Six things people believe about teeth that are not quite right.

Most of what people believe about teeth was learned at home, years ago, from someone who learned it the same way. Much of it is sensible. Some of it quietly causes the problems it was meant to prevent. Here are six beliefs we hear most weeks, and what the evidence says.

1. “Brushing harder cleans better.”

It does not. Plaque is soft and comes away with light pressure; what hard brushing removes is enamel and gum. Over years it wears a notch at the gum line and pushes the gum back, which is why so many people who brush hard also have sensitive teeth. A soft brush, a gentle hand and two full minutes do the job.

2. “If my gums bleed, I should stop brushing there.”

The opposite. Gums bleed because plaque has been left at the gum line long enough to inflame them, and the inflamed spot is the spot that most needs cleaning. Brush it gently and thoroughly for a week or two and the bleeding usually stops. Bleeding that continues is worth a look: the bleeding gums explainer goes through it.

3. “Milk teeth don’t matter: they fall out anyway.”

They hold the space for the adult teeth, they are where chewing and speech are learned, and decay in them hurts just as much as in an adult tooth. An infected milk tooth can also affect the adult tooth forming underneath. They matter for exactly as long as they are in the mouth.

4. “No pain means no problem.”

Decay and gum disease are both painless for a long time. Decay reaches the nerve before it hurts; gum disease loosens teeth before it hurts. Most of what a check-up finds, the person had not noticed, which is the point of a check-up.

5. “Whitening damages enamel.”

Professional whitening, with the gel and concentrations used under supervision, does not damage enamel. Temporary sensitivity is common and settles. What does cause harm is strong gel bought online and used for weeks without an examination, and whitening a tooth that has decay or a dead nerve, which an examination would have found first.

6. “Sugar is the only thing that causes decay.”

Sugar matters, but so does how often it is eaten. Teeth can cope with a sweet thing at a mealtime; what they cannot cope with is sipping and snacking through the day, because the mouth never gets the hour it needs to recover between acid attacks. Frequency matters more than quantity, and that includes fruit juice, sports drinks and “healthy” snacks.

And one that is true

Flossing, or an interdental brush, which many people find easier, cleans the third of each tooth that a toothbrush cannot reach. Between the teeth is where most adult decay and gum disease starts.

If any of these sounds like a habit of yours, it is a ten-minute conversation at a check-up rather than a reason to worry.