Three-dimensionally printed denture base resins modified by nanoglass particles and carbon nanotubes.

STATEMENT OF PROBLEM

Three-dimensionally (3D) printed denture base resins exhibit inferior mechanical properties compared with conventional and milled ones, a problem affecting their long-term clinical use. Improved 3D printed resins are required.

PURPOSE

The purpose of this in vitro study was to determine whether a 3D printed denture base resin with nanoglass particles and multiwalled carbon nanotubes (MWCNTs) would exhibit enhanced mechanical properties.

MATERIAL AND METHODS

The nanoglass particles and MWCNTs were silane coated and added to the resin to obtain the following groups: Control, resin modified with nanoglass particles with 2 percentages, 0.25 wt%, and 0.5 wt%; resin modified with MWCNTs with 2 percentages, 0.25 wt%, and 0.5 wt%; and a combination group with 0.25 wt% of each filler type. The printed specimens (N=330) were tested before and after thermocycling (600 cycles) for flexural strength (FS) and elastic modulus (n=22) by using a universal testing machine and for impact strength (IS) (n=22) by using a Charpy impact tester. The fractured impact specimens were then evaluated by using scanning electron microscopy (SEM). The surface roughness (Ra) (n=11) was assessed by using a profilometer. For data analysis, the 2-way ANOVA test was used for the analysis of FS, elastic modulus, and IS, and the 3-way ANOVA test was used for Ra with a subsequent Tukey post hoc test. Percentage change was compared among groups by using the Kruskal-Wallis test, followed by the Dunn post hoc test with Bonferroni correction (α=.05).

RESULTS

The filler content and thermocycling revealed a significant main interaction effect (P<.001) on FS, elastic modulus, and IS, with the 0.5% nanoglass group displaying the highest percentage decrease after thermocycling. The SEM images of fractured impact specimens revealed a brittle failure in the control and nanoglass groups. In contrast, the groups containing MWCNTs and the combination group displayed intermediate to ductile failure. Moreover, a significant inclusive interaction effect (P<.001) was found between the filler content, thermocycling, and polishing on surface roughness, with the 0.5% nanoglass group revealing the highest percentage increase in Ra of the polished surface after aging.

CONCLUSIONS

The addition of nanoglass and MWCNTs led to a significant improvement in the FS, elastic modulus, and IS of the 3D printed resin. The combination group displayed the least percentage change among all groups regarding the FS and IS, displaying intermediate to ductile failure. The control revealed the least percentage change in elastic modulus after thermocycling but with lower peak values compared with all other groups.