Study on the Synthesis of Novel Long-chain Silane Coupling Agent and Its Mechanism of Bonding for Ceramic Restoration
|School||Fourth Military Medical University|
|Keywords||silane coupling agent organic synthesis ceramic bonding all ceramic shear bond strength fourier transform infrared spectroscopy X-ray photoelectron spectroscopy|
Dental bonding technology now is widely used in many branches of dentistry. Withless cut of tooth tissue, it can repair the tooth defects, color and occlusion abnormalities bytooth-colored restorations. All-ceramic restoration can greatly restore the tooth shape,color and layering, and has excellent biocompatibility. Therefore, the all-ceramic adhesiverestoration has become one of the focuses in dental research in recent years. Permanentbonding between ceramic and resin is the key point of adhesive restoration’s long-termsuccess.At present, the deficiency of bond strength and durability is still the main problem ofthe clinical failure in restoration. It is mainly due to the inefficient wetting, shrinkagestress and weak layer on the interface between adhesive and adherends. Restorationsurface treatment is an effective way to improve the bond strength of the interface,including mechanical roughening treatment and chemical surface modification. Surface treatment by coupling agent is the simplest and also the most widely used method ofchemical modification. Silane coupling agent can play the role of ‘molecular bridge’between the inorganic and organic interface, which can connect two different materialstogether and improve the bond strength effectively, as well as avoid surface structurechange and compatibility decrease in restoration. Therefore, silane coupling agenttreatment is a prosthesis surface treatment with good prospects.In recent years, most of the dental silane coupling agents have used γ-MPS as themain functional component. Because of relatively simple molecular structure, it is difficultto obtain sufficient chemical bonding with ceramic surface. Influenced by factors asmoisture, pH, temperature and occlusal stress in oral environment, the bonding effect isnot permanent. Studies of chemical materials have suggested that long-chain silanemolecules can strengthen the interface between organic-inorganic phases.Therefore, this study is based on the latest research progress in polymer chemistryand materials science. Accoding to the characteristics and requirements of dental bonding,this study aims to synthesize a novel long-chain silane molecule, and screen efficientsynthetic route and conditions. Then, we have analyzed the effect of the new silane onceramic-resin bonding strength. And an analysis of the mechanism of interaction betweensilane with ceramic interface has also been performed, so as to provide experiment datafor the further application of long-chain silane in restoration.Part I of this study focuses on synthesis of target long-chain silane molecules throughdifferent routes and different reaction conditions.Experiment1: At room temperature, long-chain silane molecules containing amethacrylate group were synthesized following three-step reaction (hydrosilylation,alcoholysis, esterification). Molecules were characterized by FTIR and NMR.Experiment2: At room temperature, long-chain silane molecules containing amethacrylate group were synthesized following two-step reaction (hydrosilylation,esterification) with different raw materials. Molecules were characterized by FTIR andNMR. Two-step synthesis route is easy to operate and has less pollution.Experiment3: Effect of different reaction conditions on the structure of the productwas analyzed. At a room temperature of25℃, time and feeding methods ofhydrosilylation reaction had no significant effect on the structure of the product. To someextent, temperature influenced the esterification reaction product concentration and the production rate. Slow dropping of reactants is recommended in hydrosilylation reaction ata room temperature of25℃for30minutes and esterification for two hours under85℃heating refluxing, since the reaction will be complete and the productivity will be higher.Part II of this study aims to evaluate the effect of new silane treatment on ceramicbond strength, and to analyze its mechanism of interaction.Experiment1: The study showed that sample material had significant effect on theshear bond strength value. Adherend with higher elastic modulus was able to obtain highershear strength test value. Shear bond strength values were also influenced by the bondingarea. The smaller the bonding area, the higher the bond strength value is. We should useappropriate sample material and bonding area, according to the research object andpurpose, to reflect the performance of the material more accurately and realistically.Experiment2: The enhancement of new long-chain silane to ceramic-resin bondingwas confirmed. Its instant bond strength was as effective as commercial silane couplingagent. After aging treatment, the samples useing novel silane showed higher bond strengthvalues. The silane coupling effect was gradually enhanced when the concentration wasincreased. But when the concentration reached4%, the bond strength was not significantlyincreased, and even decreased in some experimental groups.Experiment3: The mechanism of the novel silane and its relation with bond strengthwere analyzed by analytical chemistry methods. ATR-FTIR results showed that the silanemolecule and the ceramic surface formed a siloxane chemical bonding. When silaneconcentration was2%or higher, each characteristic functional group got clearcharacterization. XPS analysis showed that the silane formed the Si-O-Si siloxane on theceramic surface. The proportion of each element is consistent with the silaneconcentration.Experiment4: Wettability of ceramic surface treated by the new silane was tested. Itwas confirmed that new silane treatment could significantly reduce the contact angle ofglycerol to silicon-containing ceramic surface. The long-chain silane could improve thewettability of the surface of inorganic material. SEM showed that when the silaneconcentration was too high, silicone membrane formed on the surface of inorganicmaterial. This might result in bond strength reduction. Accordingly, the new long-chainsilane should be formulated as2-4%ethanol solution to be used as the dental ceramiccoupling agent. In summary, based on polymer materials and chemical research, this study designedand synthesized a novel long-chain silane molecule with better theoretical effect. Theproducts were characterized by series chemical analysis methods. Synthetic route withhigh efficiency and low harm was screened out. On this basis, the effect of long-chainsilane molecules on bond strength between ceramic and resin were tested. By the chemicaland surface morphology studies, we analyzed the mechanism of new silane molecules onthe bonding strength. It was confirmed that the chemical bonding formed betweensilicon-containing all-ceramic surface and long-chain silane molecules.