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International Journal Of Scientific Research And Education
||Volume||2||Issue|| 3 ||Pages|354-367||2014|| ISSN (e): 2321-7545
Website: http://ijsae.in
“Teeth” –The focus of research in forensic age diagnostics
Dr. Nagalaxmi V1, Dr. Naga Jyothi M2, Dr. Kotya Naik M,3 Dr.Srikanth kodangal4
1
Professor & Head, Sri Sai College Of Dental Surgery, Vikarabad, Andhra Pradesh, India.
Post Graduate Student, Sri Sai College Of Dental Surgery, Vikarabad, Andhra Pradesh, India.
3
Post Graduate Student, Sri Sai College Of Dental Surgery, Vikarabad, Andhra Pradesh, India.
4
Senior lecturer, Sri Sai College of Dental Surgery, Vikarabad, Andhra Pradesh, India.
2
Email: [email protected]
Abstract:
Forensic dentistry is the specialized branch of forensic medicine uses dental evidence for criminal, civil,
legal proceedings, establishing the identity of unknown and missing individuals along with enormous
applications. In forensic dentistry various craniofacial structures are subjected to investigation to arrive at
conclusive data pertaining to age estimation. Age estimation using the dental evidence is an important area
of research in this field, where teeth serve as valuable tool in this specialized era of forensic age diagnostics
as they are least affected and destructed by the post-mortem changes and it also extends its applications to
other allied areas of forensic specialty like Anthropology, Palaeodontology, and Palaeoanthropology. This
review assembles various methods in forensic dental age estimation under one roof.
Keywords: Age estimation, Forensic odontology, Teeth, Bureau of Legal Dentistry.
1.Introduction:
Forensic dentistry is a specialized branch of forensic medicine and may be described as that part of
odontology which, in the interests of justice, deals with the handling and examination of dental evidence,
from which a proper evaluation and presentation of dental findings can be made. (Cameron and Sims, 1974
and Keiser-Nielson, 1980).
Forensic odontology (forensic dentistry) involves the correct collection, management, interpretation,
evaluation and presentation of dental evidence for criminal or civil legal proceedings: a combination of
various aspects of the dental, scientific and legal professions. The bones and teeth of the craniofacial region
constitute an invaluable aid in the identification of an unknown individual thus considered as the essential
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parameters by the forensic Odontologists. Forensic dentistry was relatively in a state of infancy in its
research and advancements until the 1960s when the period of renaissance awoked by the first formal
constitutional program in forensic dentistry held in the United States at the Armed Forces Institute of
Pathology. Since then the field of “forensic odontology” has ramified its branches to such an extent that the
teeth and its supporting bone alone were able to render a plenty of reliable information not only to the dental
profession, but also to law enforcement agencies and other forensic groups [1].
Saunders, a dentist, was the first to publish information regarding dental implications in age assessment by
presenting a pamphlet entitled ‘‘Teeth A Test of Age’’ to the English parliament in 1837. While quoting the
results from his study on 1000 children, he pointed out the value of dentition in age estimation [2]. Dentistry
has much to offer law enforcement in the detection and solution of crime or in civil proceedings. Forensic
identifications by their nature are multidisciplinary team efforts of law enforcement officials, forensic
pathologists, forensic odontologists, forensic anthropologists, serologists, criminalists involving a
combination of positive identification methodologies as well as presumptive or exclusionary methodologies.
Forensic dental fieldwork requires an interdisciplinary knowledge of dental science. Most often the role of
the forensic odontologist is to establish a person’s identity. Teeth, with their physiologic variations, pathoses
and the ability to withstand extreme conditions of post mortem changes comprising of decomposition,
carbonization and fragmentation, are capable of producing information that remains throughout life and
beyond.
Forensic odontology has its applications in (1) diagnostic and therapeutic examination and evaluation of
injuries to jaws, teeth, and oral soft tissues, (2) the identification of individuals, especially casualties in
criminal investigations and / or mass disasters, and (3) identification, examination, and evaluation of bite
marks in sexual assaults, child abuse cases, and in personal defense situations. The odontological
identification and examination of a decedent is based on a systematic comparison of the pre- and
postmortem dental characteristics of the individual based on the dental record and supporting radiographs
(apical films, pantomographs and medical skull films). A variety of techniques can be used to narrow the
search and are based on presumptive identification data which are often sorted with computer assistance.
The challenge for the forensic dentist is to acquire the pertinent information, organize and summarize it into
a conclusive data leading to an accurate diagnosis for the identification of the deceased.
Forensic Odontologists are confronted with the problem of determining the age of unknown bodies and also
living persons. Attempts to use teeth as an indicator of age estimation originate from England. Despite the
alleged use of the eruption of second molars by the ancient Romans to evaluate readiness for military service
(Muller,1990), age estimation (sometimes known as age evaluation, age determination, age diagnostics or
age assessment) in living individuals is a relatively recent area of applied research within the forensic
sciences. Its value and importance as an assessment tool has risen exponentially as the needs for an informed
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opinion on the age of an individual have assumed increasing importance for the assessment of both criminal
culpability and legal/social categorization. There are many areas in which the evaluation of age in the living
has become relevant but the most prevalent concern issues pertaining to refugee and asylum seekers,
criminals and their victims, human trafficking and child pornography. Age estimation is a sub-discipline of
forensic sciences and is an important part of identification process when information regarding deceased is
unavailable.
2.Methods of age estimation:
Forensic biological age estimation using dental traits utilizes the following methods;
BIOLOGICAL AGE
ESTIMATION
Morphological
Genetic
Histological
Radiological
Biochemical
2(A). Morphological Method:
It is worth to speculate the different characteristics of dentition that are taken in consideration for the
quantitative and qualitative biologic age estimation by means of either histological or biochemical or genetic
methods [3].
Appearance of tooth buds
Initial finding of calcification
Alterations in chemical composition
and discoloration of teeth
Degree of completion of
unerupted tooth
Gingival recession & root
resorption
Deposition of secondary dentin
& root dentin transparency
Dental
parameters
Formation of enamel &
neonatal line
Clinical eruption
Degree of completion of roots
of erupted teeth & resorption
of deciduous teeth
Cemental apposition
Attrition of the clinical crown
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The chronological age of an individual gives the estimate of actual age but this article replaces the term with
biological age as it deals with the age estimation methods of deceased and unidentified in the context of
forensic dentistry. The biological age determination is done at three stages of development;
1) Age estimation in prenatal, neonatal & early postnatal period.
2) Children & adolescents
3) Adults
Age estimation in children includes the sequential phases of growth and developmental changes in primary
and permanent dentition sometimes influenced by the geographic distribution, environmental influences,
hormonal, and nutritional factors where as in adults in it includes the regressive alterations of morphology
and histological composition of teeth.
Age estimation in children employs atlas and scoring system utilizing the radiographic method of
assessment. Various stages of tooth mineralization are studied radiographically and correlated with the
standard charts where the approximate age is determined.
The morphological and radiological methods of age estimation go hand-in-hand in the forensic dental age
estimation, probably radiological method can be considered as advanced front of the morphological method.
Henceforth, this is the reason this article reviews both the methods simultaneously for comprehensive
understanding of the elaborative methods.
The point scoring method of age estimation having the scores being calculated statistically to derive a
regression formula for the subsequent forensic research studies also plays a vital role these days for the
accurate age estimation.
The atlas method proposed by Schour and Massler [4] shows 20 chronological stages of tooth development
spanning from 4th month of post natal life to 21 years of adulthood depicting the appearance of tooth germ,
early spurts of tooth mineralization, eruption sequence of deciduous and permanent dentition [5]. These
charts are periodically revised and serve the useful estimate of the individual’s age. The drawback of this
method is it lacks specificity as it is not designed separate for males and females [6]. Moores, Fanning, Hunt
studied the developmental and mineralization stages of teeth in 14 steps including the third molar
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development and the mean age estimate for each stage of the permanent teeth is charted out separately for
both the sexes and specifically for each tooth[7]. They used panoramic radiographs in estimating the stages.
Delmirjian, Goldstein, Tanner [8] method enumerates the stages of teeth development in 8 phases scored in
the order of A – H for the left mandibular teeth from incisors to second molars and allotted a particular
maturity score statistically where the procedure involves the summing up of all the scores to derive total
maturity score that is compared with the standard values in the tables and graphs plotted or substituting the
standard regression formula for both boys and girls.
A- Is the initiation of calcification taking the shape of inverted cones.
B- Is the fusion of the mineralized cusps.
C- Is the coronal half with the evidence of pulp chamber is formed.
D- Is the crown formation is completed till the CEJ junction with the initial evidence of root
formation.
E- Is the initial evidence of root bifurcation in multi-rooted teeth.
F- Is the open apical ends in the form of a funnel.
G- Is the parallelism of the root canal walls with partially open apical end.
H- Is the complete closure of the apical end of the root canal with uniform width of the
periodontal membrane around the root and apex.
Formula (males) - (0.000055 ×S3) - (0.0095 × S2) + (0.647 × S) – 8.4583.
Formula (females) – (0.0000615 ×S3) - (0.0106 × S2) + (0.6997×S) – 9.3178.
Third molar development is not considered which also shows variations in age estimation and the presence
of all mandibular teeth is important [9]. Many studies used orthopantomograms as an aid in this method.
Nolla gave ten stages of development for both the maxillary and mandibular teeth including third molar for
both girls and boys as tables where the values are correlated to get actual age [10].
The earliest age estimation method for adults using retrogressive changes in the permanent dentition is the
actual scientific method can be done with or without sectioning of teeth which holds its advantage and is the
well known and familiar and widely accepted with reliable results comparatively. The following are the 6
regressive changes along with the established statistical regression formulae to compute the results.
1) Attrition of the occlusal surfaces (A).
2) Periodontal recession.(P)
3) Secondary dentin formation.(S)
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4) Cemental apposition(C)
5) Root resorption(R)
6) Root dentin transparency.(T)
Each stage is assigned a score point from 0 to 3 as A0-3, P0-3, S0-3, C0-3, R0-3, T0-3.This method can be
determined both destructively by histological ground sections and also from radiographs. The Gustafson’s
regression equation AGE = 11.43 + 4.56X (X is the total score) [11]. Error is ± 3.6years.
Maples and Rice modified the Gustafson’s equation as AGE = 13.45 + 4.26X [12].
Johanson formula using the same above criteria is given as,
AGE = 11.02 + (5.14×A) + (2.3×S) + (4.14×P) + (3.71×C) + (5.57×R) + (8.98×T) [13].
Dalitz’s regression equation using Gustafson’s criteria includes,
AGE = 8.691 + 5.146A + 5.338P + 1.866S + 8.411T [14].
Root resorption and cemental apposition is not taken into the study and limits only to the anterior teeth but
not the bicuspids and molars where they are the only teeth remaining in the deceased. Later Bang and Ramm
still simplified the above 6 criteria and considered only single tooth criteria that is the length of the apical
root dentin transparency in mm for a given tooth where they considered incisors and cuspids but not the
bicuspids and molars as the latter couldn’t give accurate readings. The distal, mesial and palatal root
surfaces are studied, the intact and sectioned teeth are taken into account. They proposed two separate
equations along with the based on the apical translucent length less than or equal to 9mm and one with
greater than 9mm.The accuracy of the readings increased when the above criteria are used.
Length (X) ≤ 9mm the regression equation for age estimation is as follows,
AGE = B0 + (B1 × X) + (B2 × X2).
Length (X) ≥ 9mm the regression formula is AGE = B0 + (B1× X).
B0, B1, B2 values are obtained from the tables given by Bang and Ramm [15].
All the above methods can be classified under combined destructive and non-destructive methods of age
estimation as they employ both histological sections and radiological interpretations.
2(B).Radiological method:
Various modalities of imaging ranging from conventional to advanced can be utilized in the age estimation
with the association of good image analysis and interpretation for accurate measurements. Kvaal et al and
Solheim [16] elaborated the radiological methods of age estimation using periapical radiographs and
orthopantomograms both conventional and digital versions and also volume rendering CT and CBCT
imaging. The basis for this is the gradual reduction in the pulp volume due to secondary dentin deposition
with age and can be performed on both living and deceased individuals without the need for tooth
preparations. Only six teeth are studied and the maxillary first premolars and molars are excluded. (11/21,
12/22, 15/25, 32/42, 33/43, 34/44) are used with the following parameters for Pulp-Tooth Ratios;
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1) Pulp/Root length(P)
2) Pulp/Tooth length(R)
3) Tooth/Root length(T)
4) Pulp/Root width at CEJ (A)
5) Pulp/Root width at midpoint between A and C (B).
6) Pulp/Root width at mid-root length(C).
Mean value of all ratios excluding T is designated as (M), Mean value of width ratios B and C as (W) and
Mean value of length ratios P and R as (L).
The regression formula as per this method is, AGE = 129.8 – (316.4 × M) - 6.8 × (W – L) [17].
The above method using periapical radiographs and orthopantomograms likely to have inherent image
distortions giving fluctuations in the above values, allows only 2-dimensional method of studying toot-pulp
ratios .Using computed tomography (CT) 3-D reconstruction images from 3-d remodeling software for all
the 4 canines, the tooth – pulp volumes and tooth surfaces can be measured accurately with an average error
of 8.3 to 12.86 years [18].This method again can be used in living and deceased as well which in turn can be
used in forensic dentistry and anthropology. All the four canines must be present which a limitation is but
canines are the last ones to get deteriorated in the process of environmental changes after death as per
literature. The ratio of pulp volume (PV) and tooth volume (TV) is calculated for each canine say
13,23,33,43 and Spearman's rank correlation coefficient is used to evaluate the correlation between age and
the PV/TV ratio×100 [19].
Right maxillary canine (13): (PV13/TV13) ×100 was coded as X13
Left maxillary canine (23):
(PV23/TV23)×100 was coded as X23
Left mandibular canine (33): (PV33/TV33) ×100 was coded as X33
Right mandibular canine (43): (PV43/TV43) ×100 was coded as X43
Maxillary canines (13 and 23): [(PV13/TV13+PV23/TV23)/2] ×100 was coded as Xmax
Mandibular canines (33 and 43) :[( PV33/TV33+PV43/TV43)/2] ×100 was coded as Xmand
Four canines (13, 23, 33 and 43):[(PV13/TV13+PV23/TV23+ PV33/TV33+PV43/TV43)/4]×100 was coded
as X4c.
The regression equations for age estimation is as follows,
13 (right maxillary canine) AGE = 74.426– 41.853X13+ 7.767X213.
23 (left maxillary canine) AGE = 74.252– 41.146X23 + 7.351X223.
33 (left mandibular canine) AGE = 71.632- 45.82X33 +10.021X233.
43 (right mandibular canine) AGE = 70.933 – 43.843X43 + 9.122X243.
Maxillary Canines AGE = 73.460– 40.051Xmax+ 7.099 X2max
Mandibular Canines AGE = 71.211– 45.195Xmand+ 9.670X2mand.
4 Canines AGE = 73.193- 43.445X4c +8.528 X24c.
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One of the radiological method using orthopantomograms (digital) more appropriately evaluates the open
apices of the teeth particularly seven left mandibular teeth at various stages of open apices. The number of
teeth with root development completed with apical ends completely closed was calculated (N0). For the teeth
with incomplete root development, which is with open apices, the distance between inner sides of the open
apex was measured (A).
For the teeth with two roots, the sum of the distances between inner sides of two open apices was evaluated.
To nullify the magnification, the measurement of open apex or apices (if multirooted) was divided by the
tooth length (L) for each tooth and these normalized measurements of seven teeth were used forage
estimation. The dental maturity was calculated as the sum of normalized open apices (S) and the numbers of
teeth with root development complete (N0).
The values are substituted in the following regression formula for age estimation [20].
AGE = 8.971 + 0.375g + 1.631×5 + 0. 674 N0 - 1.034s – 0.176s. N0.
(Where g is a variable equal to 1 for boys, and 0 for girls).
A new Indian formula from the Cameriere’s European formula [21] using the above criteria with slight
modification to fit to Indian children in age estimation is as follows,
AGE = 9.402 - 0.879 C + 0.663N0-0.711s-0.106s N0.
(Where C is a dummy variable, 0 for north and central India, and 1 for south India).
Other methods are based on measuring Coronal pulp cavity index radiographically and assessing third molar
mineralization.
2(C).Histological method:
Dental tissues show wide variations which are genetically determined and depict many changes with age
which forms the basis in forensic age diagnostics. Enamel attrition shows different patterns and it is used as
one of the scoring criteria in Gustafson’s method which can be done both histologically and radiologically.
The regular time dependency of some dental features of the tooth crown, examined by histological
techniques, allow the assessment of development to estimate chronological age.
Age is estimated from enamel by counting the prism cross striations which are bundles of hydroxyapatite
crystallites that later transform into mature enamel. These periodic structures, visible in transmitted light
microscopy of ground sections or fractured enamel, are known as prism cross striations. Another dental
feature visible in crown enamel is the incremental lines of Retzius which run from the dentinoenamel
junction (DEJ) in occlusal direction which represents the zones of hypo- mineralization during
amelogenesis. The neonatal line, which constitutes a borderline between pre and postnatal formed enamel
(and dentin), is frequently used for age at death estimation. This feature, combined with the total number of
cross-striations, gives an estimate in days for the age at death.
Dentin, contrary to enamel, is continuously deposited which we call as secondary or reparative dentin as a
normal physiological process with the increase in age. Secondary dentin formation is initiated subsequent to
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dentinogenesis (Costa 1986). There is only little difference between primary and secondary dentin, which
can sometimes be detected in stained preparations, via micro-radiography or in polarizing microscopy. This
consequently results in decreased pulp volume which is again studied in combination with radiographs
proposed by Kvaal et al.
Dentin sclerosis (root transparency) is another feature of the pulpo-dentinal complex which was first
described by Tomes in 1861, which shows variations with age. Root dentin sclerosis results in reduction of
the diameter of dentinal tubules. The refraction index of the intratubular substance becomes the same as that
of peritubular dentine. This process leads to a milk-glass like consistency of the dentin, which starts in the
late adolescence at the apex of the tooth root and progresses towards the dentino - enamel junction (DEJ),
where this histological variant is the part of the Gustafson’s criteria of age estimation.
The most accurate histological method of age estimation is by counting the tooth cemental annulations from
the histological ground sections under microscopy with stained or unstained sections. It is proved that the
absolute count can be done with a mean error of ± 5 years using advanced microscopic techniques like
polarizing microscopy, confocal laser scanning microscopy, scanning electron microscopy .These areas were
photographed and images were transmitted from the microscope to a computer monitor, and counting was
done with the help of image analysis software Alternate light and dark pairs are counted as 1 pair of
cemental line. The biological explanation for the alternating layers was given by Liberman and Schroeder
[22] who suggested that dark lines are the stop phases of mineralization during the continuous growth of
fibroblasts, leading to change in mineral crystal orientation.
The biological age of each tooth is determined by the formula E = N + T. (where E is the estimated age, N is
the number of incremental lines and T is the eruption age of each tooth) [23]. They are also useful in the
fields of Archaeology, Anthropology, and Palaeodontology in determining the age at death estimation.
2(D).Biochemical method:
The various changes in the chemical composition of the dental hard tissues are the basis of the biochemical
method of age estimation. Aspartic acid racemization is considered to be one of the advanced, reliable,
accurate and complex of the biochemical methods. Assessment of age using aspartic acid racemization
methodology was first described in 1975 by Helfman and Bada [24]. During the course of aging, L-forms of
amino acids are transformed by racemization to the D-forms. Thus, the extent of racemization of amino
acids may be used to estimate the age of various tissues. Of all stable amino acids, aspartic acid has one of
the fastest racemization rates and is therefore the amino acid most commonly used for age estimation. Rates
of change of L-form amino acids to D-forms are influenced by environmental factors, such as temperature,
humidity, pH, etc. Because of the continuous formation and removal or degradation of amino acids, tissues
with low metabolic rates provide better age estimates than those with high metabolic rates. The only
limitation here is the tooth requires sectioning mechanically.
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Among the different types of teeth examined, the rate of aspartic acid racemization (k) is the highest in the
second molar and decreases in the following order: first molar > second premolar > central incisor > first
premolar > lateral incisor > canine[25].This method gives more accurate values when performed in dentin
tissues compared to tooth enamel. All these age estimation methods use gas chromatography (GC). As an
alternative to GC, very few estimations used high performance liquid chromatography (HPLC) coupled with
ultraviolet detection [26,27] and with fluorescence detection[28].Quantification of Deoxypyridinoline crosslinks[29] and the evidence of presence of gelatinase A in human dentin SDS – PAGE electrophoresis and
Zymography[30].
Radiocarbon analysis of tooth is relatively a new technique using Accelerator Mass spectroscopy where
Radiocarbon dating of dental enamel with Carbon-14 tells us the date of birth of identified and unidentified
individuals [31,32].
2(E).Genetic methods:
Since DNA can be recovered from tooth pulp as well as dentin for forensic analysis by RFLP (Restriction
Fragment Length Polymorphisms) and PCR (Polymerase Chain Reactions), continuous research is ongoing
in this front [33]. Telomere shortening based on dental pulp DNA is anew and useful approach to estimate
age of the subject at the time of death [34]. Terminal Restriction Fragment (TRF) is taken as telomere length
in actual age estimation. Mitochondrial DNA obtained by cryogenic grinding of tooth dentin is the source of
genetic material for age estimation at death. The only disadvantage of this method is it may not be
economically feasible and the material used from tooth is available for the process in trace amounts and also
requires sectioning and chemical and mechanical manipulations of tooth material.
3.Conclusion:
The advent of sophisticated and well equipped clinical and biochemical laboratories made many
developments in the fields of medicine and dentistry. Forensic age estimation of unidentified human bodies
and human remains for the purpose of identification has been a traditional feature of forensic discipline.
They are useful in Anthropological, Palaeodontological, Palaeoanthropological and forensic investigation as
biomarkers of aging as they are preserved for a long time against post-mortem changes. In rare cases, it may
be necessary to determine the age of the living persons particularly in cases when individual is either
unwilling or unable to reveal his identity. Though there are many method proposed by many researchers the
accuracy relies on the combination methods of age estimation thus helps in avoiding inaccuracies in the
estimation. It is advisable to have regression formulae for each individual tooth instead of having a single
equation for all teeth. With the inception of Dental age calculating software it is possible to automate the
dental age calculations allowing the repeatability and reproducibility ensuring the reliable results. This
software programme enabled the forensic odontologists to feed the calculated dental parameters in the
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programme to retrieve the correct data. Tremendous research and experiments are underway in the field of
forensics to refine the conventional methods for easy and convenient applications in the coming future.
Inherent to this is the establishment of BOLD (Bureau Of Legal Dentistry) which is a forensic odontology
laboratory at the University of British Columbia, A centre of excellence aims to act as a resource for
odontologists and other forensic scientists who deal with teeth ,bones, saliva, DNA, and dental records.
Experts provide assistance with Investigations, Identifications, Analysis and Testimony.
Conflicts Of Interest : NIL
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