Bad breath caused by decayed teeth requires treatment of dental disease, filling after removal of decayed dental tissue or filling after root canal treatment to eliminate the source of odor. After tooth decay, bacteria and food residues will stay in the cavity and ferment to produce bad smell, so it is necessary to use special instruments to remove the decayed tooth tissues, and then use resin to fill the cavity if it can be filled directly. If the tooth has decayed to the pulp cavity, root canal treatment is needed to remove the infected pulp and then resin filling to prevent a large amount of food blockage can eliminate the source of odor. Rotten teeth caused by bad breath is recommended to the hospital in time to deal with, to avoid deepening of caries triggered by pain, and the need to maintain oral hygiene and cleanliness, conducive to the health of the teeth and periodontal health.