| Objective: To preliminary develop nano compositedenture base resin. Observation was made on the influence ofnano particle on Impact Strength and Rockwell Hardness ofnano composite denture base resin and the mechanism wasdiscussed.Methods: 1 .Mold manufacture: A metal mold was madewhich has six 80mm×10mm ×6mm flutes. Moreover a metallap had the same size as the mold was made, which could befixed up on the mold with the screw. 2. The configuration ofthe nano composite denture base resin compound materials:Weighted the high-purity nanometer SiO2 powder and thePMMA with the electronic balance according to①0∶100,②0.05∶99.95, ③0.10∶99.90, ④0.20∶99.80, ⑤0.40∶99.60,⑥0.80∶99.20 proportions. 3. Testing sample manufacture:The nanometer SiO2 powder was put into the MMA anddispersed by ultrasonic wave. Then this solution and PMMAwas mixed with proper percentage. The mixture was put intometal mold in a certain period to make the testing samples. Allof samples were divided into 6 groups which were signed withA, B, C, D, E and F . Every group had 6 samples. 4 .RockwellHardness testing: The test samples were put on the Rockwelltester and three points were chosen to test. The valueswere recorded and the average HR was got. 5 .ImpactStrength testing: The test samples were put on the simple beamimpact laboratorial aircraft and the records of each test sampleimpact break consumes was wrote down after carried on theimpact to the test sample. 6 .Preparation and observation ofspecimen by scanning electron microscope (SEM): The brokentest samples were collected and one sample of each group waschosen .The cross section was cut and observed by SEM aftermarked, cleaned and adhered.Results: 1.Rockwell Hardness: The experiment obtains 6groups of data were: group A 114.3±0.5HR, group B123.8±0.3HR, group C 120.3±0.4HR, group D 120.6±0.7HR,group E 121.4±0.5HR, group F 120.4±0.5HR. The RockwellHardness of group B was the biggest one (P < 0.05); group Awas the smallest one and smaller than other 5 groups (P < 0.05);group E had the significant difference with other 5 groups (P <0.05); No significant different was found among group C,group D and group F (P > 0.05). Indicated: That the contentof nano powder from low to high, its degree of hardnessvalue curve displayed the tendency also from low to high. 2.Impact Strength: The Impact Strength of 6 groups were: groupA 6.71±0.37 KJ/m~2, group B 10.15±0.54 KJ/m~2, group C9.54±0.44 KJ/m~2, group D 6.66±0.84 KJ/m~2, group E6.30±0.76 KJ/m~2, group F 4.08±0.57 KJ/m~2.The impactstrength of group B and group C were bigger than the other 4groups (P<0.05). Group F was the smallest one (P<0.005). Nosignificance difference was demonstrated between group B andgroup C (P > 0.05). There was no significant difference amonggroup A, group D and group E (P > 0.05).Indicated: That theImpact Strength value curve display the tendency from the highto low if the content of nano powder from the low to high. 3.Observation of SEM: Group A: The cross section of the testsample was obviously smooth and surfacing less than 500times electricity mirrors, similar brittle fracture. Under 2,000times of electricity mirrors the cross section was obviouslysmooth, internal obviously individual impurity pellet. Theplastic internal structure was obviously even, has not seen theair bubble under 20,000 times of electricity mirrors. Group B:Under 500 times of electricity a mirror, the test sample crosssection was obviously rough, lacerated surface was increasingand has the dispersible granule. Under 2,000 times ofelectricity mirrors, few granules internal which weredispersedly and small could obviously be seen. Under 20,000times of electricity mirrors, the nanometer SiO2 powderdispersedly, the size was even and the particle size wasbetween 80nm~100nm. Group D: Under 500 times ofelectricity mirrors, the test sample cross section wasobviously rough and many SiO2 powder reunion body in itwere visible. Many nanometer SiO2 reunion bodies in thesample under 2,000 times electricity mirrors were shown and...
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