Forensic OdontologyAn Introduction to Forensic Dentistry

ByWafaa Abdel-Ghaffar Ali

Assistant lecturer of Forensic medicine &Clinical toxicology- Sohag university

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.”

Why Teeth?

Every human body ages in a similar manner, the teeth also follow a semi-standardized pattern. These measurements help relative age estimation of person.Each human has an individual set of teeth which can be traced back to established dental records to find missing individuals.Teeth is made of enamel (hardest tissue of the body) so it can withstand trauma (decomposition, heat degradation and water immersion) better than other tissues in body .

Teeth are source of DNA: dental pulp or a crushed tooth can provide nuclear or mitochondrial DNA that help to identify a person.

Role of forensic odontology 1 .identifying unknown human remains through

dental records & cranio-facial bones

2 .age estimation of both the living and deceased

3 .recognition and analysis of bite marks found on victims

4 .analysis of oro-facial trauma associated with person abuse

5 .determining the gender of unidentified individual

6 .eliciting the ethnicity from the skeletal remains 7 .building up a picture of lifestyle and diet of

skeletal remains

Historic milestones in forensic dentistry

•1st dental identification was made ( Agrippina ,Emperor Claudius ,

Lollia Paulina)

•1837 -Dr Edwin Saunders established the eruption sequence

•1897 -Dr Oscar Amoedo ( father of forensic Odontology ) wrote the first book of forensic dentistry→ L’Art Dentaire en Medicine Legale

Historic milestones in forensic dentistry •AMERICAN SOCIETY OF FORENSIC

DENTISTRY (1970)

•INTERNATIONAL SOCIETY FOR FORENSIC ODONTO-STOMATOLOGY (1976)

•Similar organizations exist in various countries

Organizations of Forensic Odontology

Bureau of Legal Dentistry (BOLD)

American Board of Forensic Odontology (ABFO)

International Organization for Forensic Odonto-Stomatology (IOFOS)

Hardest part of body attached to jaws. IT serves to help digest food, act as a defense mechanism, etc. teeth are made of a crown with enamel surrounding a pulp.

•Each tooth has a crown (visible portion that protrudes above gum) and a root (embedded into the socket in the jaw bone)

•Crown is capped by enamel , under the enamel is a layer of dentin which surrounds the pulp cavity

• The root is surrounded by cementum

•Periodontal ligament present between cementum and bone of the jaw holds the tooth in jaw

Teeth BasicsApproximately 32 teeth in adult mouthFour types of teeth:MolarsPremolarsCanineIncisorsTeeth differ in:SizeShapeRoot type

Types of teeth. Left to right: Incisor, Canine, Premolar, molar.

:Each tooth has 5 surfaces •Incisal/occlusal Surface

•Buccal/labial/facial surface

•Lingual/palatal surface

•Mesial surface

•Distal surface

INCISORS • eight in number

•anterior teeth with wide crown and sharp, chisel like incisal/ cutting edge

•has a single root

•used for cutting purposes

CANINE • four in number

•also called cuspid , as they have a sharp/pointed cusp

•has a single root • used for tearing of the eatables

PREMOLARS • eight in number • present only in permanent dentition • each premolar typically has two cusps • premolars (other than 1st maxillary premolars

which has two roots) possess a single rootMOLARS • twelve in number • usually have 3-5 cusps • multi-rooted teeth • wide surface adapted for chewing & crushing

of food • 3rd molar is the last tooth to erupt

Teeth through the yearsChildhood Adulthood

Primary teeth sprout from milk buds and are temporary. Once they fall out, permanent teeth as seen on the other side appear .

Permanent adult teeth come in when primary teeth fall out; they are permanent because they establish roots inside the gums. Third molar come in around the mid teenage years.

Individual Characteristics

Size of toothShape of toothShape of rootPlacement of toothQuantity of teethCombinations of dental work done:CrownsExtractionsBridgeFillings

Various dental work

Analyzing TeethThe Universal SystemTeeth are given a specific number. (Primary teeth are given specific capital letter)Any dental work done on surface is notedSheets kept on dental file forever. When person is missing, files are transferred to the missing person’s office

Personal identification based on dentition

Reconstructive identification (DENTAL PROFILING):

when ante-mortem records are not available

•includes a triad of ethnic origin , gender , age

Identifying ethnic origin from teethcharacteristic dental features have evolved over time as a result of genetic and environmental factors that have influenced different population groups (Caucasoid, Negroid, Mongoloid) .

•categorized as -metric (tooth size)- non metric (tooth shape) .

•Metric features are based on measurements

•Non metric in terms of presence or absence of a particular feature

In Caucasian races :

-lateral incisors in the upper jaw smaller than central especially in females.

-long pointed canine roots.

-carabelli’s cusp

In Mongoloid races:

-shovel –shaped upper central incisors.

-enamel –pearls

Sex determination by forensic odontologist

•Gender can be determined based on data from

1-Craniofacial morphology and dimensions

2 -Sex differences in tooth size

3 -Tooth morphology

4 -Sex determination by DNA analysis .

Sex determination •Mandibular cuspid shows the maximum

sexual dimorphism.

It’s usually smaller and more pointed in females relative to males.

Root length of maxillary cuspid is >3 mm in males

Mandibular first molar often lacks afifth cusp in females, which is almost always present in males.

Dental age estimation

•Examining teeth eruption patterns

•Gustafson method (looking for six signs of wear)

•Lamendin method (looking at transparency of roots/dentin translucency)

•Amino acid racemisation

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)

e) Root resorption at the apex(R)

f) Dentine translucency(T)

d) Cementum apposition at the root apex(C)

Gustafson’s method conti • 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

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

•Age was estimated using the formula

Age = ( 11.43 + 4.56X ) years

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

Dentine translucency Root dentine starts to become translucent during the third decade of life beginning at the apex and advancing coronally.

• Therefore dental root translucency increases with advancing age.

Amino acid racemisation Enamel and dentine belong to the very few tissues that do not have metabolic turn-over after formation .

there’s a relationship between dentinal age and the extent of aspartic acid racemization in dentine.

•Therefore, there is a constant change in the ratio of L-and D-aspartic acid at different ages and this D-L ratio may be used for age estimation.

•HPLC,Gas chromatography or amino acid analyzer.

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

Shortcomings of dental identification method

•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)

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

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 persons ante-mortem sample is unavailable, the DNA pattern may be compared to a parent or a sibling, .thus allowing identification

The role of palatal rugae in identification

•useful in edentulous persons

•rugae patterns like teeth are considered unique to an individual

•rugae 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

RUGAE-PRIMARY

RUGAE (>5mm)

-SECONDARY RUGAE(35mm

-FRAGMANTARY RUGAE (2-3mm)OR

- BRANCHED

-UNIFIED

-CROSS-LINKED

- ANNULAR

-PAPILLARY

Impressions from teeth found on skin or items left at a scene. Usually outline teeth

placement.

•A mark caused by teeth either alone or in combination with

other mouth parts.

•May be caused by humans or animals; may be on tissue, food items or other objects.

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

•Animal bite ›››› V-shaped and elongated also morphology of the teeth is different

Where are bite marks found?Impressions left on food, skin or other items left at a scene.Porous surfaces that absorb the impact enough to make an impressionImpressions varyDepending on the pressure applied . The more pressure , the more detail to the bite.

twins. identical even in • Each human dentition is unique ,

• Its imprint in skin can show this individualization, making

the identification of perpetrator possible

•For this reason, bite marks have been referred to as “dental fingerprints.”

•Human bite is described as an elliptical or circular injury that records the specific characteristics of the teethClass features :

Incisor ›››› rectangularCanines ›››› triangular or rectangular

Premolars and molars ›››› spherical or point shaped

Individual features: Rotation, Dental work, fracture etc.

• 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.

(Sexual assault)

• Females ››› Breast, inner sides of thigh and legs

(• Children ››› genitals, oral & paraoral regions (child abuse

• Adult Males ››› finger, arms and shoulders (fight)

1.Cameron and Sims Classification A)Causing Agents -Humans -Animals

B)Substrate Materials -Skin , body tissue -Food stuff -Other materials

2.Mac Donald’s classifications

-Tooth pressure mark

-Tongue pressure mark

-Tooth scrape mark

3.

a. hemorrhage -- small bleeding spot

b. abrasion -- undamaging mark on skin

c. contusion -- ruptured blood vessel, bruise

d. laceration -- torn skin

e. incision -- neat puncture of skin

f. avulsion -- removal of skin

•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: dental acrylic & plaster

•Evidence collection from suspect: using informed consents or a court order , also include

photograph, two casts, bite registration and saliva swab from buccal vestibule

Analyzing bite marksBite marks are photographed

Casts of impression are takenImpression traced onto transparenciesCasts of suspects teeth are takenComparison between suspect cast and bite mark

Comparison features

•distance from cuspid to cuspid

•tooth alignment

•teeth width, thickness, spacing

•missing teeth

•wear patterns •dental history including fillings, crowns, etc .

Computer Odontology

Automatic dental code matchingBites are run through the computer to find a matchOdontoSearchCompare a data base of missing peoples, government workersAutomatic dental identification systemA few minutes will produce a list of people who have the same dental code number3D Bite mark analysis3D scans of dental casts are used to generate various pressure and deviation.

State of Florida v. Ted Bundy

Evidence, various pictures from trial

Ted Bundy, was an American serial killer who murdered numerous young women between 1974 and 1978. He confessed to 30 murders, however the total amount of victims remains unknown. He would bludgeon his victims, then strangle them to death. He engaged in rape and necrophilia.

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