Purpose: The aim of this study was to evaluate microhardness and hardness ratio of two type hybrid resin composites using different irradiance light sources.Materials and Methods: Light curing units were an LED light-curing unit and an experimental quartz-tungsten-halogen (QTH) light-curing unit. The light-cured resin composites were Clearfil AP-X (shade A3) and Estelite ∑Quick (shade A3). Composite specimens of 2-mm thickness were polymerized in Teflon molds using an energy density of 24,000 mJ/cm2. Light curing methods were LED 1,200 mW/cm2 for 20 s and QTH 600 mW/cm2 for 40 s. Just after light curing, the Knoop hardness was measured at the top and bottom surfaces of each specimen. The hardness ratio was calculated as follows: Knoop hardness of bottom surface/Knoop hardness of top surface.Results: Immediately after light curing, the Knoop hardness at the bottom surfaces of resin composites was significantly lower than that at the top surfaces with 1,200 mW/cm2 20 s for both resin composite (p < 0.05). There is no significant difference between the Knoop hardness at the top surfaces and the bottom surfaces with 600 mW/cm2 40 s for both resin composite (p > 0.05). The 600 mW/cm2 40 s showed significantly greater hardness ratio compared with that of the 1,200 mW/cm2 20 s for both resin composite (p < 0.05).Conclusion: The polymerization of resin composites at the bottom surface was inhibited compared with that of at the top surface using the regular irradiance of LED light.
Purpose: This study used electroencephalogram to examine how eliminating pain through complete denture treatment can affect cerebral function.Materials and Methods: Twenty-four individuals with full maxillary and mandibular dentures (11 males and 13 females; average age, 76) were enrolled. All were diagnosed by two prosthodontists as needing denture treatment. Twelve subjects who had complained of pain from dentures (study group) were compared to 12 without prior pain (control). Occlusal force and electroencephalogram were measured before and after treatment. Changes in brain functional activity were estimated by electroencephalogram, from which Dα was calculated using Diagnosis Method of Neuronal Dysfunction analysis. The Wilcoxon rank-sum test (α = 0.05) was used to compare Dα and occlusal force before and after treatment.Results: A significant increase in occlusal force was noted after treatment in all subjects in the study group (p < 0.01) and 11 in the control group (p < 0.01). Dα increased significantly for all study group subjects after treatment (p < 0.01).Conclusion: It was found that eliminating pain through denture treatment improves brain functional activity. Eliminating pain through denture treatment not only restored mastication but also relieved stress.
Purpose: This study aimed to evaluate the effects of various surface treatments, including resin coating, on the bond strength between lithium disilicate ceramics and luting agent. Materials and Methods: All specimens were air-abraded with alumina particles and separated into the following four groups based on the surface treatment method used: silane coupling agent (PA); multipurpose ceramic/metal primer (CP); multipurpose ceramic/metal primer with resin coating (CM); and silica coating with multipurpose ceramic/metal primer followed by resin coating (RM). A luting agent was placed on the treated surface and photopolymerized. The shear bond strengths of the materials were measured after 10,000 thermal cycles. Results: The bond strengths of the specimens in the PA group were significantly higher than those in the CP group. CM and RM groups presented with significantly higher bond strengths than CP. Conclusion: The combination of multipurpose ceramic/metal primers and resin coating can significantly increase the bond strength between lithium disilicate ceramics and luting agent.