Most of what is stuffed into the tooth for the first root canal treatment is either pulp deactivation medication or root canal disinfecting and sanitizing medication. Root canal therapy is a routine treatment for endodontitis or apical periodontitis. In the case of endodontitis, pulp inactivation, commonly known as nerve killing, is performed during the first root canal treatment with a pulp inactivator, which is also known as a nerve killing medication. Depending on the duration of the drug’s action, the time for the second follow-up is determined. In the case of chronic apical periodontitis, root canal disinfection is performed after root canal preparation, and a calcium hydroxide root canal disinfectant is commonly used. Some may also be calcium hydroxide iodoform preparations. So, the medication put in the tooth for the first root canal is related to the disease of the tooth itself, mostly deactivating agents for pulpitis and root canal disinfecting medications for periapical periodontitis, which requires a visit to the dentist.