The reasons for odor inside the teeth are large gap, cavity in the crown, blind pocket formation, and a large amount of calculus formation, as follows: 1, large gap: when the gap is large and easy to embed food fiber, it can stimulate the gingival papillae to swell, ooze blood and emit blood odor. 2, cavity in the crown: when a deep cavity is formed in the crown, the retained food residue, soft scale, etc. can produce sour odor under the fermentation of bacteria. 3.Blind pocket formation: When the eruption of wisdom tooth is incomplete, the gum covered by the far middle can form a deeper blind pocket with the crown, which is very easy to retain food and soft scale and cause repeated infection, and will form a large amount of pus and cause obvious bad breath. 4.Large amount of calculus formation: If a large amount of calculus is attached to the root surface of the tooth, it will stimulate the gum tissue to proliferate and cause alveolar abscess, resulting in more local pus overflow, thus appearing strong bad breath.