In vitro evaluation of multi-walled carbon nanotube reinforced nanofibers composites for dental application

The goal of this study was to evaluate the mechanical properties of an experimental composite resin filled with nylon-6 nanofibers (N6), nylon-6 nanofibers with multi-walled carbon nanotubes (N6-MWCN) or with pre-polymerized resin at different concentrations. The fillers/particles were obtained from nanofibers produced by electrospinning technique or from pre-polymerized composite resin. The fillers were distributed in the composite resin in four different mass fractions (2.5, 5.0, 10.0, and 20.0%), totaling 12 groups. The volumetric polymerization shrinkage (VPS), composite film thickness (CRFT), flexural strength (FS) and elastic (E) modulus of the composite resins were calculated. The data were evaluated using two-way ANOVA and Tukey test (p < .05). The interaction concentration*filler material was statistically significant for the VPS (p = .0008) and for FS (p = .0001). The smallest VPS was observed in 20% concentration without a difference to 10% for N6-MWCN particles. For FS, N6-MWCN in 2.5 and 5.0% presented the highest values (116.4 +/- 9.32; 118.5 +/- 7.72). Both factors (p = .0001) were significant for CRFT. Higher concentration (20%) showed a higher film thickness. E modulus was similar for all conditions, with p = .0590 for filler material and p = .3987 for concentration. The most indicated composite reinforcement in order to achieve suitable flexural strength with decreased polymerization shrinkage is the use of pre-polymerized composite-based material at a concentration of 20%. N6-MWCNT particles in 2.5 or 5% concentrations should be incorporated to produce a composite resin presenting adequate strength associated with reduced film thickness.