| Due to its mechanical and chemical properties commercially pure titanium is currently the main material for dental implants.However,the Ti implants need to be modified for enhancing their osseointegrative potential since they are short of bioactivity in the osseointegration process.The sandblasting and acid-etching(SLA),a commercial surface modification way for dental implants,is a way which can get a microrough surface on Ti implant surface,but poor hydrophilcity.Therefore,superhydrophilic surface was achieved by plasma oxidation on SLA surface in the paper,which is deemed to highly enhance osseointegration between an endosseous impant and bone.Fatigue life of dental implants plays a great role since they are subjected to many loading cycles during their life,mainly those produced during mastication.Fatigue may cause them break,with serious consequences from clinical standpoint.So this paper studies the fatigue behavior of dental implants.1.Freshly prepared titanium dioxide surface is characterized by superhydrophilicity.So the fresh titanium dioxide was achieved by plasma oxidation in vacuum surrounding with changing oxidation parameters.But the superhydrophilicity of Ti surface was unstable,which needs more various modifications.In this paper,to maintain or recover quickly Ti surface superhydrophilicity,its surface after oxidation was rinsed by O.lmol/L alkali and Ar plasma or directly stored in alkali and isotonic NaCl solution.The optimum parameters are selected within the test range,and that is:Working pressure(6.5Pa),O2/Ar=1(Ar=5sccm),substrate bias voltage(400V),radio frequency power(200W),oxidation time(60min).The result shows that the contact angle of Ti surface after oxidation or being stored in alkali increased inevitably when Ti was exposed to air.And the surface cantact angle hardly recovered superhydrophilicity after rinsed with alkali for 0～150s,but it could be done after rinsed with Ar plasma for 15 min.If the Ti sample after oxidation directly stored in alkali or isotonic NaCl solution,its contact angle maintained below 10° and hardly changed with time going.But stored in isotonic NaCl solution,Ti suface contact angle changed largely after rinsed with water.MTT and ALP tests show that the Ti sample instored in alkali before cell culture sinifacantly improved the bio-compatibility of Ti-surface,such as adhesion and metabolism of cells;Ti sample rinsed 10s by alkali comes second;SLA surface was the last.They all had nice morphology of cells.2.The fatigue life of dental implants is the main factors for their long-term stability.In order to evaluate long-term stability of dental implant system,standard fatigue tests must be performed in the implants.The standard used for this purpose is the "Dentistry Implant-Dynamic fatigue test for endosseous dental implants"(ISO 14801:2007,IDT).In the paper,evaluation of fatigue life includes tests and numerical evaluation.The result shows that the implant system used in the paper was failure under-10～-350N sinusoidal variation of loading.The crack initiation was at the point closer to the support,i.e.at the bottom of first coarse-pitch thread of impant.The zone of fracture of connection screw was at the junction suface between screw and implant.Numerical simulation carrived out by ansys workbench shows that the stress contribution in the implant system had a high similarity compared to theory.The fatigue life was 2423 times,which was lower than 4000 times achieved by test.In the test or numerical evaluation,the implant system meted requirements under-10～-120N sinusoidal variation of loading. |
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