What Causes Bad Breath?
The vast majority of bad breath cases start inside the mouth, not the stomach. When food particles and bacteria are left to accumulate, they release volatile sulphur compounds — the gases responsible for that unpleasant smell. Here are the most common dental causes:
- Plaque and tongue bacteria: A sticky film of bacteria coats the teeth, gumline, and especially the back of the tongue. This is the single most common source of everyday bad breath.
- Gum disease: Persistent bad breath with a metallic or rotten odour is a classic warning sign of gum infection. If you also notice bleeding gums or loose teeth, get it assessed early. Learn to spot the signs of gum disease before it advances.
- Tooth decay and old fillings: Cavities trap food and bacteria in spots a toothbrush cannot reach. Our guide on how to prevent cavities and tooth decay covers the daily habits that help.
- Dry mouth: Saliva naturally washes away bacteria. Mouth breathing, certain medications, and dehydration reduce saliva flow — which is why breath is often worse first thing in the morning.
- Food and lifestyle: Garlic, onions, coffee, and smoking all contribute. Smoking also dries the mouth and raises gum disease risk.
Less commonly, bad breath can stem from sinus infections, tonsil stones, acid reflux, or uncontrolled diabetes. If your dentist rules out an oral cause, they may refer you to your GP.
How a Dentist Can Help
A dentist can pinpoint exactly where the odour is coming from and treat it at the source — something mouthwash alone cannot do. Treatment usually involves one or more of the following:
- Professional scaling and polishing: Removing hardened plaque (tartar) from above and below the gumline eliminates the bacteria that cause odour. At Trust Dental, scaling and polishing starts from $85 before GST (9%), and is CHAS-claimable for eligible patients.
- Gum disease treatment: If gum infection is the cause, deeper cleaning or gum disease treatment (from $500, Medisave claimable for surgical procedures) clears the bacteria trapped in gum pockets.
- Treating decay or infection: Fillings, or in deeper cases root canal treatment, remove sources of trapped bacteria. A persistent bad taste alongside pain can signal infection — see our guide on what to do about a toothache.
- Oral-hygiene coaching: Our oral health therapist can show you correct brushing, flossing, and tongue-cleaning technique tailored to your mouth.
How to Prevent Bad Breath at Home
Good daily habits keep the bacteria that cause bad breath under control between dental visits:
- Brush twice a day for two minutes with a fluoride toothpaste, and gently clean your tongue with the brush or a tongue scraper
- Floss once daily to remove food and plaque from between teeth where odour-causing bacteria thrive
- Stay hydrated and chew sugar-free gum to keep saliva flowing
- Limit garlic, onions, coffee, and tobacco
- Replace your toothbrush every three months
- Visit your dentist every six months for a check-up and professional cleaning
When to See a Dentist About Bad Breath
Occasional bad breath after a strong meal is normal. However, you should book a dental appointment if the bad breath is persistent, does not improve with good brushing and flossing, or comes with bleeding gums, loose teeth, a bad taste, or tooth pain. These point to gum disease, decay, or infection that needs professional treatment — and the earlier it is caught, the simpler and more affordable it is to fix.
