This article is general information for our patients rather than a diagnosis. If something in your mouth hurts, changes, or worries you, have it examined.
Most people who grind find out from the damage, not the noise: a jaw that aches at breakfast, a tooth that zings on cold, a filling that chips for no reason. I see it most weeks here in Barrie, and it’s manageable once you know what to look for.
One thing up front, because it shapes the rest. None of the signs here is proof on its own — worn teeth, a sore jaw, a tooth that twinges each point somewhere, but a single clue can just as easily point the wrong way. What settles it is reading the whole picture together — your history, an exam, how a tooth responds to specific tests, and an X-ray, all at once. That reading happens in the chair, not off a symptom list.
The signs I look for
Grinding and clenching — the jaw muscles squeezing and sliding teeth together when they shouldn’t — is common enough to have its own name: bruxism. Roughly 1 in 10 adults grind in their sleep, and because it happens while you’re out, you may never catch yourself. You notice the trail instead:
- Worn, flat, or shortened teeth, the biting edges sanded down and front teeth losing their points — surface lost to teeth rubbing on teeth (attrition).
- A tired or aching jaw, often worst in the morning — the chewing muscles have effectively been at the gym all night.
- A scalloped, wavy edge to the tongue, from pressing it against the teeth.
- Fillings or edges that keep chipping with no decay to explain it.
- Sensitivity to cold or sweet, as wear exposes the softer layer beneath the enamel.
- Someone tells you — a partner often hears it long before you feel a thing.
No one of these confirms grinding; a few together is a stronger pattern. At a check-up I weigh them against what I can see directly — matching wear on upper and lower teeth, tender chewing muscles, a larger-than-usual muscle at the angle of the jaw. Even then it’s the combination I’m reading, not any single box ticked.
Why it happens
The thinking here has shifted. Dentists once blamed an uneven bite and tried to “balance” teeth to stop grinding; we now know it starts in the brain, not the bite, and travels with stress, low mood, and disturbed sleep — which is why a hard stretch at work or a run of bad nights can flare it. A bad bite is rarely the cause. In some people it’s tied to something else, such as sleep apnoea (breathing pauses in sleep), acid reflux, or certain antidepressants — one reason I ask about your general health, not just your teeth.
It splits in two, and the two are handled differently. Awake (daytime) clenching happens while you concentrate or feel tense, and you can learn to catch and stop it. Sleep grinding is out of your control, so the goal shifts from breaking the habit to protecting the teeth.
What it does over time
Grinding is a slow, heavy load applied night after night, and the damage tends to stack up in a fairly set order:
- Enamel wears down. The hard shell flattens and teeth shorten; over years this can change how the teeth meet and even how the face looks at rest.
- The softer layer is exposed. Beneath the enamel sits a softer, more sensitive layer (dentine); once uncovered, cold and sweet can set off short, sharp twinges — a different cause from why a tooth can stay sensitive after a filling, though it can feel much the same.
- Fillings and edges break, where the force concentrates.
- Cracks start in the tooth itself — the cracked-tooth pain I come back to below.
- The jaw muscles and joint get overworked, bringing soreness, tightness, and sometimes clicking.
For the sensitivity, a toothpaste made for sensitive teeth (some calm the nerve, others plug the tiny exposed channels) and a fluoride varnish I paint on in the chair both help — but they quiet the symptom without undoing the wear. Protecting the teeth from further grinding is the real job.
Is a custom night guard worth it over a drugstore one?
If you grind in your sleep, a guard is the main protection — you can’t will yourself to stop overnight — and a custom one fits better and lasts longer. A night guard is a plastic shield worn over the teeth at night, so the plastic takes the wear in place of your enamel. There are two routes.
| What matters | Drugstore “boil-and-bite” guard | Custom guard (made from a mould of your teeth) |
|---|---|---|
| Fit | One generic size you soften in hot water and bite into; fit is approximate | Built on a model of your own teeth, so it matches your bite |
| Comfort and bulk | Tends to be thick and bulky; many people spit it out in their sleep | Thinner and more stable, so it’s easier to keep in all night |
| Material | Softer, thinner plastic that wears through faster | Hard acrylic plastic designed to take the load |
| How long it lasts | Weeks to months for a heavy grinder | Typically 3–5 years, longer for light grinders |
| Who it suits | Trying things out, very light grinding, short-term use | Ongoing grinding, protecting fillings, crowns, or worn teeth |
| Trade-offs | Inexpensive and instant, but limited protection and lifespan | Two short visits about a week apart (taking the mould, then fitting) |
For daytime clenching, awareness does more than a guard. A line I use: your teeth should only touch when you’re chewing. Catching yourself and parting them through the day genuinely lightens the load; stubborn cases have further options, such as muscle-relaxing injections.
One honest caution: a guard isn’t right for everyone before we’ve looked. If the wear is coming from acid — reflux, frequent acidic drinks, an eating disorder — rather than grinding, a guard worn at night can trap that acid against the teeth. Telling grinding wear from acid wear is exactly the kind of call I’d rather make from an exam than a symptom, so I check the cause first.
What a cracked tooth feels like
A sharp, hard-to-place pain as you bite and let go, often with a zing to cold, from a crack too fine to see easily.
The classic story: you bite on something unremarkable and feel a quick, sharp pain as you release, not as you press, and it comes and goes. It hurts on release because biting opens the crack a fraction and lets fluid shift against the nerve; letting go snaps it shut and the nerve fires.
Grinders are more prone to it, because years of heavy force slowly weaken a tooth, and the back teeth (molars and premolars) tend to be affected most, since they take the heaviest chewing. Cracks run from harmless to beyond saving, and the type points to what happens next:
| Crack type | What it is | Can the tooth be saved? |
|---|---|---|
| Craze line | Fine surface lines in the enamel only | Yes — very common, rarely troublesome, usually just monitored |
| Fractured cusp | A corner of the tooth breaks off, often around a filling | Usually — most are straightforward to repair |
| Cracked tooth | A crack running deeper toward the centre; the one behind bite-and-release pain | Often — how deep it runs decides |
| Split tooth | The crack has separated the tooth into segments | Rarely — the outlook for keeping it is poor |
| Vertical root fracture | A crack starting down in the root | Rarely — these usually can’t be kept |
A crack stained brown is a genuine warning sign: the stain tells me it’s open enough for saliva and bacteria to seep in, so it’s likely been there a while and runs deeper than the surface.
Why we can’t just find it on an X-ray
An X-ray is a flat shadow picture, so it catches a crack only when the beam happens to travel right along the paper-thin gap; most cracks lie across the beam, cast no shadow, and stay invisible. It’s like a clean pane of glass — face-on you see straight through it, and only spot it when its edge lines up with your eye. X-rays still earn their place ruling other problems out, but to find the crack itself I lean on a few simple tests:
- A bite test — biting on a small plastic tip placed one point at a time; pain on release points to a crack there.
- A bright light through the tooth; the crack blocks it, so one part lights up and the rest stays dark at the crack line.
- Dye painted on, which can seep in and show the line.
- A close look under magnification, feeling for a catch along the line.
No single one of these settles it either. A crack can hide at first and only show itself over time, so now and then the right call is to watch it, photograph it, and reassess rather than pretend to see something we can’t. The answer comes from these tests read alongside your history and the X-ray, together — the part that has to happen in the chair.
How we fix a cracked tooth
How deep the crack runs decides where a tooth lands on the ladder — along with whether the nerve is caught up in it. Many teeth are saved with a crown, some need a root canal first, and a few can’t be kept:
- Smooth or repair a craze line or small chip. For surface lines and small breaks, often nothing or a simple repair is enough.
- Cover the tooth to hold it together. Once a crack runs into a tooth, the priority is to stop it flexing open. A crown (a cap over the whole tooth), or a smaller onlay over just the chewing surface, wraps it so the crack can’t spread. This is the workhorse repair for a cracked back tooth — and why we so often suggest a crown rather than just a filling.
- Root canal, then a crown. If the crack has reached the nerve and the tooth aches constantly or the nerve has died, the inside is cleaned out and sealed (a root canal — here’s what that actually involves), then crowned. In a long study of more than 1,200 root-canal-treated teeth, the back teeth crowned afterward survived about 94% of the time, against roughly 56% for those left with only a filling.
- Removal. A split tooth or a vertical root fracture generally can’t be saved; the path is taking it out, then a plan to replace it.
With a deep crack, we sometimes can’t be sure how far it runs until we’re treating it. We start with the tooth-saving option whenever that’s reasonable, and only move down the ladder if it proves deeper than hoped. A crowned cracked tooth often does well for years — but no repair un-cracks a tooth, so protecting it from further heavy grinding still matters.
When grinding and jaw pain travel together
Grinding loads the muscles and joint that move the jaw, not just the teeth, so morning soreness, tightness opening wide, temple headaches, or clicking can turn up alongside worn teeth. A guard that protects the teeth also rests those muscles, by holding the teeth slightly apart so they can’t clench down hard. If jaw pain is your main complaint, our companion piece on how grinding ties into jaw pain and TMJ — the TMJ is the joint just in front of your ear that the jaw hinges on — goes further; raise it at your visit so we can check it properly.
When to come in
If your jaw aches in the morning, your teeth look shorter than they did, or biting gives a sharp twinge on release, book an exam.
Until we can see you, chew on the other side, steer clear of very hot, cold, or hard foods, and use your usual over-the-counter pain relief to take the edge off — your pharmacist can point you to what’s safe for you.
These are far easier to manage early, before a worn tooth becomes a cracked one. We can check the teeth and chewing muscles, work out whether grinding, acid, or a crack is behind it — reading the signs, tests, and X-ray together — and talk through whether a custom night guard or a repair makes sense. To arrange a visit, call our Barrie office at 705-721-9229 or book an exam with us. This article is part of our Adult Patient Information library.
