RESUMO
Statement of Problem: Bonding agent composition for impregnation of fiber may increase the flexural strength of fiber-reinforced composites by means of increasing adhesion
Purpose: Investigating the impact of filler of four commercial bonding agents with different hydrophobicity on the flexural strength of a fiber-reinforced composite
Materials and Method: In this experimental study, six groups [N=15 per group] of polyethylene fiber-reinforced composite specimens were prepared. In group 1, the positive control group, the samples were prepared using composite and without fiber, whereas in group 2, as the negative group, fiber-reinforced composite without any bonding agent resination was used. The fibers in group 3 to 6 were resinated with Single bond 2, Single bond, Resist, and all bond 3, respectively. Firstly, the fiber was placed in the base of the specimen preparation mold. Then the mold was filled with composite and cured. The specimens were stored in distilled water for 24 hours. In the next step, the flexural strength was measured in Three-point bending test with Instron machine at cross- head speed of 1 mm/min. Failure mode of the specimens was observed with stereomicroscope. At last, statistical analysis was performed using ANOVA and LSD post hoc tests [p < 0.05]
Results: Ono-way ANOVA test was used for evaluating the relationship among the groups, and for pair-wise comparison, LSD post-hoc test was used. One-way ANOVA test showed a significant difference among the groups. The All bond 3 group showed a significantly higher flexural strength than the other groups [p <0.001]. Groups 3 to 6 had significantly higher flexural strength than flexural strength of the control groups [p <0.05]
Conclusion: The choice of bonding agent can have a significant impact on the flexural properties of the fiberreinforced composite. When filled hydrophobic bonding agent was used for impregnation of the fiber, compared to negative control group, flexural strength increased 4 fold
RESUMO
Statement of Problem: Polymerization shrinkage is one of the major problems of the current dental composites and it can cause marginal gap and post-operative sensitivity
Purpose: The purpose of this study was to investigate the effect of nanoporous fillers on the polymerization shrinkage and degree of conversion of an experimental dental composite in three different curing modes and also comparing its results with another experimental composite containing conventional fillers
Methods and Material: In this study, the experimental composite was prepared by mixing the silane treated fillers with monomers. The monomers consisted of 70% Bis-GMA and 30% TEG DMA by weight. The experimental composite was divided into two groups according to their filler type, i.e. conventional micro-hybrid and nanoporous. In order to make nanoporous fillers, the fillers were sintered in 1300[degree sign]c and grinded Camphorquinon and DMA EMA were used as initiator-accelerator systems. Polymerization shrinkage was measured using bonded disc method in three curing modes [High Intensity, Ramp, Standard]. The degree of convention was measured using FTIR spectroscopy
Result: The results showed that the nanoporous fillers have a positive effect on the reduction of polymerization shrinkage strain. No significant difference was found in polymerization shrinkage of the three curing modes. Neither the type of the fillers nor the mode of cure had an effect on the degree of conversion
Conclusion: Lower polymerization shrinkage strain can be achieved by using nanoporous fillers. The mode of cure does not affect the polymerization shrinkage