Teeth if deep caries, pulpitis or periapical inflammation, want to fill the teeth need to change the medicine, the number of times to change the medicine with personal constitution and the degree of inflammation, usually about three times. 1. Deep caries. Deep caries teeth in the direct filling of resin before the need to use the pulp capping agent for indirect pulp capping treatment, placed in the bottom of the cavity capping agent after the temporary sealing observation, observation for 3 to 6 months, the bottom of the cavity to form hardened dentin can be resin filling, if not yet formed need to be replaced with a new pulp capping agent and then again after the observation. The number of replacement is related to the speed of formation of hardened dentin, generally 2~3 times. 2. Pulpitis. For pulpitis bacteria only exist in the pulp cavity, root canal preparation is completed, the drug temporarily sealed once, if no symptoms can be, after filling the root canal using resin filling. 3. Periodontitis. Apical periodontitis due to the bacteria have reached the apical part of the root, need to carry out 2 to 3 times of the exchange of inflammation to subside, for the symptoms of serious people will increase the number of times of the exchange of medication. Dental fillings specifically how many times to change the drug with their own teeth and physical quality, the specific circumstances to first go to the hospital for examination.