The rotten first molar does not necessarily have to be extracted, you need to consult a doctor to see if the remaining dental tissues have retention value, and those with retention value should be treated to retain the teeth. 1. No retention value: if the first molar is rotten, the remaining dental tissue is not enough resistance, the long-term treatment effect is poor, or the rotten part has been injured to the bottom of the dental pulp chamber, the tooth loosening is obvious, it is generally considered that the tooth has no retention value, and it can be extracted at a later date. 2. Preservation value: If the remaining dentin tissue of the first molar is still good and the root is solid, root canal treatment can be carried out first, i.e., removing inflammation or decay in the root, rinsing or disinfecting, then filling the root canal tightly, and then restoring the crown after filling, so as to preserve the affected tooth without extracting it. It is recommended to consult a doctor to find out what is going on, and follow the doctor’s instructions to receive treatment.