The question of whether human teeth float in water often sparks curiosity. Unlike many lighter organic materials, teeth possess characteristics that dictate their behavior when submerged, revealing fundamental principles of density and buoyancy.
The Simple Answer: Do Teeth Float?
When placed in water, a healthy human tooth will consistently sink. Its composition makes it denser than water, leading it to descend rather than float on the surface.
Why Teeth Sink: Understanding Tooth Density
Human teeth are among the densest and hardest biological tissues, primarily due to their highly mineralized structure. Enamel, the outer layer, is the hardest substance, composed of about 96% inorganic material, mainly hydroxyapatite. Beneath the enamel lies dentin, which makes up the bulk of the tooth and is approximately 70% mineral. Cementum, covering the tooth root, also contains significant mineral content (around 65%).
While freshwater has a density of approximately 1.0 gram per cubic centimeter (g/cm³), human enamel density ranges from 2.6 to 3.0 g/cm³, and dentin falls between 1.79 to 2.12 g/cm³. This difference in density causes a tooth to displace less water than its own weight, leading it to sink in accordance with Archimedes’ principle.
What Can Affect a Tooth’s Buoyancy?
While intact human teeth consistently sink, certain alterations or environmental factors could influence their buoyancy, though rarely enough to make them float. Extensive tooth decay can reduce a tooth’s overall density by creating voids or replacing dense tissue with less dense, decayed material. Similarly, large, hollowed-out pulp chambers, especially if empty, could introduce air pockets, slightly decreasing the tooth’s average density.
Dental fillings, depending on their material, might also alter a tooth’s density; amalgam is quite dense, while modern resin composites are less so. However, these factors typically cause only minor changes to the tooth’s overall density and are usually insufficient to overcome the natural tendency to sink. Water salinity also plays a role; saltwater is denser than freshwater, averaging about 1.025 to 1.03 g/cm³. This increased density provides slightly more buoyant force, but it is still not enough to make a tooth buoyant.
Beyond the Bathtub: Real-World Insights
The density and durability of teeth have significant implications in various scientific fields. In forensic science, their robust nature makes them invaluable for identifying human remains, particularly when other tissues have decomposed or been damaged. Teeth withstand extreme conditions, providing a protected source of DNA and unique dental records for identification, even after extended periods in aquatic environments.
Archaeologists also rely on dental remains to reconstruct past human lives and environments. Teeth preserve well in various burial conditions, sometimes being the only surviving human remains. Their resistance to decomposition allows scientists to study ancient diets through isotopic analysis of enamel and dentin, and identify cultural practices through chemical analysis of dental calculus. The consistent sinking property of teeth underscores their stable, dense composition, critical for their long-term preservation and utility as a biological record.