Toothpaste (Oral Care)

Toothpaste is a delivery vehicle for fluoride. Everything else in the tube exists to make that delivery pleasant enough to repeat twice a day. The paste is a mild abrasive suspended in water and a humectant that stops it drying out, thickened with a gum, foamed by a detergent and covered in flavor.

Fluoride shows up as sodium fluoride, sodium monofluorophosphate or stannous fluoride, and ordinary adult paste carries 1,000 to 1,500 parts per million of it. Read that number instead of the claim, since a paste with no printed figure cannot be compared with anything. What fluoride does is drive mineral back into enamel that acid has softened, leaving a surface that dissolves less readily next time. Stannous fluoride does that and also slows bacteria, at the cost of a faint surface stain on some people. Abrasive level sits on a lab scale called relative dentin abrasivity, where 250 is the accepted ceiling and most everyday pastes fall under 100.

Sensitivity pastes add 5 percent potassium nitrate, which quiets the nerve, or lean on stannous fluoride to plug the microscopic tubes running through exposed root. Either route needs two to four weeks of twice daily use, so judging one after three days tells you nothing. Whitening pastes raise the abrasive and sometimes add a blue pigment that makes teeth look less yellow while it sits there. Neither trick changes tooth color the way the peroxide in Whitening Products does. Charcoal pastes are usually abrasive and often carry no fluoride at all, trading the one proven ingredient for a color.

Adults need a pea sized amount, not the ribbon along a whole head shown on the box. Children under three take a smear the size of a rice grain and three to six year olds a pea, with an adult present so it is spat out. Sodium lauryl sulfate, the detergent behind the foam, sets off mouth ulcers in some people, and a foam free paste settles that quickly. Frequent decay, dry mouth from medication or a dentist's advice can put you on a 5,000 ppm paste. This is a clinical decision rather than a shopping one.

Spit and skip the rinse. A 1,450 ppm paste leaves a concentrated film on the teeth, and a mouthful of water sends most of it down the sink, so dropping that habit is the cheapest improvement available. Cap the tube and wipe the nozzle so the thread does not seal with dried paste. A tube cooked in a car separates and loses texture, and one past its printed date has lost fluoride activity along with it.