Incorporation of dimethyl sulfoxide into experimental hydrophilic and hydrophobic adhesive resins: evaluation of cytotoxic activities.

This study evaluated the cytotoxicity of methacrylate-based resins containing dimethyl sulfoxide (DMSO). DMSO was incorporated into hydrophobic (R2) and hydrophilic (R5) resins at weight concentrations of 0, 0.01, 0.1, 1, 5, or 10 w/w %. Resin discs (n = 10/group) were prepared. Human gingival fibroblasts (HGF-1) were exposed to resin eluates for 24 h. Furthermore, dentin barrier test was performed using 3-D cultures of odontoblast-like cells (SV40 transfected pulp derived cells) with dentin slices of 400 µm thickness (n = 8). After acid etching of dentin, DMSO-modified resins were applied into the cavity part of the device and light-cured for 20 s. Cell viability (%) was assessed by MTT and analyzed spectrometrically. Data were analyzed by ANOVA and Tukey test (α = 0.05). Resin eluates showed statistically significantly lower % cell viability for all neat and DMSO-modified resins than seen for the negative control. Moreover, DMSO-R5 eluates resulted in significantly lower % cell viability than DMSO-R2 emulates. The dentin barrier test showed that DMSO-R2 did not result in significantly lower % cell viability, whereas incorporation of 1-10 w/w % DMSO into R5 resulted in significantly lower % of cell viability. Incorporating DMSO into hydrophilic self-etching resins may increase cytotoxicity. The biocompatibility is not influenced by the addition of DMSO into hydrophobic resin.

Incorporation of dimethyl sulfoxide to model adhesive resins with different hydrophilicities: Physico/mechanical properties.

OBJECTIVE: To understand dimethyl sulfoxide (DMSO) interaction with distinct methacrylate monomer blends and the impact on polymer formation by investigating the combined relationship among degree of resin hydrophilicity, presence of DMSO and specific physico/mechanical properties. METHODS: One hydrophobic (R2) and one hydrophilic (R5) methacrylate-based resins with different monomer compositions were solvated in ascending DMSO concentrations (0, 0.01, 0.1, 1, 5, and 10 w/w %). Neat resins (0 w/w % DMSO) were used as controls. The degree of conversion was determined by Fourier-transform infrared spectroscopy. Polymer crosslinking density was indirectly measured by a modified ethanol-water two-stage solvation technique and the biaxial flexural strength was measured after 24 h and 30 days of water storage at 37 ̊C. Water sorption and solubility were gravimetrically assisted during 28 days of water storage to determine the kinetics of water-polymer interactions. Data were analyzed by ANOVA and Tukey test (α = 0.05). RESULTS: Incorporation of high DMSO-concentrations significantly increased the degree of conversion of all tested formulations, specifically for the hydrophobic resin (p < 0.05). Despite the increase in degree of monomer conversion, higher water sorption/solubility values and lower biaxial flexure strengths were detected as a result of reductions in polymer crosslink density (p < 0.05). In general, low DMSO-concentrations had no impact on the biaxial flexural strength, crosslinking density and water sorption/solubility (p < 0.05). CONCLUSION: DMSO-monomer ratio and monomer composition are critical for new dental methacrylate-based adhesive formulations. High DMSO incorporation hampers physico/mechanical properties of methacrylate bonding resins, albeit to a lesser extend when hydrophilic resins are employed. Nonetheless, DMSO-solvated hydrophobic adhesives extensively outperform their hydrophilic correspondents. DMSO incorporation of 1w/w % may constitute a secure threshold regardless of monomer composition.