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Composite resin is a kind of dental material composed of resin martrix, pre-treated filler and initiating system which has been widely used in dental restoration. With its good bio-compatibility, esthetic results and acceptable mechanical properties, especially with the improvement of mechanical properties, composite resin is more widely applied today. But it’s mechanical properties is still insufficient, especially for posterior teeth and incisor edge restoration.Since its emergence, adhesive dental materials, especially enamel adhesive have been widely used and acquired satisfactory results. Although various products emerged, properties of dentine adhesive still need improve. How to improve the mechanical and bonding properties has attracted much interest in recent years.Since 1980’s, nanomaterial, which has particular character because of its size of nanoscale, has been developed. Nano-diamond is a kind of nanomaterial with high hardness, wear-resistance and bio-caopatibility. In the present study, nano-diamond has been introduced into composite resin and resin adhesive. The compressive strength, flexure strength, micro-hardness and wear- resistance of the treated composite resin were examined to evaluate the effect of nano-diamond on the mechanical properties of composite resin. The micro-tensile bond strength, shearing bonding strength of treated dentine adhesive were examined and the adhesive interface was observed by scanning electrode microscope(SEM) to evaluate the effects of nano-diamond on dentine adhesive.Part I: Effects of nano-diamond on mechanical properties of composite resin.After 0.005%, 0.02% ,0.1%,0.3%, 0.6%, 1% (WAV)nano-diamond was added to Esthet X resin respetively, the compressive strength, flexure strength, micro-hardness and wear-resistance of the composite resin have changed significantly, the compressive strength and micro-hardness of 0.1%, 0.02% group were improved, especially the 0.02% group, while the results of 0.3%, 0.005%group were not changed and the 1%, 0.6%group decreased. The flexure strength of 1%, 0.005%group were not changed while the 0.02%, 0.1%, 0.3%, 0.6%group improved, especially the 0.6% group. And wear-resistance of 1%, 0.005% group was not changed, on the contrary the 0.02%, 0.1%, 0.3%, 0.6%group decreased, especially the 0.3%group. Part II: effects of nano-diamond on the bonding ability of dentine adhesive.0.02%, 0.1%, 0.3% nano-diamond was added to Prime & Bond NT adhesive and was used in wet bonding with Esthet X and Esthet X treated with 0.02% nano-diamond, and the micro-tensile bond strength, shearing bonding strength were examined. The results showed that the bonding strength was improved after nano-diamond addition, especially the 0.02% group. Different composite resin also affected the bonding ability and Esthet X treated with 0.02% could improve bonding strength. The values of micro-tensile bond strength and shearing bonding strength were different and the former was obviously higher. Transmission electrode microscope(TEM) study showed that the nano-diamond was well dispersed in matrix resin. SEM study found hybrid layer about 4μm~5μm thick in each group, the resin tags were ranged from 15μm~35μm and there were no difference existed between each group. The fracture of micro-tensile bond testing sample occurs at the bonding interface and the fracture of shearing bonding strengthtesting sample occurred in dentine or in resin or both. This also confirmed thereliability of micro-tensile bond strength testing method.These results indicated that the mechanical properties and adhesion abilitycould be significantly improved by means of the application of nano-diamond.
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