Surface Modification Of Dental Zirconia Based Ceramic Via Deferent Coating Methods

In recent years, Zirconium-oxide(ZrO2) has gained great attention as a biomaterial due to superior mechanical properties. Furthermore, chemical and biological inertness makes it very biocompatible. In the area of dentistry , ZrO2 has become a prominent material for fabricating frame work of single crown and other fixed partial dentures. However, one of the major limitations regarding the use of ZrO2 is the difficulty to adhere to this material. Traditional adhesive chemistry is ineffective on ZrO₂ surfaces, since they are essentially non-polar and inert.Recently, a new method of surface modification inspired by the adhesive proteins secreted by mussels has become a topic of great interest. Dopamine is a small-molecule mimic of the adhesive proteins found in the'footprints'of mussels. The materials to be modified are dipped directly into an aqueous dopamine solution at pH 8.5 , auto polymerization occurs and the substrates become coated with a poly-dopamine film .Furthermore, the multifunctional coating is available for a variety of secondary reaction. In the first part of study, poly-dopamine coating was formed on the surface of ZrO2. Pentaerythritol tetrakis(2-mercaptoacetate)(PETMP) was chosen for secondary reaction ,which has been proved could be co-polymerized with Bis-GMA in resin luting agent.Main part of the second study is shear bond strength (SBS) test. After the dopamine-PETMP coatings were formed, 4 mm-diameter cylinders were built on the surface of ZrO2 ceramic with adhesive luting resin. In addition, the traditional silica coatings were prepared in another group through sol-gel process. The effects of the two kinds of coatings on the bonding strength were compared. The third part of study is the improvement of sol-gel silica coating. At present, the silica coating is somehow better than the developing dopamine coating. Although superior in terms of mechanical performance, there are some inherent problems associated with silica coating. The traces of silica left on ZrO2 are in the form of Si-OH, which are strongly hydrophobic. Analysis of the broken specimens revealed an interfacial failure indicating that the zirconia-resin interface was the weakest link in the structure. The main reason is the hydrolytic effect of water on adhesive interface. Therefore, we made our effort to modify the process of sol-gel in order to from a more hydrophobic silica layer on the surface of ZrO2 ceramic.Partâ… Surface modification of dental zirconium oxide ceramic with poly-dopamine coatingObjective: To make polydopamine-Pentaerythritol tetrakis(2-mercaptoacetate) coating on the surface of dental ZrO2 ceramic, and to evaluate the wettability with or without coating.Methods: Fifteen Y-TZP blocks were embedded in an acrylic resin base, polished, Al2O3-sandblasted and randomly divided into three groups, with five blocks per group, which received different surface treatment. Group A and Group B were covered with polydopamine coating; Group B was dipped into the solution of Pentaerythritol tetrakis(2-mercaptoacetate) for 18hrs to form a ad-layer. Group C was control with no further treatment. Contact angles of each group were measured.XPS was used to examine the surface of polydopamine- Pentaerythritol tetrakis(2-mercaptoacetate).Results: Among contact angles of three treated surface,group B were the biggest (P=0.001),and group A were the smallest (P=0.0038). XPS showed Zr2s (2532.30ev) photoelectron peaks were completely suppressed after polydopamine coating. S2p (163 eV) signal was observed.Conclusion: Zirconia ceramic could be modified with polydopamine- Pentaerythritol tetrakis(2-mercaptoacetate) coating, which could become a media of Zr2 bonding to resin. Partâ…¡Effects of poly-dopamine coating on shear bond strength of zirconium oxide ceramicObjective: To evaluate the effect of the dopamine- Pentaerythritol tetrakis(2-mercaptoacetate)(PETMP) coating on the zirconia-to-resin shear bond strength(SBS).Methods: 24 zirconia blocks were embedded in an acrylic resin base, polished, Al2O3-sandblasted and randomly divided into 3 groups. Group A was control with no further treatment; Group B was dipped into an aqueous solution of dopamine to form multifunctional polydopamine coating. PETMP was used as ad-layer through self-assembled monolayers formation; Group C was silica coated through sol-gel process. Resin-based luting agents were used to build 4 mm-diameter cylinders onto the zirconia surface. SBS testing was carried out after 24h of storage in water. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to evaluate the zirconia surface topography.Results: According to ANOVA and LSD test (p= 0.05), the association of the silane primer with the silica coating (Group A) yielded the highest SBS (9.62MPa) followed by dopamine-PETMP coating (Group B)(7.50MPa). The groups that did not receive treatment (Group C) presented the lowest SBS values (6.19MPa). The SBS test results between group A and group B have no significant difference. Conclusion: The poly-dopamine-PETMP coating can slightly increase the SBS of zirconia bond to resin but the results have no significant difference.Partâ…¢Surface Modification of Dental zirconia Ceramic with hydrophobic Silica CoatingObjective: To prepare hydrophobic Silica Coating and evaluate the wettability of dental zirconia ceramic with or without coating .Methods: Hydrophobic Silica Coating was prepared with Tetraethyl orthosilicate and Trimethoxy(methyl)silane through sol-gel process. Scanning electrical microscopy ( SEM) and energy depressive spectrum( EDS) were used to analyze the silica coating .The effect of silica sol modified by MTMS on the structure was studied with Fourier transform infrared spectroscopy (FTIR). Static contact angle was observed to evaluate the wettability of the ceramic.Result: Cross-linked structure was formed through the co-condensation reaction between hydrolysis products of TEOS and MTMS. Among contact angles of three kind of zirconia ceramic surface the modified silica coating was significantly bigger than the other two(p=0.000; p=0.000).Conclusion : Silica Coating was prepared successfully through sol-gel process and the wettability of the coating can be modified conveniently.