Modulating Bone Regeneration in Rabbit Condyle Defects with Three Surface-Structured Tricalcium Phosphate Ceramics

Tricalcium phosphate (TCP) ceramics are used as bone void fillers because of their bioactivity and resorbability, while their performance in bone regeneration and material resorption vary with their physical properties (e.g., the dimension of the crystal grain). Herein, three TCP ceramic bone substitutes (TCP-S, TCP-M, and TCP-L) with gradient crystal grain size (0.77 +/- 0.21 mu m for TCP-S, 1.21 +/- 0.35 mu m for TCP-M and 4.87 +/- 1.90 mu m for TCP-L), were evaluated in a well-established rabbit lateral condylar defect model (validated with sham) with respect to bone formation and material resorption up to 26 weeks. Surface structure dependent bone regeneration was clearly shown after 4 weeks implantation with TCP-S having most mineralized bone (20.2 +/- 3.4%), followed by TCP-M (14.0 +/- 3.5%), sham (8.1 +/- 4.2%), and mineralized bone was similar in all the three groups, but bone marrow and TCP-L (6.6 +/- 2.6%). Afterward, the amount of material resorption varied. After 26 weeks, TCP-S induced most bone tissue formation (mineralized bone + bone marrow) (61.6 +/- 7.8%) and underwent most material resorption (80.1 +/- 9.0%), followed by TCP-M (42.9 +/- 5.2% and 61.4 +/- 8.0% respectively), TCP-L (28.3 +/- 5.5% and 45.6 +/- 9.7% respectively), and sham (25.7 +/- 4.2%). Given the fact that the three ceramics are chemically identical, the results indicate that the surface structure (especially, the crystal grain size) of TCP ceramics can greatly tune their bone regeneration potential and the material resorption in rabbit condyle defect model, with the submicron surface structured TCP ceramic performing the best.