Influence of disodium (1-hydroxythylidene) diphosphonate on bonding between glass-ceramics containing apatite and wollastonite and mature male rabbit bone

Summary It has been reported that bioactive glass-ceramics containing crystalline oxy- and fluoroapatite [Ca₁₀(PO₄)₆(O,F₂) and wollastonite (CaSiO₃), chemical composition: MgO 4.6, CaO 44.9, SiO₂ 34.2, P₂O₅ 16.3, CaF₂ 0.5 in weight ratio] bond to bone tissue through the formation of an apatite (a calcium and phosphorus-rich layer) on the ceramic surface. In this study, the influence of disodium (1-hydroxythylidene) diphosphonate (DHTD) on the bonding between bone and glass-ceramics containing apatite and wollastonite was investigated. Rectangular ceramic plates (15 mm x 10 mm x 2 mm, abraded with #2000 alumina powder) were implanted into the tibial bone of mature male rabbits. DHTD was administered daily by subcutaneous injection to groups 1–5: group 1–4 at doses of 20, 5.0, 1.0, and 0.1 mg/kg body wt/day for 8 weeks; and group 5 at a dose of 5 mg/kg body wt/day for 4 weeks. Group 6 was given injections of saline as a control. At 8 weeks after implantation, the rabbits were killed. The tibiae containing the ceramics were dissected out and used for a detachment test. The failure load, when an implant became detached from the bone, or when the bone itself broke, was measured. The failure loads for groups 1–6 were 0 kg, 0 kg, 8.08±2.43 kg, 7.28±2.07 kg, 5.56±1.63 kg, and 6.38±1.30 kg, respectively. Ceramic bonding to bone tissue was inhibited by a higher dose of DHTD (groups 1 and 2). In groups 3–6, SEM-EPMA showed a calcium-phosphorus-rich layer (Ca-P-rich layer) at the interface between the ceramic and bone tissue. However, at higher doses (5 and 20 mg), the Ca-P-rich layer was not observed on the surface of the glass-ceramic. DHTD suppressed both the formation of the Ca-P-rich layer on the surface of galss-ceramics and also apatite formation by bone. Thus, bonding between the Ca-P-rich layer of glass-ceramics and the apatite of bone tissue did not occur. This study verified that the apatite crystals in bone tissue bonded chemically to the Ca-P-rich layer on the surface glass-ceramics. The organic matrix (osteoid) did not participate in the bonding between bone and glass-ceramics.