If there is a smell in the mouth, it can affect communication with people. Bad breath is mainly due to poor oral hygiene. However, most people have developed good oral hygiene habits, but still can not get rid of the trouble of bad breath. Bad breath due to oral diseases, because the symptoms are not obvious, patients do not pay enough attention, and most do not actively seek medical advice, so bad breath can exist for a long time. Generally speaking, the oral diseases that are easy to cause bad breath and easy to be ignored are caries and periodontal disease. There are bacteria breeding in the cavity, which will ferment the food residue in the cavity, not only can produce acid to decalcify and decay the teeth, but also can produce acid and hydrogen sulfide and other decomposing substances, thus producing the special acid odor. Periodontitis is induced by calculus and food residue under the action of bacteria, and pus is formed after the necrosis of inflammatory cells and bacteria, and the pus is decomposed by bacteria, which will produce a special fishy odor of corruption. Bad breath makes people unhappy, and also makes each other unpleasant when talking with others. To effectively eliminate bad breath caused by caries and periodontal disease, in addition to developing and maintaining good oral hygiene habits, it is necessary to go to dentistry in time to detect and treat caries, clean teeth, remove soft tartar and tartar, and it is best to take care of them once every 3 to 6 months.