Effect of light-curing methods on resin cement Knoop hardness at different depths.
(1/36)
This study evaluated, using Knoop hardness test, the polymerization depth of Rely-X dual-cured resin cement activated by chemical reaction alone (control group) or by chemical/physical mode with light curing through a 1.5-mm-thick ceramic layer (HeraCeram). Bovine incisors had their buccal surface flattened and hybridized. On this surface, a rubber mould (5 mm diameter; 1 mm high) was bulk filled with cement. Either a polyester strip or a 1.5-mm-thick disc of the veneering material was seated over this set. Light curing was performed with either conventional halogen light (QTH; XL2500) for 40 s, light-emitting diode (LED; Ultrablue Is) for 40 s or xenon plasma arc (PAC; Apollo 95E) for 3 s. In a control group, cement setting occurred by chemical reaction alone. After storage dry in dark (24 h/37 degrees C), the specimens (n=5) were sectioned for hardness (KHN) measurements at three depths in a microhardness tester (50 gf load/15 s). Data were submitted to ANOVA and Tukey's test (alpha = 0.05). Rely-X cement presented higher Knoop hardness values when the QTH and LED LCUs were used, compared to the control group and PAC. Light curing with PAC resulted in lower hardness compared to the control group. Cement hardness was significantly lower in deeper regions. (+info)
Comparative study of chemical and mechanical retentive systems for bonding of indirect composite resin to commercially pure titanium.
(2/36)
This study evaluated the rate of polymerization (R(p)) and degree of conversion (DC) of Panavia F when self- or dual-activated, and the influence of either using or not using a primer containing co-initiators (ED Primer) mixed with the material. The conversion reaction was monitored using real-time infrared spectroscopy with an attenuated total reflectance device. The cement was mixed, put onto the device and irradiated for 20 s (dual-cured). A self-cured group was also prepared. Similarly, dual- and self-cured groups were evaluated after mixing ED Primer with the cement. The DC was monitored for 1 h and the R(p) was calculated. For the dual-cured mode, the most significant effect of ED Primer was to reduce the R(p)(max). For the self-cured mode, the primer was shown to be essential for polymerization of Panavia F: without ED Primer, the reaction started only after approximately 500 s, with a final DC of 50%, whereas a continuous increase in conversion was observed for the group mixed with ED Primer, with a final DC of 74%. The ED primer is essential for proper polymerization of Panavia F; the cement becomes independent of the light when the primer is used. (+info)
Effect of light-curing method and indirect veneering materials on the Knoop hardness of a resin cement.
(5/36)
Development of dual-curing type experimental composite resin cement for orthodontic bonding -effect of additional amount of accelerators on the mechanical properties-.
(6/36)
In this study, a dual-curing type composite resin cement that included a photo-initiator and two accelerators was designed. In particular, special emphasis was made on addressing questions on the effects from different amounts of additional accelerators on the flexural strength of the designed experimental composite resin cement, as well as on the tensile bond strength of the bracket bonded onto the enamel surface by the experimental composite resin cement. When 0.25 mass% of the p-tolydiethanolamine and sodium p-toluenesulfinate were added, the maximum flexural strength was obtained for the chemical-cured and dual-cured experimental composite resin cement. The dual-cured experimental composite resin cement's flexural strength value was in the mid-range of the values exhibited from the commercial resin cements. However, the dual-cured experimental composite resin cement exhibited noticeably high tensile bond strength when compared with the results obtained with the commercial resin cements. (+info)
Bonding strength of autopolymerizing resin to nylon denture base polymer.
(7/36)
This study aimed to investigate the shear bond strength of an autopolymerizing resin to a nylon denture base polymer (Lucitone FRS: LT) subjected to different surface treatments, and the results thereof compared with a heat-polymerizing resin and a polycarbonate polymer. Specimens were divided into five groups according to the surface treatment method: polishing (#600), sandblasting, adhesive primer application (resin primer), sandblasting + adhesive primer application, and tribochemical coating (Rocatec system). Following which, specimens were subjected to a shear bond strength test and Si concentrations were measured using an electron probe microanalyzer (EPMA). On shear bond strength, that of LT with tribochemical coating was significantly higher than the other groups. On EPMA results, the surface of LT with tribochemical coating was found to be covered with a silica film. Therefore, findings in this study indicated that silica-coating by Rocatec system was effective in improving the bond strength of nylon denture base polymer to autopolymerizing repair resin. (+info)
Influence of methylmercaptan on the bonding strength of autopolymerizing reline resins to a heat-polymerized denture base resin.
(8/36)
Effects of methylmercaptan solution (MS), a volatile sulfur compound produced by gram-negative oral microorganisms, on the adhesion of reline denture resins were investigated. For this purpose, a total of 120 disk-shaped specimens prepared from a heat-polymerized denture base resin (Acron) immersed in MS of different concentrations (0.01, 0.1, and 1.0 mol) as well as in purified water as a control at 37 degrees C for 4 weeks. Each of three commercial autopolymerizing reline resins (Rebaron, Mild Rebaron, and Tokuyama Rebase II) was bonded to a specimen. The shear bond strength tests were conducted for the specimens, with and without the application of a primer. The bond strength with 1.0 mol MS was significantly lower than those with other solutions (p < 0.05). The primer application had a significant positive effect on the bond strength. The debonded Acron surfaces showed evidence of incomplete polymerization. The results suggested a potential adhesion-inhibiting effect of the MS on relined dentures. (+info)