| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 95 === As size of matter is reduced until few nanometers, quantum effects significantly change material''s optical, magnetic or electrical properties. The attraction of many researcher for this length scale depend on the different and often enhanced properties of matter compared with the same materials at a larger size. In this study, we mixed different kinds of nanoparticle in dental resin material. The purpose was to evaluate the possibility of decreasing the fraction or replacing the use of the fiber in fiber reinforced composite resin posts.First, the dual-cured initiator system for resin matrix (Bis-GMA + TEGDMA) was decided according to the result of microhardness test. Then, carbon nanotube (CNT) and polyhedral oligomeric Silsesquioxane (POSS) were added into resin matrix separately. Three kinds of carbon nanotube were used: unmodified multi-wall CNT, PMMA-grafted CNT and GMA-grafted CNT. POSS-MA (methacryl-POSS cage mixture) with 8 polymerizable methacrylate groups was chosen as the other nanoparticle filler in this study. In the third part, chopped glass fiber was used as reinforcement of composite.Elastic modulus of these nanoparticle/ fiber reinforced composite resin material was obtained by three point test. The fracture surface of specimens observed under SEM for evaluation of interaction among nanoparticle, glass fiber and resin matrix.
Comparing the result of carbon nanotube/composite resin, the more CNT was added in resin system, the lower the elastic modulus. Results revealed the poor dispersion in all CNT specimens. This study discovered that the functionalized CNT cannot be dissolved nor dispersed through ultrasonic tip vibration. Also, POSS-MA is not beneficial in improvement of mechanical properties probably because of incomplete polymerization. The result of FTIR explained the assumption that as POSS-MA increases, the conversion rate of the polymer decreases. When the weight fraction of glass fiber was up to about 60%, the reinforced composite resin exhibited improved elastic modulus approaching to that of human dentin (about 20 GPa). SEM observation on the failure surface of specimens indicated that the enhanced mechanism is due to the interfacial bonding between the fibers and the surrounding matrix modified by nano-sized filler. As the result, 10wt% of POSS-MA was supposed to improve the stress conduction between the different materials in resin system. The similar tendency not found in the CNT composites might resulted from the tiny amount of CNT and its poor dispersion in resin.
Nano-sized particle has the potential in development of dental composite material, but carbon nanotube should be well dispersed first. The interaction between nanoparticle and fiber, needed to be further investigated.
|
|---|
