One Tooth Suddenly Sensitive | What Does It Mean?

Every tooth has the same inner layer, dentine, which is packed with tiny tubes leading to the nerve. I call them a bundle of very tiny drinking straws, all pointing at the nerve. Normally they're sealed off. A tooth goes sensitive when something opens the ends of those straws on that tooth, and not on the others.

Think of your teeth as a row of coats hanging by the door. All but one are zipped up. One has a hole in it, and the wind finds the hole. The job is working out what made the hole, because that decides what fixes it.

Sometimes it's nothing sinister: the gum on that tooth has crept back a bit more than on its neighbours, or that tooth sits a touch further out and takes more of the toothbrush. But one tooth is also the classic sign of a local problem, which is why I take it a bit more seriously than sensitivity spread across your mouth. If it's several teeth, have a look at why are my teeth suddenly sensitive? instead.

Yes. Once decay gets through the enamel into the dentine, the tooth can start reacting to cold, heat and sweet things. Early on the pain comes when something sets it off and stops once it's gone, which is exactly how simple sensitivity behaves. That's why you can't tell the two apart from how it feels.

Clues that point towards decay:

• sweet things set it off, not just cold (more in why does chocolate make my tooth hurt?)
• you can see a brown or dark spot, or feel a rough edge or a hole with your tongue
• food keeps catching in one place

Old fillings can do the same thing. A filling that has chipped, worn or lost its seal at the edge can let the cold straight through to the dentine. If the tooth had a filling recently, that's a different, usually temporary story, covered in still sensitive to cold weeks after a filling. A new crown can be sensitive for a while too: see new crown extremely sensitive to hot or cold.

The good news with a small cavity is that it's usually a small fix, and the earlier I see it, the smaller it tends to be.

It could, and it's one of the causes I most want to rule out. Cracks are the master criminals of the tooth world: hard to spot, rarely visible on an X-ray, and they come and go. A cracked tooth is often very sensitive to cold, and gives a sharp pain when you bite on something, sometimes worse just as you let go. There's more on that last one in tooth hurts when you release your bite.

Teeth with big old fillings, and people who clench or grind, are more at risk. A crack won't heal by itself, so if your sensitive tooth also twinges on biting, please don't just switch toothpastes and wait.

I'll keep this bit straight. The most useful thing you can notice is what the pain does after the cold has gone.

• Sharp, and gone within a second or two: that's how sensitivity, early decay or a mildly irritated nerve behaves. It needs a check-up, not a panic.
• Lingers, turns into a dull throb, or starts by itself: that suggests the nerve inside the tooth is inflamed. It can keep you awake at night, and painkillers may only take the edge off. That needs seeing promptly, because toothpaste won't reach it.

If hot drinks are now the problem and cold water eases it, that's also worth a call today. See why does hot tea make my tooth hurt?

In the meantime:

• Use a toothpaste made for sensitive teeth, spit rather than rinse, and at night rub a little onto that tooth with a fingertip. My guide to stopping sensitive teeth pain fast has the details.
• Use a soft brush and be gentle around that tooth, but don't stop cleaning it.
• Avoid very cold, very hot, sweet and acidic things on that side for now.

Then book in. At the appointment I'll look closely at the tooth and the gum around it, check any fillings, test it with cold, check whether biting on it hurts, and take an X-ray if I need to look for decay. If it's simple exposed dentine, I can often seal it with fluoride varnish, a protective coating or a small tooth-coloured filling. If it's decay or a crack, finding it early usually means a simpler repair.

Call us today if:

• the pain lingers or throbs after the cold has gone
• it wakes you at night, or painkillers aren't helping
• it hurts to bite on, or a piece of tooth or filling has broken off
• there's swelling of your gum or face, a bad taste, or a temperature

The NHS advises seeing a dentist if toothache lasts more than two days.

Call 999 or go to A&E, not a dentist, if:

• it's hard to breathe, swallow or speak
• swelling is spreading towards your eye or into your neck
• your eye is swollen or painful, or your eyesight suddenly changes
• you can't open your mouth properly because of swelling

If you're near Harlow or Enfield, I'd much rather take a look at that one tooth than have you keep poking it to see if it still hurts. Ring your nearest Minti practice and tell us which tooth and what sets it off. If it has turned into proper toothache, say it's urgent and we'll do our best to see you the same day. Anywhere else, or out of hours, call NHS 111.

This article is general information, not a diagnosis. Tooth pain needs examining in person to find the cause.