Ability of commercial demineralized freeze-dried bone allograft to induce new bone formation.

Demineralized freeze-dried bone allograft (DFDBA) has been used extensively in periodontal therapy. The rationale for use of DFDBA includes the fact that proteins capable of inducing new bone; i.e., bone morphogenetic proteins, can be isolated from bone grafts. Commercial bone banks have provided DFDBA to the dental practitioner for many years; however, these organizations have not verified the osteoinductive capacity of their DFDBA preparations. The aim of this study was to determine the ability of commercial DFDBA preparations to induce new bone formation. DFDBA with particle sizes ranging from 200 to 500 microns was received from six bone banks using various bone production methods. Different lots of DFDBA from the same tissue bank were sometimes available. A total of 14 lots were examined. The surface area of bone particles in each sample was measured morphometrically and the pH of a solution containing the particles after suspension in distilled water determined. Samples from each DFDBA lot were implanted intramuscularly (10 mg) or subcutaneously (20 mg) into three different animals and tissue biopsies harvested after 4 weeks. One sample from each tissue bank was implanted and harvested after 8 weeks. At harvest, each area where DFDBA had been implanted was excised and examined by light microscopy. The ability of DFDBA to produce new bone was evaluated and the amount of residual bone particles measured. The results show that bone particles from all tissue banks had a variety of shapes and sizes, both before implantation and after 1 or 2 months of implantation. The pH of particle suspensions also varied between batches, as well as between tissue banks. None of the DFDBA induced new bone formation when implanted subcutaneously. Intramuscular implants from three banks induced new bone formation after 1 and 2 months. DFDBA from two banks caused new bone formation only after 2 months. However, DFDBA from one bank did not induce new bone at all. Particle size before implantation correlated with particle size after implantation. However, particle size did not correlate with ability to induce bone. The results show that commercial DFDBA differs in both size and ability to induce new bone formation, but that the two are not related. The study also indicates that wide variation in commercial bone bank preparations of DFDBA exist and that ability to induce new bone formation also varies widely. Furthermore, the results suggest that methods or assays for evaluating the ability of DFDBA to induce new bone should be developed and standardized.