The correct term for purple-gray blood clots should be blood clots. The absence of blood clots after wisdom tooth extraction may be normal or pathological, as follows. 1. Under normal circumstances: if the extraction wound is very small, the bleeding is small, it is possible not to form a blood clot visible to the naked eye, which will not affect the healing of the extraction wound; if the extraction wound has been sutured, the blood clot will be in the alveolar fossa under the sutured gums, which can not be seen with the naked eye. 2. Pathological cases: it may be because the blood clot is not protected after tooth extraction, such as sucking, licking the wound, etc. may lead to blood clot dislodgement, which will affect the subsequent healing; if severe pain occurs 2~3 days after tooth extraction, and at the same time, no blood clot is found in the alveolar fossa, it may be the occurrence of dry socket disease. If the above symptoms occur, it is recommended to go to the hospital in time.