Development of dental resin luting agents based on Bis-EMA4: bond strength evaluation

The aim of this study was to investigate the influence of incorporating Bis-EMA4 monomer into experimental Bis-GMA/TEGDMA-based resin luting agents on the bond strength to dentin. Seven mixtures were prepared with the following ratios (wt%) of Bis-GMA/TEGDMA/Bis-EMA4: 50/50/0, 50/30/20, 50/10/40, 50/0/50, 30/10/60, 10/10/80 and 0/0/100. Camphorquinone (0.4 wt%), N,N-dimethyl-p-toluidine (0.8 wt%) and hydroquinone (0.2 wt%) were dissolved in each mixture, which was loaded with silanated strontium glass fillers to a constant content of 60 wt%. Bond strength was evaluated by microshear testing (n = 10) on bovine dentin. Data were submitted to Analysis of Variance (p < 0.05). Modes of failure were classified under magnification (200x). Bond strength means (MPa), respective to each agent, were: 19.4, 19.8, 20.0, 19.1, 16.8, 18.7 and 17.8. No significant differences were detected among groups. Mixed failures were generally predominant for all materials. In conclusion, the addition of Bis-EMA4 presented no significant influence on the bond strength of the experimental resin luting agents to dentin.22889

Halogen and LED light curing of composite: Temperature increase and Knoop hardness

This study assessed the Knoop hardness and temperature increase provided by three light curing units when using (1) the manufacturers' recommended times of photo-activation and (2) standardizing total energy density. One halogen - XL2500 (3M/ESPE) - and two light-emitting diode (LED) curing units - Freelight (3M/ESPE) and Ultrablue IS (DMC) - were used. A type-K thermocouple registered the temperature change produced by the composite photo-activation in a mold. Twenty-four hours after the photo-activation procedures, the composite specimens were submitted to a hardness test. Both temperature increase and hardness data were submitted to ANOVA and Tukey's test (5% significance). Using the first set of photo-activation conditions, the halogen unit produced a statistically higher temperature increase than did both LED units, and the Freelight LED resulted in a lower hardness than did the other curing units. When applying the second set of photo-activation conditions, the two LED units produced statistically greater temperature increase than did the halogen unit, whereas there were no statistical differences in hardness among the curing units.101667

Nanohybrid Resin Composites: Nanofiller Loaded Materials or Traditional Microhybrid Resins?

Nanohybrid resin composites present conventional particles to be mixed with nanomeric fillers and, therefore, it is unknown whether they may perform similarly to nanofilled or microhybrid resins. The current study investigated the properties of nanohybrid resins (TPH(3), Grandio, Premise, Concept Advanced) in comparison with a nanofilled (Supreme XT) and a microhybrid (Z250) composite. The inorganic fillers were characterized by SEM/EDS analysis. Diametral tensile strength (DTS), surface roughness before and after toothbrush abrasion, Knoop Hardness (KHN), water sorption and solubility were evaluated. The data were separately analyzed by ANOVA and the Student-Newman-Keuls' tests (p<0.05). The results of all analyses were material-dependent. Noticeable differences in filler size and shape were detected among the materials. Supreme XT generally showed higher DTS and KHN compared to all the nanohybrids and also showed lower surface roughness before and after toothbrush abrasion compared to most of the materials tested. Similar results were generally detected for the nanohybrids compared with the microhybrid material. In conclusion, the nanohybrid resins generally presented inferior properties compared with the nanofilled composite and either similar or slightly better properties compared to the microhybrid material. Under clinical conditions, nanohybrid resins may not perform similarly to nanofilled materials.34555155