Accelerating Bone Generation and Bone Mineralization in the Interparietal Sutures of Rats Using an rhBMP-2/ACS Composite after Rapid Expansion

This study aims to investigate the effects of rhBMP-2/ACS composite on bone regeneration and mineralization during expansion of the interparietal suture in rats. Forty 10-week-old Sprague-Dawley rats were divided into four groups (n=10). The first group (intact group) did not receive any intervention. The second group (expansion control group) received an expansion force of 60 g. The remaining two groups received an expansion force of 60 g and were implanted with an atelo-type I absorbable collagen sponge and rhBMP-2/ACS composite positioned on the suture beneath the periosteum. The relapse, relapse ratio, relevant bone remodelling, and calcium and osteocalcin contents were evaluated. Bone regeneration in the interparietal suture was estimated by the histological method. The osteocalcin content was measured by radioimmunoassay, and the calcium content was measured by atomic absorption spectrophotometry. Bone regeneration was more active in the suture after application of the expansion force compared with that of the suture without any intervention. Bone bridges formed in the rhBMP-2/collagen composite group. Both osteocalcin and calcium content were higher in the rhBMP-2/collagen composite group than in the other three groups (P<0.01). The relapse ratio in the rhBMP-2/collagen group was much lower than that in the other two expansion groups (P<0.01). RhBMP-2/ACS composite can promote bone regeneration and bone mineralization in the expanded suture and decrease the relapse ratio. Thus, the rhBMP-2/ACS composite may be therapeutically beneficial to the inhibition of relapse and shortening of the retention period during rapid expansion.