| Titanium has been widely used in areas of dental implants due to the favorablecharacteristics of mechanical property, corrosion resistance and biocompatibility.Nonetheless, deficiencies of Titanium as medical implant materials, such as theelastic modulus mismatch between materials and bones which could cause stressshielding effect, posed a threat on the failure of implantation. As biological inertmetal, Titanium lacks of osteoinduction ability, which means it has to bond withbones depending on mechanical interlocking instead of chemical bond. Therefore,aiming at improving the bone-bonding ability, increasing researches are done to findbetter dental implant methods of surface treatment recently.To improve the bio-inert of titanium alloy, many studies about implant surfacemodification have illuminated the possible methods, among which, depositing thebio-active coating on the implant surface has been becoming a research focus.Specifically, it has been demonstrated experimentally that the calcium phosphatecoating (Ca-P coating) has favorable bio-compatibility, osteoconduction andoseteoinduction since it shows similar properties to human bone tissue, structurallyand chemically. Furthermore, the release of elements (Ca, P, etc.) from the Ca-Pcoating can be cleared through the series of metabolic pathways. In addition, afterimplanted, the Ca-P coating can form chemical bond between its surface and thebone tissueas well as providing the scaffolding for bone formationin the meantime.The Ca-P coating will be replaced by new bones eventually with its ongoing ofdegradation and absorption. Besides, many researches claim that pure hydroxyapatite(HA) with a high crystalline is the most ideal Ca-P coating.As a revolutionary technique, Rapid Prototyping (RP) can generate the objectsdirectly using the basis of virtual3D data. Being a branch of RP, Direct Laser Metal Forming (DLMF) has been applied to produce a new laser sintered titaniumimplant--the Tixos implant (Leader srl, Milano, Italy). The surface of Tixos implant,which shows a porous three-dimensional network of intercommunicating path, wasproved to provide space for the growth and production of cells. The surfacemorphology and elastic modulus, proposed from the aspect of bionics, weredesigned to simulate the natural form of alveolar bone. Meanwhile, experimentsshowed that the center of the specimen kept the excellent mechanical properties oftitanium, which assured the overall strength and rigidity of implants.Objective and methods:Part1: The influence of electrolytic concentration on the electrochemicallydeposited Ca-P coating of the TixOs surfacepurpose of this part is:1) to explore the influence of compositions appearanceand structure of Ca-P coatings by different concentrations of electrolyte; and2) tofabricate the Ca-P coating on the surface of TixOs implant using electrochemicaldeposition and thus to simulate the compositions and forms of natural bones.Part2: The influence of Zinc concentration on the electrochemically depositedCa-P coating of the TixOs surfaceAccording to the optimum parameters of part one, the coating mixed with Zinccan be fabricated by electrochemically deposition. This part aims to explore theinfluence of compositions appearance and structure of Ca-P coatings by differentconcentrations of Zinc ions. Also, the release behavior of Zinc ions in Tris buffersolution will be observed to evaluate the solubility of different coatings.Results:In high concentration, the component of the coating was proved to be DCPD byXRD and FTIR testing. The coating was thick and disorderly stack and themicro-pores of TixOs plates were filled up with Ca-P deposits. In contrast, in lowconcentration, the results revealed that the deposits were dominant HA phase and thesurface morphology was porous, well-ordered and latticed.The MG-63cells culturedon Ca-P coating spread well. Especially, cells in group10-3were spindle on thesurface with thick pseudopodia adhered to the rough and porous surface with fusionstate.The coatings mixed with Zinc were proved to be HA. The morphology ofcoatings mixed with10%or20%Zinc was well-ordered and latticed. By contrast, mixing with30%Zinc made the coating appearflocculent and amorphous. XRDresults showed that the crystals of coatings decreased as the Zinc concentrationincreased.The release tests of Zinc showed the coatings of30%Zn-HA-Ti groupdegraded rapidly, however, the release curves of other groups increased gently. Thevariance above was due to the fall of crystallinity and the rise of solubility, whichresulted from doping with Zinc. |
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