Effect of Carbon Nanotubes on Mechanical Properties of Denture Resin

Objectives: Denture resin base fracture is not uncommon for clinicians. The purpose of this study was to exam the effect of functionalized multi-walled carbon nanotubes (MWCNT) on properties of a polymethyl methacrylate (PMMA) denture resin.

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.