Eli5: why is when a bone shatters it can rebuild itself but when a tooth gets a hole in it it just keeps eating away at it
In: Biology
ONE I CAN ANSWER!!!!!
TLDR: It does!….. sorta.
So I’m assuming when you say “gets a hole” you mean a cavity. And when you say a cavity, I’m assuming the normal person term and not the dental way of thinking. A normal person thinks of a cavity as a hold in a tooth while dentistry sees it as a de-calcification/soft spot or a de-calcification/soft spot that destroyed structure (non-cavitated vs cavitated).
Now if we are a soft spot or de-calcification but the tooth looks normal, then improved care can REVERSE that cavity. Lay off the sweets, brush better, maybe a mouth rinse and BINGO no more cavity. Ever present calcium in the mouth can move into the crystal matrix of the tooth to make it hard again. This doesn’t always happen but it can extremely often.
Now with a soft spot or de-calcification that makes the tooth look different, that’s a hole or what you would call in normal speak a cavity. You have lost crystal structure and there are no more cells to rebuild it. But we aren’t done yet. If you improve your care and brush and lay off the sweets and maybe a mouth rinse then you can stop that cavity from getting any bigger. It’s an infection of the tooth structure and you can stop it essentially by starving the bacteria and hardening the tooth. Most times, the tooth will take on a black appearance but will be incredibly hard. So hard in fact, that the possibility of cavity forming on that structure again is lower than a cavity forming on any other normal tooth structure.
Well now that we are missing enamel or the structure that you think of when you think of teeth, the dentin layer or the layer under the enamel will respond to the trauma. It acts as a separating layer between the nerves/blood vessels of the tooth and the outer enamel structure. In response to this cavity and loss of tooth, the dentin will actually grow inward filling the nerve space more so. At the end of this process you will have a smaller enamel layer, a larger dentin layer, and a smaller nerve space.
So yes, the tooth can respond to a cavity and yes it can sort of rebuild itself but not completely due to lack of living cells in the enamel. This is why the American Dental Association recommends NOT drilling teeth unless there is a “hole” and other dental groups (UK, Europe, Japan) recommend not drilling teeth even if there is a hole. Most small cavities can be reversed with a glass ionomer or a sealant on the tooth and allowing the tooth to heal itself.
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