Effect of Dimethyl Sulfoxide on Biaxial Flexural Strength of Resins

Objectives: The objective of this study was to evaluate the effect of DMSO concentration on the biaxial flexural strength of experimental hydrophobic or hydrophilic resin mixtures.
Methods: DMSO was incorporated toa hydrophobic(R2; Bis-GMA, TEGDMA, CQ, EDMAB) or hydrophilic resins (R5; Bis-GMA, HEMA, 2MP, CQ, EDMAB) at various concentrations (0.01, 0.1, 1, 5, 10%). For biaxial testing, resin discs (0.6-mm thick, 6.2-mm diameter) from DMSO/resin mixtures were applied incrementally to the Teflon molds (n=10) and light-cured for 30 s (3M ESPE Elipar, Germany). Resin discs without addition of DMSO were used as controls. Discs were water-stored for 24 hrs or 30 days at 37 C before testing to flexural failure (1.27 mm/min, Shimadzu corporation- Japan). Flexural data were statistically analyzed by ANOVA and Tukey's post-hoc test at a pre-set alpha of 0.05.
Results: Both resins composition and DMSO content showed significant effect on biaxial flexural strength (p<0.05). The biaxial flexural strength of hydrophobic resin was significantly higher than the hydrophilic resin p<0.05. Incorporation of 5% or more DMSO significantly reduced the flexural strength for both experimental resins (p<0.05). After 30 days of incubation, all groups had a slight decrease in flexural strength, which was only significant for hydrophobic resin with 5 or 10% DMSO addition (p<0.05).
Conclusions: In both experimental resins used, addition of 5-10% of DMSO significantly influenced the flexural strength. Including high concentrations of DMSO (5% or more) may compromise the mechanical properties of resin.