A Study Of Porosity And Mechanical Property On Nano Composite Base Resin

Objective: To study the effect on the porosity and mechanical property of nano composite denture base resin added silicon dioxide.Method:1. Use the common resin of base(PMMA),nano-composite resin (PMMA/SiO2) to make 96 test pieces together by means of heat polymerization in water bath and microwave polymerization. These test pieces are 65mm long, 40mm wide, 3mm,5mm,7mm,9mm thick divided into 16 groups. Fininsh and polish these test pieces. Measure these specimen,s weight after drying and hydrating to calculate the porosity by formula.2. Use the common resin of base(PMMA),nano-composite resin (PMMA/SiO2) to make 64mm×10mm×2.5mm and 50mm×6mm×4mm test pieces by means of heat polymerization in water bath and microwave polymerization. These are 4 groups. Each group has 32 resin test piece. Measuring flexural strength and flexural modulus by electronic almighty experimental machine.Results:1. There has no remarkable differece between different material test specimen's porosity (p>0.05), but different polymerization has remarkable effect on test specimen's porosity(p<0.01)。Porosity of the heat polymerization in water bath is smaller than that of the microwave polymerization. Porosity of different thickness has the remarkable difference(p<0.01) , In 2-2 tom-parisons , there is remarkable differences in 2-2 comparisons of 4 thickness group .2. Bending strength and impact strength of different material have remarkable difference(p<0.05), bending strength and impact strength of different polymerization have no remarkable difference(p>0.05).Conclusion:1. There has no remarkable differece between porosities of common resin of base(PMMA) and nano-composite resin (PMMA/SiO2).2. thickness has great effect on the porosity and porosity will increase with the thickness increasing.3. porosity of the heat polymerization in water bath is smaller than that of the microwave polymerization.4. bending strength and impact strength of the nano-composite resin is better than that of the common resin of base.5. bending strength and impact strength. have no statistically differences between microwave groups and in water bath groups.