Browsing by Author "Fawzy, Amr"

Objective:To evaluate the effect of a new application method of bulk-fill flowable compositeresin material on bond-strength, nanoleakage, and mechanical properties of dentine bonding agents.Materials and methods: Sound extracted human molars were randomly divided into: manufacturer ’sinstructions (MI), manual blend 2 mm (MB2), and manual blend 4 mm (MB4). Occlusal enamelwas removed and flattened, dentin surfaces were bonded by Prime & Bond universal (Dentsplyand Optibond FL, Kerr). For the MI group, adhesives were applied following the manufacturer’sinstructions then light-cured. For MB groups, SDR flow+bulk-fill flowable composite resin wasapplied in 2- or 4-mm increment then manually rubbed by a micro brush for 15 s with uncured dentinebonding agents and the mixture was light-cured. Composite buildup was fabricated incrementallyusing Ceram.X One, Dentsply nanohybrid composite resin restorative material. After 24-h waterstorage, the teeth were sectioned to obtain beams of about 0.8 mm2for 24-h and thermocycledmicro-tensile bond strength at 0.5 mm/min crosshead speed. Degree of conversion was evaluatedwith micro-Raman spectroscopy. Contraction gaps at 24 h after polymerization were evaluated andatomic force microscopy (AFM) nano-indentation processes were undertaken for measuring thehardness across the interface. Depth of resin penetration was studied using a scanning electronmicroscope (SEM). Bond strength data was expressed using two-way ANOVA followed by Tukey’stest. Nanoindentation hardness was separately analyzed using one-way ANOVA. Results: Factors“storage F=6.3” and “application F=30.11” significantly affected the bond strength to dentine.For Optibond FL, no significant difference in nanoleakage was found in MI/MB4 groups betweenbaseline and aged specimens; significant difference in nanoleakage score was observed in MB2 groups.Confocal microscopy analysis showed MB2 Optibond FL and Prime & Bond universal specimensdiffusing within the dentine. Contraction gap was significantly reduced in MB2 specimens in bothadhesive systems. Degree of conversion (DC) of the MB2 specimens were numerically more comparedto MS1 in both adhesive systems. Conclusion: Present study suggests that the new co-blend techniquemight have a positive effect on bond strengths of etch-and-rinse adhesives to dentine.

This study aimed at evaluating the physicochemical and biological properties of experimental epoxy-resin sealers containing polyphenols such as resveratrol and pyrogallol. A conventional epoxy resin (OB) was modified by adding different concentrations of resveratrol (RS) or pyrogallol (PY) to its composition. Antibacterial and antioxidant activities, mechanical properties, along with wettability and morphological changes were investigated. The results were statistically analyzed using ANOVA and multiple comparison tests ( = 0.05). The incorporation of the tested polyphenols into the epoxy resin enhanced its mechanical properties. PY demonstrated much better antioxidant and antibacterial activities than RS, which were associated with a higher release of PY. In contrast, PY showed a higher cytotoxicity than OB and OB doped with RS. OB containing PY presented a rougher surface and higher water absorption than OB doped with RS. Both tested polyphenols caused no notable changes to the overall porosity of OB. Resveratrol and pyrogallol may not only influence the morphology and mechanical properties of epoxy-resin sealers, but could also enhance antioxidant activity and antibacterial effects against Enterococcus faecalis. Most epoxy-resin sealers currently available in the market can be considered as “passive” materials. Thus, doping their composition with specific polyphenols may be a suitable strategy to confer some antibacterial properties, antioxidant potential, along with improvement of some mechanical properties.

This study aimed at evaluating the shear bond strength (SBS) of modern self-adhesive resin cements and resin-modified glass ionomer cements applied to di erent prosthetic substrates. Zirconia, lithium-disilicate glass-ceramic and a noble metal alloy were used as bonding substrates. They were all sand-blasted with alumina, while LD was further etched with 9.6% hydrofluoric acid (10 s). A light-curing resin-modified glass ionomer cement (3M-GIC: Ketac Cem Plus) and a self-curing resin-modified glass ionomer cement (GC-GIC: FujiCEM 2) were compared to self-adhesive resin cements (PAN: Panavia SA Universal) and (3M-RES: Rely X Unicem 2). Ten specimens for each substrate were produced and up to five cylinders of each cement were bonded to each substrate. The shear bond strength (SBS) was evaluated after 24 h or after thermocycling (TC) aging (5000 cycles). The data was statistically analysed by two-way ANOVA and Student–Newman–Keuls test ( = 0.05). Failure modes were analysed through stereoscopic microscopy. The greatest SBS was attained with PAN, whilst 3M-GIC showed the lowest SBS and failed prevalently in adhesive mode. No di erence in SBS was observed between GC-GIC and 3M-RES. After TC aging, all cements showed significant drop (p < 0.05) in SBS, but PAN showed the greatest SBS. Reliable bond strength to prosthetic substrates can be achieved with specific universal resin-luting cements and may be an alternative to glass ionomer cements when luting alloy substrates.