Flexural strength of autopolymerizing denture reline resins with microwave postpolymerization treatment

Statement of problem. Microwave postpolymerization has been Suggested as a method to improve the mechanical strength of repaired denture base materials. However, the effect of microwave heating oil the flexural strength of the autopolymerizing denture reline resins has not been investigated.Purpose. This study analyzed the effect of microwave postpolymerization on the flexural strength of 4 autopolymerizing reline resins (Duraliner II, Kooliner, Ufi Gel Hard, and Tokuso Rebase Fast) and 1 heat-polymerized resin (Lucitone 550).Material and methods. For each material, 80 specimens (64 X 10 X 3.3 mm) were polymerized according to the manufacturer's instructions and divided into 10 groups (n = 8). Control group specimens remained as processed. Before testing, the specimens were Subjected to postpolymerization in a microwave oven using different power (500, 5,50, or 650 W) and time (3, 4, or 5 Minutes) settings. Load measurements (newtons) were made at a crosshead speed of 5 mm/min using a 3-point bending device with a span of 50 mill. The flexural strength values were calculated in MPa. Data analyses included 3-way and 2-way analysis of variance and the Tukey Honestly Significant Difference test (alpha=.05).Results. The flexural strengths of resins Duraliner 11 and Kooliner were significantly increased (P=.0015 and P=.0046, respectively) with the application of microwave irradiation using different time/power combinations. The materials Lucitone 550, Tokuso Rebase Fast, and Ufi Gel Hard demonstrated no significant strength improvement compared to the corresponding control. Only after microwave postpolymerization irradiation for 3 minutes at 550 W did Lucitione 550 show significantly higher flexural strength than Tokuso Rebase Fast and Ufi Gel Hard relining resins.Conclusion. Microwave postpolymerization irradiation can be an effective method for increasing the flexural strength of Duraliner II (at 650 W) and Kooliner (at 550 W and 650 W for 5 minutes).

Effect of mechanical cycling on the flexural strength of densely sintered ceramics

Objectives. The aim of this study was to evaluate the effect of mechanical cycling on the biaxial flexural strength of two densely sintered ceramic materials.Methods. Disc shaped zirconia (In-Ceram Zirconia) and high alumina (Procera AllCeram) ceramic specimens (diameter: 15 min and thickness: 1.2 mm) were fabricated according to the manufacturers' instructions. The specimens from each ceramic material (N = 40, n = 10/per group) were tested for flexural strength either with or without being subjected to mechanical cycling (20,000 cycles under 50 N load, immersion in distilled water at 37 degrees C) in a universal testing machine (1 mm/min). Data were statistically analyzed using two-way ANOVA and Tukey's test (alpha = 0.05).Results. High alumina ceramic specimens revealed significantly higher flexural strength values without and with mechanical cycling (647 +/- 48 and 630 +/- 143 MPa, respectively) than those of zirconia ceramic (497 +/- 35 and 458 +/- 53 MPa, respectively) (p < 0.05). Mechanical cycling for 20,000 times under 50 N decreased the flexural strength values for both high alumina andSignificance. High alumina ceramic revealed significantly higher mean flexural strength values than that of zirconia ceramic tested in this study either with or without mechanical cycling conditions. (C) 2005 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The Sao Vicente earthquake of 2008 April and seismicity in the continental shelf off SE Brazil: further evidence for flexural stresses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of the flexural strength of carbon fiber-, quartz fiber-, and glass fiber-based posts

This study investigated the flexural strength of eight fiber posts (one carbon fiber, one carbon/quartz fiber, one opaque quartz fiber, two translucent quartz fiber, and three glass fiber posts). Eighty fiber posts were used and divided into eight groups (n = 10): G1: C-POST (Bisco); G2: ÆSTHETI-POST (Bisco); G3: ÆSTHETI-PLUS (Bisco); G4: LIGHT-POST (Bisco); G5: D.T. LIGHT-POST (Bisco); G6: PARAPOST WHITE (Coltene); G7: FIBERKOR (Pentron); G8: REFORPOST (Angelus). All of the samples were tested using the three-point bending test. The averages obtained were submitted to the ANOVA and to Tukey's test (p < 0.05). The mean values (MPa) of the groups ÆSTHETI-POST - carbon/ quartz fiber post (Bisco) and ÆSTHETI-PLUS - quartz fiber post (Bisco) were statistically similar and higher than the mean values of the other groups. The mean values of the groups C-POST - carbon fiber post (Bisco), LIGHT-POST - translucent quartz fiber post (Bisco), D.T. LIGHT-POST - double tapered translucent quartz fiber post (Bisco), PARAPOST WHITE - glass fiber post (Coltene) and FIBREKOR - glass fiber post (Pentron) were similar and higher than the group REFORPOST - glass fiber post (Angelus). Copyright © 2005 by the American Association of Endodontists.

Effect of silica coating on flexural strength of fiber posts

Purpose: Fiber-reinforced composite (FRC) posts can be air-abraded to obtain good attachment to the resin cement. This study tested the effect of silica coating on the flexural strength of carbon, opaque, and translucent quartz FRC posts. Materials and Methods: Six experimental groups of FRC posts (n = 10 per group) were tested, either as received from the manufacturer or after chairside silica coating (30-μm CoJet-Sand). Results: There was no significant difference in the flexural strength of nonconditioned (504 to 525 MPa) and silica-coated (514 to 565 MPa) specimens (P > .05) (analysis of variance). The type of post did have a significant effect on flexural strength (P < .05). Conclusion: Chairside silica coating did not affect the flexural strength of both carbon and quartz FRC posts.

Effect of a post-polymerization treatments on the flexural strength and vickers hardness of reline and acrylic denture base resins

This study evaluated the effect of water-bath and microwave post-polymerization treatments on the flexural strength and Vickers hardness of four autopolymerizing reline resins (Duraliner II-D, Kooliner-K, Tokuso Rebase Fast-TR and Ufi Gel Hard C-UGH) and one heat-polymerized acrylic resin (Lucitone 550-L), processed using two polymerization cycles (short cycle - 90 minutes at 73°C and 100°C for 30 minutes; and long cycle - 9 hours at 71°C). For each material, thirty specimens (64 x 10 x 3.3 mm) were made and divided into 3 groups (n=10). Specimens were tested after: processing (control group); water-bath at 55°C for 10 minutes (reline materials) or 60 minutes (L); and microwave irradiation. Flexural strength tests were performed at a crosshead speed of 5 mm/min using a three-point bending device with a span of 50 mm. The flexural strengths values were calculated in MPa. One fragment of each specimen was submitted to Vickers hardness test. Data were analyzed by 2-way ANOVA followed by Tukey's HSD test (α=0.05). L microwaved specimens (short cycle) exhibited significantly higher flexural strength means than its respective control group (p<0.05). Water-bath promoted a significant increase (p<0.05) in flexural strength of K and L (long cycle). The hardness of the tested materials was not influenced by the post-polymerization treatments. Post-polymerization treatments could be used to improve the flexural strength of some materials tested.

Influence of thermal and mechanical cycling on the flexural strength of ceramics with titanium or gold alloy frameworks

Objectives: The aim of this study was to evaluate the effect of thermal and mechanical cycling alone or in combination, on the flexural strength of ceramic and metallic frameworks cast in gold alloy or titanium. Methods: Metallic frameworks (25 mm × 3 mm × 0.5 mm) (N = 96) cast in gold alloy or commercial pure titanium (Ti cp) were obtained using acrylic templates. They were airborne particle-abraded with 150 μm aluminum oxide at the central area of the frameworks (8 mm × 3 mm). Bonding agent and opaque were applied on the particle-abraded surfaces and the corresponding ceramic for each metal was fired onto them. The thickness of the ceramic layer was standardized by positioning the frameworks in a metallic template (height: 1 mm). The specimens from each ceramic-metal combination (N = 96, n = 12 per group) were randomly assigned into four experimental fatigue conditions, namely water storage at 37 °C for 24 h (control group), thermal cycling (3000 cycles, between 4 and 55 °C, dwell time: 10 s), mechanical cycling (20,000 cycles under 10 N load, immersion in distilled water at 37 °C) and, thermal and mechanical cycling. A flexural strength test was performed in a universal testing machine (crosshead speed: 1.5 mm/min). Data were statistically analyzed using two-way ANOVA and Tukey's test (α = 0.05). Results: The mean flexural strength values for the ceramic-gold alloy combination (55 ± 7.2 MPa) were significantly higher than those of the ceramic-Ti cp combination (32 ± 6.7 MPa) regardless of the fatigue conditions performed (p < 0.05). Mechanical and thermo-mechanical fatigue decreased the flexural strength results significantly for both ceramic-gold alloy (52 ± 6.6 and 53 ± 5.6 MPa, respectively) and ceramic-Ti cp combinations (29 ± 6.8 and 29 ± 6.8 MPa, respectively) compared to the control group (58 ± 7.8 and 39 ± 5.1 MPa, for gold and Ti cp, respectively) (p < 0.05) (Tukey's test). While ceramic-Ti cp combinations failed adhesively at the metal-opaque interface, gold alloy frameworks exhibited a residue of ceramic material on the surface in all experimental groups. Significance: Mechanical and thermo-mechanical fatigue conditions decreased the flexural strength values for both ceramic-gold alloy and ceramic-Ti cp combinations with the results being significantly lower for the latter in all experimental conditions. © 2007 Academy of Dental Materials.

Effect of radiotherapy on the radiopacity and flexural strength of a composite resin.

The aim of this study was to evaluate the effect of radiotherapy on the radiopacity and flexural strength of composite resin. Forty Z250 composite resin specimens were polymerized using a halogen light-curing unit and divided into 5 groups, in accordance with the radiotherapy dose: G1- without irradiation, G2- 30 Gy, G3- 40 Gy, G4- 50 Gy and GS- 60 Gy Digital images were obtained using a GE 100 X-ray. Radiopacity values were obtained with the Digora digital imaging system and the flexural strength was evaluated with an EMIC universal testing machine. Data were submitted to ANOVA and Tukey 's test. G1 presented the highest radiopacity value, followed by G3, G5, G4 and G2. For flexural strength, G1 presented the lowest value, followed by G2, G5, G3 and G4. Differences were no significant (p>0.05). The commonly used dosage of radiotherapy treatment, did not cause alteration in the radiopacity and flexural strength of resin-based composites.

Strengthening development: the interplay of macro- and microeconomics

Includes bibliography