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Water Storage Time (water + storage_time)
Selected AbstractsPhysicochemical evaluation of silica-glass fiber reinforced polymers for prosthodontic applicationsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2005Gökçe Meriç This investigation was designed to formulate silica-glass fiber reinforced polymeric materials. Fused silica-glass fibers were chosen for the study. They were heat-treated at various temperatures (500°C, 800°C and 1100°C), silanized, sized and incorporated in two modified resin mixtures (A and B). The flexural properties in dry and wet conditions were tested and statistically analyzed, and the content of residual methyl methacrylate (MMA) monomer, dimensional changes with temperature, water sorption and solubility were determined. Woven fibers [36.9% (wt/wt)], heat-treated at 500°C, gave the highest strength values for the polymeric composites (an ultimate transverse strength of 200 Mpa and a flexural modulus of 10 GPa) compared with the fibers heat-treated at other temperatures. There was no statistically significant difference in the measured flexural properties between resins A and B regarding fiber treatment and water storage time. These fiber composites had a small quantity of residual MMA content [0.37 ± 0.007% (wt/wt)] and very low water solubility, indicating good biocompatibility. It was suggested that silica-glass fibers could be used for reinforcement as a result of their anticipated good qualities in aqueous environments, such as the oral environment. [source] Effect of water storage time and composite cement thickness on fatigue of a glass-ceramic trilayer systemJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008Nelson R. F. A. Silva Abstract Aim. Static Hertzian contact tests of monolayer glass-ceramics in trilayer configurations (glass-ceramic/cement/composite) have shown that thick cement layers lower strength. This study sought to test the hypothesis that thick resin cement layers lower mouth motion fatigue reliability for flat glass-ceramic/cement/composite trilayer systems and that aging in water reduces reliability. Methods. Dicor plates (n , 12 per group) (10 × 10 × 0.8 mm3) were aluminum-oxide abraded (50 ,m), etched (60 s), silanized, and bonded (Rely X ARC) to water aged (30 days) Z100 resin blocks (10 × 10 × 4 mm3). Four groups were prepared: (1) thick cement layer (>100 ,m) stored in water for 24,48 h, (2) thick cement layer stored for 60 days, (3) thin cement layer (,100 ,m) stored for 24,48 h, and (4) thin cement layer stored for 60 days. The layered structures were fatigued (2 Hz) utilizing mouth motion loading with a step-stress acceleration method. A master Weibull distribution was calculated and reliability determined (with 90% confidence intervals) at a given number of cycles and load. Results. The aged group (60 d) with thick cement layer had statistically lower reliability for 20,000 cycles at 150 N peak load (0.11) compared with both nonaged groups (24,48 h) (thin layer = 0.90 and thick layer = 0.82) and aged group with thin cement layer (0.89). Conclusion. Trilayer specimens with thick cement layers exhibited significantly lower reliability under fatigue testing only when stored for 60 days in water. The hypothesis was accepted. These results suggest that diffusion of water into the resin cement and also to the glass-ceramic interface is delayed in the thick cement specimens at 24,48 h. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2008 [source] Effect of Microwave Disinfection Procedures on Torsional Bond Strengths of Two Hard Chairside Denture Reline MaterialsJOURNAL OF PROSTHODONTICS, Issue 6 2006Ana Lucia Machado DDS Purpose: This study evaluated the potential effects of denture base resin water storage time and an effective denture disinfection method (microwave irradiation at 650 W for 6 minutes) on the torsional bond strength between two hard chairside reline resins (GC Reline and New Truliner) and one heat-polymerizing denture base acrylic resin (Lucitone 199). Materials and Methods: Cylindrical (30 × 3.9 mm) denture base specimens (n= 160) were stored in water at 37°C (2 or 30 days) before bonding. A section (3.0 mm) was removed from the center of the specimens, surfaces prepared, and the reline materials packed into the space. After polymerization, specimens were divided into four groups (n= 10): Group 1 (G1),tests performed after bonding; Group 2 (G2),specimens immersed in water (200 ml) and irradiated twice (650 W for 6 minutes); Group 3 (G3),specimens irradiated daily until seven cycles of disinfection; Group 4 (G4),specimens immersed in water (37°C) for 7 days. Specimens were submitted to a torsional test (0.1 Nm/min), and the torsional strengths (MPa) and the mode of failure were recorded. Data from each reline material were analyzed by a two-way analysis of variance, followed by Neuman-Keuls test (p= 0.05). Results: For both Lucitone 199 water storage periods, before bonding to GC Reline resin, the mean torsional strengths of G2 (2 days,138 MPa; 30 days,132 MPa), G3 (2 days,126 MPa; 30 days,130 MPa), and G4 (2 days,130 MPa; 30 days,137 MPa) were significantly higher (p < 0.05) than G1 (2 days,108 MPa; 30 days,115 MPa). Similar results were found for Lucitone 199 specimens bonded to New Truliner resin, with G1 specimens (2 days,73 MPa; 30 days,71 MPa) exhibiting significantly lower mean torsional bond strength (p < 0.05) than G2 (2 day,86 MPa; 30 days,90 MPa), G3 (2 days,82 MPa; 30 days,82 MPa), and G4 specimens (2 days,78 MPa; 30 days,79 MPa). The adhesion of both materials was not affected by water storage time of Lucitone 199 (p > 0.05). GC reline showed a mixed mode of failure (adhesive/cohesive) and New Truliner failed adhesively. Conclusions: Up to seven microwave disinfection cycles did not decrease the torsional bond strengths between the hard reline resins, GC Reline and New Truliner to the denture base resin Lucitone 199. The effect of additional disinfection cycles on reline material may be clinically significant and requires further study. [source] | ||||||||||