Halitosis is a word dentists use to describe bad breath. Almost everyone, including children, suffers from bad breath at one time or another. For most, it goes away when teeth are brushed and flossed and/or mouthwash is used. For others, almost nothing seems to rid them of breath that can knock flies down dead out of the air. If your bad breath seems to be a case of the latter, talk to your dentist. He/she may find that it is the result of one (or more) of the following causes, and then he/she will treat your bad breath accordingly.
Rotten Tooth, Gum, and/or Infection
When a tooth is rotting, you will initially feel a lot of pain. If you wait it out, the nerve to that tooth will die, and then it will no longer hurt. However, if you wait that long, then the tooth, which is a collection of living tissues supplied by blood and soft inner tissue (i.e., the pulp), the tooth begins to rot. A rotting tooth is most definitely the source of bad breath that will not go away with brushing. Additionally, rotting gums or gum tissues that have an abscess (i.e., a pocket of pus in the gum tissue that swells up until it ruptures or begins to leak) will also cause equally foul breath. The solution is to remove the rotten tooth, extract the pus safely, and rinse often with a medicated mouthwash to destroy bacteria and odors.
Your tonsils sit in flesh pockets at the back of your throat. These flesh pockets collect mucus and small bits of food and drink. Along with the usual oral bacteria, the mucous, food, and drink begin to form a mushy blob of fermenting/rotting material. Eventually, the centers of these blobs become hard and continue to grow, almost like pearls in an oyster.
They are known as "tonsiliths," a.k.a., "tonsil stones." Your tonsils eventually expel the "stones" through coughing or swallowing, causing you to ingest the bits of rot. While they form, tonsiliths are foul-smelling things that send their stink up into your sinuses and throughout your mouth. Your dentist can express them digitally, use a water pik to rinse out the tonsil pockets, and/or teach you how to "express" the pockets yourself to keep your breath fresher.
If you tend to sleep with your mouth open at night, you snore, or you have a CPAP machine for sleep apnea, your nose, throat, and mouth get very dry. The less moisture there is, the more bacteria can create a powerful stink. Rinsing with a mouthwash that encourages saliva production before bed and using the hot steam component in your CPAP machine will reduce stinky bacteria production.