The cavity after tooth extraction is called extraction trauma, which can be closed under normal circumstances, if infection occurs, it will affect its normal healing as follows. 1. Under normal circumstances: 15-30 minutes after tooth extraction, blood clot can be formed, after the blood clot mechanization, granulation tissue gradually replace the blood clot, and then connective tissue and epithelial tissue to replace the granulation tissue. 3-4 days after tooth extraction, the original fiber-like bone fills the extraction socket, and then bone tissue is formed completely after 3 months, and normal bone structure appears after 3-6 months, and the extraction wound is basically healed. 2. Infection: The residual tooth pieces, bone pieces, tartar and other foreign materials and residual granulation tissue in the extraction wound may cause chronic infection, which will lead to poor healing of the wound. If the wound does not heal for a long time, it is recommended to go to the hospital in time to receive regular treatment as soon as possible.