Osteogenic potential of nonvital tissues and synthetic implant materials

Following the application of various techniques to restore or rebuild alveolar bone with different implants, results are generally unpredictable. In successful cases it is not clear whether the materials are capable of initiating osteogenesis by metaplastic induction, where endogenous bone formation had failed, or initiating osteogenesis by stimulating the regeneration of existing vital bone tissue by irritation. In order to discriminate between these two possibilities, 40 Sprague-Dawley descent rats were implanted with both devitalized tissues and synthetic materials in an area where bone is not usually formed: the anterior eye chamber. The test materials consisted of two devitalized tissues: boiled bone marrow and demineralized dentin, and six synthetic materials: formalin 10% and 40%, formic acid 10% and 88%, plaster of Paris, and ceramic tricalcium phosphate (Durapatite). Test materials were inserted into 59 chambers, but bone was not formed in any of these cases following a three-week experimental test period. Following implantation of 21 control chambers with viable mature marrow, bone was formed in 5 of 21 cases (24%), following the three-week test period. These findings appear to indicate that the reported cases where bone regeneration successfully occurred following implantation probably resulted from unpredictable irritational factors upon the existing vital bone tissue rather than by metaplastic induction.