Page 33 - Curriculum Visions Dynamic Book

The outer wall of a bone contains plates of calcite. Inside are rods of calcite that carry blood vessels. This is a much softer material, often referred to as bone marrow.
 Leg and spinal bones are thick because they carry the weight of the body. Nevertheless they are all hollow. This hollow shape, which
is similar to a cylinder, is extremely strong. If the bone were solid (like a rod), it would be more easily deformed. A cylinder is also
much lighter than a rod.
Teeth
Teeth are a very hard form of calcium carbonate (calcite) specially designed to resist
wear. The outer layer of a
tooth, called the enamel,
has cells arranged in long rods, making them extremely hard and strong.
However, this type of cell is not replaceable in the same way as bones inside the body, which is why teeth do not have the self- repairing properties of other bones and thus must be repaired by dentists.
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 A tooth that has decayed. The surface thickness of calcite crystals has reacted with
acids in the mouth produced by bacteria digesting sweet foods. This tooth belonged to an 18-year-old girl who had not been looking after her teeth properly.