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Mm/min Crosshead Speed (min + crosshead_speed)
Selected AbstractsEffect of Net Fiber Reinforcement Surface Treatment on Soft Denture Liner Retention and LongevityJOURNAL OF PROSTHODONTICS, Issue 4 2010MPhil, Muhanad M. Hatamleh BSc Abstract Purpose: To evaluate shear bond strength of Molloplast-B soft liner attached to different acrylic surfaces (smooth, rough, and Sticktech net fiber-reinforced interfaces) after 3000 thermal cycles. Materials and Methods: Sixty-nine specimens were fabricated by attaching Molloplast-B soft liner to acrylic bases of three interfaces (n= 23); smooth (Group 1, control), rough (Group 2), and Sticktech net fiber-reinforced interface (Group 3). The specimens underwent 3000 thermocycles (5 and 55°C) before being subject to a shear bond test at 2 mm/min crosshead speed. Debonding sites were investigated using an optical microscope at 40× magnification. Bond failures were categorized as adhesive, cohesive, or mixed. Results: Mean (SD) bond strength values (MPa) were: 0.71 (0.15); 0.63 (0.07); and 0.83 (0.12) for smooth, rough, and fiber-reinforced acrylic interfaces, respectively. The mean values were analyzed using one-way ANOVA and Bonferroni post hoc test for pairwise comparisons (p, 0.05). The net fiber-reinforced acrylic interface exhibited a statistically significantly higher bond strength value when compared to smooth and rough acrylic interfaces (P= 0.003 and P= 0.000, respectively). Modes of failure were mainly cohesive (91%), followed by mixed failures (9%). Conclusions: Molloplast-B exhibited a stronger bond to StickTech Net fiber-reinforced surfaces when compared to smooth and rough acrylic interfaces after thermocycling. This may enhance prosthesis serviceability during clinical use. [source] Effect of Aluminum Oxide Addition on the Flexural Strength and Thermal Diffusivity of Heat-Polymerized Acrylic ResinJOURNAL OF PROSTHODONTICS, Issue 6 2008Ayman E. Ellakwa BDS Abstract Purpose: This work was undertaken to investigate the effect of adding from 5% to 20% by weight aluminum oxide powder on the flexural strength and thermal diffusivity of heat-polymerized acrylic resin. Materials and Methods: Seventy-five specimens of heat-polymerized acrylic resin were fabricated. The specimens were divided into five groups (n = 15) coded A to E. Group A was the control group (i.e., unmodified acrylic resin specimens). The specimens of the remaining four groups were reinforced with aluminum oxide (Al2O3) powder to achieve loadings of 5%, 10%, 15%, and 20% by weight. Specimens were stored in distilled water at 37°C for 1 week before flexural strength testing to failure (5 mm/min crosshead speed) in a universal testing machine. Results were analyzed by one-way analysis of variance and post hoc Tukey paired group comparison tests (p < 0.05). Weibull analysis was used to calculate the Weibull modulus, characteristic strength, and the required stress for 1% and 5% probabilities of failure. Cylindrical test specimens (5 specimens/group) containing an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 to 70°C). Results: The mean flexural strength values of the heat-polymerized acrylic resin were (in MPa) 99.45, 119.92, 121.19, 130.08, and 127.60 for groups A, B, C, D, and E, respectively. The flexural strength increased significantly after incorporation of 10% Al2O3. The mean thermal diffusivity values of the heat-polymerized acrylic resin (in m2/sec) were 6.8, 7.2, 8.0, 8.5, and 9.3 for groups A, B, C, D, and E, respectively. Thermal diffusivities of the composites were found to be significantly higher than the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the weight percentage of alumina filler, which suggested that the proper distribution of alumina powders through the insulating polymer matrix might form a pathway for heat conduction. Conclusion: Al2O3 fillers have potential as added components in denture bases to provide increased flexural strength and thermal diffusivity. Increasing the flexural strength and heat transfer characteristics of the acrylic resin base material could lead to more patient satisfaction. [source] An In Vitro Investigation of a Comparison of Bond Strengths of Composite to Etched and Air-Abraded Human Enamel SurfacesJOURNAL OF PROSTHODONTICS, Issue 1 2006G.B. Gray BDS Purpose: The purposes of the study were to measure the tensile bond strength of composite resin to human enamel specimens that had been either etched or air-abraded, and to compare the quality of the marginal seal, through the assessment of microleakage, of composite resin to human enamel specimens that had been either etched or air-abraded. Materials and Methods: Thirty mandibular molar teeth were decoronated and sectioned mesio-distally to produce six groups, each containing ten specimens that were embedded in acrylic resin using a jig. In each of the four treatment groups, the specimen surfaces were treated by either abrasion with 27 or 50 ,m alumina at 4 mm or 20 mm distance, and a composite resin was bonded to the treated surfaces in a standardized manner. In the two control groups the specimens were treated with 15 seconds exposure to 36% phosphoric acid gel and then similarly treated before being stored in sterile water for 1 week. All specimens were then subjected to tensile bond strength testing at either 1 or 5 mm/min crosshead speed. For the microleakage study, the degree of dye penetration was measured 32 times for each treatment group, using a neutral methylene blue dye at the interface between composite and either 27 or 50 ,m air-abraded tooth structure or etched enamel surfaces. Results: The mean bond strength values recorded for Group 1 (phosphoric acid etch, 5 mm/min crosshead speed) was 25.4 MPa; Group 2 (phosphoric acid etch, 1 mm/min), 22.2 MPa; Group 3 (27 ,m alumina at 4 mm distance), 16.8 MPa; Group 4 (50 ,m alumina at 4 mm distance), 16.9 MPa; Group 5 (27 ,m alumina at 20 mm distance), 4.2 MPa; and for Group 6 (50 ,m alumina at 20 mm distance) 3.4 MPa. An analysis of variance (ANOVA) demonstrated significant differences among the groups, and a multiple comparison test (Tukey) demonstrated that conventionally etched specimens had a greater bond strength than air-abraded specimen groups. No significant difference in dye penetration could be demonstrated among the groups (p= 0.58). Conclusions: Composite resin applied to enamel surfaces prepared using an acid etch procedure exhibited higher bond strengths than those prepared with air abrasion technology. The abrasion particle size did not affect the bond strength produced, but the latter was adversely affected by the distance of the air abrasion nozzle from the enamel surface. The crosshead speed of the bond testing apparatus had no effect on the bond strengths recorded. The marginal seal of composite to prepared enamel was unaffected by the method of enamel preparation. [source] Shear bond strength of luting agents to fixed prosthodontic restorative core materialsAUSTRALIAN DENTAL JOURNAL, Issue 4 2009N Capa Abstract Background:, Bonding properties of luting cements are important for retention of restorative core materials. The aim of this study was to compare the bonding performance of a resin-modified glass ionomer cement and a self-adhesive resin cement to various fixed prosthodontic core materials. Methods:, Cylindrical specimens with a thickness of 2 mm and a diameter of 5 mm were fabricated from Au-Pd-Ag, Co-Cr, Ni-Cr-Mo, Ni-Cr-Fe alloys, titanium, zirconia and Empress II (n = 20). Each group was divided into two subgroups to be luted with two different luting agents. Composite resin blocks were cemented onto specimens with RelyXUnicem and FujiCem. A shear bond strength machine with 50 kg load cell and 0.50 mm/min crosshead speed was used. Kruskal Wallis test, Dunn's Multiple Range test and Mann-Whitney-U test were used for statistical analysis. The results were evaluated in a confidence interval of p < 0.05. Results:, The highest bond strength was obtained between Ni-Cr-Fe-RelyXUnicem (8.22 ± 2.15 MPa) and the lowest was between Empress II-FujiCem (1.48 ± 0.9 MPa). In FujiCem groups, Co-Cr and Ni-Cr-Fe showed significantly higher bond strength than Au-Pd-Ag and Empress II. In RelyX Unicem groups, Ni-Cr-Fe showed higher bond strength than Empress II. Conclusions:, The types of luting agents and restorative core materials may have a significant influence on bond strength. [source] | ||||||||||