There are a few reasons why people could still have mouth odor, commonly called halitosis after brushing. One reason is that they could have a few bad teeth, that need to be removed or taken care of. Or they could have a build-up or coating of bacteria on their tongues. Usually you have to give your tongue the same affection or hygiene that you give the teeth in your mouth. Using a tongue blade or scraper which can be purchased in a pharmacy, will help remove extra bacteria, from your tongue that can cause bad breath or other odors. Also try using a good mouthwash, this will in turn help with mouth odors and/or bad breath. In addition, some problems causing mouth odor, arise from the stomach. Usually when you have a stomach ulcer or GERD, or some other stomach issue, the acids from your stomach can eventually work their way up through the esophagus and into the mouth, causing unpleasant odors. Hope this helped answer your question a little.