Synthesis And Evaluation Of Chemically Modified SLA Titanium Surface

IntroductionTitanium (Ti)and its alloys have widely proved to have good mechanical properties and to be biocompatible for orthopaedic and dental implants, but data on Ti implant failures acquired over the past decades suggest that some osseintegration and bone regeneration problems still exist. It has been shown that surface blasting and acid etching can increase the rate and amount of bone formation on the implant surface and that the sandblasted and acid-etched (SLA) surface demonstrated higher removal torque values in biomechanical testing. Recently, it has been demonstrated that Ti implants with alkali- and heat- treatments (AH) remarkably enhanced bone bonding ability and early bone formation.In this study, we verified the hypothesis that the surface topographies introduced by combination of chemical processes can be more effective in bone regeneration and apposition at interface of bone and implants than the surface produced by topography alone. Materials and methodsPlates of commercially pure titanium were made and divided into three groups of treatments: Group A was pure with smooth surface; Group B was sandblasted and then etched with mixed acid of HCL and H₂SO₄; Group C was SLA treated followed by immersion in 6N NaOH solution and heat to 600℃. Then the three kinds of plates were soaked in simulated body fliud, and their surfaces were characterized by SEM, EDX, XRD and AES microanalysis.Toassess the biocompatibility of SLA-AH titanium surface, three biological tests were done as hemolysis test, acute toxicity test and test of local effects after implantation. MG-63 were used for in vitro assays. The cell culture were performed on implants in 24-well cell culture plates for measurement of cell attachment rate, cell proliferation rate and ALP activity. The implants were also sterilized conventionally with ethylene oxide gas before Surgical procedures. They were transcortically implanted into the proximal metaphyses of bilateral tibiae of mature New Zealand white rabbits. five rabbits of each group were killed at 4, 8 and 12 weeks after the operation. Interfacial shear strength of implants with different surfaces was measured by pull-out mechanical testing. All data were expressed as mean± standard deviation and assessed using SPSS 11.0 statistical package. For histological examination, the undecalcifiedsections were ground to a thickness of about 90 μm. After toludine bluestaining, the sections were examined by light microscopy. A SEM was used toexamine metal surfaces after cell culture and pull-out testing.ResultsThe SEM examination revealed that a macro-rough surfaces structure was formed after the sandblasted and dual acid treatments. After alkali and heat treatment, the implant surface showed finely irregular microrough structure.After soaked in SBF, apatite formed on the SLA-AH surface.and furthermore.the contents of Ca,P and 0 decreased while that of Ti increased with the increasing of depth and a graded structure was formed near its surface. The hemolysis rate of the diluted rabbit blood in SLA-AH surface steep was only 0.8%. No any toxic symptems appeared among those 20 mice that received the acute toxicity test.Calcium nod formed on the SLA-AH surface and no inflammation was found.Compared with on the smooth /SLA titanium surfaces, cell culture on the SLA-AH surfaces showed that the osteoblast-like cell had spread more extensively and flattened. The results of the cell attachment rate and ALPactivity indicated that the indexes of the SLA-AH surfaces were higher than that of SLA or smooth surfaces, the SLA-AH treated implants showed significantly higher shear strengths than the smooth/SLA implants at 4,8 and 12 weeks, respectively(p<0.01/0.05). For the SLA-AH treated implants, new bone formed in the gap created at the implantation site within 4 weeks, and the new bone was in direct contact with the implant. In the groups of the smooth and SLA treated implants, an intervening fibrous layer or a small amount of bone was observed. Scanning electron microscopy revealed almost the same findings as those noted in the toludine blue staining samples.Previous results suggested that sandblasting before acid etching has a beneficial effect on the interfacial shear strength. However, the manner in which titanium interacts with bone is complex and not only dependent on surface topography. Other factors such as the chemical composition of the surface play a crucial role in early stages of bone formation. We developed SLA-AH surface and compared to those data, the results suggest that SLA surface following by alkali and heat treatments could result in a dramatic increase in bony bonding and osteoblast-like cells deposition, leading to better biological performances.An important finding of this study was that the surface topographies introduced by combination of chemical processes, exemplified here by alkali and heat treatments, can be more significantly and more effective in bone regeneration .enhance bone-implant contact and cell apposition than surfaces produced by topography process alone. Conclusion1. After SLA titanium surface treated with alkali-heat, SLA-AH titanium surface acquired the properties of bioactivity besides its roughness.2. After soaked in SBF, graded apatite coatings were formed on SLA-AH titanium surface.3. The SLA-AH titanium surface showed well biocompatibility in the biological tests.4. the SLA-AH titanium surface promoted bone osseointegration during earlystages of bone regeneration at the bone-implant interface.