Oral biochemistry

Why this matters

Everything the block has taught converges here. Saliva is supersaturated with the mineral your teeth are made of, which on thermodynamics alone should cement the dentition solid — and does not, because a handful of proteins hold it back. Understanding why is understanding caries, calculus, erosion and dry mouth as one problem rather than four. And the mouth turns out to run metabolism the body cannot, with consequences that reach well beyond it.

The big picture

Saliva is not a bath the teeth sit in. It is a thin, fast-moving film whose composition changes with flow, held permanently on the edge of precipitation by proteins that also coat every surface in the mouth. Demineralisation and remineralisation are one equilibrium read in two directions, and calculus is what happens when the restraint fails.

The 14 cards in this lesson

1. 01The duct takes back the salt and cannot follow it with water
2. 02Buffering follows flow
3. 03Not a bath — a film a tenth of a millimetre thick
4. 04Thermodynamics says precipitate. Two phosphoserines say wait.
5. 05Six proteins, and the honest caveat on each
6. 06The film chooses its own composition, in seconds
7. 07The protein that protects the tooth becomes the handle bacteria grab
8. 08Not a threshold — a ratio
9. 09A cave with a roof
10. 10Clinical alert — in the lesson
11. 11Calculus is not hydroxyapatite when it starts
12. 12Three ways to be wrong about oral pH
13. 13Clinical alert — in the lesson
14. 14The mouth runs chemistry your cells cannot

You have got it when

You are ready when you can explain why saliva does not spontaneously precipitate, say what actually determines whether enamel dissolves, and name two reactions your patient's mouth performs that their own cells cannot.