ABSTRACT
The advantages of repair of the restorations include preservation of tooth structure and increased the longevity of the restoration at low cost. Previous studies have shown that composite resin as well as conventional glass-ionomer cements can be repaired, but the possibility for repair of the new hybrids is not well known. The objective of this study was to investigate the flexural strength for repaired resin-modified glass-ionomer and polyacid-modified resin composite materials using two period of aging prior to repair. Four different materials were used, Fuji X, Fuji II LC, Vitremer and Dyract, under two different conditions of [1] repair after thirty minutes and [2] repair after seven days. Specimens [2x2x25 mm] of each material were prepared, aged and sectioned. The cut surfaces of the material were pretreated before newly mixed material was added to repair specimen. Seven days after the repair was made, the flexural strength of the specimen was determined and compared to that of the seven days old unsectioned specimen. Of the unrepaired [control] specimens, Dyract had the highest flexural strength [101.6 MPa] and Fuji IX had the lowest [17.8 MPa]. The flexural strengths of the repaired specimens were always lower than those of the unrepaired specimens, although for Fuji II LC these differences were not statistically significant [P>0.05]. Only the Fuji II LC repaired specimens were insensitive to age. Microscopic examination of the fractured surfaces showed either adhesive, cohesive or adhesive/cohesive failure depending upon the material under examination. Under the conditions of this study, Fuji IX and Dyract showed only a limited facility for repair, but repair or addition could be made on a Fuji II LC of Vitremer materials
ABSTRACT
A core restoration is often required after tooth fracture or extensive caries removal. The core should posses sufficient fracture toughness to resist occlusal and to be retained in tooth structure
Objectives: The aim of this work was to compare the torque fracture resistance of four core build-up materials. The effect of water aging on torque fracture resistance of these material was also, studied
Materials and Methods: Four direct core build-up materials were tested: [1] Vietremer [resin-modified glass-ionomer], [2] Arabesk Top [glass-ceramic microhybrid composite], [3] Build-It FR [Fiber-reinforced, fluoride-releasing, resin composite], [4] Fluorocore [fluoride-releasing, resin composite]. Notched disc test specimens of 5 mm diameter and 2 mm depth with a 90[degree sign] notch angle were prepared in specially designed Teflon mold. 20 specimens from each material were prepared according to manufacturer's instruction and then stored in distilled water at 37[degree sign] C until the time of testing. Half the specimens of each material [n=10] were tested after 1 day, and the other half were tested after 7 days. Fracture was accomplished in a Shimadzu testing machine with a 3 mm diameter roller in a two-point opening [Mode I] tensile load at a crosshead speed of 1 mm/min. The maximum loads were determined from which the torque to fracture values [T] were calculated. Data was analyzed by one-way ANOVA and post hoc Tukey tests among the materials and two-independent sample tests between aging intervals were performed at a preset alpha of p<0.05
Results: The mean torque fracture resistance [T] values in N/mm obtained, after 1 day and 7 days, were as follows: [1] Vitremere, 6.4 and 9.4; [2] Arabesk Top, 20.5 and 20.4; [3] Build-It FR, 24.4 and 23.8; [4] Fluorocore, 39.8 and 38.9. There was significant difference in T values among all materials either at 1 day or 7 days. After conditioning in water for 7 days, only the T value of Vitnemer was significantly increased, while that of Arabesk Top, Build-It FR, and Fluorocore was not affected
Conclusions: Fluorocore had the highest torque fracture resistance values and Vitremer had the lowest, while Build-It FR and Arabesk Top yielded intermediate values, either at 1 days or 7 days. Only, the torque fracture resistance of vitremer was significantly increased with water storage for 7 days
ABSTRACT
New injection molding techniques for processing denture acrylic resins may improve the physic-mechanical properties. A major factor that affects a dental prosthesis is that it suffers wear during its function or whilst being cleaned. As wear is due to abrasion, surface hardness is an important property
Purpose: This study evaluate the effect of new injection molding techniques [INJ], in comparison to compression molding technique [COM], on Rockwell superficial indentation [an indication of hardness] and recovery % of three denture base resins
Materials and methods: The denture base resins used in this study were: Two heat cured [Lucitone 199 and Fricke Hi-I] and one microwave cured [Acron MC] acrylic resins. 20 specimens [30x10x3 mm] of each material were fabricated, 10 specimens were prepared using compression-packed technique and the other 10 specimens were prepared using injection-processing technique. For injection-processing, three different injection systems were used. Each material specimens were processed using the injection system of the same company. Rockwell superficial indentation [RSI] and recovery % were determined using Rockwell superficial hardness tester. Means and standard deviations of RSI and recovery % were computed. Data were analyzed by non-parametric tests and Mann-Whitney U and Kruskal-Wallis tests at 0.05 significance level were used for multiple comparison
Results: The hardness of the injection-molded Acron MC resin was significantly increased in comparison to its compression-molded counterpart, while the hardness of the other resins tested was not affected. The recovery % of each resin tested was insignificantly improved by using injection-molding technique. When all materials/molding techniques combination were compared, it was found that only injection-processed Acron MC had a significant higher hardness in comparison to all other materials, while no significant differences, in recovery%, were noted between all materials
Conclusions: Processing of microwave-cured denture resin [Acron MC] by injection molding technique improved its hardness and recovery properties
ABSTRACT
Statement of problem: Because water sorption of acrylic resins is accompanied by volumetric change, it is a physical property of importance. As a residual monomer leaches into the oral fluids causes tissue irritation, low solubility of these resins is desired
Purpose: This study was made to compare the water sorption and solubility of four different types of acrylic resins using injection molding technique in comparison with heat cured acrylic resin using compression molding technique
Results: All injection processed resins exhibited less water sorption than the compression processed resin [control group]. No significant difference was noted in the water sorption of all injection processed resins. Microwave polymerized acrylic resin [Acron MC] showed significant increase in the solubility value than the other tested acrylic denture base resins
ABSTRACT
Objectives: The aim of this study was to evaluate the effects of food-simulating liquids on flex-ural strength and hardness of composites and polyacid-modified composite restorative materials. The materials were, also compared
Materials and methods: Four composites [Two hybrids, Spectrum TPH [STPH] and Tetric Ceram [TC] one packable, Tetric Ceram HB [TCHB]; and one flowable, Tctric Flow [TF]] and one polyacid-modified composite [Compoglass F [CGF]l were used for this study. 25 specimens for flexural strength testing and 15 specimens for microhardness testing were prepared from each material. Each group of 25 and 15 specimens was subdivided into five groups of 5 and 3, respectively for each material-medium combination. Flexural strength specimens [25 x 2 x 2 mm] and hardness specimens [2 mm thick, and 5 mm diameter] were prepared according to manufacturer's recommendations. After light polymerization, the specimens were removed from their molds and conditioned for one week at 37°C as follows: [1] Air [control], [2] distilled water, [3] 0.02 M lactic acid, [4] Heptane, [5] 50% ethanol-water solution. After conditioning, flexural strength testing was carried out using Shimadzu Autograph Measuring Unit at a crosshead speed of 0.5 mm/ minute and microhrdness testing was carried out on MHT-1 Vickers microhardness tester at 100 gm load for 30 seconds. Data were analyzed using ANOVA and post-hoc Tukey HSD tests at a significance level 0.05
Results: The flexural strength of all restoratives was not affected after conditioning in heptane, which at the same time was significantly greater than that after conditioning in all other mediums. With the exception of Spectrum TPH, The flexural strength of all restoratives conditioned in ethanol-water solution was found significantly decreased than that conditioned in water and lactic acid. In all conditioning mediums used, Spectrum TPH had the significantly highest flexural strength and Compoglass F had the lowest. With the exception of Tetric Flow, no significant changes in surface hardness was noted with conditioning of all other restoratives in water, lactic acid, and heptane; however the surface hardness of all materials was significantly deteriorated after conditioning in ethanol-water solution. For comparing the materials after conditioning in various food-simulating liquids, Tetric Ceram HB was found had the highest Vickers hardness number [VHN] and Tetric Flow had the lowest
Conclusion: Ethanol-water solution was found the only food-simulating liquid, which had a significant deterioration effect on flexural strength and hardness of all materials tested at the same time. Despite flexural strength values of all composites tested; specially the more recent composites, TCHB and TF; was also reduced with conditioning in water and lactic acid, but still exceeded the minimum flexural strength limit of ISO for polymer-based restorative materials