The Comparative Study On The Effect Of Surface Modification Technology Of The Titanium Implantt

Titanium is viewed as the best implant material currently due to its favourable biocompatibility and excellent chinability.Nowadays,dental implants made of pure titanium or titanium alloys are widely used in clinic practice.Because of the thin oxide coating of the natural titanium, more waiting time was needed to acquire successful implant.So Surface Modification of Pure Titanium was used in order to shorten the cure period of dental implant and improve its success rate.Recently,the studies of Surface Modification of Titanium were payed more and more attention to enhance the bioactivity of the implant materials.Many research found that the velocity and intensity of osseointegration was closely related to the surface bioactivity of the implant,whereas the latter was closely linked with the physical and chemical properties of the surface.The most used surface modification technology includes hydroxyapatite (HA),sandblast,acid-etching,micro-arc and Ultraviolet (UV) photocatalysis,et al.They can significantly improve the bioactivities of the implant surface and enhance the osseointegration of the implant.However,the parameters were different by different researchers during surface modification.We do not have a comparing research between different parameters.In order to determine the most suitable parameters,we did many comparing researches about each parameters and gain the following results:1.The titanium micro-arc oxidation coating surfaces’morphology, microroughness,hardness,weigh,thickness,phase and element composition vary with different oxidation time correspondingly, and the micro-arc oxidation coatings finish growing on pure titanium at20min.The models of titanium micro-arc oxidation process indicate certain links between the microstructures or phase compositions of oxide coatings and the process parameters,in which the treatment time t is the most necessary one,and it determines the intensity of oxidation process,affecting the coatings’microstructures and the other parameters.2.The surface of sandblasted titanium substrate performs a better combination of microroughness and hardness at the blasting intensity of45s.3.The titanium substrate and its oxide film are etched in the mixed HF-HCI-solution, being influenced on its microstructure and mechanical properties, and the surface of etched titanium substrate shows a distinct combination of α-β-phase structure at the etching intensity of90s.4.Blast-etching mainly produces a compound function on the titanium samples.When the substrate is sandblasted for45s and etched for120s,its so-prepared surface synthesizes a complex effect of the combined sandblasting and acid-etching, being got rid of the sandblasting residuals.According to the upper results,we determined the most suitable parameters of sandblast, acid-etching,blast-etching and micro-arc for implant surface modification.This research tested the validity of the parameters of acid-etching and micro-arc in implant surface modification,the study includes three parts:Part1Implant surface modificationTo evaluate the validity of acid-etching and micro-arc in implant surface modification by certain parameters,and make a material preparation for cell curture in vitro and animal experiment in vivo.Three specifications(Φ5.0、Φ8.0、Φ12.0) of TA2commersial pure titanium were chosed in this study.They were processed into two type of cylindrical TA2samples(Φ3.0×10mm and Φ8.0×3.0mm),the surface microroughness of the samples were burnished to Ra=0.2mm.Then acid-etching,blast-etching and micro-arc were used to modificate the sample surfaces.The surface morphology of the samples were observed by scanning electron microscope (SEM),and their element concentration were analyzed by X-ray energy Dispersive spectrum (EDS).The microhardness HV0.25and microroughness Ra of the samples were also tested.SPSS13.0was used to carry out statistic anaylysis.The sample surface of the acid-etching group showed many parallel needle-like ditches and marks,while blast-etching group showed not only cutting marks by blast but also needle-like ditches by acid-etching.The unsmooth and uniformly continuous oxidation coatings were found in the sample surfaces of the micro-arc group.There are many round and oval microporous in the sample surfaces which may be helpful to osseointegration.The microroughness Ra of the smooth burnished group is0.2μm,while the acid-etching group is1.08μm,the blast-etching group is1.67, and the micro-arc group is1.68μm.The alternation of the microroughness can influence the dynamic contact angle of the sample surface,which may change the hydrophilic of the implant material.The microhardness of the pure titanium,the acid-etching group,the blast-etching group and the micro-arc group is220,181,259and670HV0.025respectively.For element concentration analysis,99.336%Ti was found on the sample surface of the pure titanium plus some small amount of other elements.The acid-etching group showed little Al,Si on the sample surface,which indicated that HF could get rid of the contamination of Al2O3and SiO2.The blast-etching group showed decreased Si and C elements.More O and Ti elements was detected by EDS on micro-arc group.We also found some Ca and P elements in the micro-arc oxidation coating surfaces. Part2Cells cultureST2cells were cultured with fetal bovine serum on the surface of four groups of pure titanium specimen with different pretreatments,and this study is to explore the change of biological properties of different pretreatment on the surface of pure titanium surface by scanning electron microscope, inverted microscope, radiation detector instrument,etc.The specimen surface developed porous constructions that are rich in calcium phosphate and increased the surface roughness after micro-arc oxidation treatment which facilitated material for protein adsorption and mediated cell adhesion. The adhesion rate of osteoblast of D group was obviously higher than that of group A, B, C.The MTT results illustrated the effects of different treatment of titanium surface on the early adhesion and late proliferation of ST cells according to the different time points respectively. After1,3,5and7days of cell culture, the cell growth curve showed that the surface of pure titanium after optimized was helpful of cell proliferationHigher ALP activity, synthesis of type I collagen, the expressing of osteocalcin (OC) and osteopontin are cell differentiation markers. The high level of ALP activity in the cell layers can promote the formation of mineralized tissue and accelerate bone formation. The expression of ALP is associated with the differentiation of cells. The level of ALP activity represents the degree of cell differentiation. In this study, the ALP activity of ST2cells on the surface of titanium were consistent with the trend of roughness in each sample. After3,5,7days, the ALP levels of the pure titanium specimen after micro-arc oxidation modificion were at the highest level at the same time period. The ALP levels of group B, C and D were higher than that of group A, and there were significant differences (P<0.05);Group B is higher than that of group C, but there were no significant differences(P (P>0.05); Group D is higher than group B and group C, and there were significant differences(P<0.05). Part3Animal experiment24Newzealand rabbits were randomly divided into two groups(Groupl and Group2),each group own12rabbits.The surface modificated samples were divided into4groups-GroupA(the control),GroupB(acid-etching),GroupC(blast-etching) and GroupD(micro-arc).Select the back legs of the rabbits for implant placement.GroupA and GroupB were placed in the mesial part of Group1and the distal part of Group2,while GroupC and GroupD were placed in the distal part of Group1and the mesial part of Group2.Four weeks after surgery,half of the animals in each group was sacrificed;Eight weeks after surgery,all the residual animals were also sacrificed.The spicemens underwent radiographic test,push out test,SEM test and histological analysis.All the animals survived.we did not detected any missing or loosen of the implants.4weeks after surgery,we can see new bone formation near the marrow cavity.8weeks after surgery,we can see more bone formation,there are no gaps between the implant and the original bone.The push out test show that in each time point,the shear strengths sequence of the groups is A<B<C<D.There are significant difference between GroupB,C,D and GroupA(P<0.05).GroupB,C and GroupD also has significant difference(P<0.05).4weeks after surgery,there are only a little new bone formation in GroupA,the interface of the implants are meanly connective tissue and osteiod.we can find bone trabecula in other groups.8weeks after surgery,we can see bone formation in every group,the maturity sequence of the bones is GroupA<B<C<D. Conclusions1.In different degrees,Acid-etching,Blast-etching and Micro-arc can modificate the implant surfaces and improve theirs biological properties.2.Blast-etching is better than single acid-etching in surface modification,while micro-arc is better than blast-etching and acid-etching. Study on the Synergistic of the various methods in surface modification will be a new research focus.