Methods: 4 groups of denture resin (Luciton 199, Densply Inc.) specimens were fabricated as: control, 0.5%, 1%, and 2% of MWCNT by weight. MWCNTs were dispersed to monomer by sonication. Each specimen was 10mmx40mmx3mm in size. 10 specimens of each group without thermocycles (TC) were subject to 3-point-bending test up to failure at a loading rate of 5 mm/min. Another 4 groups underwent 2000 thermo-cycles from 200C to 800C at one minute interval. Knoop microhardness was performed on the control and experimental groups before and after thermocycling. 2-way ANOVA and Duncan’s test were used to identify any statistical differences. Fractured surfaces were analyzed by SEM.
Results:
Based on displacement vs. load curve, flexural strength, flexural modulus, yield stress, yield strain, and resilience were calculated for each specimen. Statistical analyses reveal that there is a significant difference of mechanical properties between before and after thermocycles. 2% MWCNT is harder and weakest among the groups. Summary of average maximum flexural strength as follows.
|
Control |
0.5% MWCNT |
1% MWCNT |
2% MWCNT |
Before TC |
103.25+3.6 |
103.45+4.4 |
103.17+5.4 |
86.85+5.91 |
After TC |
83.93+5.5 |
95.40+4.90 |
90.36+2.87 |
80.29+6.87 |
Conclusions:
05% MWNCT significantly improved yield stress (20%) and resilience (14%) than control group as arrester/retarder for crack propagation. The higher % of WMCNT dispersed in PMMA was not beneficial. SEM analysis showed sporadic agglomerations presented on fracture surface of 2% WMCNT samples.
Keywords: Dental materials, Polymers, Prostheses, Stain and Stress