There is a sharp and hard thing on the gums after tooth extraction, which is considered to be caused by residual fragments, alveolar bone protrusion, local hematoma and other factors. 1. Remaining debris, if the tooth is not completely extracted during the extraction process and there is debris left behind, this symptom may occur. 2. Alveolar bone protrusion, if the alveolar bone protrudes from the surface after extraction, this symptom may occur, but will disappear gradually with the reconstruction of the alveolar bone. 3. Local hematoma, after tooth extraction due to tissue fluid exudation, hematoma occurs, long time is not removed, may appear this symptom of something hard. If this symptom appears, it is recommended to consult a doctor for examination in time to determine whether there is any hematoma or residual piece left behind, and if necessary, residual piece extraction needs to be performed again.