Thin sol-gel-derived silica coatings on dental pure titanium casting

The sol-gel dipping process, in which liquid silicon alkoxide is transforme d into a solid silicon-oxygen network, can produce a thin film coating of s ilica (SiO2). The features of this method are high homogeneity and purity o f the thin SiO2 film and a low sinter temperature, which are important in t he preparation of coating films that can protect metallic ion release from the metal substrate and prevent attachment of dental plaque. We evaluated t he surface properties of dental pure titanium casting coated with a thin Si O2 or SiO2/F-hybrid film by the sol-gel dipping process. The metal specimen s were pretreated by dipping in isopropylalcohol solution containing 10 wt% 3-aminopropyl trimethoxysilane and treated by dipping in the silica precur sor solution for 5 min, withdrawal at a speed of 2 mm/min, air-drying for 2 0 min at room temperature, heating at 120 degrees C for 20 min, and then st oring at room temperature. Both SiO2 and SiO2/F films bonded strongly (abov e 55 MPa) to pure titanium substrate by a tensile test. SiO2- and SiO2/F-co ated specimens immersed in 1 wt% of lactic acid solution for two weeks show ed significantly less release of titanium ions (30.5 ppb/cm(2) and 9.5 ppb/ cm(2), respectively) from the substrate than noncoated specimens (235.2 ppb /cm2). Hydrophobilization of SiO2- and SiO2/F-coated surfaces resulted in s ignificant increases of contact angle of water (81.6 degrees and 105.7 degr ees, respectively) compared with noncoated metal specimens (62.1 degrees), The formation of both thin SiO2 and SiO2/F-hybrid films by the sol-gel dipp ing process on the surface of dental pure titanium casting may be useful cl inically in enhancing the bond strength of dental resin cements to titanium , preventing titanium ions release from the substrate, and reducing the acc umulation of dental plaque attaching to intraoral dental restorations, (C) 1999 John Wiley & Sons, Inc.