Teeth Basics Approximately 32 teeth in the adult mouth, 20 teeth in adolescents Four Types of Teeth: Molars Premolars Canine or cuspid Incisors

Teeth Basics Most dentists in the US use the Universal System to distinguish between the different teeth. Each tooth is assigned a number. Number one is the upper right third molar (also called the wisdom tooth) while number 32 is the lower right third molar. Adolescent teeth are designated using a letter

Teeth Basics Each surface of the tooth also has a designated name. Occlusal: the biting surface. It has 2 elements: Cusps: raised parts Grooves: indentations Mesial: surface towards the front of the tooth Distal: surface towards the rear of the mouth Palatal: surface towards the tongue on the upper jaw Lingual: surface towards the tongue on the lower jaw Buccal: surface towards the cheeks

Teeth Basics Structure of a tooth Enamel: the hardest, white outer part of the tooth Dentin: the layer underneath the enamel. It contains microscopic tubes. Pulp: the softer, living, inner structure of teeth that contains blood vessels and nerves. Cementum and periodontal ligament: tissues that hold the teeth to the gums and jaw bones.

Teeth Basics Structure of a tooth (continued) Crown: the part of the tooth that protrudes into the mouth Root: the part of the tooth that descends below the gum line to the jaw.

Forensic Odontology Forensic odontology is a unique field that combines the skills of a specially trained dentist with those of law enforcement. The forensic dentist’s primary duty is human identification. Missing and unidentified persons Recognition, documentation, and preservation of bite mark evidence The objective of bite mark analysis is to connect or eliminate a suspect to a bite mark.

Analysis of Bite Marks Unlike fingerprints, teeth change greatly throughout a person’s lifetime. These changes are based on activity, health, and dental treatment. They can result in the creation of a unique dental profile for an individual. Can also cause a false elimination of a suspect if too much time has passed between the collection of the evidence and the collection of the bite mark (called a dental standard) from the suspect.

Analysis of Bite Marks Bite mark analysis is based on the assumption that bite marks are unique to each person. Research shows that this isn’t necessarily the case. Bite marks are better used for excluding possible suspects than pinpointing a single individual.

Analysis of bite marks Because the skin is elastic and heals quickly, bite marks may not have a lot of detail. Many bite marks are not well defined or distorted. In addition, objects between the teeth and the skin, such as a shirt, keep the entire bite mark from being recovered. Forensic dentists rely on the variations that occur in tooth size, shape, and position between individual teeth to provide the uniqueness required for a forensic comparison.

Types of bite marks Impressions based on pressure: Clear: significant pressure Obvious: medium pressure Noticeable: violent pressure

Types of bite marks Tooth pressure marks-direct application of pressure by teeth Abrasion: a scrape on the skin Artifact: when a piece of the body, such as an earlobe, is removed through biting Avulsion: a bite resulting in the removal of skin Contusion: a bruise Hemorrhage: a profusely bleeding bite Incision: a clean, neat wound Laceration: a puncture wound

Analysis of Bite Marks Common traits of bite marks are: Semi-circular Two opposing U-shaped arches separated by a space at their bases A series of round bruises around the arches made by the teeth Possible small cuts

Analysis of Bite Marks The first step in bite mark analysis is to determine which marks are from the upper and lower jaws. Front teeth are seen as primary biting teeth. There are 6 upper and 6 lower front teeth. A bite mark will show 12 teeth severely marking the skin. The upper jaw is wider than the lower jaw.

Analysis of Bite Marks The next step is to determine which marks were made from which teeth. The upper 4 front teeth make rectangular marks. The central incisors are wider than lateral incisors.

Analysis of Bite Marks The next step is to determine which marks were made from which teeth. The upper and lower canines/cuspids tend to leave round or oval-shaped marks. The lower 4 front teeth make rectangular marks that are all similar in width.

Analysis of Bite Marks A gap between the individual bruises caused by the biting teeth are attributed to a missing, short, or damaged tooth. This can also be caused by: an object becoming trapped between the skin and tooth the skin could have moved to relieve stress there was variation in the biting mechanism itself.

Analysis of bite marks Other unique characteristics: Crooked teeth will create crooked impressions Chipped teeth will create jagged looking impressions of varying depth. Braces and partials also leave distinctive impressions.

Analysis of Bite Marks After the teeth have been identified, the bite mark pattern is measured and photographed with scale. The tooth mark size as well as distances between teeth are measured. Skin stretching may deform the pattern and these measurements may not matter. The skin of a deceased victim containing the bite will often be removed and preserved in formalin. A silicon cast of the bite mark is often made

Analysis of Bite Marks Once the data has been collected, the forensic dentist is asked to compare the evidence to the suspect’s teeth. For standards to compare, the forensic dentist may make castings of the suspect’s bite with dental stone. Notes on tooth damage are taken and checked against the unknown bite mark.

Analysis of Bite Marks The photographs of the unknown bite mark are reproduced at 1:1 scale and compared to the casting. Transparent overlays of the bite mark photos may be used to aid in comparison.

Analysis of Bite Marks First, the forensic dentist compares the size and shape of the arch in the evidence with the suspect. This can quickly eliminate a suspect with no additional analysis. Next, the prominent dental features, like tooth size and positioning, are compared. Last, secondary features like gaps or broken teeth, are compared. Both the prominent and secondary dental features have to match for the bite mark to be considered a match. Wax bite impressions may be used to capture the biting edges of teeth and are useful for comparison purposes.