MODULE No.3: Determination of Age from Teeth

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

SUBJECT FORENSIC SCIENCE

Paper No. and Title PAPER No. 14: Forensic Medicine

Module No. and Title MODULE No.3: Determination of Age from Teeth

Module Tag FSC_P14_M3

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

TABLE OF CONTENTS

1. Learning Outcomes 2. Introduction

3. Growth Pattern 4. Age Estimation 5. Forensic Significance 6. Summary

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

1. Learning Outcomes

After studying this module, you will be able to know about-

 The anatomy of tooth

 Chronology of tooth eruption

 The Growth Pattern of Teeth

 The age estimation by teeth

2. Introduction

The anatomy of the tooth is divided into two parts the visible part is called crown and the hidden part embedded in the bony socket with connective tissue is the root (acrodont).

Both the crown and the root consist of hard and soft tissues. The crown portion of the tooth is made of enamel (hardest substance in the body). Dentine (bulk of the tooth is made up of this material) and pulp tissue which is housed in a hollow cavity. The pulp tissue supplies the blood and nerve supply to the tooth. The outer most portion of the root is called the cementum. Dentine and the pulp tissue form the other two layers of the tooth root. The root portion of the tooth may be single with one apex or terminal end, as usually found in anterior teeth and some of the premolars, or multiple with bifurcation or trifurcation , dividing the root portion in two or more extension or roots with their apices or terminal ends, as found in all molars and in some premolars. The portion of jaw serving as support for the tooth is called the alveolar process. The bone of the tooth socket is called alveolus (plural alveoli). The crown portion is never covered by bony tissue after full eruption in humans, but it is partly covered at cervical third in young adults by soft tissue of the mouth known as gingival tissue or gums.

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Fig: Showing diagrammatic representation of tooth

3. Growth Pattern

Calcification of primary teeth begins in utero from 13 to 16 weeks post fertilization. By 18 to 20 weeks all primary teeth begin to calcify. Lower deciduous teeth erupt first thus initiating the deciduous dentition. The appearance of the deciduous second molars completes the deciduous dentition by 2 to 2 ½ years of age. Eruption dates are variable.

Deciduous teeth shed earlier and permanent teeth erupt earlier in girls. The root of a deciduous tooth is completely formed in just about one year after eruption of that tooth into the mouth. The intact root is short lived and then it begins to resorb at the apex or depending upon the position of the permanent teeth. The mixed dentition exists from approximately age 6 years to 12 years. Upper molars have three roots, lowers have two roots. Upper and lower second deciduous molars resemble first permanent molars in the same quadrant. Upper first deciduous molars vaguely resemble upper premolars. -Lower first deciduous molars are odd and unique unto themselves.

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Chronology of human dentition

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Eruption Sequence of Permanent Dentition in Indian population

Tooth Upper Lower

Right Left Right Left

Central incisors 6.77 7.13 6.02 6.17

Lateral incisors 8.04 7.84 7.13 7.17

Canine 9.89 9.89 9.70 9.70

1st Premolars 9.70 9.68 10.08 9.84

2nd Premolars 10.60 10.60 10.85 10.83

1st Molars 5.65 5.68 5.64 5.68

2nd Molars 11.64 11.59 11.34 11.34

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Development of the human dentition to the sixth year

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Development of the human dentition from the seventh year to maturity

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Eruption sequence:

Eruption is the process where a tooth moves from within the crypts, erupts through the alveolar bone and occludes with the opposing teeth in the mouth.

 Lower deciduous teeth erupt first thus initiating the deciduous dentition.

 The appearance of the deciduous second molars completes the deciduous dentition by 2 to 2 ½ years of age.

 Eruption dates are variable.

 Deciduous teeth shed earlier and permanent teeth erupt earlier in girls.

 The root of a deciduous tooth is completely formed in just about one year after eruption of that tooth into the mouth.

 The intact root is short lived and then it begins to resorb at the apex or depending upon the position of the permanent teeth.

 The mixed dentition exists from approximately age 6 years to 12 years.

 Upper molars have three roots, lowers have two roots.

 Upper and lower second deciduous molars resemble first permanent molars in the same quadrant.

 Upper first deciduous molars vaguely resemble upper premolars. Lower first deciduous molars are odd and unique.

4. Age Estimation

Age estimation is an important activity that is frequently carried out in the medico legal work. Administration of justice often requires estimation of age of an individual in litigations involving both civil and criminal cases such as issues related to consent, employment and retirement, marriages, cases of sexual offence, kidnapping ,abduction, criminal responsibility, juvenility etc. A medico legal expert takes into account various parameters related to development of body for assessing the age of an individual that represent the normal trend of population at large. These parameters must be clearly discernible, readily attainable and reasonably fixed so that these can be applied to the individuals of the population with the element of certainty.

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

ossification centers in long bones, eruption of temporary and permanent dentition and appearance of facial, maxillary and pubic hairs are in plenty and they correlate sufficiently to supplement each other in deciding the age of an individual. Dental examination is one of the parameters that help us to identify the age of an individual.

Teeth are known to aid in personal identification and age determination, as they are highly durable to resist the effect of putrefaction by chemical and other environment factors. They may also be helpful when no other way of identification and age estimation is available such as in cases where only skull is available for examination. Even sometimes only a single tooth may help in establishing the identity and/or age of an individual.

Age Determination

 The teeth develop in a regular and sequential manner until the age of 15 years, permitting the age estimation within 1 year.

 The deciduous dentition begins to develop during the 6th week of intra-uterine life followed by mineralization which begins at 14 ± 2 weeks and continues after birth.

 The permanent dentition begins to calcify at birth, starting with the first molar and continuing until the root of the second molar is complete by age 15 ±1 year.

Neonatal lines

 The trauma of childbirth induces metabolic stress on the tooth-forming cells. This cellular disruption results in a thin band of altered enamel and dentin called the neonatal line.

 The neonatal line indelibly inscribes the event of birth into any tooth undergoing enamel and dentin apposition at the time.

 Crude age assessment is theoretically possible in deceased children by measuring the thickness of tooth structure beyond the neonatal line.

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Age related dental changes

1. Loss of permeability and increase in the brittleness of enamel 2. Increased width and annulations of cementum

3. Various dentin changes such as

• Increased secondary, peritubular, and sclerotic (transparent) dentin

• Increased dentin mineralization

• Decreased dentinal tubules 4. Various dental pulp changes such as

• Compromised circulation and innervations

• Fat droplet deposition

• Odontoblast vacuolization

• Reticular atrophy

• Pulpal fibrosis

• Hyaline degeneration

• Fat replacement

• Pulpal “cysts”

• Mucoid degeneration

• Calcifications

Methods of age estimation

 Dental age estimation in Children and adolescent

 Atlas method (radiographic method)

 Schour and Massler

 Demirjan method

 Dental age estimation in Adults

 Gustafson’s method (Morphological techniques)

 Radiographic method

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

 Other methods

 Visual method

 Amino acid racemization

Nevertheless a number of age estimation methods have been developed for adult teeth.

Dental age estimation in Children and adolescent (a) Atlas approach

 Radiographs are used to morphologically assess the distinct stages of mineralization of all teeth.

 The tooth mineralization stages are much less affected by variation in nutritional and endocrine status unlike bone hence provide a more accurate indication of chronological age.

Advantages Dental radiographs:

 Dental radiographs are non-destructible that can be used more reliably and readily

 Dental radiographs prove to be a good method when all the ossification of long bones has been fixed

 Dental radiographs are of enormous value to determine the age when only skull has been found and other body parts or long bones are not available for the purpose of age estimation

(b) Schour and Massler

They described 20 chronological stages of dental development starting from four months after birth to 21 years of age. The individual dental status was compared with this table to estimate age.

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

(c) Demirjian technique

 Thousands of radiographs of French- Canadian children ranging from 2-20 years were used for standardization.

 The development of each left permanent mandibular tooth except for the third molar was rated on an 8-stage scale from A to H.

 Each letter corresponds to a score.

 The summed scores of all seven teeth represents the dental maturity score.

 The dental maturity score can be converted directly into dental age using either a graph or a table of standards.

Dental age estimation in Adults (a) Gustafson method

Most of the methods used in adults use various regressive changes of hard and soft tissues of the teeth. Gustafson (1950) studied the changes occurring in individual teeth and succeeded in estimating the age with some accuracy.

The following 6 dental changes were studied for age estimation.

(i) Attrition: The occlusal aspect of the tooth is worn out gradually with age. enamel is worn out first ,then dentin and lastly the pulp is exposed

(ii) Periodontosis: recession occurs in the gums and the surrounding periodontal tissues with advancing age.

(iii)Secondary dentin: The secondary dentin develops within the walls of the pulp cavity and decreases the size of the pulp cavity which could be due to ageing and partially due to pathological conditions like caries.

(iv) Cementum apposition: The age can be calculated by counting the incremental lines of the cementum ( formed due to the deposition of secondary cementum)

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

characteristically sharp grooves.

(vi) Transparency of the root: With age the dentinal tubules are filled with minerals and turn opaque. This is the most reliable criteria of the all.

Other methods (a) Visual method

 The simplest age estimation method

 Method based on clinical experience without using formal method.

 Can be questionable

(b) Amino Acid Racemization

 The relationship between the extent of aspartic acid racemization in dentinal biopsy specimens and age is very close and facilitates age estimation. As age advances L -aspartic acid will change into D -aspartic acid.

 Amino acid racemization (AAR) is used to determine relative dates of biological materials such as bone, shell and teeth and has been used in an archaeological context for over 30 years. At present, based on accuracy, simplicity, and the time required, teeth are the best organ for the estimating age. This method is exclusively used in the age estimation of unidentified corpses. The method involves extraction of one or more teeth hence this method was not applied on living humans due to ethical concern. Therefore a biopsy technique applicable to dentin was developed which causes only minor discomfort to the subject.

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

 The type of teeth chosen for the analysis may influence the results of estimation of age at death since dental age is not equivalent to chronological age. The level of proteins are high in dentine than enamel hence dentin is preferred over enamel for age estimation. The procedure is as follows:

Sample handling Sample handling is vital since fixation influences racemization.

Fixatives such as ethanol, formalin and formaldehyde are recommended as standard fixatives for dental age estimation.

Bleach treatment In this procedure, adherent soft tissue is removed from the teeth, using sodium hypochlorite

Washing solution The tooth samples are washed with acetone followed by 0.2 N HCl.

Pulverization Calcified tissue is often pulverized during sample preparation prior to demineralization. Pulverization increases the amount of extracted organic material that contains more soluble collagen.

Proteins are extracted using a chelating agent such as ethylene diamine tetra-acetic acid (EDTA) rather than mineral acids.

Demineralization Demineralization is done by mineral acid (HCl or EDTA) to isolate a fraction of the total dentine protein. A concentration of 0.6 N HCl, with continuous agitation at 4°C, causes much faster and simpler demineralization and can be used for dentine fragments.

Hydrolysis The temperature for hydrolysis ranges from 100-110°C and the time periods can range from 6-20 hrs.

Chromatographic separation

High pressure gas chromatography (HPGC) and gas chromatography (GC) have been used to separate and quantify D- aspartic and L-aspartic enantiomers in dentine. GC is the method typically used in forensic settings. The amino acids are usually derived as N-trifluoroacetic acid isopropyl esters and all the amino acids can be separated and quantified on a chiral capillary column in one chromatographic run.

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Age determination:

Age can be calculated by the following equation:

Coefficient of racemization KR: a x Age + b

KR=Ln 1+ (D/L) / (1- (D/L)

Where: D & l are integrated peak areas of the respective enantiomer a: rate constant of racemization of asp in dentin

b: y-intercept

5. Forensic Significance

Post mortem dental profiling

The role of the forensic dentist is to narrow down the identification process by giving information about the sex, race , age, socio economic status, occupation, dietary habits, dental and some systemic diseases as well by careful examination of the deceased or the left over human remains at the site of disaster. These characteristics are complemented by various secondary characteristics like features, personal belongings (pocket contents, clothes including any mark, defect, stitching, jewellery etc) hairs, scars, tattoos, external peculiarities including deformities (whether natural or due to disease, occupational stigmata, race, religion or nationality.

Race

Careful examination of the skull and its form and its shape Shovel shaped incisors

Multi cusped pre-molars Talon’s cusp

Taurodonts Cusp of Carabelli

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

Gender

Dorion’s method

Y chromatin and DNA analyses from the microscopic examination of the teeth

Occupation /Dietary Habits

Erosion

Alcohol, substance abuse, working in an industry with use of acids, excessive consumption of carbonated beverages or disorders like anorexia nervosa, other eating disorders like hiatus hernia.

Stains

Smoking, tetracycline, chewing betel nut and smokeless tobacco, dental fluorosis.

Unusual wear pattern

Habitual placement of nails between the teeth, opening bobby pins, cutting of threads, placement of pipe stems, cigarette holders, hair pins.

notching of incisors Previous orthodontic treatment

Gives information on the

 dental attitude and awareness of the individual

 Quality and quantity of dental treatment

Some clues on the socio-economic status

FORENSIC SCIENCE PAPER No.14: Forensic Medicine

MODULE No.3: Determination of Age from Teeth

6. Summary

 Child of 2-3 yrs will have 20 temporary teeth. It will remain till 6-7 years of age.

 First permanent molar erupts at 6-7 yrs then total no of teeth become 24.

 Period of mixed dentition is 6-12 years and so total number of teeth will remain 24.

 Second permanent molar erupts at 12-14 yrs then total no of teeth becomes 28.

 Between 12-17 years there occurs lengthening of ramus and space behind second molar is created.

 Third molar erupts between age of 17-25 years and may be in 60% population only.

Age

Below 18 Calcification of enamel

Formation of root Eruption sequence

18 – 25 Assessment of third molars

 Crown formation Root formation

 Eruption

Above 25 Occlusion

Gustafson’s method Amino acid racemization