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.

Controlled and orthogonal partitioning of large particles into biomolecular condensates.

Biomolecular condensates arising from liquid-liquid phase separation contribute to diverse cellular processes, such as gene expression. Partitioning of client molecules into condensates is critical to regulating the composition and function of condensates. Previous studies suggest that client size limits partitioning, with dextrans >5 nm excluded from condensates. Here, we asked whether larger particles, such as macromolecular complexes, can partition into condensates based on particle-condensate interactions. We sought to discover the biophysical principles that govern particle inclusion in or exclusion from condensates using polymer nanoparticles with tailored surface chemistries as models of macromolecular complexes. Particles coated with polyethylene glycol (PEG) did not partition into condensates. We next leveraged the PEGylated particles as an inert platform to which we conjugated specific adhesive moieties. Particles functionalized with biotin partitioned into condensates containing streptavidin, driven by high-affinity biotin-streptavidin binding. Oligonucleotide-decorated particles exhibited varying degrees of partitioning into condensates, depending on condensate composition. Partitioning of oligonucleotide-coated particles was tuned by altering salt concentration, oligonucleotide length, and oligonucleotide surface density. Remarkably, beads with distinct surface chemistries partitioned orthogonally into immiscible condensates. Based on our experiments, we conclude that arbitrarily large particles can controllably partition into biomolecular condensates given sufficiently strong condensate-particle interactions, a conclusion also supported by our coarse-grained molecular dynamics simulations and theory. These findings may provide insights into how various cellular processes are achieved based on partitioning of large clients into biomolecular condensates, as well as offer design principles for the development of drug delivery systems that selectively target disease-related biomolecular condensates.

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.

Selective dentin etching: A potential method to improve bonding effectiveness of universal adhesives.

OBJECTIVES: To evaluate whether selective dentin etching protocols using reduced phosphoric acid (H3PO4) etching-times would affect the resin-dentin interaction of a universal adhesive to improve long-term bonding effectiveness. METHODS: Mid-coronal flat dentin surfaces were produced on sound third molars, selectively etched with 32% H3PO4 for 3, 5, 10 or 15 s and bonded with a universal adhesive (Scotchbond Universal, 3 M ESPE: SU). SU in self-etch mode and a three-step etch-and-rinse adhesive were used as control groups. Bonded specimens were stored in deionized water for 24 h and sectioned into beams (cross sectional area of 0.7 mm2). Micro-tensile bond strength test (n = 6) and nanoleakage evaluation were performed immediately, after thermocycling or 6-month storage in artificial saliva. Energy dispersive X-ray analysis (n = 6) was performed to determine the residual Ca-content ratio at the hybrid layers and scanning electron microscopy (SEM) was used to observe the micromorphology of the etched dentin surfaces before and after SU application. Data were analyzed by ANOVA and Tukey test (α = 0.05). RESULTS: Selective dentin etching for 3 s improved the interaction depth of the tested universal adhesive without overexposing demineralized collagen or reducing Ca-content availability at the bonded interface. The improved immediate bond strengths of the selective etching protocol remained significantly higher (p < 0.05) after long-term aging producing hybrid layers without significant differences (p > 0.05) in silver uptake levels compared to those produced on non-etched dentin. CONCLUSIONS: Despite the adjunctive conclusion that universal adhesives used in self-etch mode produce superior long-term dentin bonding compared to the etch-and-rinse mode, selective etching for 3 s with conventionally used H3PO4 improves dentin bonding effectiveness; nonetheless, longer etching times should be strictly avoided.

Effect of various dimethyl sulfoxide concentrations on the durability of dentin bonding and hybrid layer quality.

The objective was to evaluate effect of dimethyl sulfoxide (DMSO) on microtensile bond strength (µTBS) and nanoleakage (NL). Superficial dentin was acid-etched and pretreated with DMSO. Etch-and-rinse adhesive was applied and restored with resin composite incrementally. After 24 h, teeth were sectioned, stored in artificial saliva for 24-h or 6-months before µTBS evaluation. Failure modes were examined. Six beams per group were submitted to nanoleakage evaluation using SEM. Data were analyzed using ANOVA and Tukey's test (α=0.05). Pretreatment had no significant effect on µTBS after 24 h (p>0.05). After 6 months storage, µTBS of control decreased significantly, more than with the groups treated with 0.01% or higher (p<0.05). DMSO-pretreated groups preserved µTBS in all groups. After 6-months, all groups except 0.001% showed significantly lower nanoleakege compared to control (p<0.05). DMSO (0.01-20%) may improve the hybrid layer integrity and bonding durability. The best results were seen with low (1-5%) of DMSO concentrations.