Forensic Dentistry

Hey everyone,

This entry is about the forensic strand of dentistry. In many TV programmes and series we often find that police identify suspects based on ‘dental records’. During one of my work experience placements, the clinic manager also informed me of the importance of such records within the law and police records. This entry aims to provide a clearer view to what is actually involved in particular in this process.

First a few key phrases….

Forensic Science: The application of science to those criminal and civil laws that are enforced by police agencies in a criminal justice system.
Forensic Anthropology: Identifies human skeletal remains. Also tries to reconstruct from remains, the physical appearance of the deceased.
Forensic Odontology: Identifies the person by their teeth or bite marks.

Determination of sex

- In males, crests and ridges are more pronounced in males (A, B, C)
- In males, the chin is significantly more square (E)
- In males, the jaw and mastoid process is wide and robust (I, E)
- In males the forehead slopes more (F)

Determination of race

- The cranium is the only reliable bone to tell the general race category
- Nasal index: The ratio of the width of the nose, multiplied by 100
- Nasal Spine: Feel the base of the nasal cavity, on either side of the nasal spine and you will find sharp ridges, rounded ridges or no ridges at all 
- Shape of eye orbits: Round or square
- Mongoloid (Asian and Native American decent) – wider cheekbones, concave incisors and a great width between eyes
- Negrid (African and West Indian decent) – prominent ridges and wider nasal opening
- Caucasian – most features are narrow 

Facial reconstruction

- These were developed for a variety of reasons including criminal investigations, historically valuable remains, remains of humans and prehistoric hominids
- In order to help determine facial features, the following clues from the skull may be used: brow ridge, distance between the eye orbits, shape of nasal chamber, shape and projection of nasal bones, the form of the chin and the overall profile of the facial bones
- 2D reconstructions are hand-drawn facial mages based on skull photos and are usually produced with the cooperation between and artist and forensic anthropologist
- 3D reconstructions are sculptures created with modelling clay which usually require both and artist and forensic anthropologist. Computer programmes may be used to manoeuvre scanned photographs of remains and facial features and reconstruction includes building muscles
- During reconstruction certain rules need to be taken into concentration, for example the fact that ears are usually the same length as the nose although elderly people usually have longer ears 
   
Computer superimposition

- Superimposing photographs of individual believed to be the owner of skeletal remains over x-ray of the unidentified skull
- If x-ray and photograph are from the same individual, the anatomical features of the face should align accurately

Forensic Odontology

- Identification of bite marks on victim
- Comparison of bite marks with teeth of suspect
- Identification of unknown bodies through dental records
- Age estimations of skeletal remains
- Victim identification through DNA analysis

Why teeth?

- Every human body ages in a similar manner, the teeth also follow a semi-standardized pattern and such quantitative measures help to establish the relative age of the individual
- Each human has an individual set of teeth which can be traced back to established dental records to find missing individuals
- Teeth are made of enamel and so can withstand trauma (decomposition, heat degradation, water immersion and desiccation) better than other tissues in the body
- Teeth are a source of DNA as dental pulp or crushed tooth can provide nuclear/mitochondrial DNA to help identify an individual
- Individual characteristics include: Size, shape and placement of tooth, shape of root, quantity of teeth and combinations of dental work (Crowns, Extractions, Bridges, Fillings, Root canals)

Identification through teeth

- Dental treatment: The quality of the dental treatment, the metals and techniques used could indicate which country the individual is from (or where they had the dental treatment)
- Dental records: Records such as old models can be used to compare the suspected victim with unidentified remains
- X-ray evaluation: Ante and post mortem dental x-rays can be compared

Bite marks

- These are impressions from teeth found on skin or items left at a scene which usually outline teeth placement
- They can be classified into 2 groups:
1) Cameron and Sims Classification – Agents (Humans or Animals) and Materials ( Skin, body tissue, food or other materials)
2) Mac Donald’s Classifications – Tooth pressure marks, tongue pressure marks or tooth scrape marks
- Bite marks are photographed with a scale, casts of impression are taken, cats of suspects teeth are taken and a comparison between suspect cast and bite mark is made
- Physical characteristics of bite marks include distance from cuspid to cuspid, tooth alignment, tooth width, thickness and spacing, missing teeth, wear patterns such as chips and grinding and dental history such as fillings, crown etc.
- Computer Odontology: This is a 3D bite mark analysis whereby 3D scans of dental casts are used to generate overlays using various pressure and deviation and the overlays are compared with the photograph of the bite marks

Identification from dental DNA

- Teeth are an excellent source of DNA as they can resist extreme conditions
- If the individual’s ante mortem sample Is unavailable, the DNA pattern from the teeth can be compared to a parent or a sibling
- The best source of dental DNA is pulpal tissue
- Cryogenic grinding may be used to extract DNA whereby the whole tooth is cooled to extremely low temperatures and then mechanically grinded to a fine powder thus resulting is the tooth being completely crushed
- Another method is the drilling of the root canals, scraping the pulpal area with a medical needle and subsequently flushing the tissue debris

Using the Palatal Rugae in identification

- Useful in cases where patients are edentulous (lack teeth)
- Rugae patterns are considered unique to an individual
- Rugae patterns on the descendant’s maxilla or maxillary dentures may be compared to old dentures that may be recovered from the descendents residence or plaster model from the dental office

Lip prints identification

- Examination of lip print-cheiloscopy
- Grooves are heritable and individualistic so material evidence left at a crime scene may be used similar to finger prints
- Lip prints are classified as:
1) Simple wrinkles – straight line, curved line, angled line, sine shaped curve
2) Compound wrinkles – bifurcated, trifurcated, anomalous
- Invisible prints can be lifted using materials such as aluminium powder, magnetic powder
- One disadvantage may be that trauma and surgical treatment can affect the size and shape of the lip
- Another disadvantage is that the zone of transition close to vermilian border is extremely mobile so prints produced may differ depending on direction and amount of pressure applied

Case Study 1

- Investigators were unable to identify and so requested a post-mortem dental profile
- The skeletal pattern and dental characteristics suggested the following: Caucasian male, aged 25-35 years at death, moderate adult periodontitis (gum disease), nicotine stains, lack of recent dental treatment and previous treatment to Canadian standards
- Using this information, a facial reproduction was reproduced by a forensic artist

- Subsequently, the body was identified as that of a 28 year-old missing white male smoker

Case study 2

- Circumstantial evidence established the probable identity of a found human skull
- Ante mortem dental records were not available for comparison
- Medical records revealed the availability of a cervical smear
- Partial degradation of DNA from teeth produced a profile at eight genetic loci
- These were compared with the DNA profile obtained from the Pap smear and established that the samples originated from the same source     

Conclusion

- Dental practitioners should be aware of the forensic application of dentistry
- Dental records can be used to provide patients with optimal dental service but can also be beneficial to legal authorities during an identification process – therefore it is important that all forms of dental treatment should be recorded and kept safe
- Dentists should also be aware and detect signs of violence appearing on their patients – this should be done by being aware of the criteria of abusive injuries and the reporting mechanisms to ensure a correct response by the concerned authorities.

Zahra :)

Bibliography: The information on this entry was produced from http://www.smile-mag.com/art_files/Forensic_Odontology.pdf and a downloaded PDF file. No copyright intended by any means.