Effect of a hydroxyapatite tricalcium phosphate alloplast on osseous repair in the rat calvarium

Background: Bony defects caused by periodontitis are often treated by regenerative therapy using autografts and/or allografts. Alloplasts, such as hydroxyapatite or ceramics, are also used as osteoconductive materials that serve as a scaffold for new bony ingrowth. The purpose of this study was to determine the effect of hydroxyapatite tricalcium phosphate (HA-TCP) on osseous repair in the rat calvarium. Methods: Forty-four adult male Harlan Sprague-Dawley rats were assigned to one of four treatment groups: HA-TCP macroporous disk, HA-TCP microporous disk, HA-TCP granules, and demineralized freeze-dried bone (DFDB). The materials were placed into 8-mm calvarial critical-size defects (CSD). Calvariae were harvested at 10 weeks post-surgery and evaluated histomorphometrically. Results: The DFDB group had significantly (P < 0.05) more new bone formation (47%) than any other group. The HA-TCP macroporous disk group had significantly (P < 0.05) more new bone formation (19.7%) than the HA-TCP microporous disk (8.5%) or HA-TCP granule (6.9%) groups. Conclusions: The HA-TCP macroporous disk may elicit significant new bone formation due to its rigid space-maintaining scaffold and pore size for vascular ingrowth. It is well tolerated by host tissues and may be a suitable carrier for growth factors.