At first glance, teeth look a lot like bones: Both are hard, white and rich in calcium. So why aren't teeth considered part of the skeletal system? Even though teeth and bones share a few basic similarities, they're actually quite different.
The major resemblance between teeth and bones is what they're made of: hard tissue composed of minerals, such as calcium, phosphorus, fluoride and magnesium. On a molecular level, these minerals form a solid crystal structure, which is what makes both teeth and bones so much harder than everything else in the body.
