If the tooth decay has already penetrated into the pulp cavity, the medicine is mostly used to reduce the tooth sensitivity and to remove the bacteria in the mouth, so as to avoid the inflammation reaction in the mouth again after the filling, causing pain and other uncomfortable symptoms in the teeth and gums. If the decay has damaged the dental nerve, plugging medicine for one week is also to completely kill the dental nerve, so as to facilitate the root canal treatment later. 1, reduce tooth sensitivity: the filling will first carry out the removal of decayed material, if it is near the pulp angle and other sensitive parts, it will use clove oil and other drugs to fill in for about one week to reduce the symptoms of tooth sensitivity and play the role of soothing and analgesic; 2, sterilization: if the filling is plugged with calcium hydroxide, The purpose is to remove the bacteria from the tooth tissue and nearby tissues in order to avoid residual bacteria from causing infection, toothache and other undesirable symptoms after the filling; 3, kill the nerve: the first step of root canal treatment requires the use of drugs to kill the nerve, generally using polyformaldehyde pulp inactivator, plugging the drug for a week to make the pulp dehydrated and necrosis, so that the subsequent Root canal treatment. During the period of medication plugging, you can eat and brush your teeth normally, which will not affect the effect of medication, but do not chew hard food. After the filling is completed, because most of the teeth with deep decay have lost the nerve, blood vessels and other sources of nutrition, they are easy to become brittle and broken, so if necessary, the doctor needs to perform crown treatment to protect the teeth.