Bioactive glass coating on zirconia by vacuum
The introduction of dental implants based on the concept of osseointegration has provided a reliable option for elderly people to replace missing teeth. The emphasis on aesthetics has resulted in a quest for metal free alternative materials for fabrication of implants, as a result, zirconia has been proposed as an alternative material1,2) Zirconium dioxide, ZrO2 (zirconia) especially, yttria doped zirconia, 3Y TZP, standing for 3 mol% yttria doped zirconia tetragonal polycristals are often offered as the alternative to titanium3) Zirconia is one of the most promising bio ceramics that used as a dental implant owing its very high mechanical properties for example measured average load bearing capacities of 755 N for zirconia restorations4) and comparable osseointegration5) translucency6) radiopaque7) bacterial colonization8) and biocompatibility9,10) with titanium. Besides because of zirconia tooth like color its aesthetics improved compared with other metallic dental implants11) Therefore, zirconia dental implants gaining more attention in recent years. First vitallium oral endosteal implants coated with zirconia was used on 197512) Akagawa et al. used the zirconia for endosseous dental implant in vivo on 19935) Animal experiment showed satisfactory osseointegration and good soft and hard tissue biocompatibility of zirconia implants after a 4 week healing period13) Interestingly these days it is possible to adjust the zirconia implants color with a different part of applied areas14) which is an enormous advantage for the zirconia ceramics. A healing time of 3 to 6 months is recommended for bio inert implants. To reduce the healing time duration several methods recommended such as coating by a bioactive ceramics15 17) However zirconia is considered as a bio inert ceramic18) and to have surface with bioactive property, the surface treatments is required19) A bioactive glass (BG) is a well known, degradable bioactive ceramic material20,21) Usage of BGs has been enlarged in biomedical applications. The use of BG as coatings on zirconia is proposed in order to combine the mechanical properties of this high strength material with the biological properties of the bioactive coatings22) Ceramic 45S5 BG (45%SiO2, 24.5%Na2O, 24.5%CaO, and 6%P2O5 by weight) have gained researchers attention as a functional biomaterial due to its bioactive surface and osseointegration ability. It has been approved that BG 45S5 can heal and repair bone damages23,24) 45S5 BG could be produced by different techniques with different crystallinity such as crystalline melt cast, amorphous melt cast and crystalline sol gel methods25) Hench et al. reported that partially crystallized glass ceramic accelerated the ossification process and crystallization of 45S5 BG will not inhibit apatite formation on the coating layer23) On the other hand, The BG crystallinity could improve BG mechanical property and that is not playing role in directing protein adsorption25) Zirconia substrate has been coated with melted BG powder produced by conventional or sol gel derived methods previously19,22,26,27) Dip coating of zirconia in the sol gel solution followed by sintering was reported by Matsuda et al.28) and fabrication of the 45S5 BG coating by dip coating method in the sol gel solution and its apatite formation ability in the simulated body fluid (SBF) on Mg substrates are reported previously29,30) Bioactive glass coating on zirconia by vacuum sol dipping method