Preparation And Properties Of Fe³⁺-doped TiO₂ Film On Co-Cr Alloy

Removable partial denture(RPD)with cobalt-chromium metal framework is one of major restoration which has been widely used for dentition defect.However,various clinical observation and experimental studies have reported an increased incidence of caries and periodontal breakdown when RPDs are worn.In recent years,it has been recognized by researchers that titanium dioxide(TiO₂)has excellent antibacterial properties and good biocompatibility.Therefore,it has been applied in denture base resin,implants,orthodontic brackets,etc.In this study,Fe³⁺-doped TiO₂ thin films were prepared by a sol-gel technique with dip coating method on Co-Cr alloy to make them antibacterial.Its mechanical and antibacterial properties were evaluated to supply theoretical basis and experimental support for clinical applications. Part 1 Preparation of Fe³⁺-doped TiO₂ film on Co-Cr alloyObjective:To prepare Fe³⁺-doped TiO₂ film on Co-Cr alloy.Methods:Fe³⁺-doped TiO₂ thin films were prepared by a sol-gel technique with dip coating method on Co-Cr alloy using Ti(OC₄H₉)₄ ethanol solution as a precursor.The structure and morphology of samples were characterized by scanning electron microscopy(SEM),atomic force microscopy(AFM), X-ray diffraction(XRD),Fourier transform infrared spectrometer(FT-IR)and energy dispersive spectroscopy(EDS).Their bonding force and wear resistance were measured by scratch method and pin-on-disc wear test, respectively.Results:The smooth and compact Fe³⁺-doped anatase TiO₂ film with 267～310nm thickness was formed on the surface of Co-Cr alloy and composed of O,Ti,Fe.The average value of bonding force is 68.37 N.Under the same experimental condition,the weight loss of coated samples is only 42 percent of that of uncoated ones.Conclusion:The smooth and compact Fe³⁺-doped TiO₂ film with satisfactory interface adhesive strength and clinical value can be prepared by sol-gel technique.Part 2 Antibacterial Properties of Fe³⁺-doped TiO₂ film on Co-Cr alloy against Streptococcus mutansObjective:To evaluate the antibacterial properties of Fe³⁺-doped TiO₂ film against Streptococcus mutans.Methods:Pure TiO₂ film and Fe³⁺-doped TiO₂ films were prepared by a sol-gel technique with dip coating method on Co-Cr alloy,and antibacterial properties against Streptococcus mutans were evaluated by sticking-membrane method under ultraviolet(UV),fluorescent light or in the darkness.Results:The antibacterial ratios of Fe³⁺-doped TiO₂ films under UV, fluorescent light or dark conditions were 92.06%,86.04%and 74.04%, respectively.While the antibacterrial ratios of pure TiO₂ films were 69.39%, 54.73%and 39.62%,respectively.As for antibacterial effects,there were significant differences between Fe³⁺-doped TiO₂ film and pure TiO₂ film under three light conditions(P＜0.05).In addition,antibacterial activity of the same films are also significant differences under different light conditions (P＜0.05).The Fe³⁺-doped TiO₂ film appears good antibacterial activity with the n_Fe3+/n_Tiof 2%under UV and dark conditions,while n(Fe3+)/n(Ti) of 1.5%in fluorescent light.Conclusion:The Fe³⁺-doped TiO₂ film has more active antibacterial property than the pure TiO₂ film.And the antibacterial activity can be improved by changing the relative value of n_Fe3+/n_Ti.