Shark teeth are biological tools, finely tuned for their role in predation. Their effectiveness stems from a unique composition and structure, which allows them to withstand the intense forces of biting and tearing. Understanding what these teeth are made of and how they are built provides insight into their durability.
The Core Components
Shark teeth are primarily composed of a highly mineralized tissue called fluorapatite. This mineral is a calcium phosphate that incorporates fluoride, which distinguishes it from the hydroxyapatite that forms the enamel of human teeth. The presence of fluoride in fluorapatite contributes to its increased mechanical strength and stability, making it exceptionally resistant to dissolution and wear.
While the outer layer is fluorapatite, the inner part of a shark tooth consists of dentin, a softer, bone-like tissue that provides support. Similar to human teeth, shark teeth also contain a pulp cavity, which houses nerves and blood vessels.
Specialized Structure for Strength
The outer layer of a shark tooth, often referred to as “enameloid,” is not true enamel like that found in mammals. Enameloid is a unique hard tissue developed differently from mammalian enamel, though it serves a similar function. It is formed by both odontoblasts and dental epithelial cells, unlike enamel which is solely produced by dental epithelial cells.
This enameloid possesses a highly crystalline structure, with nanoscale fluorapatite crystallites arranged in intricate patterns. These crystallites are densely packed. This precise, hierarchical arrangement of mineral crystals, along with a small amount of organic matrix, provides the enameloid with its exceptional hardness and resistance to mechanical stress and acid.
The Continuous Replacement System
Sharks possess a unique and continuous tooth replacement system throughout their lives. Unlike humans who have only two sets of teeth, sharks have multiple rows of teeth that continuously develop and move forward. This process ensures that a shark always has a sharp, functional set of teeth, as older or damaged teeth are constantly replaced.
This “dental conveyor belt” mechanism allows sharks to replace teeth rapidly. New teeth form behind the active ones and gradually rotate into position as the front teeth wear down or fall out. The durability offered by the fluorapatite composition of their teeth makes this continuous renewal an efficient adaptation for their predatory lifestyle.