An Experiment Study On Reconstruction Of Alveolar Bone Defect With Strontium-containing Brushite Bone Cements

Objectives To evaluate the ability of repairing bone defect with strontium-containing brushite and to explore the mechanism of materials by testing physical,chemical,biological and imageological properties and observing the expression and distribution of basic fibroblast growth factor(b-FGF) and osteoprotegerin(OPG) in the new osseous tissue. Discussing whether strontium-containing brushite can be used in clinic as bone substitute. Methods To make 5% and 10% strontium-containing brushite by adding strontium chloride according to the Sr/(Sr + Ca). To test and analysis the property, surface morphology and compressive strength of materials by X-ray diffraction, scanning electron microscopy, Cone beam computed tomography. To detect the biocompatibility and safety of materials with acute hemolytic test and skin irritation reaction test. Healthy 36 male rabbits are divided into four groups randomly: blank control group(blank group); brushite bone cement group(DCPD group); doped 5% strontium brushite bone cement group(doped strontium 5% group); doped 10% strontium brushite bone cement group(doped strontium 10% group). Rabbits are defected 10×3×4mm in bilateral mandibular and implanted materials corresponding, except the blank group. To observe the status of bone defect with images of Cone beam computed tomography and expression and distribution of basic fibroblast growth factor(b-FGF) and osteoprotegerin(OPG) in fourth, eighth, and twelfth week. To measure the average optical density(MOD) of b-FGF and OPG positive expression in the same multiples with Image-Pro-Plus 6.0 software, comparing each group at the same and statistics processing.Results 1 Making 5% and 10% strontium-containing brushite successfully; X-ray diffraction results prove strontium form hydrogen phosphate strontium in bone cement; Many short bar, sheet, clusters of crystal structure and different sizes of micropore among structure is showed in images of scanning electron microscopy; 2 Compressive strength reduce because of adding strontium, namely that the more of strontium the lower of compressive strength. The rates of hemolysis below the national standard, then prove three of samples all safety and non-toxic both in vitro and vivo test. 3 The blank group defect still not repair at 12 week; DCPD group have repaired done at 12 week and formed bone trabecular structure; two groups with strontium have repaired at 8 week earlier than DCPD group, the repair effect of doped 10% strontium group is better than 5% group, the trabecular bone is wide enough and new bone surface smooth. 4 Immunohistochemical results: when compare in the group, the expression of b-FGF and OPG decline with time long; comparing the MOD of b-FGF each group at 4 week we will see significant difference in every two groups(P<0.05), the smallest is blank group and the most is doped 10% strontium group; at 8 week, there are significant differences in every two groups(P<0.05), the most MOD is doped 5% strontium group, group with strontium higher than DCPD group, blank group is the smallest; there is no significant different among groups at 12 week. Comparing the MOD of OPG at 4,8 week doped 5% strontium group is the most, then doped 10% strontium group higher than DCPD group, blank group is the smallest, there are significant differences in every two groups(P<0.05),; there is no significant different between blank group and DCPD group(P>0.05), no significant different between two strontium group(P>0.05), when cross comparison two strontium groups MOD higher than the other two, there are significant differences in every two groups(P<0.05). That all prove strontium can increase the expression of b-FGF andOPG, promoting osteogenesis. Conclusions 1 The method of making bone cement is reliable; replicating easily; and the compressive strength close to the strength of the cancellous bone. 2 Brushite bone cement, doped 5% strontium brushite bone cement and doped 10% strontium brushite bone cement are safety and non-toxic material. 3 Strontium brushite can increase b-FGF and OPG to promote osteogenesis inhibiting osteoclasts. 4 Doped 5% strontium and doped 10% strontium bone cements both can shorten the postoperative recovery time, repairing earlier than brushite group; when doped 10% strontium, the effect is more obvious..