age estimation

Forensic odontology Prof.Dr. Azza Fouad

Age estimation

Forensic Odontologists assist in the identification process when all other paths of identification have been exhausted.

When do we use teeth in estimation of age?In the living: chronological age is needed for civil and social rights when the individuals have:

Amnesia No acceptable identification documents as:

1.Illegal immigrants, 2.adopted children of unknown age, and3. Refugees.

In dead persons, when:1. The identity is unknown; an age estimate may be of importance in the

identification process. Age estimates enable more efficient approach because:It can be useful circumstantial information in the identification process. Helpful in segregating individuals in cases of multiple, commingled decedents. Narrowing down search within missing persons’ files

2. When only the skeleton of a body remains, age estimation may be even more important in helping to make a positive identification.

3. Even when the police have some indication of the identity, an estimate of the age may be used to help confirm the identity if other evidence is weak.

4. In archeological search, estimation of age at death is an aid in paleodemography.

Why we can use teeth in determination of age?1. Teeth are considered as a reliable means of determining age from approximately

10 weeks intrauterine up to old age. 2. Teeth, being the hardest calcified tissue in the body, tend to be intact and

preserved even when other components of the skeleton have disintegrated.3. The high resistance of teeth to severe insults such as cold, heat, fire and

chemicals make them the favorite tissue in forensic and archeological investigations.

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4. Unlike bones, they can be directly examined in living individuals.

What are Methods of teeth age estimation?Age estimation in children and adolescents:

Dentition: 1.Teeth development2.Sequence of eruption.

Techniques used:1. Clinical examination2. Radiographic methods 3. Histological incremental line analysis

Age estimation in sub-adults group: Radiographic methods

1. Development of 3rd molar and calcification.2. Periodontal recession.

Age estimation in adults:

1. Histological (morphological ) methods:1. Gustafson’s six variables and 2. Johanson’s modification, 3. Bang & Ramm’s dentine translucency

2. Radiographic method of Kvaal et al.

I.Determination of age in children and adolescents including fetuses and neonates

The main criteria for dental age estimation in this age group are the following indicators of biological development: dentition status and tooth mineralization.

Tooth eruption refers to the gingival emergence of the apex of the tooth crown. It is diagnosed by inspecting the oral cavity of the person concerned and does not require an X-ray or expensive tools.

Except for third molars, eruption of permanent teeth is complete around the age of 12, on average.

The relative stage of maturity can be compared with developmental charts such as those developed by Ubelaker who graphically illustrates the state of development of the dentition from 5 months in utero to 35 years, showing the deciduous, mixed, and permanent dentitions.

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This provides an estimate of age for an unknown individual. Conclusions are usually accurate to approximately ± 5 years.

Ubelaker chart

Calcification begins during the 4th m of fetal life. By the end of the 6th m, all of the deciduous teeth have begun calcification.

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Prenatal Period

Medico-legal importance of age estimation in prenatal period (including neonates):

1. In cases of putrefaction or skeletonisation: Aging of human remains in the prenatal period cannot be separated from the

determination of a human origin for skeletal remains. Osteological indicators of maturity and morphological features should be

cross-checked. The possibility of commingled remains or twins should be excluded by

checking number and symmetry of teeth.2. Accurate age estimation is reached if the remains have been wrapped so we can

recover most or all of the developing tooth caps.3. Decision of being live birth: The presence of neonatal line (birth or Orban's

line) in both dentine and enamel indicates live birth. It is possible that the time period of survival can be estimated by measuring postnatal deposition of these hard tissues.

Histological methods:

Used to assess the stage of tooth development during the pre-mineralization period.

Some of the histological methods can detect early mineralization 12 weeks before being detectable in the radiographs.

The neonatal line:

It is considered as an indicator of live birth. Neonatal lines are present in both enamel and dentin of deciduous teeth and

permanent first molars à development during the transitional period between intrauterine and extra uterine environments.

So it can be used to assess the amount of pre and post natal enamel formation.

Stress markers and incremental lines analysis:

The dentin incremental lines of Von Ebner and contour lines of Owen are used to estimate age of the neonates or foetus at death.

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Incremental lines of Retzius are caused by variation in the rhythmic mineralization of enamel prisms which is altered by various external factors so that the lines may appear closer or the rest periods may be prolonged.

Incremental line analysis is usually done on ground sections of longitudinally sectioned dentition which results in the destruction of the dental structures.

In 1991, Skinner and Anderson reported a case study involving enamel histology used for identification based on the presence in the enamel of the primary and secondary dentition of stress markers, termed striae of Retzius, which could be correlated with known stressors in the life of the presumed missing child.

Gustafson demonstrated in 1955 the similarity in incremental lines between contralateral pairs of teeth from a single individual.

Other methods: Stack has provided a regression line of weight of growing dental tissues

against the age. By weighing the teeth specimen, age of unknown can be obtained from 5

months in-utero to postnatal age till 7 months.

The First Few Months of Postnatal Life This period still remains the one which least is recorded in the literature. The jaws are enclosing the growing tooth germs of developing teeth. This period comes to an end about 6 months after birth when the first deciduous

teeth emerge into the oral cavity. Stages of dentition:

o Dental germs

o Deciduous teeth.(6m-3yrs).

o Mixed dentition.(6-12) yrs

o Permanent dentition.

Later Development of the Deciduous Dentition The deciduous teeth emerge sequentially and contralateral pairs of teeth emerge

at similar times. Once all the deciduous teeth have formed completely it is much less reliable to

estimate age using these features alone.

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Just as the tips of the last deciduous molars are forming at the back of the mouth, the roots of the incisors, which formed much earlier, are beginning to resorb.

Resorption of the deciduous dentition is an internal cell mediated process whereby the hard tissues of the tooth roots and even some of the enamel of the crown of the tooth are degraded. The process is phasic with periods of resorption being interposed with periods of hard-tissue repair.

Each period of resorption erodes progressively more and more of the tooth roots until the tooth crown is eventually lost. This provides space in the jaw for the permanent successor.

If the successional tooth is absent or displaced, deciduous teeth may be retained long into adulthood, but this is uncommon and would provide unique characteristic for individualization.

Mixed Dentition At the age of 6 years all the crowns of the 20 teeth of the deciduous dentition

remain in the oral cavity despite resorption of roots occurring within the jaws. Growth of the facial skeleton makes space for the first permanent molar to erupt

at the back of the dental arch in each quadrant of the mouth, thereby enlarging the dentition.

For the ensuing 5 or 6 years there is then a progressive complete replacement of deciduous teeth by their permanent successors. This process ends around 12 years of age when the permanent maxillary canines emerge.

Once the last deciduous tooth has been replaced the period of the mixed dentition comes to an end. Techniques:

1. Study of tooth development is divided into an arbitrary number of identifiable stages, using data obtained from radiographs.

2. Indirect measurement of tooth size from the radiograph is used as the growth parameter plotted against known age to obtain the necessary regression equations then used for the aging of unknown remains e.g. A recent study from the UK examined the use of root length in the determination of age in paediatric cases.

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Differences between Deciduous and permanent teeth

Deciduous are:o Fewer and smaller.

o Enamel is thinner and whiter.

o The crowns are rounded.

o Constricted at the neck (cervix).

o Enamel cervical ridges more prominent.

o Deciduous molars are wider mesiodistally than the premolars.

o The roots of d. molars are longer and more slender than the roots of

the permanent molars.

o Deciduous anteriors are narrower mesiodistally than their

permanent successors.

o The roots of deciduous anteriors are longer and narrower.

Permanent Dentition At the age of 12 or 13 years all the teeth present in the mouth are now

permanent. It is around this age that the second permanent molars are added to the dental arches, bringing the number of teeth present to 28.

Only the third molars or wisdom teeth remain to erupt between 17 and 25 years of age.

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Some researchers prefer tooth formation to tooth eruption (i.e. actual emergence of the tooth in the oral cavity) for assessment of age due to:

1. The eruption dates of teeth are highly variable because eruption can be influenced by exogenous factors such as:

Infection, Injury at the area, earlier extraction of deciduous teeth etc. Obstruction and overcrowding.

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2. Teeth formation is a continuous process until the tooth is completely calcified. The actual developmental stages of the teeth are more accurate because the dental development is tightly controlled and protected against disturbances so not markedly affected by diseases, drug intake and dietary changes. (A process known as canalization).

3. The incremental pattern of mineralization is subject to periodic disturbances that affect the developing teeth in a unique way like: Birth, diseases, drug intake, dietary deficiencies and changes, and the uptake of certain chemical elements.

II. Sub adult age groups

The third molar development the most important choice for age assessment from the late teens to the early twenties up to about the age of 23 years when the apices of the roots of the third molars are complete because:

1.All permanent teeth except the third molars have finished their development after the median ages of 15 or 16 yr.

i. Third molars usually erupt after age 17 (at least in Caucasian populations).

ii. After another two to four years, the occlusal plane is reached. iii. If the third molar crowns are less than half complete, it is virtually

certain that the subject is less than 14 yr old. iv. Late in adolescence, the third molars have completed their crown

developments, and the roots are the only dental structure that can be used for age estimation up to a median age of about 19–20 yr, when apex closure has taken place.

v. In younger adults, the calcification stages of the third molars are the most reliable dental indicators, but in living individuals, they can be examined only by X-rays.

2. The use of other biological indicators such as epiphyseal fusion, changes of the pubic symphysis, wrist bones and fusion of cranial sutures are not credible during these years. 3.Those who advocate third molar use claim an accuracy of 4 years.

Disadvantages of using 3rd molar eruptionas an indicator of age: The third molar is very variable in position, anatomy and timing of

development.

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Sometimes it does not exist at all. These teeth are frequently congenitally absent or restrained from entering the dental arches due to lack of available space when they become jammed (impacted) against other teeth.

It may even be larger than the 1st.and 2nd molar with the roots fused and delineated by vertical grooves. The maxillary molar generally consists of 3 cusps, whereas some exhibit 4 cusps. In the mandible, the variability is between 4 or 5 cusps.

The third molar formation and eruption occur earlier in males than in females and maxillary was slightly advanced over mandibular third molars, and root formation occurred earlier in males than females. This is opposite to the development of the other teeth.

Demirjian’s system

It is the worldwide reference method of age determination in living individuals. It classifies 8 stages of crown and root formation and mineraization and is used

to score the third molar development: It defines four stages of crown mineralization (A–D) and four stages of root mineralization (E–H).

The degree of mineralization of second molars allows estimates of age approximately until the age of 16 years.

Tooth mineralization is evaluated using an orthopantomogram.

Schematic drawing of the eight stages of crown - root formation of the molars as proposed by Demirjian et al.

Tooth mineralization begins with the development of the crown at the occlusal surface and progresses over the neck of the tooth down to the root.

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If the third molar root apices are completely closed, and the periodontal ligament has attained a uniform width (stage H of Demirjian’s system), there is a high probability that an individual is at least 18.

Limitations of the Demirjian’s system

1. It is based on observations derived from radiographs, 2. The choice of the tooth developmental stage is quite subjective,3. Age cannot be precisely evaluated after 16 yr specifically around 18 yr and the

analysis of the wisdom teeth do not yield precise conclusions as even before the age of 18, some or all third molars might have reached complete root development.

4. The third molar is a non ideal developmental marker because it is the most variable tooth in the dentition with regard to size, time of formation, and time of eruption, and it can be congenitally absent, malformed, impacted, or extracted.

5. In impacted teeth, completion of root formation may be delayed 3 years.

Periodontal recession

Olze et al. study the periodontal recession as an indication of whether a person has attained the age of 21 years.An increasing periodontal recession correlated well with an increasing age of the subjects.

Individuals 21 years old periodontal recession

50% Incipient stage 1

75% Advanced stage 2

100% Severe stage 3

Stage 3 was hardly found in the examined age group. It was concluded that the periodontal recession seems to be suitable as an additional criterion for the forensic age diagnostics of young adults.

III. Older people

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For individuals who have attained full dental maturity, dental development is useless as an age estimator. When the teeth are relatively stable in the mouth, certain changes occur within the tooth, which enable an age estimation of the older unknown body to be made. Accuracy using these highly-variable markers is in the range of 10–12 years.

Destructive methods:

• Gustafson's method (1950) • Johanson's modifications (1971) • Bang and Ramm (1970) • Incremental lines of cementum

Gustafson's method for age determination from teeth

Gustafson's method (1950) is based on the evaluation of ground sections of teeth to detect structural changes on fully erupted teeth.His method use combined scores from measurements of 6 parameters of histological changes:

Attrition of incisal or occlusal surface, Periodontitis (level of attachment of the periodontal tissues), Secondary dentine deposited around the pulp chamber, Cementum apposition, Root resorption and Root dentine translucency (The extent of sclerotic or translucent dentine spreading from the apex of the tooth).

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Technique: One or more teeth are extracted from the body, and Ground longitudinal

sections are prepared. The age-associated 6 parameters are evaluated in the ground section: Two of

these changes, transparency of radicular dentin and secondary dentin, have the highest correlation with age.

Gustafson used 4 scores (0, 1, 2, and 3) to indicate the various changes. The point values of each age change are added according to formula:

An+Pn+Sn+Cn+Rn+Tn = points The increase in points corresponds to increase age. The points are entered in the regression curve of age versus the age-associated

changes in sections taken from teeth of known age.

Limitations:

1.It can't be used in living person, only in dead when extraction of teeth is allowed.2.Point values are subjective evaluation of the changes.3.Time consuming method.4.Periodontitis is impossible to determine due to decomposition of soft tissues.5.Regression line is given for all teeth ignoring eruption time and morphological differences of various teeth.6.The method assumes that all 6 parameters of equal importance and ignore the interrelationship between parameters.

Gustafson has become the basis for all other techniques which aim at the increase of precision of measurement.

Johanson's modifications:

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Johanson (1971) tested Gustafson’s method on a larger sample and he added two major refinements Intermediate grades for scoring each variable to reach 7 stages and multiple regressions.

Maples (1978) Transparency of root dentin and secondary dentin, have the highest

correlation with age. Translucency of the root apex increases with age. Elimination of root resorption, attrition increase accuracy. This means that teeth with broken crown still give accurate age estimate

Bang and Ramm (1970): Transparency of radicular (apex) dentin

This feature is the most useful method of estimating age because it occur independent of any pathological process affecting the tooth and the least influenced by environmental effects and is likely to be the most physiologically regulated.

Translucency of the root apex increases with age, and so a determination of its extent can provide information as to the age of the owner of the tooth.

Traditionally, the translucent dentine can be measured under a light microscope and plotted against known age.

Advantages:1. Simple and rapid2. Objective method: not based on point system but on measurements.3. Applied without extensive training or expensive equipment.4. No difference between dead and living.

Disadvantages:1. underestimation of age in older age groups due to slowing down of dentin

sclerosis 2. Irregular junction at translucent and non translucent zones will make

difficulties in measuring the length.

Additional methods to overcome that include:

1. The use of SEM-EDXA, a method used to examine root dentine translucency in relation to age determination also detect teeth restorations.

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2. High-resolution micro-focused computed tomography scanning is now becoming more available and is capable of quantifying mineral density in three dimensions throughout the entire domain of the dentine of the tooth.

Kashyap and Koteswara Rao's method (1990)It is based on the quantitative evaluation of four markers:

the attrition , the secondary dentine, the secondary cementum and the transparency of root.

They omitted periodontosis and root resorption from Gustafson’s methodThey calculated the index values of various parameters undergoing regressive changes.

The index values are plotted against the known ages and statistically analysed to derive regression equation.

The index value of attrition It is calculated by measuring the width of attrited area in relation to the

width of the teeth How to apply the equation?

a Index value of attrition = ---- x 100 A

‘a’ is width in mm of attrited teeth ’A’ is the width in mm of the teeth at the cervical margin.

The incremental lines of cementum The incremental lines of cementum will help to determine the age of

adults. The disadvantages:

1. The necessity to extract or section the tooth. 2. It is not practical among living individuals.

Non destructive methods:Examination of the teeth can provide information on the possible age of the deceased by:

I.Examining the amount of tooth wear, II.Color of the teeth:

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o Principle: teeth tend to darken with age

o Changes in the color of tooth roots with age have been studied and this

color change may be related to the same changes in the optical properties of the dental tissues, which also give rise to translucency.

o The colour changes in the cementum and dentin are caused by infusion

of decomposition products from erythrocytes.o Measurement of intensity of fluorescence in dentin and cementum,

which shows strong correlation between age, deepening of colour of the tooth and increase in intensity of fluorescence.

o Age estimation techniques based on color change alone have never found

widespread application.III.Size of the pulp chamber (as seen radio graphically); pulp chambers become smaller with age. IV.Presence or absence of periodontal diseases and amount of alveolar bone loss may also help in determining a possible age.Periodontal disease progression, excessive wear, multiple restorations, extractions, bone pathosis and complex restorative work may indicate an older individual.

Radiological method:

Indications of using radiological method:1. Living persons2. Fragile tissues: burnt bodies.3. Skeletal remains from archeological excavations to avoid destruction

kvaal and Solheim (1994) and Bosmans et al.,2005

They estimate age from the size of pulp cavity without tooth extraction. The size of the pulp cavity is reduced by secondary dentine deposition so measurements correlate with age.Using radiographs the measure pulp length and width as well as root length and width. Then different ratios between root and pulp were measured.

Yang et al., (2006)

Use cone beam CT scanning for generating the 3D images of teeth in living individuals and calculating the ratio of pulp/tooth volume.

How to estimate the age?

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1. Visual assessment 2. Radiographs 3. Extraction and preparation of teeth if dead or living with indiction to

extract teeth e.g. malocclusion

Accuracy of using teeth in assessment of age

Actually, the 100% confidence in dental age assessment has been never reached, and no one can make an exact judgment or a certain prediction of age.

Therefore, it is impossible to give a precise age; the only appropriate way is to give an age interval for a specific confidence.

Assessment of age reflects greater accuracy when derived from multiple indicators.

The accuracy of any method of age assessment using teeth is much better in children than adults where any estimate may be very inaccurate (Solheim and Kvaal 2000).

This is because in children:a. Many teeth are undergoing development and calcification simultaneously.b. The intervals between morphological stages are shorter, and therefore, more

precise. However, the older a person becomes, the more inaccurate will be age determination from teeth (Whittaker and MacDonald 1989).

While in adults, it becomes much harder to estimate age because the features which have to be used are much more susceptible to modification due to:

o Environmental factors, some of which cannot be known or inferred when

postmortem remains are being examinedo The ethnic, cultural influences that may affect the rate of change of structure in

the teeth and jaws.

References:1. Encyclopedia of Forensic and Legal Medicine, Forensic Odontology,

Elsevier (USA), 2004; 391-5.2. Paul G. Stimson, Curtis A. Mertz, Forensic Dentistry, CRC Press (London),

1997; 20-21. 3. C. Michael Bowers, Forensic Dental Evidence: An Investigator’s Handbook,

First Edition, Elsevier (USA), 2004; 82.4. http://pafmat.com/2006_4.htm 5. Translation from" traité de médicine légale"

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http://pafmat.com/2006_4.htm


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age estimation

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