| Because of its good function and aesthetic effect,dental implants have been developed into the current clinical treatment of tooth defects recognized by the public.However,due to the present characteristics of conventional dental implants,such as they are time-cunsuming(The patient usually takes more than 3 months from the beginning of the tooth extraction until the tooth is completely repaired in the end),which makes the way isn't fully accepted by the patients.At present,implant surface treatment is considered to be the most effective method to improve the osseointegration of implant.The surface morphology,surface wettability and surface chemical composition of dental implants can be changed by surface treatment.The most classical change of the surface morphology of pure titanium implant is the micrometer surface formed by sand-blasted and acid-etched.The micrometer surface morphology of the implant will affect the adhesion of osteoblasts on its surface,thus the subsequent biological behaviors such as proliferation and differentiation will also be affected.On the other hand,the surface microstructure can increase the contact area between bone and implant,which is more conductive to the distribution of stress.Nowadays,the surface treatment technology has become the most widely used in oral implant market,and this method has also been verified by people.However,some changes in surface morphology do not have an unlimited effect on the surrounding tissue of the patient.Therefore,the current research is more focused on how to enhance the impact of dental implants on the surrounding tissues.However,the current use of a new element on the implant surface can change the implant biochemical properties,and then enhance the activity of osteoblasts on its surface,thus strengthen the combination of surface bone and implant.As a microelement necessary for human body,studies have shown that strontium has a certain role in bone remodeling,it not only can promote bone formation,but also has a certain inhibitory effect on bone resorption.At present,this element is mainly present in the form of strontium reina acid compound in the form of a treatment drug for patients with osteoporosis.But studies have shown that when the use of strontium in patients with systemic medication can not only bring certain side effects but also make the local site of systemic osteogenesis irrealizable.Therefore,people turn to the local treatment of patients,and the development of this aspect has become the focus of current research.In this study,the magnetron sputtering technique was used to promote the binding and inhibit the absorption of bone into dental implants.It was then combined with sand-blasted and acid-etched method in order to assemble Sr-doped biochemistry coating on the implant surface.Then the binding effect of implant and surrounding bone and the biological behavior of osteoblasts were verified by in vivo and in vitro experiments.This research will provide experimental support for clinical application of implants.Objectives of the study:1.The magnetron sputtering technology and the large particle sand-blasted and acid-etched technology were used to construct the Sr-doped biochemistry coating on the implant and titanium surface,and the physicochemical properties were evaluated.2.To explore the effect of strontium-doped and non-strontium-doped implants on cell adhesion,differentiation and proliferation of osteoblast precursor cells of MC3T3-E1,we need to do in vitro experiment.3.The bone histomorphology of the patients at early stage was studied by the implantation of strontium and non-strontium in vivo experiment.Research methods:Part1 The preparation and physical and chemical performance analysis of strontium-doped titanium implant surfaceAt first,the pure titanium implant and titanium disk were machined by Weigaojielikang Company,and the surface was treated by sandblasting and acid etching.The specific methods are as follows:The pure titanium implant and the titanium disk are sprayed on the implant surface 30s by spraying the abrasive material alumina(Al2O3)with the particle diameter 25-250?m by the high velocity airflow under the pressure of the 5×105Pa,thus causing the surface to sag and then using a 1:2 proportion of the hot hydrochloric acid(HCL)and sulfuric acid(H2SO4)The surface of the implant was treated with acid etching,and the irregular micron-level rough surface was eventually formed.The dental implants and titanium disks were treated by magnetron sputtering in the Laboratory of Materials Science,School of Materials,Shandong University.The specific methods and parameters are as follows:The treated implants and titanium sheets were put into the operation box of magnetron sputtering apparatus.In the high concentration argon gas flow,the purity of 99.99%strontium titanate target was applied to 30min under the condition of direct current,and the distance between target and implant was 5.5cm from the power 80W power.After removal,clean and dry,plastic packaging,cobalt 60 irradiation disinfection and set aside.The surface morphology of two groups of samples was observed by scanning electron microscope(SEM).X-ray spectroscopic analysis(EDS)was used to analyze systematically the chemical composition on the surface of two groups of samples.Part2 The effect of strontium-doped titanium implant surface on osteoblastIn Shanghai Municipal Academy of Sciences,the MC3T3-E1 line of mouse embryonic osteoblast cells was purchased from the Chinese Academy of Sciences,and the culture medium containing 1%streptomycin and penicillin and 10%fetal bovine serum was cultured.The sterilized material is placed on a 24-orifice plate,and the MC3T3-E1 cells are inoculated to the sample at a density of 2×104 m/L and 1 ml/pores,placed in a constant temperature incubator,and removed from the incubator after Id.Then the laser confocal microscopy and scanning electron microscope(SEM)were used to observe the adhesion of cell material and the morphological changes of its surface.The proliferation ability of cells on the surface of the material was detected by MTT method at a fixed time point.The differentiation ability of osteoblasts on different surfaces was measured by alizarin red staining and alkaline phosphatase semi-quantitative method.Part3 The effect of strontium-doped titanium implant surface on early osseointegrationTwenty female SD rats were randomly divided into two groups.Two groups of implants were implanted on both sides of each rat near the proximal center of tibia.3%Chloral hydrate was first injected into the peritoneum before the start of the experiment.The subjects were disinfected and towel laid by routine methods.The subcutaneous tissue and skin were cut in turn at about 2cm near the tibial end,the muscles were separated,and the periosteum incision was carried out at the same time to reveal the bone surface.Use the dental slow machine to prepare the hole,use the special carrier to rotate the threaded implant into the nest hole,ensure the implant end enters the bone completely,and inject 4%saline to cool the whole course.we drew materials and made the hard tissue sections at the same time at the 2 and 8 week.Then we observed the function of the coating for the implant combine with the bone.Maximal pull-out tests were used to evaluate the biomechanical properties.ResultPart1 The preparation and physical and chemical performance analysis of strontium-doped titanium implant surfaceSEM observation showed that there were some irregular pores on the surface of SLA.The diameter of the pits with diameter of about 100 ?m was about 1-3 ?m,and the average roughness was about 3.2 ?m.The surface of Sr-SLA is similar to that of SLA,and there is no obvious difference in pore size and roughness between them.The results of X-ray energy spectrometer showed that Sr elements appeared on the surface of Sr-SLA in addition to the original O and Ti elements in SLA group.It is suggested that a certain amount of Sr element was loaded on the implant surface after magnetron sputtering of strontium titanate target.The quantitative results of X-ray spectrometer show that the atomic content of O and Ti elements on SLA surface is 19.93%and the atomic content of 80.07%,Sr-SLA surface O,Ti and Sr elements are 31.74%,66.08%and 2.18%respectively.Part2 The effect of strontium-doped titanium implant surface on osteoblastAfter MC3T3-E1 cells were cultured on the surface of SLA and Sr-SLA,SEM and laser confocal microscopy showed that the cells on the surface of SLA and Sr-SLA both extended filamentous pseudopodia and dispersed on the surface of the material.Compared with SLA group,the cells of Sr-SLA group were more fully spread.The results of MTT showed that the effects of two kinds of samples on the proliferation of osteoblasts increased gradually with the passage of time.The proliferative activity of the 1 and 7d,MC3T3-E1 cells on the surface of 2 kinds of materials was slightly different,but there was no statistical significance.The proliferative activity of cells on Sr-SLA surface was significantly higher than that of SLA surface after culture of 3 and 5d.The results showed that the expression of ALP on the surface of Sr-SLA was significantly higher than that of SLA on the surface of 2 samples of cultured osteoblasts 7 and 14d after culture 7 and 14d.The results of 14 and 28d Alizarin red staining on 2 samples of Osteoblast showed that the results of MC3T3-E1 cells were not statistically different and their mineralization activity was low after the 14d culture of SLA and Sr-SLA surfaces?At 28d,the mineralization activity of Sr-SLA surface MC3T3-E1 cells was significantly higher than that of SLA group.Real-time PCR results showed that the expression of Runx2 and OCN on Sr-SLA surface was slightly higher than that of SLA surface when cultured to 3 6d,but the results were not statistically significant,and the expression level of both on Sr-SLA sample surface was significantly higher than that in SLA group at 9d.The expression of COLI on the surface of both groups reached the peak on the 6th day However,there was no significant difference in the expression of COLI between the two groups on the surface of Sr-SLA at day 6 and day 9 compared with that on the surface of SLA on day 3.Part3 The effect of strontium-doped titanium implant surface on early osseointegrationHistological staining showed that both groups had a close bond with bone tissue during the 2 and 8 weeks of implantation,and there was no inflammatory response.In the tibia of rats,new bone was formed on the surface of implants 2 weeks and 8 weeks after implantation.The new bone formation in strontium group was significantly more than that in non-strontium group,and the new bone was more continuous.The results of bone-implant contact rate and bone area measurement showed that the bone binding rate and bone binding area of strontium doped group were higher than those of non-strontium doped strontium group at 2 and 8 weeks,but there was no statistical difference between the two groups at 2 weeks and 8 weeks.The axial pull-out test showed that the maximum pull-out force(Maximal Pull-out force,Fmax)in the experimental group was higher than that in the strontium free group at 2 and 8 weeks.All of them were significantly higher than those of non-strontium doped group.Conclusion:(1)Using magnetron sputtering technology,we successfully introduced strontium on the surface of pure titanium implants,and constructed a new strontium doped biomimetic coating on the implant surface,and the concentration of strontium ion was about 2%.(2)The new Sr-doped biochemistry coating can promote cell adhesion,proliferation and differentiation osteogenesis in vitro.(3)The new Sr-doped biochemistry coating can promote early osseointegration. |
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