INFLUENCE OF DISODIUM (1-HYDROXYTHYLIDENE) DIPHOSPHONATE ON BONDING BETWEEN GLASS-CERAMICS CONTAINING APATITE AND WOLLASTONITE AND MATURE MALE RABBIT BONE

It has been reported that bioactive glass-ceramics containing crystall ine 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 a patite (a calcium and phosphorus-rich layer) on the ceramic surface. I n this study, the influence of disodium (1-hydroxythylidene) diphospho nate (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 implant ed 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 2 0, 5.0, 1.0, and 0.1 mg/kg body wt/day for 8 weeks; and group 5 at a d ose of 5 mg/kg body wt/day for 4 weeks. Group 6 was given injections o f saline as a control. At 8 weeks after implantation, the rabbits were killed. The tibiae containing the ceramics were dissected out and use d for a detachment test. The failure load, when an implant became deta ched from the bone, or when the bone itself broke, was measured. The f ailure 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. Ceram ic bonding to bone tissue was inhibited by a higher dose of DHTD (grou ps 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 wa s not observed on the surface of the glass-ceramic. DHTD suppressed bo th the formation of the Ca-P-rich layer on the surface of glass-cerami cs 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 oc cur. This study verified that the apatite crystals in bone tissue bond ed chemically to the Ca-P-rich layer on the surface glass-ceramics. Th e organic matrix (osteoid) did not participate in the bonding between bone and glass-ceramics.