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

Bone void fillers are widely used in orthopedic and dental applications due to their biocompatibility and resorbability. Tricalcium phosphate (TCP) ceramics are a popular choice because they support bone regeneration. However, the performance of these materials can vary based on their physical properties, such as crystal grain size. Prior research has shown that TCP's bioactivity and resorption rates are influenced by structural characteristics. Yet, how surface structure specifically affects bone regeneration remains unclear. This uncertainty drives the need for controlled studies comparing TCP ceramics with different grain sizes. The rabbit condyle defect model is a well-validated system for such investigations. No prior work has directly compared the impact of gradient grain sizes on bone formation and material resorption in this model. This gap motivates a focused study to isolate the role of surface structure in TCP performance. Understanding these effects could improve material design for clinical use.

This study aimed to evaluate how the surface structure of tricalcium phosphate (TCP) ceramics influences bone regeneration and material resorption in a rabbit condyle defect model. The specific problem addressed is the lack of clarity on how varying crystal grain sizes affect TCP performance. The motivation stems from the need to optimize bone graft materials for predictable outcomes. The study compared three TCP ceramics with different grain sizes: TCP-S (submicron), TCP-M (medium), and TCP-L (large). The goal was to determine if surface structure alone could modulate bone formation and resorption. The rabbit condyle defect model was chosen for its established reliability in bone regeneration studies. The study sought to isolate the effect of grain size from other variables. The results could inform material design for enhanced bone regeneration.

The study used three tricalcium phosphate (TCP) ceramics with defined crystal grain sizes: TCP-S (0.77 ± 0.21 μm), TCP-M (1.21 ± 0.35 μm), and TCP-L (4.87 ± 1.90 μm). These materials were implanted into rabbit lateral condylar defects. The model was validated using a sham group as a control. Bone formation and material resorption were assessed using histological and radiographic techniques. The evaluation period ranged from 4 to 26 weeks post-implantation. Data collection focused on mineralized bone volume and marrow formation. Material resorption was quantified using microcomputed tomography. The study avoided confounding variables by keeping the chemical composition of the ceramics identical. The experimental design allowed for direct comparison of structural effects.

At 4 weeks, TCP-S showed the highest mineralized bone formation (20.2 ± 3.4%), followed by TCP-M (14.0 ± 3.5%), sham (8.1 ± 4.2%), and TCP-L (6.6 ± 2.6%). By 26 weeks, all groups had similar mineralized bone volumes, but marrow and resorption varied. TCP-S induced the most total bone tissue (61.6 ± 7.8%) and material resorption (80.1 ± 9.0%). TCP-M followed with 42.9 ± 5.2% bone tissue and 61.4 ± 8.0% resorption. TCP-L had 28.3 ± 5.5% bone tissue and 45.6 ± 9.7% resorption. The sham group had 25.7 ± 4.2% bone tissue. These results indicate that crystal grain size significantly affects early bone formation and long-term resorption. The submicron grain size (TCP-S) outperformed the others. No differences in chemical composition were observed among the groups.

The study suggests that the surface structure of tricalcium phosphate (TCP) ceramics influences bone regeneration and material resorption in rabbit condyle defects. The authors propose that crystal grain size is a key factor in modulating these outcomes. The results indicate that submicron grain size (TCP-S) enhances early bone formation and long-term resorption. The authors suggest that structural design can be optimized for improved clinical performance. The findings are specific to the rabbit model and do not generalize to other species. The study confirms that chemical identity does not override structural effects. The authors emphasize the importance of surface structure in material design. These conclusions are based on the observed differences in bone volume and resorption rates.