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

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.

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.

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 nucleating sites observed within the demineralized bone matrix.

Cryoprotected corticocancellous allogeneic bone-graft demonstrated osteoconductive, osteoinductive, and osteogenic properties, yielding unique healing patterns which does warrant further investigation.