In vitro and in vivo evaluation of lyophilized bovine bone biocompatibility

INTRODUCTION: The use of bone grafts in orthopedic, maxillofacial and dental surgery has been growing. Nevertheless, both fresh autografts and frozen allografts have limitations, and therefore, alternative synthetic or natural biomaterials, such as processed and lyophilized bovine bone graft have been developed. OBJECTIVE: To evaluate in vitro and in vivo biocompatibility of lyophilized bovine bone manufactured in a semi-industrial scale, according to a modifical protocol developed by the authors. METHODS: Samples of bovine cancellous bone were processed according to a protocol developed by Kakiuchi et al., and modi¬fied to process samples of bovine cancellous bone. The following trials were performed: in vitro cytotoxicity, in vivo acute systemic toxicity, in vivo oral irritation potential, in vitro pyrogenic reaction, and bioburden. RESULTS: The in vitro evaluation of lyophilized bovine cancellous bone revealed an absence of cytotoxicity in 100% of the samples. Regarding in vivo evaluation of acute systemic toxicity, neither macroscopic abnormalities nor deaths were noted in the animals. Pyrogenicity was not greater than 0.125 UE/ml in any of the samples. The bioburden revealed negative results for microbial growth before sterilization. Regarding the oral irritation potential, in vivo evaluation at 24 and 72 hours showed that the animals had no edema or erythema on the oral mucosa. CONCLUSION: The protocol changes established by the authors to prepare lyophilized bovine cancellous bone at a semi-industrial scale is reproducible and yielded a product with excellent biocompatibility