Part 1 : Question 1

Source:  Part 1 : Question 1    Tag:  extraoral radiographs
QUESTION 1 We have all heard of how Forensic Dentistry has helped in the identification of burnt victims and also victims with bite marks. Explain more about these and describe how is Forensic Dentistry could be useful in the identification of murder victims?

Generally, forensic dentists are responsible for six main areas of practice: [1]
• Identification of human remains or casualties
• Identification in mass death incidents
• Bite mark analysis
• Assessment of cases of abuse
• Civil cases involving malpractice
• Age estimation (age of a human specimen be narrowed by evaluating the patterns of tooth eruption and tooth wear)

Below is a video of how odontology is used to solve crimes: 

          Mosby’s dental dictionary (2nd edition) defines bite marks as the distinctive tooth patterns in a tooth that may have forensic or legal implications. Bite marks can be delivered by human, animal or insect.

Figure 1.0: Human bite mark
Figure 1.1 : Bed bug bites

Figure 1.2: Dog bites with claw marks found in vicinity of the wound

 Forensic odontologists use seven different terms to describe the type of bite mark: [2]
  • Abrasion - scrape or wearing away of the skin
  • Artifact - when a piece of the body, such as an ear lobe, is removed through biting
  • Avulsion - bite resulting in the removal or tearing of skin
  • Contusion - region of injured skin or tissue in which blood capillaries have been ruptured/  a bruise
  • Hemorrhage - profusely bleeding bite due to ruptured blood vessels
  • Incision - clean and neat wound
  • Laceration - tear or deeply cut wound

           Bite marks are usually found on perpetrators. They may be made up of two hyperbolic arches that are separated at their bases by an open space. The diameter of the hyperbolic arches ranges from 25-40mm. Also, bruises can be found within the bite marks. Individual characteristics recorded in the bite mark is essential in identification of the perpetrator.

Below is a figure of visual index of the bitemark severity and significance scale

Figure 1.3: Bite mark severity according to forensic significance scale
The bite mark severity and forensic significance scale 
1 :  Very mild bruising, no individual tooth marks present, diffuse arches visible, might be caused by something other than teeth 
- [ low forensic significance]

2 : Obvious bruising with individual, discrete areas associated with teeth, skin remains intact 
- [moderate forensic significance]

3 : Very obvious bruising with small lacerations associated with teeth on the most severe aspects of the injury, likely to be assessed as definite bitemark 
[high forensic significance]

4 : Numerous areas of laceration, with some brusing, some areas of the wound may be incised. Unlikely to be confused with any other injury mechanism
- [high forensic significance]

5 : Partial avulsion of tissue, some lacerations present indicating teeth as the probable cause of the injury 
- [moderate forensic significance]

6 : Complete avulsion of tissue,, possibly some scalloping of the injury margins suggested that teeth may have been responsible for the injury. May not be an obvious bite injury 
-[ low forensic significance]

Figure 1.4 : Anatomical location of 148 bitemarks, including bites in nonhuman substrates.

The total number of bitemarks included in the study was 148.
Four bites were found on non-human substrates (apple, cheese, paper
towel, and sandwich).

          According to the statistics shown above, females were four times more likely to be bitten. The victims were predominantly bitten on the breasts and arms.

          So, what is the significance of bite marks in forensic odontology

          Well, human bite marks can be used as forensic biological evidence. This helps in identification of both the murderer and murder victim. Identification can be done via analysing saliva deposited on the bite mark surface. With the use of high-intensity alternative light sources and lasers, forensic odontologists are able to locate saliva stains deposited on skin even without the presence of bite marks! After analysing the salivary DNA, the depositor’s DNA profile can be compared with the DNA profile of any suspect of the murder case. If both the DNA profile matches, there might be two possible outcomes. It can be either the suspect is the depositor or someone else is possessing identical or similar DNA profile as the depositor.  Therefore, besides DNA,  blood group ABO antigens can be collected from the saliva. This will help in narrowing the scope in identifying  the murderer. On top of that, oral bacteria obtained from bite marks can be used in identifying the depositor as each person's mouth has their own unique collection of microflora with their own distinct genotype. 

         Besides, from the bite mark, we can analyse and compare the patterns of bite marks found in the crime scene with the bite marks of the suspects. Each individual’s bite mark is unique. Different individuals present different bite marks due to their own dental structure for example restorations, fillings, rotations, tooth loss, breakage and  injury. Also, different races will present different dental arch trait. For instance, Asians have more rounded maxillary arch trait and Europeans have a more parabolic maxillary arch trait.

          On top of that, forensic odontologists can determine whether the victim was alive or dead by examining the type of bleeding beneath the skin. Besides, forensic odontologists can tell the process of how the bite mark was delivered. For example, rotations of the bite mark and abrasions from sharp or uneven teeth moving over the skin surface might occur if the victim was struggling.

          Bite mark is not necessary to be found ONLY on victim’s skin! It can also be found on the food remains in the crime scene, for example apples, cheese and chewing gum. It can also be found on leather products and wood. These imprints offer a three-dimensional impression, which can give a better evidence compared to the two-dimensional bite marks found on the skin.

          However, there are many factors that can affect the accuracy of bite mark identification.
These include: 
  • time dependent changes of the bite mark on living bodies
  •  effects of where the bite mark was found
  • damage on soft tissue
  • similarities of dentition among individuals
  • elasticity of human tissue
  • inflammatory process of human tissue 

On the other hand, o n severely burnt human victims, facial features and fingerprints may be damaged and hence physical recognition is almost impossible.

Figure 1.5: Deceased suffering from severe burn trauma (>90%),
found in a air plane crash.

As you can see, physical recognition is almost impossible to be done here as the facial and bodily features were heavily damaged. Here, the skull, teeth and related dental structures are preserved to aid forensic odontologists in identification of victim.

Disturbances of tooth eruption, pathological conditions and records of dental treatments are useful in dental identification. Through dental identification, age, gender, racial background, socioeconomic status, dietary habits and oral parafunctional habits of the victim can be identified. And this helps in narrowing the scope of identification of victim in burn tragedies.

Intact or sound, filled, missing teeth, fixed or removable prosthetics are some criteria needed for postmortem registration of teeth. The detailed antemortem records(dental treatments and records), postmortem records(INTERPOL DVI forms) and radiographs are collected and compared. The nature of accident, the nationality and country of residence of the victims, the incidence of dental treatment , the availability of sufficient dental records and the extent of dental injury can greatly affect the success rate of dental identification.

          Through the study of extraoral radiographs, dental eruption and mineralization of permanent and deciduous teeth can determine age. At the same time, age of the victim can be determined via cementum annulations. Cementum annulations can be done by examining the incremental lies on the cementum.

                Gender of the victim can be identified by examining the victim’s skull as male skulls are different from that of female skulls. Besides, the sex of the victim can be recognized by analyzing the pulpal tissue. The gender of the victim depends on the absence or presence of X-chromosome in the pulpal tissue.

Figure 1.6: Distinctive facial feature of three different races
          On top of that, racial background of victim can be determined by studying the dental arch traits. For example, Africans have a more hyperbolic maxillary dental arch whereas Asians have a more rounded maxillary dental arch. Also, forensic odontologists can determine the racial background of the victim by studying the structure of the skull and tooth. This is because each race has their own distinctive facial and tooth structures. For instance, Caucasians have a narrow face with high-bridged nasal bone. Besides, Caucasians have flat incisors on the lingual surface. On the other hand, rate of appearance of cusp of Carabelli is higher in the Japanese compared to the Chinese population.

Below is a list of characteristic features which can be seen on the skull from 3 different races. [3]
Figure 1.7: Distinctive facial feature of three different races

       Socioeconomic status of the victim can be identified by studying the patterns of dental caries and oral hygiene. Victims with bad oral hygiene and dietary habits may present with periodontal disease which shows recession of alveolar bone. Finally, victims who practice oral parafunctional habits such as bruxism will show wearing of cusps on occlusal surface which will lead to exposed dentin and loosen teeth.


Online lecture slides