week 7

Forensic Odontology Notes

1. Learning Objectives

  • By the end of this lesson, students should be able to:

    • Visually and verbally identify various teeth.

    • Have a working knowledge of dental eruption patterns and their use in juvenile age estimation.

    • Comment on occlusion variations.

    • Understand the forensic value of teeth.

    • Appreciate the use of and obstacles to bite mark analysis.

Recommended Readings

  • Işcan M. Y. & Steyn M. (2013). The Human Skeleton in Forensic Medicine (3rd ed.). CC Thomas Publ.

  • Papers 8.2. – 8.4. on myLMS.

2. Dentition

  • Students are expected to be able to visually identify tooth types, although not specifically upper/lower or left/right.

  • Images: Using Google Images for reference:

    • Adult: posterior view (upper and lower) and anterior view (upper and lower).

    • Deciduous teeth have a similar appearance to adult teeth but are much smaller with reduced root length. Key differences:

    • Absence of premolars and third molars.

  • Writing/Numbering Conventions for Teeth:

    • Specific teeth are annotated as follows: Upper left I2, lower right Pm1, etc.

2.1. Dental Eruption Patterns

  • Estimating age through dental eruption is highly accurate, especially in adolescents.

  • Various charts are available, including the London Atlas of Human Tooth Development and Eruption from AlQahtani et al. (2010).

2.2. Occlusal Patterns

  • The occlusal surfaces of teeth are areas that touch each other when biting down.

  • Types of Occlusion Patterns:

    • Orthognathism: Normal occlusion where the upper and lower jaws are properly aligned.

    • Retrognathism: Condition where the mandible is positioned further back than the maxilla.

    • Prognathism: Condition where the mandible protrudes beyond the maxilla.

3. Forensic Odontology

  • Forensic Odontology deals with various aspects of teeth and the mouth in a forensic context, such as:

    • Identification of unknown deceased persons.

    • Evidence against a perpetrator.

    • Techniques include using teeth for age, sex, and ancestry estimations, as well as bite mark analysis.

    • DNA extraction can be performed from teeth, which preserve DNA better than other skeletal sources due to their hard enamel layers and the pulp cavity.

3.1. Age Estimation

  • Dental Eruption Patterns: Effective in estimating age in juveniles.

  • Biological Age Estimation in Adults: Utilizes various techniques related to teeth.

    • Gustafson Method (1950): Adjusted by subsequent studies.

    • Based on scoring six characteristics:

      1. Attrition

      2. Secondary dentine

      3. Periodontosis

      4. Cementum

      5. Root resorption

      6. Root transparency

  • Calculation: Total score is plugged into a regression formula for age estimation.

  • Lamendin Technique (Lamendin et al., 1992): Focuses on single-rooted teeth, measuring root transparency (RT) and periodontosis (P).

    • Formula:
      A(age)=(0.18imesP)+(0.42imesRT)+25.53A (age) = (0.18 imes P) + (0.42 imes RT) + 25.53

    • Where:

      • $P = rac{ ext{periodontosis height} imes 100}{ ext{root height}}$

      • $RT = rac{ ext{root transparency} imes 100}{ ext{root height}}$

  • Mean error reported between actual and estimated age:

    • ± 10 years for working sample.

    • ± 8.4 years for control sample.

  • Cementum Annulation Method (TCA): Involves assessing incremental lines in cementum under a microscope to estimate age.

    • Technique is complex, requiring labor-intensive preparation and expensive equipment.

3.2. Sex Estimation

  • Measurements Used: Various tooth crown measurements for statistical analysis.

    • Discriminant function formulas categorize estimates by cutoff values for male and female.

    • Complicated by shape variation and small size; expert measurement advisable.

    • Common measurements include:

    • Mesiodistal (MD) Crown Diameter: Measurement between two parallel lines perpendicular to the mesiodistal axial plane of the tooth (left to right).

    • Buccolingual (BL) Crown Diameter: Greatest distance between the buccal/labial and lingual surfaces (front to back).

  • Discriminant Function Analyses: Population-specific with variable accuracy, ranging from 58% to 94%.

3.3. Ancestry Estimation

  • Estimation using dental features is problematic, often yielding lower accuracy than other skeletal elements.

  • Estimation involves:

    • Measurements of teeth and the inter-canine distance.

    • Notable morphological features such as:

    • Fourth molar presence.

    • Dental size.

    • Shovel-shaped incisors.

    • Additional cusps.

  • Caution advised due to few comprehensive South African studies on this subject.

3.4. Bite Mark Analysis

  • Considered an important aspect of forensic odontology.

  • Recent studies (e.g., Xu, 2021) indicate bite marks are admissible in South African courts, though evaluation must be careful and supported by corroborating evidence.

  • Bite imprints can be measured in size and compared to references to assist in suspect elimination.

    • DNA Collection: Saliva on bite marks aids in gathering DNA.

    • Unique dental patterns provide valuable identifiers; variations can personalize profiles.

  • Challenges include distortion of bite marks on varying materials due to applied biting force, leading to inaccuracies in dimensions and characteristics.

  • Use of bite marks as evidence remains controversial and not universally accepted in legal proceedings.

  • Further readings expand on techniques used in bite mark analysis.