Pain caused by tooth decay can be seen in reproducible pulpitis, irreducible pulpitis or apical periodontitis, corresponding to the need for medication or root canal treatment. 1. Reproducible pulpitis. When tooth decay is too deep and close to the pulp, it will cause transient pain to external hot and cold stimuli. The treatment usually removes decayed tooth tissue and puts in clove oil to eliminate the mild inflammation of the pulp, and then resin filling is performed after medication is applied to the bottom of the pulp when there is no obvious symptom. 2. Irreducible pulpitis and apical periodontitis. When the tooth decay is too deep and reaches the pulp cavity, it can cause irreversible pulp inflammation or pulp necrosis. At this time, it is necessary to carry out root canal treatment to remove the infected and necrotic pulp tissues, eliminate the inflammation in the apical area of the root canal, and then carry out crown restoration after filling. The pain caused by tooth decay, it is recommended to go to the hospital in a timely manner to avoid the spread of inflammation and aggravation of pain affecting work and life.