompass a general health screening, any abnormal medical, hard and soft tissue pathology noted would be included in the written report. An intraoral examination of the individual shall be undertaken in a suitably equipped dental operatory by a fully trained and experienced forensic odontologist or by a qualified and registered radiologist. A panel of qualified, registered, and experienced practitioners, chaired by a forensic odontologist (including anthropologists, radiologists, pediatricians, or orthodontists), shall assess all information gathered. A clinical report shall be written covering all the aspects of the general oral condition, including hard and soft tissue anomalies that may be found. An age assessment of the individual shall be given, which will include an age range.
Comprehensive knowledge of growth and development is important to understand the morphological variation in children. Assessing dental development is fundamental in the evaluation of the overall maturity and can be used to compare growth and health between individuals and populations. In addition, the state of dental development is used to estimate chronological age.
7.2 Dental development Humans have two sets of teeth: 20 deciduous teeth (4 incisors, 2 canines, and 4 molars in each jaw) and 32 permanent teeth (4 incisors, 2 canine, 4 premolars, and 6 molars in each jaw). The process of dental development is divided into two main parts: tooth formation and tooth eruption. Tooth formation is the laying down and the mineralization of dental tissues (enamel, dentin, and cementum) in a robust predictable pattern. Eruption is the dynamic continuous movement of the
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developing tooth in an axial direction, from the depth to the edge of the alveolar bone, and further to the occlusal level [5 8]. Clinical tooth emergence, which is a part of tooth eruption, is the piercing of the cusps of a tooth through the gums [5].
7.3 Tooth formation Tooth development passes through several stages starting from the cellular level with tooth initiation, where the evolving tooth starts as a collection of cells (bud) that is connected to the epithelial layer, through the dental lamina where the jaws are. This tooth bud appears with unarranged cells in this stage. The epithelial cells proliferate into ectomesenchymal cells unequally, which leads to the formation of a cap-like shape. The growth continues, and the cap shape becomes bell shaped. The cells then start to differentiate into enamel-forming cells (ameloblasts) and dentin-forming cells (odontoblasts). The timing of the initial formation histologically starts around the 6th week intrauterus. At first, deciduous central incisors begin to form, followed by the deciduous first molars, then the deciduous laterals, deciduous canine, and the last are the deciduous second molars, each type of teeth are 2 weeks apart [9 11]. The advanced bell stage, where the shape of the future crown is formed, is called: morphodifferentiation. In this stage, the hard tissues such as enamel, dentin, and cementum, start to form. Hard tissue formation happens in a process called amelogenesis for enamel, dentinogenesis for dentin, and cementogenesis for cementum. The forming cells deposit the tissues layer by layer; then these layers get mineralized or calcified around the 13th week intrauterus. This is followed by the formation of the components of the periodontium including the periodontal ligament (PDL): alveolar bone and gingiva along with the nerve and vascular formation. The first permanent molars begin calcification around 32 weeks in utero [10] and become visible in a radiograph around a month after full gestation birth. Among the molars, the mesiobuccal cusp is always the first to begin developing, followed by the mesiolingual, distobuccal, and distolingual cusps, respectively. Lastly, a fifth, distal cusp generally develops on the lower molars [10 13]. At birth, the state of development of the teeth is dependent upon the duration of gestation and the overall extent of tooth development while in the uterus [11,14]. The tooth crown is completed when the production of enamel stops, depending on the crown size and the rate of deposition, time varies. In deciduous teeth, crown completion takes from 7 to 14 months, and in permanent teeth, completion requires 3 6 years [14].
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Root formation is more variable than crown completion and depends on the root’s overall length and the rate of dentin apposition. In general, the deciduous roots require 1.5 2 years for completion, and the permanent roots require 5 7 years [14]. The permanent third molar is highly variable and usually does not begin formation until the other crowns have completed their development, with initiation beginning anywhere from 7 to 14 years of age [11,14,15]. Research has shown that there are no statistically significant differences between races, and the differences present are merely biological ones [16 23]. The presence of these biological differences necessitates knowing the full range of variation in the timing of tooth development, for full list refer to [14].
7.4 Tooth eruption Tooth eruption is defined as the tooth breaking through the alveolar bone until it reaches an antagonist or an obstacle. It continues as each tooth moves into occlusion and beyond to compensate for the effects of wear, making it a continuous process that never completely ceases [11,24]. Tooth clinical emergence, on the other hand, is when the tooth pierces the gums [5]. There are many theories as to the processes that cause a tooth to emerge into the oral cavity. Biological forces play a major role in this process in conjunction with local factors that may influence the time of eruption of each tooth. These factors include genetic factors and endocrine reactions [25 28], sex and ancestry as well as nutrition and the environment [25].
7.4.1
Dental age assessment
Dental age assessment can be done in an invasive or noninvasive way: G
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Noninvasive methods: G Sequential tooth eruption and/or emergence [14,29 37] G Development by means of calcification and/or root maturation: Developmental schemas [14,38] Dental developmental stages [13,39 65] Root developmental stages [66 69] G Morphological tooth parameters [70 80] G Tooth measurements [81 88] Invasive methods: G Biomarkers [89 91]
7.4.2
Techniques using dental development
The strengths of using dental developmental stages to estimate dental age are that they provide a point estimate based on calculations where different
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estimates for teeth are averaged or given different weights. The limitations of methods based on dental developmental stages are that most of them are based on permanent teeth only, and evidence is scarce for the initiation of development of lower permanent anterior teeth and lower posterior deciduous teeth [61]. Moreover, they are applicable on limited age range or having missing age cohorts. When assessing tooth development for age estimation, the assessor has to keep in mind that only intact teeth should be used that have no periapical pathology, no extensive caries, no extensive restorations, or exhibit dental morphologic abnormalities. The assessment of tooth development from dental radiographs can be improved by using internal hard tissues, such as the shape of the pulp chamber or root canal, improving sensitivity and performance measures. Crown assessment: Thickness and continuity of enamel in the incisal or occlusal surface of any tooth should be assessed, followed by the presence of dentin and ending with the shape of the roof of the pulp. Root assessment: Root is initiated with small divergent spicules from the edges of the crown. The amount of root developed should be compared to the size of the crown (lengthwise) until the length of the root exceeds the length of the crown, then all attention should be on the root apex in terms of maturity (open, closed, and the width of the apical PDL space). The two most widely used staging techniques of tooth formation are: Demirjian’s [92] and Moorrees et al. [43,44].
7.5 Moorrees, fanning, and hunt stages This staging system has been the basis of many dental age estimation methods [14,54,61]. There are 13 stages of formation for single-rooted teeth and 14 stages of formation for multirooted teeth starting from cusp tip initiation (Ci) up until the maturation of the root (Ac) (Figs. 7.1 7.3). They have separate data tables for males and females.
7.5.1
Method
Assess the radiograph to identify the developing teeth (teeth with closed apices should not be included). Assign stage of development for each tooth. From the male and female tables, find age of attainment for each tooth according to its developmental stage. The formula is: Dental age 5 sum (value for tooth developmental stage from table)/ number of teeth assessed
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FIGURE 7.1 Description of Moorrees’ stages of dental development of single rooted teeth.
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FIGURE 7.2 Description of Moorrees’ stages of dental development of multi rooted teeth.
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FIGURE 7.3 Description of Moorrees’ stages of root resorption
7.6 Demirjian’s stages It is one of the most widely used methods [29,55,92], although using it with self-weighted maturity scores and modified regression models to reflect local sample gives better results. Each stage of dental development is given a score that provides an estimate of dental maturity on a scale of 0 100. There are eight stages of dental development in this method (A H).
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The assessor can use either seven mandibular teeth [92] or four mandibular teeth [29], missing teeth from one side can be substituted by the same tooth type from the other side of the jaw, and a missing first molar can be substituted with a central incisor. The limitations of this method, however, are that it can only be applied on mandibular teeth, has no scores for third molars, and doesn’t count for missing teeth or fragmented remains.
7.6.1
Method
Assign stage to each tooth, then get the corresponding weighted score (the sum 5 maturity score). Dental age corresponds to the maturity score from the table.
7.7 Schemas of dental development Schemas of dental development, although they use dental developmental stages, they provide an overview of the overall dental development for age cohort, and the age estimation they provide is an age category. Using dental development has the advantage of observing a continuous process of tooth development. Schemas of dental development are simpler to use, due to the fact that they are based on direct comparison between an illustration of dental development of a certain age cohort and a radiograph or isolated teeth (Fig. 7.4).
7.8 Age estimation methods 7.8.1
Prenatal, neonatal, and postnatal
Histological tooth development starts from the 6th week in utero, and mineralization that allows teeth to be visible on a radiograph wouldn’t happen until the second trimester in the form of cusp tips of the deciduous teeth, around 13 weeks after histological tooth development. These cusp tips are very small and are held in their crypt by soft tissues. The challenge in dealing with neonates in this age-group is to preserve and find these cusp tips and incisal edges that could be easily misplaced or lost after soft tissue decomposition. The loss of the supporting soft tissues within the crypt and the porosity of the jaw bone in this age can lead to these cusp tips to fall off and be misplaced in the surrounding soil if the neonate was buried, or within the cloth
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FIGURE 7.4 Atlas of Tooth Development and Eruption
or garment if the neonate was wrapped. Therefore it is important that the forensic odontologist examines the body of the neonate before it is moved from its place to locate the cusp tips and incisal edges necessary for age estimation. In crime scenes, usually the forensic pathologist starts the body examination, but the only one who knows what to look for and where, in regard to teeth, is the forensic odontologist. If a body of a neonate is found, the area around it should be secured and the body covered from weather ailments, and a forensic odontologist has to be called to the scene. Great care should be exercised not to lose or overlook any cusp tips or break the fragile occlusal cusps that started to coalesce. If no mineralized tooth tissue is present, a radiograph should be taken of the jaw then histological examination is carried away by dissecting the jaw and looking into the crypt of the teeth. If isolated cusp tips were recovered, they can be examined with the naked eye. Age estimation can be done either by dry weighing method of [81,82] or comparing them to the diagrams supplied in The London Atlas (Fig. 7.4). In the cases of skeletal remains, radiographs should be taken of the skull and dental development compared to the diagrams of The London Atlas.
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7.8.1.1 Neonatal line While aging a neonate using tooth developmental stages, corrected gestation age should be followed, (40 gestational weeks) [14] keeping in mind that birth is an event that doesn’t affect dental development. The neonatal line forms a clear demarcation between the prenatal and postnatal enamel deposition, and it is independent of gestational age or size at birth [93]. Finding the neonatal line will reveal that the infant was in fact born alive and lived for at least 7 10 days, which is the time necessary for the visualization of the neonatal line as a band between pre- and postnatal enamel. The amount of enamel formed after birth can then be measured to evaluate the duration of postnatal survival in skeletal remains (Chapter 11, The neonatal line as evidence of live birth).
7.8.2
Infant 0 to ,2 years
This age-group starts with no teeth in the oral cavity, but within months, deciduous teeth start to emerge through the gums of the infant. The sequence of eruption and tooth count may be the only way to estimate the age of the living infant as radiographs are contraindicated in this age-group, and the difficulty of obtaining a radiograph from an infant is predictable. Keeping in mind that tooth eruption is highly affected by nutrition, infection, pathology, trauma, tooth agenesis, tooth loss, and teeth crowding, the assessor should be familiar with these limitations and also with the anatomy and anomalies of teeth. In the cases of skeletal remains or crime scenes, a radiograph would be appropriate to examine the tooth development and compare that to appropriate method (Table 7.1). A lateral oblique radiograph and/or an anterior radiograph would be optimal to show all the developing dentition.
7.8.3
Children and adolescent 2 to ,18 years
This age-group displays the full deciduous dentition in the oral cavity at the age of 2 and the beginning of permanent tooth eruption at around age 5. Using the eruption of the permanent dentition could be utilized for age assessment between the ages 5 and 14, keeping in mind the limitations of relying on tooth eruption alone mentioned earlier. Extra studies that evaluated the eruption of permanent teeth in different populations can be referred to as well. The radiographic analysis of the developing dentition as well as the clinical tooth emergence in various phases will help in age estimation. Good quality radiograph is invaluable, would it be panoramic dental radiograph, periapical radiograph, a CT scan, or even a lateral oblique.
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TABLE 7.1 Techniques and methods for fetal and children dental age estimation Technique
Method
Age range
Teeth to be used
Sex/Ancestry
Moorrees, Fanning, and Hunt tooth developmental stages (deciduous and/or permanent teeth) and corresponding age estimation tables
Moorrees et al. [43,44]
Birth 21 years
Developing teeth (better to use more than one tooth)
Sex specific (There are EuropeanAmerican and African-American ancestral population studies available)
Anderson et al. [54]
3 18 years
Demirjian et al. tooth developmental stages and corresponding age estimation data (addition of stage 0 for no calcification) [55]
7 teeth system
2.5 14 years
4 teeth system
Sex specific (There are EuropeanCanadian ancestral population study available) All lower left permanent teeth excluding third molars (if one tooth is unavailable, use the contralateral tooth)
Sex specific (There are multiple ancestral population studies available)
Requires the use of four lower left permanent teeth in one of two combinations:
Sex specific (There is only FrenchCanadian ancestral population study available)
(M2, M1, PM2, PM1) Or (M2, PM2, PM1, I1) if one tooth is unavailable, use the contralateral tooth Ubelaker’s dental development atlas [38]
Nonstaged illustration of dental development
5 months in utero 15 years
Gingival eruption The London atlas of tooth development [14]
Diagrams depicted are defined by Moorrees, Fanning, and Hunt staging system of tooth development Alveolar eruption
28 weeks in utero 15.5 years
All available teeth
Not sex or ancestry specific
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7.9 Conclusion There are a variety of methods that can be applied for age estimation with many population-specific data, and there is a trend of automation of the statistical calculations. However, there isn’t a single, universally applicable standard for age prediction. When doing age assessment, be familiar with the methods that you use, its limitations, and applications. Keeping in mind that single data can mislead, assess multiple teeth and use multiple methods to improve the accuracy and also use multiple examiners. Rules: G
G G
If the full tooth wasn’t clear in a radiograph, assessment shouldn’t be made. That tooth should be excluded. When between stages, assign earliest or lesser stage. Stages are NOT all the same. Be familiar with the method you are applying.
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[58] Van der Linden FP, Wasenberg HJ, Bakker PJ. [Development of the human dentition. Ii]. Dent Cadmos 1985;53(7):19 21 22, 25 30. [59] Nystr€om M, Haataja J, Kataja M, Ev€alahti M, Peck L, Kleemola-Kujala E. Dental maturity in Finnish children, estimated from the development of seven permanent mandibular teeth. Acta Odontol Scand 1986;44(4):193 208. [60] Carels CE, Kuijpers-Jagtman AM, Van Der Linden FP, Van’t Hof MA. Age reference charts of tooth length in Dutch children. J Biol Buccale 1991;19(4):297 303. [61] Smith BH. Standards of human tooth formation and dental age assessment. In: Kelley MA, Larsen CS, editors. Advances in dental anthropology. New York: Wiley-Liss; 1991. p. 143 68. [62] Mincer H, Harris E, Berryman H. The A.B.F.O. study of third molar development and its use as an estimator of chronological age. J Forensic Sci 1993;38(2):379 90. [63] K€ohler S, Schmelzle R, Loitz C, P€uschel K. Die entwicklung des weisheitszahnes als kriterium der lebensalterbestimmung. Ann Anat 1994;176:339 45. [64] M€ornstad H, Staaf V, Welander U. Age estimation with the aid of tooth development: a new method based on objective measurements. Eur J Oral Sci 1994;102(3):137 43. [65] Mesotten K, Gunst K, Carbonez A, Willems G. Dental age estimation and third molars: a preliminary study. Forensic Sci Int 2002;129(2):110 15. [66] Harris MJ, Nortje CJ. The mesial root of the third mandibular molar: a possible indicator of age. J Forensic Odontostomatol 1984;2(2):39 43. [67] Kullman L, Johanson G, Akesson L. Root development of the lower third molar and its relation to chronological age. Swed Dent J 1992;16(4):161 7. [68] Gunst K, Mesotten K, Carbonez A, Willems G. Third molar root development in relation to chronological age: a large-sample-sized retrospective study. Forensic Sci Int 2003;136 (1 3):52 7. [69] Rai B, Krishan K, Kaur J, Anand S. Age estimation from mandible by lateral cephalogram: a preliminary study. J Forensic Odontostomatol 2008;26(1):24 8. [70] Gustafson G. Age determination on teeth. J Am Dent Assoc 1950;41(1):45 54. [71] Dalitz GD. Age determination of adult human remain by teeth examination. J Forensic Sci Soc 1962;3:11 21. [72] Johanson G. Age determination from human teeth: a critical evaluation with special consideration of changes after fourteen years of age. Odontol Revy 1971;22(Suppl. 21): l 126. [73] Moore WJ, Corbett ME. The distribution of dental caries in ancient British populations. I. Anglo-saxon period. Caries Res 1971;5:151 68. [74] Moore WJ, Corbett ME. The distribution of dental caries in ancient British populations. II. Iron age, Romano-British and mediaeval periods. Caries Res 1973;7:139 53. [75] Miles A. Teeth as an indicator of age in man. In: Butler PM, Joysey KA, editors. Development, function and evolution of teeth. London: Academic Press; 1978. [76] Brothwell DR. Digging up bones: the excavation, treatment, and study of human skeletal remains. Ithaca, NY: Cornell University Press; 1981. [77] Lovejoy CO. Dental wear in the Libben population: its functional pattern and role in the determination of adult skeletal age at death. Am J Phys Anthropol 1985;68(1):47 56. [78] Solheim T. A new method for dental age estimation in adults. Forensic Sci Int 1993;59:137 47. [79] Kvaal SI, Solheim T. A non-destructive dental method for age estimation. J Forensic Odontostomatol 1994;12(1):6 11.
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[80] Constandse-Westermann TS. Age estimation by dental attrition in an independently controlled early 19th century sample from Zwolle, the Netherlands. Hum Evol 1997;12 (4):269 85. [81] Stack MV. Forensic estimation of age in infancy by gravimetric observations on the developing dentition. J Forensic Sci Soc 1960;1(1):49 59. [82] Stack MV. Vertical growth rates of the deciduous teeth. J Dent Res 1967;46(5):879 82. [83] Liversidge HM, Dean MC, Molleson TI. Increasing human tooth length between birth and 5.4 years. Am J Phys Anthropol 1993;90(3):307 13. [84] Kullman L, Martinsson T, Zimmerman M, Welander U. Computerized measurements of the lower third molar related to chronologic age in young adults. Acta Odontol Scand 1995;53(4):211 16. [85] Kvaal SI, Kolltveit KM, Thomsen IO, Solheim T. Age estimation of adults from dental radiographs. Forensic Sci Int 1995;74:175 85. [86] Liversidge HM, Molleson TI. Deciduous tooth size and morphogenetic fields in children from Christ Church, Spitalfields. Arch Oral Biol 1999;44(1):7 13. [87] Liversidge HM, Molleson TI. Developing permanent tooth length as an estimate of age. J Forensic Sci 1999;44(5):917 20. [88] Aka PS, Canturk N, Dagalp R, Yagan M. Age determination from central incisors of fetuses and infants. Forensic Sci Int 2009;184(1 3):15 20. [89] Wehner F, Secker K, Wehner H, Gehring K, Schulz M. Immunohistochemical proof of amelogenin in teeth: a contribution to the evaluation of the age in the identification of unknown corpses. Arch Kriminol 2007;220(1 2):44 50. [90] Alkass K, Buchholz BA, Ohtani S, Yamamoto T, Druid H, Spalding KL. Age estimation in forensic sciences: application of combined aspartic acid racemization and radiocarbon analysis. Mol Cell Proteomics 2009;9(5):1022 30. [91] Griffin RC, Chamberlain AT, Hotz G, Penkman KEH, Collins MJ. Age estimation of archaeological remains using amino acid racemization in dental enamel: a comparison of morphological, biochemical, and known ages-at-death. Am J Phys Anthropol 2009;140 (2):244 52. [92] Demirjian A. [Dental development: index of physiologic maturation]. Med Hyg (Geneve) 1978;36(1302):3154 9. [93] Smith P, Avishai G. The use of dental criteria for estimating postnatal survival in skeletal remains of infants. J Archaeol Sci 2005;32(1):83 9.
Dental age estimation in fetal and children Sakher AlQahtani College of Dentistry, King Saud University, Riyadh, Saudi Arabia
7.1 Introduction Knowing the age is a basic human right and having it documented is what gives identity to the individual [1]. In the society we live in, date of birth is the epitome of one’s entity, and the time elapsed since then is defined as the chronological age [2]. This age determines when a child enters school, if he/she is entitled to minor’s asylum, when he/she can work as well as incriminating offenders rightfully according to their age and protect them and the people around them. Currently, there are 30% 50% of the 50 million births each year, which are unrecorded [3], which is in the violation of children’s human rights. The age of criminal responsibility can be as young as 7 years in Switzerland and South Africa, to as old as 18 years in Belgium and the United States of America. No finalized government guidelines and/or protocol are in place so far, and no country has got it right. In the absence of documents, or when age is disputed, age estimation is inevitable. The surge of asylum seekers with no documents during the war in Bosnia in the early 1990s was just the beginning of a big movement of refugees seeking shelter in safer countries: people fleeing famine in East Africa, ethnic cleansing in Middle and West Africa, genocides in the Middle East, and oppressive regimes in the near and far East. Minors make up a big bulk of refugees and asylum seekers. Checking their correct age not only benefits the hosting country but also protects the minors from exploitation and ensures they get the support they need. Moreover, countries sometimes need to age their own citizens who were not recorded at birth, got their documents stolen, or those who have been kidnaped at some point. Age assessment is done when there is a serious doubt, and it is the last resource, keeping the best interest of the child as the main priority and Age Estimation. DOI: https://doi.org/10.1016/B978-0-12-814491-6.00007-8 Copyright © 2019 Elsevier Inc. All rights reserved.
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giving the benefit of the doubt. However, law is biased toward social services assessment using Merton Age Compliance Guidelines published in 2003 [4], instead of using ionizing radiation examination which includes assessing physical appearance, the interaction of the individual during the assessment process, social history, family composition, how does the individual respond to authority/instruction, education, independent/self-care skills, health, medical assessment and information from documentation, and other sources. Choosing the right age assessment method relies heavily on the individual in question, in regard to the presence of teeth in the oral cavity or not and whether the subject is alive or not. In the cases of living children, the guidelines for dealing with those cases of age dispute according to the United Nations Convention on the Rights of the Child and the United Kingdom Border Agency are as follows: G
G
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Nondiscrimination against race, color, sex, language, religion, political or other opinion, national, ethnic or social origin, property, disability, birth, or other status. Best interests of the child in all actions concerning children, whether undertaken by public or private social welfare institutions, courts of law, administrative authorities or legislative bodies, the best interests of the child shall be a primary consideration. Ensure that the child has protection and care as it is necessary for his or her well-being, taking into account the rights and duties of his or her parents, legal guardians, or other individuals legally responsible for him or her, and, to this end, shall take all appropriate legislative and administrative measures. Every child matters, even if he/she is someone, subject to immigration control. Children should have their cases dealt with in a way that minimizes the uncertainty that they may experience. An accompanied or unaccompanied child (over the age of 12), who has his/her age disputed, has his/her own right to be interviewed about the substance of his/her assessment, unless the child is unfit or unable to be interviewed. The assessment should be conducted in the presence of a responsible adult (i.e., a parent, guardian, representative or another adult who has responsibility for the child but is independent of the Secretary of State). The assessor should have specialist training in the age assessment of children and have particular regard to the possibility that the child feels inhibited or alarmed; if the child appears tired or distressed, the assessment will be suspended.
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The assessment process should obtain details about: the child’s identity, country of origin and family, their health and any special needs, and the identity of anyone accompanying the child or acting as his/her responsible adult. Children must be dealt with as a priority in view of their vulnerability.
For general cases of age dispute in the living, the following points should be taken into consideration: G
G
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A signed, written informed consent must be obtained from the individual or his/her guardian/legal representative, before any examination is undertaken. The informed consent must clearly explain to the individual that the examination is primarily to assess his/her age. However, since the examination would encompass a general health screening, any abnormal medical, hard and soft tissue pathology noted would be included in the written report. An intraoral examination of the individual shall be undertaken in a suitably equipped dental operatory by a fully trained and experienced forensic odontologist or by a qualified and registered radiologist. A panel of qualified, registered, and experienced practitioners, chaired by a forensic odontologist (including anthropologists, radiologists, pediatricians, or orthodontists), shall assess all information gathered. A clinical report shall be written covering all the aspects of the general oral condition, including hard and soft tissue anomalies that may be found. An age assessment of the individual shall be given, which will include an age range.
Comprehensive knowledge of growth and development is important to understand the morphological variation in children. Assessing dental development is fundamental in the evaluation of the overall maturity and can be used to compare growth and health between individuals and populations. In addition, the state of dental development is used to estimate chronological age.
7.2 Dental development Humans have two sets of teeth: 20 deciduous teeth (4 incisors, 2 canines, and 4 molars in each jaw) and 32 permanent teeth (4 incisors, 2 canine, 4 premolars, and 6 molars in each jaw). The process of dental development is divided into two main parts: tooth formation and tooth eruption. Tooth formation is the laying down and the mineralization of dental tissues (enamel, dentin, and cementum) in a robust predictable pattern. Eruption is the dynamic continuous movement of the
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developing tooth in an axial direction, from the depth to the edge of the alveolar bone, and further to the occlusal level [5 8]. Clinical tooth emergence, which is a part of tooth eruption, is the piercing of the cusps of a tooth through the gums [5].
7.3 Tooth formation Tooth development passes through several stages starting from the cellular level with tooth initiation, where the evolving tooth starts as a collection of cells (bud) that is connected to the epithelial layer, through the dental lamina where the jaws are. This tooth bud appears with unarranged cells in this stage. The epithelial cells proliferate into ectomesenchymal cells unequally, which leads to the formation of a cap-like shape. The growth continues, and the cap shape becomes bell shaped. The cells then start to differentiate into enamel-forming cells (ameloblasts) and dentin-forming cells (odontoblasts). The timing of the initial formation histologically starts around the 6th week intrauterus. At first, deciduous central incisors begin to form, followed by the deciduous first molars, then the deciduous laterals, deciduous canine, and the last are the deciduous second molars, each type of teeth are 2 weeks apart [9 11]. The advanced bell stage, where the shape of the future crown is formed, is called: morphodifferentiation. In this stage, the hard tissues such as enamel, dentin, and cementum, start to form. Hard tissue formation happens in a process called amelogenesis for enamel, dentinogenesis for dentin, and cementogenesis for cementum. The forming cells deposit the tissues layer by layer; then these layers get mineralized or calcified around the 13th week intrauterus. This is followed by the formation of the components of the periodontium including the periodontal ligament (PDL): alveolar bone and gingiva along with the nerve and vascular formation. The first permanent molars begin calcification around 32 weeks in utero [10] and become visible in a radiograph around a month after full gestation birth. Among the molars, the mesiobuccal cusp is always the first to begin developing, followed by the mesiolingual, distobuccal, and distolingual cusps, respectively. Lastly, a fifth, distal cusp generally develops on the lower molars [10 13]. At birth, the state of development of the teeth is dependent upon the duration of gestation and the overall extent of tooth development while in the uterus [11,14]. The tooth crown is completed when the production of enamel stops, depending on the crown size and the rate of deposition, time varies. In deciduous teeth, crown completion takes from 7 to 14 months, and in permanent teeth, completion requires 3 6 years [14].
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Root formation is more variable than crown completion and depends on the root’s overall length and the rate of dentin apposition. In general, the deciduous roots require 1.5 2 years for completion, and the permanent roots require 5 7 years [14]. The permanent third molar is highly variable and usually does not begin formation until the other crowns have completed their development, with initiation beginning anywhere from 7 to 14 years of age [11,14,15]. Research has shown that there are no statistically significant differences between races, and the differences present are merely biological ones [16 23]. The presence of these biological differences necessitates knowing the full range of variation in the timing of tooth development, for full list refer to [14].
7.4 Tooth eruption Tooth eruption is defined as the tooth breaking through the alveolar bone until it reaches an antagonist or an obstacle. It continues as each tooth moves into occlusion and beyond to compensate for the effects of wear, making it a continuous process that never completely ceases [11,24]. Tooth clinical emergence, on the other hand, is when the tooth pierces the gums [5]. There are many theories as to the processes that cause a tooth to emerge into the oral cavity. Biological forces play a major role in this process in conjunction with local factors that may influence the time of eruption of each tooth. These factors include genetic factors and endocrine reactions [25 28], sex and ancestry as well as nutrition and the environment [25].
7.4.1
Dental age assessment
Dental age assessment can be done in an invasive or noninvasive way: G
G G G
G
Noninvasive methods: G Sequential tooth eruption and/or emergence [14,29 37] G Development by means of calcification and/or root maturation: Developmental schemas [14,38] Dental developmental stages [13,39 65] Root developmental stages [66 69] G Morphological tooth parameters [70 80] G Tooth measurements [81 88] Invasive methods: G Biomarkers [89 91]
7.4.2
Techniques using dental development
The strengths of using dental developmental stages to estimate dental age are that they provide a point estimate based on calculations where different
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estimates for teeth are averaged or given different weights. The limitations of methods based on dental developmental stages are that most of them are based on permanent teeth only, and evidence is scarce for the initiation of development of lower permanent anterior teeth and lower posterior deciduous teeth [61]. Moreover, they are applicable on limited age range or having missing age cohorts. When assessing tooth development for age estimation, the assessor has to keep in mind that only intact teeth should be used that have no periapical pathology, no extensive caries, no extensive restorations, or exhibit dental morphologic abnormalities. The assessment of tooth development from dental radiographs can be improved by using internal hard tissues, such as the shape of the pulp chamber or root canal, improving sensitivity and performance measures. Crown assessment: Thickness and continuity of enamel in the incisal or occlusal surface of any tooth should be assessed, followed by the presence of dentin and ending with the shape of the roof of the pulp. Root assessment: Root is initiated with small divergent spicules from the edges of the crown. The amount of root developed should be compared to the size of the crown (lengthwise) until the length of the root exceeds the length of the crown, then all attention should be on the root apex in terms of maturity (open, closed, and the width of the apical PDL space). The two most widely used staging techniques of tooth formation are: Demirjian’s [92] and Moorrees et al. [43,44].
7.5 Moorrees, fanning, and hunt stages This staging system has been the basis of many dental age estimation methods [14,54,61]. There are 13 stages of formation for single-rooted teeth and 14 stages of formation for multirooted teeth starting from cusp tip initiation (Ci) up until the maturation of the root (Ac) (Figs. 7.1 7.3). They have separate data tables for males and females.
7.5.1
Method
Assess the radiograph to identify the developing teeth (teeth with closed apices should not be included). Assign stage of development for each tooth. From the male and female tables, find age of attainment for each tooth according to its developmental stage. The formula is: Dental age 5 sum (value for tooth developmental stage from table)/ number of teeth assessed
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FIGURE 7.1 Description of Moorrees’ stages of dental development of single rooted teeth.
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FIGURE 7.2 Description of Moorrees’ stages of dental development of multi rooted teeth.
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FIGURE 7.3 Description of Moorrees’ stages of root resorption
7.6 Demirjian’s stages It is one of the most widely used methods [29,55,92], although using it with self-weighted maturity scores and modified regression models to reflect local sample gives better results. Each stage of dental development is given a score that provides an estimate of dental maturity on a scale of 0 100. There are eight stages of dental development in this method (A H).
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The assessor can use either seven mandibular teeth [92] or four mandibular teeth [29], missing teeth from one side can be substituted by the same tooth type from the other side of the jaw, and a missing first molar can be substituted with a central incisor. The limitations of this method, however, are that it can only be applied on mandibular teeth, has no scores for third molars, and doesn’t count for missing teeth or fragmented remains.
7.6.1
Method
Assign stage to each tooth, then get the corresponding weighted score (the sum 5 maturity score). Dental age corresponds to the maturity score from the table.
7.7 Schemas of dental development Schemas of dental development, although they use dental developmental stages, they provide an overview of the overall dental development for age cohort, and the age estimation they provide is an age category. Using dental development has the advantage of observing a continuous process of tooth development. Schemas of dental development are simpler to use, due to the fact that they are based on direct comparison between an illustration of dental development of a certain age cohort and a radiograph or isolated teeth (Fig. 7.4).
7.8 Age estimation methods 7.8.1
Prenatal, neonatal, and postnatal
Histological tooth development starts from the 6th week in utero, and mineralization that allows teeth to be visible on a radiograph wouldn’t happen until the second trimester in the form of cusp tips of the deciduous teeth, around 13 weeks after histological tooth development. These cusp tips are very small and are held in their crypt by soft tissues. The challenge in dealing with neonates in this age-group is to preserve and find these cusp tips and incisal edges that could be easily misplaced or lost after soft tissue decomposition. The loss of the supporting soft tissues within the crypt and the porosity of the jaw bone in this age can lead to these cusp tips to fall off and be misplaced in the surrounding soil if the neonate was buried, or within the cloth
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FIGURE 7.4 Atlas of Tooth Development and Eruption
or garment if the neonate was wrapped. Therefore it is important that the forensic odontologist examines the body of the neonate before it is moved from its place to locate the cusp tips and incisal edges necessary for age estimation. In crime scenes, usually the forensic pathologist starts the body examination, but the only one who knows what to look for and where, in regard to teeth, is the forensic odontologist. If a body of a neonate is found, the area around it should be secured and the body covered from weather ailments, and a forensic odontologist has to be called to the scene. Great care should be exercised not to lose or overlook any cusp tips or break the fragile occlusal cusps that started to coalesce. If no mineralized tooth tissue is present, a radiograph should be taken of the jaw then histological examination is carried away by dissecting the jaw and looking into the crypt of the teeth. If isolated cusp tips were recovered, they can be examined with the naked eye. Age estimation can be done either by dry weighing method of [81,82] or comparing them to the diagrams supplied in The London Atlas (Fig. 7.4). In the cases of skeletal remains, radiographs should be taken of the skull and dental development compared to the diagrams of The London Atlas.
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7.8.1.1 Neonatal line While aging a neonate using tooth developmental stages, corrected gestation age should be followed, (40 gestational weeks) [14] keeping in mind that birth is an event that doesn’t affect dental development. The neonatal line forms a clear demarcation between the prenatal and postnatal enamel deposition, and it is independent of gestational age or size at birth [93]. Finding the neonatal line will reveal that the infant was in fact born alive and lived for at least 7 10 days, which is the time necessary for the visualization of the neonatal line as a band between pre- and postnatal enamel. The amount of enamel formed after birth can then be measured to evaluate the duration of postnatal survival in skeletal remains (Chapter 11, The neonatal line as evidence of live birth).
7.8.2
Infant 0 to ,2 years
This age-group starts with no teeth in the oral cavity, but within months, deciduous teeth start to emerge through the gums of the infant. The sequence of eruption and tooth count may be the only way to estimate the age of the living infant as radiographs are contraindicated in this age-group, and the difficulty of obtaining a radiograph from an infant is predictable. Keeping in mind that tooth eruption is highly affected by nutrition, infection, pathology, trauma, tooth agenesis, tooth loss, and teeth crowding, the assessor should be familiar with these limitations and also with the anatomy and anomalies of teeth. In the cases of skeletal remains or crime scenes, a radiograph would be appropriate to examine the tooth development and compare that to appropriate method (Table 7.1). A lateral oblique radiograph and/or an anterior radiograph would be optimal to show all the developing dentition.
7.8.3
Children and adolescent 2 to ,18 years
This age-group displays the full deciduous dentition in the oral cavity at the age of 2 and the beginning of permanent tooth eruption at around age 5. Using the eruption of the permanent dentition could be utilized for age assessment between the ages 5 and 14, keeping in mind the limitations of relying on tooth eruption alone mentioned earlier. Extra studies that evaluated the eruption of permanent teeth in different populations can be referred to as well. The radiographic analysis of the developing dentition as well as the clinical tooth emergence in various phases will help in age estimation. Good quality radiograph is invaluable, would it be panoramic dental radiograph, periapical radiograph, a CT scan, or even a lateral oblique.
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TABLE 7.1 Techniques and methods for fetal and children dental age estimation Technique
Method
Age range
Teeth to be used
Sex/Ancestry
Moorrees, Fanning, and Hunt tooth developmental stages (deciduous and/or permanent teeth) and corresponding age estimation tables
Moorrees et al. [43,44]
Birth 21 years
Developing teeth (better to use more than one tooth)
Sex specific (There are EuropeanAmerican and African-American ancestral population studies available)
Anderson et al. [54]
3 18 years
Demirjian et al. tooth developmental stages and corresponding age estimation data (addition of stage 0 for no calcification) [55]
7 teeth system
2.5 14 years
4 teeth system
Sex specific (There are EuropeanCanadian ancestral population study available) All lower left permanent teeth excluding third molars (if one tooth is unavailable, use the contralateral tooth)
Sex specific (There are multiple ancestral population studies available)
Requires the use of four lower left permanent teeth in one of two combinations:
Sex specific (There is only FrenchCanadian ancestral population study available)
(M2, M1, PM2, PM1) Or (M2, PM2, PM1, I1) if one tooth is unavailable, use the contralateral tooth Ubelaker’s dental development atlas [38]
Nonstaged illustration of dental development
5 months in utero 15 years
Gingival eruption The London atlas of tooth development [14]
Diagrams depicted are defined by Moorrees, Fanning, and Hunt staging system of tooth development Alveolar eruption
28 weeks in utero 15.5 years
All available teeth
Not sex or ancestry specific
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7.9 Conclusion There are a variety of methods that can be applied for age estimation with many population-specific data, and there is a trend of automation of the statistical calculations. However, there isn’t a single, universally applicable standard for age prediction. When doing age assessment, be familiar with the methods that you use, its limitations, and applications. Keeping in mind that single data can mislead, assess multiple teeth and use multiple methods to improve the accuracy and also use multiple examiners. Rules: G
G G
If the full tooth wasn’t clear in a radiograph, assessment shouldn’t be made. That tooth should be excluded. When between stages, assign earliest or lesser stage. Stages are NOT all the same. Be familiar with the method you are applying.
References [1] Children’s Rights Alliance. Summary of the UN convention on the rights of the child; 2013. [2] Krogman WM. Biological timing and the dento-facial complex. Part I. J Dent Child 1968;35(4):175 85. [3] UNICEF. Fact sheets: birth registration. ,https://www.unicef.org/newsline/2003/03fsbirthregistration.htm.; 2012 [accessed 01.05.12]. [4] Crawley H. Asylum age disputes and the process of age assessment. In: Kelly E, Bokhari F, editors. Safeguarding children from abroad: refugee, asylum-seeking and trafficked children in the UK. London: Jessica Kingsley Publishers; 2012. p. 55 68. [5] Demirjian A. Dentition. In: Falkner F, Tanner J, editors. Human growth: a comprehensive treatise, vol. 2. New York: Plenum Press; 1986. p. 269 98. [6] Kardos TB. The mechanism of tooth eruption. Br Dent J 1996;181(3):91 5. [7] Wise GE, Frazier-Bowers S, D’Souza RN. Cellular, molecular, and genetic determinants of tooth eruption. Crit Rev Oral Biol Med 2002;13(4):323 35. [8] Craddock HL, Youngson CC. Eruptive tooth movement: the current state of knowledge. Br Dent J 2004;197(7):385 91. [9] Kraus BS. Calcification of the human deciduous teeth. J Am Dent Ass 1959;59 (5):1128 36. [10] Kraus BS, Jordan RE. The human dentition before birth. Philadelphia, PA: Lea & Febiger; 1965. [11] Hillson S. Dental anthropology. Cambridge: Cambridge University Press; 1996. [12] Schour I, Massler M. The development of the human dentition. J Am Dent Assoc 1941;28:1153 60. [13] Gleiser I, Hunt EE. The permanent mandibular first molar: its calcification, eruption and decay. Am J Phys Anthropol 1955;13(2):253 83.
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