Halitosis, or bad breath, may be caused by periodontitis, food impaction and other diseases, and the treatment modalities are periodontal treatment and combined treatment, as follows. 1. Periodontitis: the periodontitis-causing bacteria in the deep periodontal pockets have the ability to produce odor, and the symptoms of bad breath can be improved through perfect periodontal treatment, such as supragingival cleaning, subgingival scraping and root planing, periodontal surgery, and so on. 2. Food impaction: implanted food decay will cause oral odor, can be rebuilt or adjusted marginal ridge, reconstruction of food overflow groove, restore the physiological shape of the cusp, increase the adductor gap, adjacent surface filling, full crown or joint crown restoration and other combination of treatment modalities to treat food impaction, so as to improve the oral odor. Oral odor may also be related to digestive system diseases, respiratory system diseases, etc. It is recommended to go to the hospital in time to receive professional treatment as soon as possible.