Ivana Radovic

Light transmission through fiber post: The effect on adhesion, elastic modulus and hardness of dual-cure resin cement

OBJECTIVES The aim of this study was to investigate the effect of fiber post light transmitting ability to the continuity of resin cement-root dentin (C-RD) and resin cement-fiber post (C-FP) interface, elastic modulus and hardness of a dual-cure resin cement. METHODS Spectrophotometric measurements were applied for the determination of light transmission at coronal, middle and apical level as well as at the apical tip through Tech 21 X-OP (TECH) and DT Light Post (DT). Posts were cemented using dual-cured resin cement (Calibra). Roots were sectioned longitudinally through the post. Epoxy resin replicas were made and used to evaluate C-RD and C-FP interface under SEM. Modulus of elasticity (E) and Vickers hardness (VH) of the cement layer were assessed. RESULTS No light transmission was detected through TECH. Light transmission through DT decreased from coronal to apical and rose at the apical tip. TECH presented a significantly lower percentage of continuous C-RD and C-FP interface in comparison to DT. Coronal third of C-RD interface in TECH specimens had a significantly higher percentage of continuity than apical third. No regional differences in continuity of C-RD interface were found in DT specimens. E and VH were significantly lower when TECH was used, and decreased from coronal to apical for both posts. SIGNIFICANCE Cementation of fiber post with no light transmitting ability using a dual-cured resin cement resulted in lower E and VH of the cement layer, and lower percentage of continuous C-RD and C-FP interface in comparison to cementation of light transmitting fiber post.

Effect of intermediate agents and pre-heating of repairing resin on composite-repair bonds

This study investigated the composite-to-composite microtensile bond strength and interfacial quality after using different combinations of intermediate agents and pre-curing temperatures of repairing resin. Forty-five composite discs (8x4 mm) of Gradia Direct Anterior (GC Corp), stored in a saline solution at 37 degrees C for one month, were sandblasted (50 microm aluminum oxide), cleaned (35% phosphoric acid) and randomly divided into three groups (n=15) according to the intermediate agent applied: (1) no treatment; (2) unfilled resin (Scotchbond Multi-Purpose Adhesive, 3M ESPE); (3) flowable composite (Gradia LoFlo, GC Corp). Each disc was incrementally repaired (8x8 mm) with the same resin as the substrate. For each group, three subgroups (n=5) were created, depending on the pre-curing temperature of the repairing resin-4 degrees C, 23 degrees C or 37 degrees C. Two bonded specimens per group were prepared to evaluate the composite-to-composite interfacial quality via scanning electron microscope. Microtensile bond strength measurements were performed with the remaining three specimens and failure mode was examined by stereomicroscopy. Two-way ANOVA revealed that temperature (p < 0.001), intermediate agent (p < 0.001) and the interaction (p = 0.002) significantly affected the repair strength. Post-hoc comparisons revealed that bond strengths were significantly lower using a 4 degrees C repairing resin in groups where intermediate agents were used. The highest bond strengths were recorded when flowable composite was used as an intermediate agent under each of the three temperature conditions. Interfacial quality improved by raising the resin temperature from 4 degrees C to 37 degrees C.

The impact of Trichinella spiralis excretory-secretory products on dendritic cells.

Parasitic nematode Trichinella spiralis exert immunomodulatory effect on the host immune response through excretory-secretory products (ES L1) released from the encysted muscle larvae. Rat bone-marrow derived dendritic cells (DCs) stimulated with ES L1 antigens acquire semi-matured status and induce Th2 and regulatory responses in vitro and in vivo. Priming naïve T cells in vitro with ES L1 pulsed DCs caused strong Th2 polarization, accompanied by elevated production of regulatory cytokines IL-10 and TGF-β and no increase in the proportion of CD4+CD25+Foxp3+ among the effector T cell population. In vivo T cell priming resulted in mixed Th1/Th2 cytokine response, with the dominance of the Th2 type and elevated levels of regulatory cytokines. Significant increase in the proportion of CD4+CD25+Foxp3+ cells was found among recipients spleen cells. We have achieved to create immune status characteristic for the live infection by in vivo application of DCs educated with ES L1 antigens.

Microtensile vs microshear bond strength of all-in-one adhesives to unground enamel.

PURPOSE to determine the bond strength to unground enamel of all-in-one adhesives in comparison with an etch-andrinse system and to compare the reliability of microtensile and microshear methods in providing such measurements. MATERIALS AND METHODS the bonding procedure was performed on enamel of 64 extracted molars. The tested all-inone adhesives were: Bond Force (Tokuyama), AdheSE One (Ivoclar-Vivadent), and Xeno V (Dentsply). Prime&Bond NT (Dentsply) served as control. Microtensile specimens were obtained from 4 teeth per group. Twelve teeth per group were used for microshear testing. Microtensile specimens that failed prior to testing were included in statistical calculations; they were assigned the lowest value measured in the respective group. Failure modes were observed under light microscope and classified (cohesive within substrates, adhesive, mixed). Statistically significant differences in bond strength were assessed among the adhesives within each testing method and between microshear and microtensile data for each adhesive. Failure mode distributions were compared using the chi-square test. RESULTS all-in-one adhesives had similar microshear and microtensile bond strengths. In both testing methods, the etch-and-rinse system achieved the strongest bond. For all adhesives, significantly higher bond strengths were measured with the microshear test. In microtensile testing, specimens bonded with the etch-and-rinse adhesive exhibited a significantly different distribution of failure modes. The coefficients of variation were extremely high for microtensile bond strength data, particularly of all-in-one adhesives. CONCLUSION the adhesive potential to intact enamel of recently introduced all-in-one adhesives was inferior to that of an etch-and-rinse system. When testing bond strength to enamel of all-in-one adhesives, microshear testing may be a more accurate method than microtensile.

Morphological Evaluation of 2- and 1-step Self-etching System Interfaces with Dentin

This in vitro study evaluated the resin-dentin interface formed by two 2-step and two 1-step self-etching adhesive systems under SEM. Class V cavities (4 x 2.5 x 1.5 mm) were prepared on the buccal surfaces of 25 extracted intact human third molars using a carbide bur in a high-speed handpiece. Four self-etching systems with corresponding resins were used: two 2-step systems, AdheSE (Ivoclar Vivadent) and Contax (DMG Hamburg), one 1-step/2 components system Futurabond NR (Voco) and a 1-step/1 component adhesive G-Bond (GC Corp). An etch and rinse system, PQ Clear (Ultradent), was used as a control. The teeth were thermocycled (500 cycles, 5 degrees /55 degrees C, 30 seconds dwell time), and 2 sections were made longitudinally through the restorations with a low-speed diamond saw, producing approximately 1-mm wide samples. The samples were polished with silicon carbide paper of increasing grit (400-1000), demineralized (6N HCl, 30 seconds), deproteinized (2.5% NaOC1, 10 minutes), left to air dry for 24 hours in a desiccator under low vacuum pressure, gold sputtered and viewed under SEM (JEOL-JSM-6460LV). In the AdheSE, Contax and Futurabond NR specimens, resin tag penetration into the tubules and lateral tags could be seen. G-Bond showed different interface morphology, with a tight, thin continuous junction and almost no resin penetration into tubules. PQ Clear samples exhibited the highest number of resin tags with numerous lateral tags. A clearly defined hybrid layer was seen in the Contax and PQ Clear specimens. Investigated self-etching systems showed similar interfacial morphology with dentin, except for the 1 step/1 component adhesive G-Bond. The degree of demineralization and interaction with dentin correlated with the acidity of the self-etching primers/adhesives. Fewer resin tags were formed with self-etching primers/adhesives than with the etch and rinse system.

Immunomodulatory effects of Trichinella spiralis-derived excretory–secretory antigens

Helminth-derived products, either released into the circulation during the course of the infection or isolated after in vitro cultivation of the parasite and applied by the injection, are able to suppress the host immune response to autoantigens and allergens, but mechanisms could differ. Prophylactic application of Trichinella spiralis excretory–secretory muscle larvae (ES L1) products ameliorates experimental autoimmune encephalomyelitis (EAE) with the same success as infection did. However, a shift to the Th2-type response in the periphery and in the central nervous system, accompanied by activation of regulatory mechanisms, had a striking, new feature of increased proportion of unconventional CD4+CD25−Foxp3+ regulatory cells both in the periphery and in the central nervous system of animals treated with ES L1 before the induction of EAE.

Trichinella spiralis shares epitopes with human autoantigens

Like other helminths, Trichinella spiralis has evolved strategies to allow it to survive in the host organism, including the expression of epitopes similar to those present in either expressed or hidden host antigens. To identify T. spiralis-derived antigens that are evolutionarily conserved in the parasite and its host and that could be responsible for its evasion of the host immune response, we examined the reactivity of six different types of autoantibodies to T. spiralis larvae from muscle. T. spiralis antigens that share epitopes with human autoantigens were identified by assessing the cross-reactivity of autoantibody-containing serum samples with T. spiralis antigens in the absence of specific anti-parasite antibodies. Of the 55 autoantibody-containing human serum samples that we analysed by immunohistological screening, 24 (43.6%) recognised T. spiralis muscle larvae structures such as the subcuticular region, the genital primordium or the midgut. Using Western blots, we demonstrated that the same sera reacted with 24 protein components of T. spiralis muscle larvae excretory-secretory L1 antigens. We found that the human autoantibodies predominantly bound antigens belonging to the TSL1 group; more specifically, the autoantibody-containing sera reacted most frequently with the 53-kDa component. Thus, this protein is a good candidate for further studies of the mechanisms of T. spiralis-mediated immunomodulation.

Healing efficiency of polystyrene electrospun nanofibers with Grubbs’ catalyst in thermosetting composite

The study presents a novel method for the protection of Grubbs’ catalyst, by incorporation in polystyrene fibres via electrospinning technique. Epoxy-glass fibre composite with embedded self-healing agents (polystyrene fibres with Grubbs’ and microcapsules with dicyclopentadiene) was processed. Fibres retained pale purple colour during processing, revealing that fibres provided good protection of the catalyst from the amine hardener. The influence of self-healing agents’ content and thermal treatment on self-healing efficiency was investigated. Fourier transform infrared spectroscopy revealed that a polydicyclopentadiene formed at the healed interface. Thermal analysis revealed that ‘bleed’ at the healing sites from different samples had similar concentration of polydicyclopentadiene, indicating that the same amount of the catalyst has been provided to dicyclopentadiene for polymerization. This finding lead to assumption that electrospun polymer fibres enabled good dispersion of the catalyst in the composites. The low energy impact tests of the samples showed a recovery of 90% after 24 h at room temperature and up to 111% after repeated heating cycles.

Identification of the Trichinella species by PCR method.

Serbia is country with a high prevalence of Trichinella infection in pigs, which continues to be a serious human health problem. In Serbia, only a few isolates of Trichinella found in pork have been genetically specified to date, and all were proven as T. spiralis. New data shows that in the sylvatic cycle in Serbia, at least in the Belgrade district, more than one Trichinella species co-exist (T. spiralis and T. britovi). Increased awareness of the possible overlap among sylvatic and domestic Trichinella cycles indicates the need for continuous monitoring of Trichinella species circulation and strongly points to the need that all isolates of Trichinella found in meat for human consumption should be subject to a determination of the Trichinella species (due to the risk of transmission of infection with T. britovi to domestic pigs and humans). This is why we examined using PCR the Trichinella larvae found in pig meat that caused a human outbreak (Trichinella infection) in Grocka (Belgrade district) during February 2011. The isolated larvae belonged to T. spiralis. [Projekat Ministarstva nauke Republike Srbije, br. 173047]

Electrospun Poly(styrene) Fibers as a Protection for the First- and the Second-Generation Grubbs’ Catalyst

ABSTRACT The study presents a novel method for protection of the first- and the second-generation Grubbs’ catalyst, by incorporation in poly(styrene) fibers through electrospinning technique. Both catalysts are sensitive to the presence of the amine hardeners in the epoxy-based self-healing composites and require protection from deactivation to retain their ability to promote polymerization reaction of the healing agent. Comparison of healing efficiencies of both catalysts suggested that poly(styrene) fibers offer better protection and dispersion for the first-generation Grubbs’ catalyst, although all the samples exhibited high-healing efficiency. Difference in stereoselectivity between two catalysts was also indicated. GRAPHICAL ABSTRACT