| Objective:Titanium was widely used for its good mechanical, corrosion- resistance and biological properties. Titanium and Ti-6Al-4V are mostly used in dental restoration field. Considering the low tensile strength, bad wear resistance, and difficulties in processing technology of the titanium in the current clinical applications and researches, loop fracture offen appears in clinical medicine, Ti-6A1-4V contain Al&V, which restricted its application in the field of prosthodontics. Therefore, it is necessary to develop a new type of titanium alloy for dental restoration with better mechanical properties, biocompatibility and easy to process, which can enhance the effect of dental reparation and to expand the indications in the dental restoration.Methods:1. Preparation of alloy: Ti, Zr, Nb, Sn were selected as alloy elements. According to proportion of Ti-12.5Zr-3Nb-2.5Sn (wt%), raw materials were weighed and alloy was prepared by high vacuum arc melting alloy.2. Evaluation of mechanical properties. Ti-Zr-Nb-Sn alloy was made into standard samples, the mechanical properties was tested by universal tensile test machine after quenching process at 850℃for 1.5 hours and aging treatment at 850℃for 3 hours; Micro Vickers hardness was tested by MH-6 micro-hardness tester; the microstructure and the fracture morphology were scanned and observed by electron microscope; the alloy microstructure was analyzed with X-ray diffraction phase.3. Evaluation of biological performance. According to correlative standards, a series of in vivo and in vitro tests, such as the cell toxicity test, toxicity test, oral mucosa stimulate experiment and sensitization experiments was made to study the biological safety of the new titanium alloys and evaluate its biological properties.4. Evaluation of casting performance. Produced wax type tester, embedded as embedding materials, cast by LZ5-centrifugal casting machine, to study casting temperature of the titanium alloy and to test the alloy casting flow rate, evaluation of alloy casting reaction layer and linear shrinkage.Results: 1. Organizational structure and mechanical properties. The tensile strength, yield strength, elongation, elastic modulus and hardness of alloy were 671.3±24.7MPa, of 561.5±39.9 MPa,18.1±4.6%,92.5±8.0Gpa,250.7±16.1HV respectively. It clearly showed necking phenomenon, fibrous by naked eye, the color gray. Specimen fracture electron microscopy revealed the formation of organizations in the expansion area. In the metallographic structure, it was showed that the distribution of needle-like a in the thick ofβgrains. XRD display alloy was nearlyα-Ti.2. Biological properties. Cytotoxic test showed that the degree of cell relative proliferation was 124% and cell toxicity grading was grade 0; Systemic acute toxicity test showed no significant differences in reaction symptom and body weight compared with the control group after 72h; Oral mucous membrane irritation test showed no buccal congestion, no swelling, no erosion, no ulcer reaction when alloy was fixed on hamster buccal surface for 14 days. Histological observation found no adverse reaction at the tested sample area animal contact with; Sensitization experiments showed no skin edema, erythema or other allergic reactions on the test sample group and negative control animals. Sensitization rate was 0.3. Casting properties. Samples were waxed, embedded and roasted by demand, cast at 400℃. The casting flow rate was 100%. Linear shrinkage and the surface reaction layer met the demand.Conclusions:1. The mechanical properties was prior to Titanium obviously, after quenching process and aging treatment and the former could meet the performance demand to the metal material used for oral restoration.2. Biology experiment showed that the alloy cytotoxicity reaction level was 0; no acute toxic reactions, irritation to the oral mucosa, or skin sensitization.3. The surface reaction layer and linear shrinkage met the accuracy requirements of dental demands. The casting stand and flap were complete. The model emplacement, grinding and polishing were excellent.
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