When a person dies, most body tissues decompose quickly, but teeth exhibit remarkable resilience. Their unique strength and composition allow them to remain intact long after other body parts have deteriorated, withstanding environmental degradation.
Initial Post-Mortem Alterations
Immediately following death, the oral cavity undergoes significant changes. Saliva production ceases, eliminating its protective and cleansing functions, including acid neutralization and enamel remineralization. The absence of blood circulation means no new nutrients or immune cells are delivered. Soft tissues surrounding the teeth, such as gums, tongue, and cheeks, begin to decompose due to bacteria and enzymes. This decomposition can cause gums to recede and teeth to loosen as supporting periodontal tissues deteriorate, exposing teeth to external conditions.
Exceptional Durability
The extraordinary persistence of teeth after death stems from their unique composition. Enamel, the outermost layer of the tooth crown, is the most mineralized tissue in the human body, consisting of approximately 96% inorganic material, making it exceptionally hard and resistant to physical degradation. Beneath enamel lies dentin, the tooth’s bulk, which is also highly mineralized (70% inorganic material) and provides hardness and elasticity, supporting the more brittle enamel. The dense, inorganic structure of both enamel and dentin contrasts sharply with most other body tissues, which are largely organic and water-based and susceptible to rapid decomposition. This structural integrity allows teeth to resist decay for extended periods, even centuries.
External Factors Influencing Preservation
Numerous external environmental factors influence the long-term preservation or degradation of teeth post-mortem. Soil composition, including pH level, plays a role; acidic soils accelerate demineralization, while alkaline conditions offer better preservation. Moisture levels are also important, as very dry or waterlogged environments inhibit microbial activity, slowing decomposition. Temperature extremes affect preservation; high temperatures can cause teeth to crack, change color, and become fragile, though they often remain identifiable. Conversely, consistently cold temperatures significantly slow all decomposition processes. Exposure to scavengers or microorganisms can lead to physical damage, but the dense structure of teeth offers considerable resistance to biological breakdown.
Role in Identification
The remarkable durability of teeth makes them invaluable in forensic identification, especially when other methods like fingerprints or DNA profiling are compromised or unavailable. Forensic odontologists utilize dental records to identify deceased individuals. These records, including X-rays, dental charts detailing fillings, crowns, extractions, and unique morphological features like tooth shape, size, and alignment, provide a distinct “dental signature” unique to each person, much like fingerprints. By comparing ante-mortem (before death) dental records with post-mortem (after death) findings, odontologists can establish a positive identification. This process is useful in cases of mass disasters, fires, or advanced decomposition where visual identification is impossible, and teeth can also offer clues about age, habits, and ancestry even without prior dental records.