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Scrubbing, and rebuilding

What Is Toothpaste Actually Doing?

Most of the cleaning is the brush. The paste is mild grit, a foaming agent, and one ingredient that repairs enamel.

Mild grit that scrubsfilm offDetergent to spread andfoamFlavour, so it feelscleanFluoride, whichrebuilds enamel
Only one of these actually repairs anything.

  1. Step 1 of 5

    The problem is acid, not sugar.

    1 Sugar is lefton the teeth2 Bacteria eat itand make acid3 The aciddissolves theenamel

    Bacteria living on your teeth eat leftover sugar and give off acid. That acid dissolves minerals out of the enamel, and if it happens often enough a hole is the result.

  2. Step 2 of 5

    The grit is deliberately mild.

    The sticky filmsoft — must comeoffToothpaste gritharder than thefilmTooth enamelharder still —stays put

    Toothpaste contains fine particles to scrub the sticky film off. They have to be harder than the film and softer than enamel, which is a narrow window — and why scouring powder would ruin your teeth.

  3. Step 3 of 5

    The foam is not doing the cleaning.

    The brush Does nearly all theactual cleaningThe foam Spreads the paste andfeels right

    A detergent makes the paste spread and foam. It helps lift grease and it makes the whole thing feel like it is working, but the scrubbing is the brush, not the bubbles.

  4. Step 4 of 5

    Fluoride rebuilds the surface.

    Acid dissolves minerals out Fluoridejoins therepair A tougher mineral forms The cyclekeeps goingall day

    Enamel is constantly losing and regaining minerals. Fluoride joins in the rebuilding and makes a slightly tougher mineral than the original — one that acid finds harder to dissolve.

  5. Step 5 of 5

    Rinsing washes the useful part away.

    Spit only A repairing film staysbehindRinse well Most of the fluoride iswashed off

    The fluoride works by staying on the teeth. Spitting and not rinsing leaves a thin film behind to keep repairing; a big rinse with water sends most of it down the drain.

    Toothpaste is barely two centuries old. Before it, people scrubbed with things like crushed shell, chalk, charcoal and salt.

The short version

Toothpaste is mild grit, detergent and flavour — plus fluoride, which is the part that actually rebuilds enamel.

Try it yourself

Rub toothpaste between your fingers. That faint grittiness is the abrasive, and it has to be gentler than your enamel.

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