Hard and soft tissue composition in the extraction socket during longer healing periods was documented in a study by Cardaropoli and coworkers, in which the entire healing cascade after tooth extraction was evaluated in a dog model. The following images are histologic specimens representing the stages of healing observed in their study. On the day of extraction, the outline of the socket can be seen as a region of pink-stained bone. The inner lining of the bone is bundle bone, which was previously attached to the extracted tooth by the periodontal ligament. Within the socket, the coagulum appears as a non-homogenous mixture of fibrin, red blood cells, and inflammatory cells.