Comparing the Rate of Dissolution of Two Commercially Available Synthetic Bone Graft Substitutes.

This study characterized the dissolution properties of two commercially available bone substitutes: 1) A calcium sulfate hemihydrate (CSH)/brushite/β-tricalcium phosphate (TCP) graft containing 75% calcium sulfate (CaS) and 25% calcium phosphate; and 2) a CaS/hydroxyapatite (HA) bone graft substitute composed of 40% HA and 60% CaS. Graft material was cast into pellets (4.8mm OD x 3.2mm). Each pellet was placed into a fritted thimble and weighed before being placed into 200 mL of deionized water. The pellets were removed from water at days 1, 2, 3, 4, 6, 8, 14, 18 or until no longer visible. The mass and volume of each pellet was calculated at each timepoint to determine rate of dissolution. Analysis of variance (ANOVA) was performed on all data. Statistical significance was defined as p < 0.05. The CaS/HA pellets were completely dissolved after day 8, while the CSH/brushite/β- TCP pellets remained until day 18. The CSH/brushite/β-TCP pellets had significantly more mass and volume at days 1, 2, 3, 4, 6, and 8 timepoints. The CSH/brushite/β-TCP pellets lost 46% less mass and 53% less volume over the first 4 days as compared to CaS/HA pellets. The CSH/brushite/β-TCP pellets had a rough, porous texture, while the CaS/HA pellets had a smooth outer surface. Overall the CSH/brushite/β-TCP pellets dissolved approximately twice as slow as the CaS/HA pellets in vitro. As these in-vitro findings might have in-vivo implications, further clinical data is required to further confirm and establish the optimal synthetic bone substitute strategy or antibiotic delivery carrier.