Objectives: The purpose of this study was to investigate the effect of preheat temperatures on polymerization contraction stress and mechanical properties of three resin composites. Methods: Three resin composites (Fi...Objectives: The purpose of this study was to investigate the effect of preheat temperatures on polymerization contraction stress and mechanical properties of three resin composites. Methods: Three resin composites (Filtek Supreme XT, GC Kalore, and Gradia Direct X) at room temperature, 37°C, and 60°C were investigated. Stress development and maximum contraction stress of the composites were evaluated. Directly after preheating, samples were light-cured for 40 seconds and the force recorded for 15 minutes. Subsequent calculations were done to account for the system’s compliance and to obtain the shrinkage stress of the composites. In addition, composite discs (5 mm? and1 mmthick) were light-cured for 40 seconds at the preheat temperature. Hardness, elastic modulus, and creep of composites were investigated using a nano-indentation system (UMIS 2000). The results were analyzed using Two-way Analysis of Variance (2-way ANOVA) and Tukey’s Post-Hoc test (α = 0.05). Results: The results indicated that preheating composites to 37°C and 60°C increased the polymerization contraction forces, but did not significantly affect hardness, elastic modulus, and creep behaviour of the materials. Analysis of the contraction force upon allowing for thermal contraction indicated only a minor influence of preheat temperature. Significance: Preheating composites, upon allowing for system thermal contraction, showed a slight increase of the polymerization contraction stress but did not significantly affect the composites’ mechanical properties.展开更多
The loss of interfacial integrity was identified as one of the major causes for replacement of resin composite restorations. Preheating procedure has been proven to enhance flowability and adaptation of resin composit...The loss of interfacial integrity was identified as one of the major causes for replacement of resin composite restorations. Preheating procedure has been proven to enhance flowability and adaptation of resin composites and increase their degree of conversion. The purpose of this study was to investigate polymerization contraction stress produced in resin composites after preheating to 37℃ and 60℃, and measure microleakage of Class V restorations restored with preheated composites. Three resin composites (GC Kalore, Gradia Direct X, Filtek Supreme XT) at room temperature, 37℃, and 60℃ were investigated. Maximum contraction stress of the composites (n = 5) was evaluated in a modified low-compliance device. Samples were light-cured for 40 seconds and the maximum force was recorded during 15 minutes. Calculations were done to adjust for the system’s compliance and obtain linear shrinkage values of composites. Data were analyzed by Multivariated Analysis of Variance (MANOVA) and Tukey’s test for multiple comparisons (α = 0.05). Seventy-two Class V cavities were prepared on the buccal surfaces of extracted premolars and divided into 9 groups. The teeth were restored with composites at 3 temperatures and were thermo-cycled between 5℃ and 55℃ with a one-minute dwell-time for 1000 cycles. The teeth were sealed with wax and nail vanish before placed in 0.5% toluidine blue dye for 24 hours. The teeth were embedded in self-curing resin and sectioned bucco-lingually with a slow-speed diamond saw, providing 3 sections per restoration. Microleakage was rated by two evaluators using a 0 - 4 ordinal scale at the occlusal and cervical margins under light microscope. Microleakage data were analyzed with Kruskal-Wallis ANOVA and Mann-Whitney U test (α = 0.05). Results indicate that preheating composites to 37℃ and 60℃ significantly increased polymerization contraction stress of composites (p 0.05). A significantly greater amount of leakage was found at the cervical margins (p 0.05). For all tested materials, preheating composites to 60℃ resulted in significantly less microleakage at the cervical margin.展开更多
The left ventricular apical systolic dysfunction syndrome was a rare acute cardiac syndrome.Its clinical presentation and electrocardiography were similar to acute myocardial infarction.The syndrome was characterized ...The left ventricular apical systolic dysfunction syndrome was a rare acute cardiac syndrome.Its clinical presentation and electrocardiography were similar to acute myocardial infarction.The syndrome was characterized by transient ventricular wall-motion abnormalities involving the left ventricular apex and mid-ventricle in the absence of obstructive epicardial coronary disease.Cardiac enzyme was normal or minor elevation.At present,the cause of the syndrome is unknown.In this paper,we describe a 56-year-old female patient.She was admitted in hospital for acute appendititis and the transient left ventricular apical ballooning syndrome.She developed acute heart failure and septic shock in the hospital.The drainage of the appendiceal abscess was done and the heart failure and septic shock recovered completely in a few days.展开更多
文摘Objectives: The purpose of this study was to investigate the effect of preheat temperatures on polymerization contraction stress and mechanical properties of three resin composites. Methods: Three resin composites (Filtek Supreme XT, GC Kalore, and Gradia Direct X) at room temperature, 37°C, and 60°C were investigated. Stress development and maximum contraction stress of the composites were evaluated. Directly after preheating, samples were light-cured for 40 seconds and the force recorded for 15 minutes. Subsequent calculations were done to account for the system’s compliance and to obtain the shrinkage stress of the composites. In addition, composite discs (5 mm? and1 mmthick) were light-cured for 40 seconds at the preheat temperature. Hardness, elastic modulus, and creep of composites were investigated using a nano-indentation system (UMIS 2000). The results were analyzed using Two-way Analysis of Variance (2-way ANOVA) and Tukey’s Post-Hoc test (α = 0.05). Results: The results indicated that preheating composites to 37°C and 60°C increased the polymerization contraction forces, but did not significantly affect hardness, elastic modulus, and creep behaviour of the materials. Analysis of the contraction force upon allowing for thermal contraction indicated only a minor influence of preheat temperature. Significance: Preheating composites, upon allowing for system thermal contraction, showed a slight increase of the polymerization contraction stress but did not significantly affect the composites’ mechanical properties.
文摘The loss of interfacial integrity was identified as one of the major causes for replacement of resin composite restorations. Preheating procedure has been proven to enhance flowability and adaptation of resin composites and increase their degree of conversion. The purpose of this study was to investigate polymerization contraction stress produced in resin composites after preheating to 37℃ and 60℃, and measure microleakage of Class V restorations restored with preheated composites. Three resin composites (GC Kalore, Gradia Direct X, Filtek Supreme XT) at room temperature, 37℃, and 60℃ were investigated. Maximum contraction stress of the composites (n = 5) was evaluated in a modified low-compliance device. Samples were light-cured for 40 seconds and the maximum force was recorded during 15 minutes. Calculations were done to adjust for the system’s compliance and obtain linear shrinkage values of composites. Data were analyzed by Multivariated Analysis of Variance (MANOVA) and Tukey’s test for multiple comparisons (α = 0.05). Seventy-two Class V cavities were prepared on the buccal surfaces of extracted premolars and divided into 9 groups. The teeth were restored with composites at 3 temperatures and were thermo-cycled between 5℃ and 55℃ with a one-minute dwell-time for 1000 cycles. The teeth were sealed with wax and nail vanish before placed in 0.5% toluidine blue dye for 24 hours. The teeth were embedded in self-curing resin and sectioned bucco-lingually with a slow-speed diamond saw, providing 3 sections per restoration. Microleakage was rated by two evaluators using a 0 - 4 ordinal scale at the occlusal and cervical margins under light microscope. Microleakage data were analyzed with Kruskal-Wallis ANOVA and Mann-Whitney U test (α = 0.05). Results indicate that preheating composites to 37℃ and 60℃ significantly increased polymerization contraction stress of composites (p 0.05). A significantly greater amount of leakage was found at the cervical margins (p 0.05). For all tested materials, preheating composites to 60℃ resulted in significantly less microleakage at the cervical margin.
文摘The left ventricular apical systolic dysfunction syndrome was a rare acute cardiac syndrome.Its clinical presentation and electrocardiography were similar to acute myocardial infarction.The syndrome was characterized by transient ventricular wall-motion abnormalities involving the left ventricular apex and mid-ventricle in the absence of obstructive epicardial coronary disease.Cardiac enzyme was normal or minor elevation.At present,the cause of the syndrome is unknown.In this paper,we describe a 56-year-old female patient.She was admitted in hospital for acute appendititis and the transient left ventricular apical ballooning syndrome.She developed acute heart failure and septic shock in the hospital.The drainage of the appendiceal abscess was done and the heart failure and septic shock recovered completely in a few days.
