Forensic dentistry

By Muhammad AwadineOral Biology Department

Forensic Dentistry

Definition

• The branch of dentistry which deals with the proper handling, examination & evaluation of dental evidences and with the proper presentation of dental findings in the interest of justice.

Basic Concept

The THEORY behind forensic dentistry is that no two mouths are alike (even identical twins are different), and that teeth, like tools, leave recognizable marks.

Most people have dental Records, or these can be created through making a dental impression from a suspect.

These can then be COMPARED to either teeth found on a dead body or bite marks found at the scene of a crime.

It relies on sound KNOWLEDGE of teeth and jaws, possessed by dentist and incorporates dental anatomy, histology radiography, dental materials and developmental anomalies of dentition.

The INTRPRITATION of dental evidence is a specialist task, undertaken by a forensic dentist who may be called as an expert witness in a case.

Historical Aspects

The earliest known identification from teeth is in 1775 by Paul Revere. – Paul Revere made a silver bridge for one man. The man was killed in the War. – Body was in mass grave and identified by his silver dental work.

1837- Dr Edwin Saunders established the eruption sequence.

1897- Dr Oscar Amoedo ( father of forensic odontology ) wrote the first book of forensic dentistry.

Dental records including radiographs and spare crowns identified the body of Adolf Hitler.

Scope of Forensic Dentisrty

1-Dental identification.

2- Bite marks investigations.

3- Analysis of dental malpractice.

4- oral evaluation of child abuse.

5- Presenting evidence in court as an expert witness.

When Identification is Required ?

Decomposing remains. Skeletonized remains. Charred remains. Intact remains without any putative

victim. Multiple bodies recovered from a common

location.Mass disaster.

Why Dentition is a good scientific identifier ?

1. Stable & durable (tooth material & restorative materials) – Teeth are the most durable organs in the body and can be heated to temperature of 1600°C without appreciable loss of micro structure.

2. Uniqueness (size/shape/pattern/wear/repair) – The 16 missing teeth can produce is approximately 600 million different number of combinations . Four missing and four filled teeth in a mouth combined can produce more than 700 million combinations. Although teeth are relatively resistant to environmental insults after death.

3. Previous records

4• Since teeth can resist extreme conditions, they are the excellent source of DNA.

Types of Dental Identification

Methods

1- Comparative identification.

2- DNA identification.

3- Edentulous identification.

4- Dental Profiling.

Comparative dental Identification Procedures

1. Oral autopsy 2. Securing ante-mortem records 3. Comparison 4. Writing the final report and drawing conclusions

1- Oral Autopsy

Oral examination is an essential part of post-mortem procedure.

Thorough examination of soft tissue injuries, fractures and presence of foreign bodies is undertaken and samples of hard and soft tissues may be obtained for further investigations.

All this information is entered on to the standard “Interpol postmortem form” which is color coded in

pink.

2- Obtaining Dental Records

Dental records contain information of treatment and dental status of a person during his/her lifetime.

Such records may be in the form of dental charts, radio graphs, casts and/or photographs.

The contents of all available dental records should be transcribed onto the standard “Interpol ante-

mortem form” which is color coded in yellow.

3- Comparing Post- and Ante-Mortem Dental

Data

Parameters to be compared1. Teeth. 2. Prosthetic appliance– bridges, partials, crown, false teeth.

3. Shape, form (morphological) features.

4. Genetic anomalies.

4- Writing A Report and Drawing Conclusions

A detailed report and factual conclusion, based on comparison, must be clearly stated.

Acharya and Taylor have suggested a range of conclusions, which include:

1. Confirms Identification 2. Probable Identification3. Possible Identification 4. Insufficient Information5. Excludes Identification

Identification From Dental DNA

Since teeth can resist extreme conditions, they are the excellent source of DNA.

This facilitates comparison with the known biological ante-mortem sample of the person such as hair, epithelial cells from a tooth brush or a biopsy specimen.

If the person’s ante-mortem sample is unavailable, the DNA pattern may be compared to a parent or a sibling.

The Role of Palatal Rugae in

Identification

Useful in edentulous personsRugae patterns like teeth are

considered unique to an individualRugae patterns on the decedent’s

maxilla or maxillary dentures may be compared to old dentures that may be recovered from the decedent’s residence or plaster model from dental office.

RUGAEPRIMARY RUGAE (>5mm) SECONDARY RUGAE(3- 5mm)

FRAGMANTARY RUGAE (2-3mm)

OR -BRANCHED -UNIFIED -CROSS-LINKED -ANNULAR -PAPILLARY

DENTAL PROFILING

Dental profiling includes extracting a triad of information-the decedent’s ethnic origin, gender and age.

The information from this process will enable a more focused search for ante-mortem records .

Identifying Ethnic Origin From Teeth

Anthropologists have divided race into following broad groups- (i) Caucasoid (ii) Negroid (iii) Mongoloid

(iv) Eskimos (v) American Indians.Dental features used to describe population differences

are broadly categorized as metric (tooth size) and non metric (tooth shape).

Metric features are based on measurements and non metric in terms of presence or absence of a particular feature , e.g: whether carabelli’s cusp is present or absent.

Metric FeaturesSize of teeth: Both deciduous and permanent dentitions are

considered. The size of the teeth varies in different races Larger teeth are seen in Australian, South American Indian

tribes. Lateral incisor is relatively large compared to central incisor in

mongoloids. Intermediate sized teeth are seen in Taiwanese Aborigines and

Australian whites respectively.

Sex Determination From Teeth

Gender can be determined based on data from Cranio-facial morphology and dimensions Sex differences in tooth dimensions Tooth morphology Sex determination by DNA analysis

Amelogenin (AMEL) is one of the major matrix proteins secreted by the ameloblasts of the enamel.

The AMEL gene, coding for a highly conserved protein, is located on X- and Y chromosomes in humans.

Thus the females (XX) have two identical AMEL genes but the males (XY) have two non identical genes.

Sex determination

Mandibular cuspid shows the maximum sexual dimorphism-Mesio-distal diameter < 6.7 mm (in females)Mesio-distal diameter > 7 mm (in male) Root length of maxillary cuspid is >3 mm more in males than

females.Distance b/w tips of coronoid processes(cm) x distance b/w

angles of jawif > 90 ; then male ,if < 78 ; then female

Age estimation from dentition

*Dental age estimation makes use of morphologic, radiographic, histologic, and biochemical methods to examine the age dependent changes in teeth.

It is grouped into three phases:1. Ageing in prenatal, neonatal and early postnatal.

2. Age estimation in children and adolescents.

3. Age estimation in adults.

Phases in tooth development and eruption

1. Utero ( from 16 weeks) to eruption of 1st tooth at 6 months.

2. Primary dentition (milk teeth): from 6 months to 6 years.

3. Mixed dentition: 6 to 12 years.

4. Permanent dentition: From 12 years on

Age Estimation

*Presence of neonatal line indicates a live births Histological examination is more precise in neonatal age estimation than radiography.

Age Estimation

Examining teeth eruption patterns

(A) Last erupted tooth—21; approximate dental age = 7–8 years; (B) Last erupted tooth—31, 41; approximate dental age = 6–7 years; (C) Erupting teeth—13; approximate dental age = 11–12 years; (D) Erupting teeth—25 and 13; approximate dental age = 10–12 years

Age Estimation

GUSTAFSON’S METHOD

* This method is based on morphological and histological changes of the teeth.

* • This assessed regressive changes such as:

* a) Amount of occlusal attrition(A)

* b) Coronal secondary dentine deposition(S)

* c) Loss of periodontal attachment(P)

* d) Cementum apposition at the root apex(C)

* e) Root resorption at the apex(R)

* f) Dentine translucency(T)

* An+ Sn+ Pn+ Cn+ Rn+ Tn = X; a total score

* •Age was estimated using the formula Age = ( 11.43 + 3.63X ) years

* •It was found that an increase in the total score corresponds to an increase in age


*Regressive changes *• For each of these regressive changes or variables,

different scores ranging from 0-3 were assigned.

*STAGE 0 – indicates no change

* STAGE 1 – beginning of change

*STAGE 2 – obvious change

* STAGE 3 maximum change

* Attrition (A) * A0—no attrition * A1—attrition limited to enamel level * A2—attrition limited to dentine level * A3—attrition up to pulp cavity

* Secondary Dentin (S) * S0—no secondary dentin formation * S1—secondary dentin up to upper part of pulp

cavity * S2—secondary dentin up to 2/3rd of the pulp cavity* S3—diffuse calcification of entire pulp cavity

* Periodontal Disease (P) * P0—no obvious periodontal disease * P1—beginning of periodontal disease but no bone

loss * P2—periodontal disease more than 1/3rd of the

root * P3—periodontal disease more than 2/3rd of the

root



* Root Translucency (T) * T0—no translucency * T1—beginning of translucency * T2—translucency more than 1/3rd of the apical

root * T3—translucency more than 2/3rd of the apical

root

* Cementum Apposition (C) * C0—normal cementum * C1—thickness of cementum more normal * C2—abnormal thickness of cementum near the

apex of the root * C3—generalized abnormal thickness of cementum

throughout the apex of the root

* Root Resorption (R) * R0- no resorption * R1- apical 1/3rd root resoption * R2- apical 2/3rd root resorption * R3- comlete root resorption

Dentin Translucency

* Bang and Ramm were the first to use dentine translucency alone for estimating age.

* • Root dentine starts to become translucent during the third decade (30s) of life beginning at the apex and advancing coronally.

* • Root dentin starts to become translucent due to the increased intratubular calcification.

* • Therefore dental root translucency increases with advancing age.

*All amino acids (except glycine) are optically active, having a stereocenter at their α-C atom.* This means that the amino acid can have two different

configurations, "D" or "L" which are mirror images of each other. *Living organisms keep all their amino acids in the "L"

configuration. *When an organism dies, control over the configuration of

the amino acids ceases, and the ratio of D to L moves from a value near 0 towards an equilibrium value near 1, a process called racemization. *Thus, measuring the ratio of D to L in a sample enables

one to estimate how long ago the specimen died.

*Amino acid racemization

*Amino acid racemization

*Helfman and Bada first suggested a relationship between dentinal age and the extent of aspartic acid racemisation in dentine.

*• The extent of racemization of aspartic acid in coronal dentin of normal permanent teeth can be used to estimate the age of an individual at the time of death.

*• This method is accurate with age estimates within plus/minus three years of actual age.

* Some other techniques of age determination..

* 1. Pulp diameter to crown diameter ratio and* pulp / root length, pulp /root width was

measured.

* 2. An interesting method using 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. The colour changes in the cementum and dentin are caused by infusion of decomposition products from erythrocytes.

* 3. The incremental lines of cementum will help to determine the age of adults. A major disadvantage of this method is the necessity to extract or section the tooth. It is not practical among living individuals.

Age Estimation

Bite marks (Dental Finger

Prints)

Can you tell the differences of these bite

marks?

What to look for..?

*The shape or curvature* No. of tooth marks* Horizontal diameter* Vertical diameter*Depth of depression*Distances between two teeth *Orientation of each tooth

Bite-mark

*Cutaneous bitemarks represent patterned injuries in skin produced by teeth.

*May be inflicted by humans or animals (most commonly by dogs and cats); may be on tissue, food items or other objects.

*• Human bite broad, U-shaped somewhat circular or oval.

*• Animal bite narrow in the anterior aspect , V shaped and elongated also morphology of the teeth is different.

*The Concept • Each human dentition is unique, differing even in identical twins. *For this reason, bite marks have

been referred to as “dental fingerprints”.*Diagrammatic depiction of human

bite mark showing typical pattern of contacting surfaces of teeth *• Is composed of two separate,

curved arches facing one another. *• Each arch is composed of a row

of contusions, abrasions, lacerations or depressions approximating the size & shape of biting surfaces of human front teeth.

Typical presentation of bite mark injuries

• A representative human bite is described as an elliptical or circular injury that records the specific characteristics of the teeth • Alternatively, it may be composed of two U-shaped arches that are separated at their bases by an open space. • The diameter of the injury typically ranges from 25-40 mm.

• This extra-vascular bleeding is caused by pressure from the teeth as they compress the tissue inward from the perimeter of the mark. Class features: Incisor=rectangular Canines=triangular or rectangular Premolars and molars= spherical or point shaped Individual features: Rotation, Dental work, diastema, fracture etc.

CLASSIFICATION OF BITE MARKS

A. Cameron and Sims Classification 1. Causing Agentsi-Humans ii–Animals 2. Substrate Materials -Skin , body tissuei-Food stuff ii-Other materials B. Mac Donald’s classificationsI -Tooth pressure mark Ii -Tongue pressure mark Iii -Tooth scrape mark C. Based on severity of injurya. hemorrhage -- small bleeding spot b. abrasion -- undamaging mark on skinc. contusion -- ruptured blood vessel, bruise d. laceration -- punctured or torn skine. incision -- neat puncture of skin f. avulsion -- removal of skin

Bite Mark Investigation

I- Bite mark evidence collection from the victims Steps: 1.Visual examination.2.Photography -Orientation photographs -close-up photographs. 3.Saliva swab: -WBC and sloughed epithelial cells, potential source of DNA.4.Impression: Vinyl polysiloxane, dental acrylic & plaster.

II- Evidence collection from suspect using a signed and informed consents or a court order (warrant) also include:1-photograph.2-two casts.3-bite registration in centric occlusion. 4-saliva swab from buccal vestibule.

• Physical characteristics to be studied are:1- Distance from cuspid to cuspid 2– Tooth alignment 3– Teeth width, thickness, spacing 4– Missing teeth 5– Wear patterns including chips and grinding 6– Dental history including fillings, crowns, etc.

Human or Animal bite

Animal Features of dentition

Conclusion

I- Positive bite-mark•An injury showing a pattern that may or may not be caused by teeth; could be caused by other factors but biting cannot be ruled out.

II- Possible bite-mark •The pattern strongly suggests or supports origin from teeth but could conceivably be caused by something else.

III- Definite bite-mark •There is no reasonable doubt that teeth created the pattern; other possibilities were considered and excluded.

Dental Malpractice

Dental Malpractice Claims

*Malpractice suit claims -Alterations of face , jaw , or chin -Unnecessary dental work -Careless/improper dental work.

*Role of Forensic dentist

• Examines dentition & oral tissues to establish degree of trauma , its possible cause and its potential impact on ability to chew food properly

•Present testimony regarding their findings

Child Abuse

Oral findings of child abuse or maltreatment

*Multiple broken, discolored, missing or avulsed teeth.* Repeated episodes of mouth trauma

Peculiar malocclusions & non occluding jaw segments.* Healed jaw fractures which were

displaced Laceration of labial or lingual frena Forceful lip pulling or slapping.* Isolated laceration of soft palate

Insertion of utensils during forced feeding.* Horizontal abrasions or contusions

extending from lip commissures. *adult bite (anger biting). *Rampant caries/Nursing Bottle

Syndrome.

FORENSIC DENTIST AS AN EXPERT WITNESS

• FREQUENTLY CALLED IN TO GIVE SWORN TESTIMONY IN COURTROOMS IN VARIOUS CASES SUCH AS:

* DENTAL IDENTIFICATION * BITE MARK ANALYSIS * AGE ESTIMATION * CHILD ABUSE CASES * DENTAL FRAUD etc.

Shortcomings of Forensic Dentistry

Shortcomings of dental identification :

* • Difficult to locate than fingerprints

* • Records may be inadequate

* • No standardization of dental records (no recognized minimum no. of concordant features required for positive identification)

* • Written entries are subject to error

* • Alterations (decayed , filled or extracted) after the last ante-mortem entry

Health & Medicine

Forensic dentistry