TL;DR
A mouthguard picks up a bacterial film every single night, and the two things that ruin one are heat and storage while damp. Rinse it the second it comes out, brush it with a soft brush and a mild soap, and let it dry completely in open air before it goes in a case. Never boil a fitted guard, never run it through a dishwasher, and never soak it in bleach.
Why a mouthguard gets funky so fast
A night guard or sports guard sits in your mouth for hours in a warm, wet environment. Saliva leaves behind proteins and minerals, and the ordinary bacteria in your mouth settle onto the surface as a soft film.
That film is called biofilm. Left alone it hardens into the same chalky deposit that forms on teeth, which is why an old guard can feel gritty and look cloudy.
Then the guard goes into a closed case while still wet. A sealed, damp, dark container is close to ideal for microbial growth, so the smell you notice by week two is a storage problem as much as a cleaning problem.
The same pattern shows up across almost every item on a bathroom counter, which is the theme of our guide to cleaning the personal items you use every day.
How do you clean a mouthguard?
Rinse it under cool running water as soon as you take it out, then brush every surface with a soft toothbrush and a drop of mild liquid soap. Rinse thoroughly, shake off the water, and leave it in open air on a clean surface until it is bone dry before storing it in a ventilated case.
The daily routine, step by step
1. Rinse the moment it comes out. Cool or lukewarm water only. Rinsing while the film is still soft removes most of it and takes about five seconds.
2. Brush all surfaces with a soft brush. Use a soft-bristled toothbrush kept for this purpose, not the one you brush your teeth with. Get inside every tooth impression, where film collects most.
3. Use a mild soap, not toothpaste. Most toothpaste contains mild abrasives that scratch soft guard material. Those scratches hold bacteria and make the guard cloudy. A drop of unscented liquid hand soap or dish soap does the job without scratching.
4. Rinse until it feels squeaky, not slippery. Soap residue tastes bad and can irritate gums.
5. Dry it fully in open air. Set it on a clean dry towel for fifteen to thirty minutes. This step does more to stop odor than anything else.
6. Store it in a ventilated case. A case with air holes, kept dry, on a shelf rather than in a steamy bathroom drawer.
What will damage a mouthguard
Boiling water. Fitted guards are thermoplastic. Heat is what let them be molded to your teeth in the first place, and heat is what will warp them back out of shape. A warped guard does not protect anything and can put uneven pressure on teeth.
The dishwasher. Same problem, plus harsh detergent.
A hot car or a sunny windowsill. Both get hot enough to deform a guard.
Bleach and household disinfectants. They degrade the material, and the residue goes in your mouth. There is no household disinfectant worth that trade.
Alcohol-based mouthwash used as a soak. Long soaks in alcohol make many guard plastics brittle and cloudy over time. A brief rinse is a different thing from an overnight soak.
Abrasive scrubbing. Baking soda paste, whitening toothpaste, and stiff brushes all leave micro-scratches.
Retainers are made from similar plastics and follow nearly identical rules, which we cover in how to clean a retainer without warping it.
Why does my mouthguard smell bad?
Odor comes from bacteria multiplying on leftover film, almost always because the guard went into a closed case while still damp. Rinse and brush daily, dry it completely in open air before storing, and wash the case itself with soap and water twice a week. Persistent odor after that is worth mentioning to your dentist.
Deeper cleaning without heat or bleach
Once a week, give the guard something stronger than a soap wash.
A soak in a solution of one part white vinegar to three parts cool water for fifteen to thirty minutes loosens mineral deposits. Rinse very thoroughly afterward.
Effervescent denture or retainer cleaning tablets are made for this exact purpose. Follow the package directions on water temperature and soak time, and never leave a guard in longer than the label says.
Pick one method per session. Do not combine cleaning products in a single container -- mixing household products is where genuine chemical hazards come from, and there is no benefit to it here.
If the guard has gone chalky white and will not come clean, that is hardened mineral deposit. Your dentist can often clear it in the office, and can tell you whether the guard is worth keeping.
Source: American Dental Association consumer guidance on oral appliance care
Keeping the case clean too
The case is half the problem. A guard cleaned daily and stored in a dirty case is recontaminated every night.
Wash the case with warm water and soap two or three times a week, scrubbing corners with a brush. Let it air dry fully, open, before the guard goes back in.
Replace the case every few months, or sooner if it stops drying properly or develops a smell you cannot wash out. The same logic applies to how to clean a denture case, and it is why storage matters as much as brushing in how to clean a toothbrush and store it right.
When should you replace a mouthguard?
Replace it when you see thin spots, cracks, holes worn through by grinding, a loose fit, or permanent cloudiness that will not clean off. Custom guards often last a few years, while over-the-counter boil-and-bite guards wear out much sooner. Have your dentist check the fit at regular visits.
A guard that no longer fits snugly is not doing its job, and a cracked one can harbor bacteria in places no brush reaches.
Cleaning a mouthguard reduces bacteria and odor. It does not treat gum disease, tooth decay, jaw pain, or sleep apnea. Any real symptom belongs with a dentist or doctor, not a cleaning routine.
FAQ
How often should you clean a mouthguard?
Rinse and brush it every single time you take it out, which for a night guard means once a day. Give it a deeper clean once a week with a vinegar solution or a cleaning tablet made for oral appliances. Wash the storage case two or three times a week.
Can you boil a mouthguard to sanitize it?
No. Fitted guards are made from thermoplastic that softens with heat, so boiling water will warp the guard and ruin the fit. A warped guard does not protect your teeth and can create uneven bite pressure. Use cool or lukewarm water and a soft brush instead.
Can you use toothpaste on a mouthguard?
It is not a good idea. Most toothpaste contains mild abrasives meant for tooth enamel, and those abrasives leave micro-scratches in the softer guard material. Scratches hold bacteria and turn the guard cloudy. A drop of mild liquid soap cleans just as well without scratching.
Why is my mouthguard turning cloudy or white?
Cloudiness is usually hardened mineral deposit from saliva, the same material that becomes tartar on teeth, sometimes combined with scratches from abrasive cleaning. A weekly vinegar soak or a cleaning tablet slows it down. Once it is set hard, a dentist can often remove it in the office.
Should you store a mouthguard in water?
No. Storing a guard in water or in a sealed damp case encourages bacterial growth and is the usual reason a guard starts to smell. Dry it completely in open air first, then store it in a ventilated case. Some retainer types have different instructions, so follow your dentist.
Can you use mouthwash to clean a mouthguard?
A quick rinse is harmless, but long soaks in alcohol-based mouthwash make many guard plastics brittle and cloudy over time. Mild soap and a soft brush do a better job daily, with a vinegar solution or an appliance cleaning tablet weekly.
A clean guard is a two-minute habit. Keeping the bathroom it lives in genuinely clean is a bigger job, and one you can hand off. Get a quote or read more about house cleaning services.