Atypical histological presentation of bone regeneration after insertion of cryoprotected allogeneic bone graft

Background: To evaluate bone regenerative capacity of cryoprotected corticocancellous allogeneic bone graft performed in type II and III post-extraction sockets for ridge preservation after twelve weeks in-vivo. Material and Methods: Twenty-seven type II or III bony-walled extraction sockets (mandible and maxilla) were selected for this study. Following atraumatic tooth-extraction a cryoprotected corticocancellous allogeneic bone graft material and a resorbable porcine-derived collagen membrane were used for ridge preservation. During re-entry surgery at approximately 12 weeks, bone core biopsies were obtained using a 3.2 mm trephine drill and samples were histologically processed and subjected to qualitative and quantitative histomorphometric analysis. Quantitative data was analyzed using a general linear mixed model with results presented as mean values with the corresponding 95% confidence interval values. Results: Healing without incident and ridge preservation allowed for the placement of dental implants after 12 weeks in 25 out of the 27 treated socket sites. Analyses yielded an average of-21.0 +/- 7% of old/native bone,-17 +/- 5.5% of newly regenerated bone (total of-38 +/- 12.8% for all bone), 0.23 +/- 0.14% of new bone presenting with nucleating sites within the matrix,-52 +/- 5.12% of soft tissue, and 3.6 +/- 2.09% of damaged bone. The average regenerated bone was statistically analogous to that of old/native bone (p= 0.355). Furthermore, an atypical histological pattern of bone regeneration was observed, with newly formed bone exhibiting "infiltration-like" behavior and with new bone nucle-ating sites observed within the demineralized bone matrix.Conclusions: Cryoprotected corticocancellous allogeneic bone-graft demonstrated osteoconductive, osteoinductive, and osteogenic properties, yielding unique healing patterns which does warrant further investigation.