By Joanna M. | Director of Telehealth Clinical Operations | Fact-Checked for Clinical Accuracy
Waking up to find a hole in your night guard — or a clean split down the middle — is frustrating and a little alarming. You bought the guard to protect your teeth, and now the guard itself is the thing falling apart. The good news: biting through a night guard is rarely a sign that night guards "don't work for you." It's almost always a mismatch between the guard's thickness and material and how hard you actually grind.
This guide breaks down why night guards crack and wear through, which thickness and material heavy grinders actually need, and how to get a durable custom night guard in Canada without paying dental-clinic prices.
Most over-the-counter and entry-level guards are designed for light to moderate clenching. Heavy grinders — people whose partners can hear the grinding from across the room, or who already have visible tooth wear — generate enough force to chew through soft material in a matter of months. If your guard has a worn groove or a hole where your lower teeth sit, your grinding has simply outpaced what that guard was made to handle.
Night guards are not one-size-fits-all. A soft, flexible guard feels comfortable but sacrifices durability; a hard acrylic guard is rigid and lasts longer under heavy force but takes more getting used to. Many people who bite through their guard chose the softest option for comfort — and for a heavy grinder, that's the wrong trade-off. For related context on how material choice affects protection, see our hard vs soft night guard Canada guide.
Boil-and-bite guards from a drugstore are made from thermoplastic that softens in hot water — which is exactly why they fit, and exactly why they fail. Under sustained nightly force, that same material deforms, thins out, and tears. If you've been cycling through cheap guards every few weeks, that's the design, not your fault. A custom-fabricated guard from a dental lab uses harder, lab-grade materials engineered for repeated nightly wear.
Even the right guard wears out. Hot water, leaving it in a hot car, or cleaning with abrasive toothpaste all degrade the material faster. A guard that's been warped by heat won't seat evenly, which concentrates force on one spot and speeds up cracking. Knowing when to replace your night guard is part of not ending up biting through it.
It's tempting to keep wearing a guard with a small crack "just until the replacement arrives." Don't. A cracked guard has lost its structural integrity, which means:
A hairline crack becomes a full split quickly under grinding force. Once you see a crack or a worn-through spot, retire the guard that day and order a replacement.
Thickness is the single biggest factor in whether a guard survives heavy grinding. Most custom guards fall between 1mm and 3mm, and the right choice tracks directly with how hard you grind:
| Thickness | Typical material | Best for | Durability under heavy grinding |
|---|---|---|---|
| 1mm | Soft / thin thermoplastic | Light clenching, daytime use | Low — bites through fast |
| 1.5mm | Soft EVA or hard acrylic | Light to moderate grinding | Low–moderate |
| 2mm | Hybrid (hard outer, soft inner) | Moderate grinding — most popular | Moderate |
| 3mm | Hard acrylic / extra-durable | Heavy to severe grinding | High — built to take force |
The pattern is simple: the harder and thicker the material, the more grinding force it absorbs before failing. If you've bitten through a 1mm or soft guard, step up to a 2mm hybrid or a 3mm hard guard. Going thicker than 3mm usually isn't necessary and can feel bulky enough to strain your jaw.
A custom night guard through a Canadian dental clinic typically runs several hundred dollars and requires in-office appointments. An online custom provider cuts out the clinic overhead: NewSmile's custom night guard is from $139 CAD on subscription / $199 CAD one-time, fabricated from a home impression kit and shipped to your door. For heavy grinders who go through guards faster, the subscription lowers the per-guard cost and keeps a fresh one coming before the old one wears through.
If bruxism has also started shifting your teeth and you need to hold your alignment, a custom clear retainer in Canada can run alongside your night guard — they solve different problems, and some grinders use both.
Stop replacing guards that bite through.
Get a custom night guard matched to your grinding level — fabricated from a home impression kit, shipped in Canada, from $139 CAD on subscription.
Yes — a custom guard can still crack or wear through if it's too thin or too soft for your bite force. Heavy grinders who choose a soft 1mm guard can bite through it in months. Choosing a harder or thicker material (2–3mm) is what prevents it.
Heavy to severe grinders generally do best with a 3mm hard or extra-durable guard, or a 2mm hybrid. Anything 1mm or soft is built for light clenching and will fail quickly under heavy grinding.
There's no single number because it depends on material and force, but a hard custom guard lasts meaningfully longer than a soft one for a heavy grinder. If you're replacing a soft guard every few months, stepping up in thickness and material extends that interval considerably.
Hard. Soft guards flex and absorb light force comfortably, but heavy grinding deforms them. A hard acrylic guard resists the force instead of yielding to it, which is exactly what a heavy grinder needs.
Through a dental clinic, several hundred CAD. Through an online custom provider like NewSmile, a custom night guard starts from $139 CAD on subscription or $199 CAD one-time, made from a home impression kit.
No. A cracked guard no longer protects the cracked area, can cut your soft tissue, and may split further and become a choking hazard. Stop using it as soon as you notice the crack and order a replacement right away.
By Joanna M. | Director of Telehealth Clinical Operations | Fact-Checked for Clinical Accuracy
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