Bone physiology in human grafted and non-grafted extraction sockets - an immunohistochemical study

Purpose The aim of the present immunohistological investigation was to define and compare the osteogenic potential with the vascularization of the provisional matrix in grafted and ungrafted extraction sockets after 4 and 12weeks of healing. Methods A total of 33 Patients (15 women, 18 men) with 65 extraction sites with a mean age of 54.4years (30-73years) participated in this study. After tooth extraction, the sockets were augmented with Bio-Oss collagen or non-augmented. At implant placement after 4 or 12weeks bone biopsies were obtained. Within the specimens the osteogenic and endothelial potential of mesenchymal cells was analyzed in the provisional matrix using immunohistochemical analysis with three monoclonal antibodies Cbfa1/Runx2, Osteocalcin (OC), and CD31. Statistical analysis was performed using Mann-Whitney U-test, Spearman's rank-order correlation coefficient, and the two-factorial analysis for repeated measurements. Results Of the 65 extraction sockets, 25 (13 non-augmented, 12 augmented) sites after 4weeks healing time and 40 (19 non-augmented, 21 augmented) sites after 12weeks healing time were involved in the study. No signs of acute or chronic inflammation were noted in any specimens. After 4weeks, a median amount of 56% (10-85%) of Cbfa1 positive cells and a median amount of cells expressing OC of 21% (5-42%) were measured. A median CD31 score of 5 was observed. After 12weeks, a median amount of 61% (19-90%) positive cells expressed by Cbfa1/Runx2 staining a median amount of OC positive cells of 9% (2-17%) was measured. The results at 12weeks revealed a median score of CD31 positive cells of 3. Discussion Osteoblastic activity in the provisional matrix was highest after 4weeks of healing period. The active zone of bone formation is found in the apical region of the extraction socket during the early healing phase, shifting to the coronal region after 12weeks. A peak of osteoblast activity within the first weeks is followed by a reduction in mature osteoblasts with osteoblasts remaining in an inactive stage. The vascularity changed in likewise fashion to the maturation of osteoblasts within the observation period. The results have shown that with increasing age a decreasing endothelial potential was observed not after 4weeks, but after 12weeks, thus it suggests that angiogenesis is diminished in older patients in the later phase of healing in extraction sockets.