Effect Of Hierarchical Micro/nano Surface Titanium Implant On Osseointegration In Ovariectomized Sheep

Experiment 1 Establishment of a Postmenopausal Osteoporosis Ovine Jaw Model by OvariectomyObjective To study the time to establishment of an osteoporosis ovine jaw model through ovariectomy (OVX). To evaluate the micro-architectural and biomechanical changes of jaw bone after OVX and compare to other bones. Method 12 adult sheep were randomly divided into two groups: OVX group (n=7), sham-operated group (n=5). At the time of operation and after 12 months, all sheep underwent dual energy x-ray absorptiometry (DEXA) of jaw and lumbar vertebrae. 12 months after operation, all sheep were sacrificed. The trabecular bone (jaw, spine, femoral condyle, rib) and cortical bone (jaw) were harvested and compared by MicroCT. Axial compression tests were used to evaluate the mechanical properties of jaw. Results 12 months after operation, jaw BMD in OVX group decreased by 31.0% compared with that in control group (P < 0.05). The maxium compression strain of jaw in OVX group decreased by 34.2% compared with that in Sham group (P < 0.05). BV/TV,Tb.Th,Tb.N and Tb.Sp of trabecular bone decreased significantly (P <0.05). Histomorphologically, trabecular bone of jaw decreased significantly in OVX group compared with that in control group. Micro-fracture and micro-defect in trabecular bone of jaw could be seen in OVX group. Conclusions①Ovariectomy can establish post-menopausal osteoporosis ovine jaw model. The ovariectomized phase should be maintained 12 months at least to ensure the animal model could be established successfully.②The jaw osteoporosis could be found after OVX, though the bone loss in jaw occurs slower than that in spine.Experiment 2 Effect of hierarchical micro/nano surface titanium implant on osseointegrationObjective To investigate the effects of three morphologically differing titanium implants (machined surface, micro-textured surface, hierarchical micro/nano- textured surface) on osseointegration in ovine jaw. Method The machined surface of pure titanium implant was fabricated by acid in 0.5% (wt/v) hydrofluoric (HF) to form the micro-textured surface, then the micro-textured surface was further anodized in HF acid electrolytes to form the hierarchical micro/nano-textured surface. The three morphologically differing titanium implants were placed in ovine mandibles respectively. 3 months after implantation, resonance frequency analysis (RFA), MicroCT, histomorphometry and biomechanical tests were applied to detect the osseointegration of the three morphologically differing titanium implants. Results 3 months after implantation, the implant stability quotient (ISQ) values in micro/nano surface group increased by 15.47%, 11.50% compared with that in machined surface group and micro surface group (P <0.05). MicroCT analysis showed that there were significant differences between BV/TV, Tb.Sp and TBPf in the micro/nano group and that in machined surface group and micro surface group (P <0.05). The bone implant contact (BIC) increased by 34.07%, 23.15% compared with that in machined surface group and micro surface group (P <0.05). The maximum pull-out forces increased by 24.35%, 1.77% compared with that in machined surface group and micro surface group (P <0.05). Conclusions①Implant modification by HF acid etching and anodization to form a hierarchical micro/nano-textured surface could improve titanium implant osseointegration.②MicroCT images show 3D information of trabecular bone around implant clearly, which cannot be obtained using 2D histomorphometry. Due to the limitations of scanning at the tissue–implant interface, conventional histomorphometrical analysis and MicroCT are neither interchangeable, nor independent techniques, but need to be considered as complementary techniques.Experiment 3 Effect of hierarchical micro/nano surface titanium implant on osseointegration in ovariectomized sheepObjective To investigate the effects of three morphologically differing titanium implants (machined surface, micro-textured surface, hierarchical micro/nano- textured surface) on osseointegration in OVX ovine jaw. Method The machined surface of pure titanium implant was fabricated by acid in 0.5% (wt/v) hydrofluoric (HF) to form the micro-textured surface, then the micro-textured surface was further anodized in HF acid electrolytes to form the hierarchical micro/nano-textured surface. The three morphologically differing titanium implants were placed in mandibles of OVX sheep respectively. 3 months after implantation, resonance frequency analysis (RFA), MicroCT, histomorphometry and biomechanical tests were applied to detect the osseointegration of the three morphologically differing titanium implants. Results 3 months after implantation, the implant stability quotient (ISQ) values in micro/nano surface group increased by 29.22%, 28.17% compared with that in machined surface group and micro surface group (P <0.05). MicroCT analysis showed that there were significant differences between BV/TV, Tb.Sp and TBPf in the micro/nano group and that in machined surface group and micro surface group (P <0.05). The bone implant contact (BIC) increased by 47.51%, 36.78% compared with that in machined surface group and micro surface group (P <0.05). The maximum pull-out forces increased by 34.41%, 19.30 % compared with that in machined surface group and micro surface group (P <0.05). Conclusions①Osseointegration of dental implant can be achieved in osteoporotic bone, but it does worse than in normal bone.②Implant modification by HF acid etching and anodization to form a hierarchical micro/nano-textured surface could improve titanium implant osseointegration in OVX sheep.