The Effect Of Different Activators And Application Conditions On Coupling Performance Of Experimental Silane Coupling Agent

With the development of dental materials, more and more all ceramic restorations, such as all ceramic crowns, porcelain inlays and porcelain laminate veneers, have being used in dental clinic. However, the dentists and researchers were puzzled by the debonding and secondary caries of all ceramic restorations. The main reasons of debonding and poor bonding durability are caused by poor wettability of resin cement, undesirable stress distributed on the bonded surface and complicated intraoral environment. Surface treatment is the key factor that would influence the bonding performance between restorations and resin composites. The frequently used surface treatments include abrading, sandblasting, etching and silanization. The mechanical treatment combined with chemical coupling agent application is widely accepted surface treatment for ceramic bonding.Coupling agent can form a "bridge" between organic and inorganic materials. When coupling agent was applied on the bonding surface, the adhesive property and wettability on the surface can be modified, therefore, improving the bond strength between different substrates. The main component of the commercial dental silane coupling age nt is γ- MPS. Due to the short chain molecular structure of γ- MPS, the chemical bond between resin and porcelain is not stable enough. Consequently, the research and development of new dental silane coupling agent became one of the research focuses in dentistry recently.Our research group designed and synthesized a new dental silane coupling agent, which molecular chain contains 11 carbon atoms. Previous studies have shown that the new long chain silane coupling agent can increase the bond strength betwee n porcelain and resin, while the bonding durability was significantly improved.In this study, a new kind of two-component dental coupling agent was designed, which consist of activator and experimental long-chain silane. Basing on being stored separately, the condensation of silanol in the hydrolyzed silane coupling agent can be prevent, therefore the validity period can be extended and chemical activity of silane coupling agent can be improved. The application conditions of this new kind of two-component dental coupling agent were also evaluated by several groups of parallel experiments, so as to provide guidance for dental clinic.The total study was divided into three parts.:In the part one, acetic acid, lauric acid and acid adhesive monomer were used as activator respectively. Three mixtures were applied onto the surface of porcelain. Then, the bond strength between porcelain and resin were measured. The results confirmed that the coupling effect of two-component dental coupling agent is better than one-component. The acetic acid was appropriate as experimental activator for the experimental long-chain silane coupling agent.In the part two, after being treated with three mixtures of two-component silane coupling agent respectively, the porcelain surfaces were evaluated by the contact angle measurement and scanning electron microscope observation. we found that the two-component silane coupling agent significantly reduces the contact angle of the adhesive on the porcelain surface. The mixture of long-chain silane and acetic acid showed a uniform distribution on the porcelain surface, while no self polymerization was found on the surface.In the part three, we evaluated different conditions, such as the solvent, temperature, and hydrolysis time on the bonding performance of two-component silane coupling agent. Finally we found that the deionized water and ethanol mixture was appropriate as solvent; 60℃ temperature was suit for the silane coupling agent application; hydrolysis time of the silane mixture should be controlled within 30 min.In summary, the results of this study indicated that acetic acid should be used as activator for the experiment two-component silane coupling agent, while its distribution on the porcelain surface is uniform. The experimental long-chain silane coupling agent, containing acetic acid, showed better bonding performance than traditional silane coupling agent. The deionized water and ethanol mixture was appropriate as solvent; 60 ℃ temperature was suit for the silane coupling agent application; hydrolysis time of the silane mixture should be within 30 min before used.