Why Does My Tooth Hurt When I Clench but Not When I Chew? A Dentist Explains

Here’s a fact that surprises nearly everyone I tell it to. Your teeth are only supposed to touch each other for less than twenty minutes a day, in total, mostly in brief taps while you chew and swallow. The rest of the time they’re meant to be slightly apart, on a break. Teeth are part-time workers.

Chewing is a series of quick taps, each lasting a fraction of a second, mostly with food in between. Clenching is a different animal. It’s tooth directly on tooth, held for anything from a second to half a minute at a time, with nothing in between to take the edge off. It’s the difference between tapping a drawing pin and standing on it.

Each tooth sits in a thin ligament full of pressure sensors. Brief taps are what it’s built for. Long, hard squeezes are more than it was designed to handle, and an overworked ligament gets inflamed and tender. So when you clench, you press on the sore spot good and proper, and when you chew, you mostly don’t. There’s also a geometry point, and this is my own way of explaining it: when you clench, your teeth lock into their fully-closed position, so if one tooth meets a fraction early, that’s the moment it takes the hit.

It’s the first thing I’d think of. Dentists call clenching and grinding bruxism, and the awkward thing is that most people who do it have no idea. The night-time version happens while you’re asleep, so the first you know of it is the evidence. It’s like being handed the bill for a party you don’t remember.

The NHS lists the signs as a painful jaw, headaches, earache, disturbed sleep, and teeth that are worn, broken or sensitive. Sore ligaments that make teeth tender to bite on are part of the same picture. Timing is a good clue, and it’s one of the first questions I ask. If it’s worst when you wake up and eases through the morning, you’re probably doing it in your sleep. If it builds through the day and peaks around the time you’re sat in traffic or staring at a spreadsheet, you’re likely clenching while awake.

The NHS says stress and anxiety are the most common cause, with sleep problems, some medicines, smoking, alcohol and caffeine also on the list. Your jaw, it turns out, is where a lot of people store their inbox. None of this is a character flaw. It’s just a habit your jaw has picked up without consulting you.

One thing to be aware of: sometimes the ache on clenching isn’t the tooth at all but the chewing muscles, which can feel remarkably like toothache. If the soreness is more in front of your ear, at your temples or along the jaw, and comes with clicking or a tired jaw, the muscles and joint are my prime suspects.

It can, and I’ll be honest about where it sits on my list. A cracked tooth classically hurts when you chew: a sharp, sudden pain on biting something, often on something grainy like seeded bread, and famously a second jolt just as you let go. It often dislikes the cold too. So if chewing is completely comfortable, a crack is less likely than a sore ligament.

Less likely isn’t ruled out, though. Pain from a crack tends to get worse the harder you bite, and a full clench is about the hardest bite you’ve got. Cracks are also erratic, which is what makes them so annoying for everyone, me included. The pain comes and goes, and they rarely show up on an X-ray.

The people most at risk are, you guessed it, clenchers and grinders, particularly in teeth with big old fillings. So the two causes aren’t rivals. One can lead to the other. A crack won’t heal the way a bone does, which is the main reason I’d rather check a suspicious tooth early. What’s needed, if anything, depends entirely on where the crack is and how deep, and I can’t judge that from a description.

Absolutely, and if your pain started within days of a new filling or crown, this goes straight to the top of my list. When you’re numb and lying back with your mouth open, it’s hard to bite normally, so now and then a filling ends up a whisker proud. I’ve done it myself, and every honest dentist has. And I do mean a whisker. A high spot of less than a millimetre is enough for that one tooth to meet first and take the force meant for the whole row.

It fits your symptom neatly. With food between your teeth, the extra height can go unnoticed. When you close fully on nothing, that tooth arrives at the party early and gets squashed. The ligament gets sore, and the tooth can end up tender to bite on or to tap.

The good news is that this is one of the quickest fixes in dentistry. It’s usually a short visit to ease the high spot, and the soreness generally settles once the tooth stops being hit first. Don’t wait for it to “wear in”, and don’t feel awkward about going back. No dentist minds. I’d far rather adjust it than have you put up with it.

First I’ll ask questions that sound nosy but aren’t. When did it start? Any recent dental work? Worse in the morning or the evening? Does your jaw click? How’s work? Has anyone complained about noises in the night?

Then the detective work:

• Marking paper. Basically fancy carbon paper. You bite and slide on it and it leaves coloured dots where your teeth meet. A tooth that’s hitting early grasses itself up with a big heavy mark.
• Signs of wear. Flattened tips, polished shiny patches, little chips, and fillings that keep breaking all tell me the story of a grinder, even one who swears they aren’t.
• A gentle tap and a wobble test. An overloaded tooth is often tender to tap and can be a touch looser than its neighbours.
• A bite test. Biting on a small plastic tool, one corner of the tooth at a time, to hunt for a crack. Sometimes a bright light shone through the tooth helps too.
• A cold test and an X-ray. To make sure the nerve inside the tooth is healthy and nothing is brewing at the root.
• Your jaw muscles and joints. Pressing on the chewing muscles to see if the pain is coming from there instead.

If it’s mild, only there when you deliberately clench, and you can link it to a stressful few weeks, it’s reasonable to give it a little time. The helpful bit is that soreness from overloading is usually reversible once the overload stops. Two things help in the meantime. Stop testing it, because every test clench is another squeeze on a sore ligament. And try the rule I give everyone: lips together, teeth apart. If you catch your teeth touching while you’re reading this, that’s the habit. Let the jaw drop a few millimetres and rest.

Book an ordinary appointment if it’s still there after a week or two, if it began after dental work, if you’re waking with a sore jaw or headaches, or if you’ve noticed chips or wear. For night grinding, I may suggest a mouth guard or splint to wear in bed. It won’t stop you grinding, but it protects your teeth from it. It won’t do much for daytime clenching, since it lives in your bedside drawer, so that part is about catching the habit. If stress is driving it, the NHS suggests your GP can help with that side of things.

Call sooner, today if you can, if:

• the tooth has started hurting when you chew as well, or gives a sharp pain when you release a bite
• it throbs by itself, lingers after hot or cold, or keeps you awake
• a piece of tooth or filling has broken off
• there’s swelling of the gum or face, a bad taste, or a temperature

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

• you’re finding it hard to breathe, swallow or speak
• swelling is spreading towards your eye or down into your neck
• you can’t open your mouth properly because of the swelling

If you’re near Harlow or Enfield, I’d much rather have a proper look for the tooth that’s hitting first than have you clench-testing it for another month. Ring your nearest Minti practice and tell us what you’ve noticed. 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 and jaw pain needs examining in person to find the cause.