Abstract
OBJECTIVE: This study aimed to compare the effect of two different generations of bisphosphonates (BPs) on bone repair assisted by an alloplastic bone graft (spheres of nanostructured carbonate apatite/calcium, CHA) in a non-critical defect in the rat femur. MATERIALS AND METHODS: Thirty-six female Wistar rats were randomly assigned into six groups: Control group (blood clot), carbonate apatite (CHA) alone, Zoledronate (Zol) with blood clot, Clodronate (Clo) with blood clot, Zol+CHA, and Clo+CHA. Drugs were administered intraperitoneally (Zol: 0.6 mg/kg; Clo: 20 mg/kg) every 30 days for 60 days before surgery. Standardized monocortical femoral defects (2 mm) were created and filled according to group assignment. After 30 days of healing, samples were harvested for histological and histomorphometrical evaluation. New bone formation and remnant biomaterial were quantified. Statistical analysis included the Kruskal-Wallis test and Dunn's post hoc (p < 0.05), along with Pearson and Spearman correlation analyses. RESULTS: Histological analysis revealed enhanced new bone formation in groups treated with BPs, especially when combined with CHA. The Zol+CHA group exhibited the highest new bone formation (24.0 ± 4.0%), significantly greater than Control (2.0 ± 0.5%; p = 0.011) and CHA (5.0 ± 1.2%; p = 0.0017). The Clo and Clo+CHA groups also showed significant improvements (19%) compared to the Control (p = 0.03) and CHA (p = 0.04). Remnant biomaterial was significantly greater in Zol+CHA (15.0 ± 2.0) and Clo+CHA (15.0 ± 2.0%) than in CHA alone (8.0 ± 1.0%; p = 0.022), suggesting inhibition of bone graft resorption by BPs. Correlation analysis revealed a strong positive association between remnant biomaterial and new bone formation (Spearman ρ = 0.94, p = 0.005; Pearson r = 0.88, p = 0.021), supporting the biological synergy of CHA and BPs in bone repair. CONCLUSION: Both bisphosphonates enhanced bone repair in the femoral defect model, demonstrating a synergistic effect when combined with nanostructured CHA. Zoledronate required the presence of the biomaterial to exert its osteogenic influence, while Clodronate stimulated new bone formation independently. These findings indicate that generation-specific differences among bisphosphonates may guide their future use in bone tissue engineering strategies.