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The objectives of this study were to compare the fracture strength of endocrown restorations fabricated with different preparation depth and various CAD/CAM ceramics, and to assess the fracture types. Endodontically treated 100 extracted human permanent maxillary centrals were divided into two preparation depth groups as short (S: 3-mm-deep) and long (L: 6-mm-deep), then five ceramic subgroups, namely: feldspathic-ceramic (Vita Mark II-VM2), lithium-disilicate glass-ceramic (IPS e.max CAD-E.max), resin-ceramic (LAVA Ultimate-LU), polymer infiltrated ceramic (Vita Enamic-VE) and monoblock zirconia (inCoris TZI-TZI) (n=10/subgroup). The endocrowns were fabricated by CAD/CAM and were cemented with resin cement (RelyX U200). The teeth were thermally cycled (5,000cycles) and fracture tests were performed at 45º angle to the teeth. The data were statistically analyzed (Kruskal-Wallis, Mann Whitney U), failure modes were evaluated with stereomicroscopy. Zirconia group provided the statistically highest fracture strength, but also exhibited non-repairable failures. Preparation depth has an effect on the fracture strength only for feldspathic ceramic.

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This study investigates solid particle erosive wear behavior of glass mat reinforced polyphenylene sulfide (PPS) matrix composites under A preliminary draft of this article was presented at the Fifth International Workshop on Thermoplastic Matrix Composites (THEPLAC 2011), various test parameters. PPS composite was manufactured by using the compression-molding process. Composite samples were eroded in a specially designed sandblasting system employing various parameters, and variation of the erosion rate was investigated. Samples were eroded at different erosion times, particle impingement angles, and under various pressures by using three different sizes of alumina particles. Impingement velocities of erodent particles were measured by using the double disk method. The results are also discussed regarding impingement velocity of the erodent particles. Glass mat reinforced PPS composites exhibited semiductile erosion behavior by showing a maximum erosion rate at 30 • and 45 • impingement angles. The erosion rate of the composite was increased with augmentation in erosion time, velocity, pressure, and particle size. Maximum erosion was observed when the composite was eroded after 10 s at 45 • impingement angle under 4 bar pressure by using 60 mesh size erodent particles. The morphology of eroded surfaces was examined by using a scanning electron microscope, and possible wear mechanisms were discussed. C 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E386-E398, 2013; View this article online at wileyonlinelibrary.com.

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It is a common practice to use particle materials as fillers to improve engineering properties of polymer composites and to lower the cost of final products. There is an obvious cost advantage of compounding volcanic ash (VA) in polymers, either to replace traditional fillers. This study is concerned with thermal, mechanical, and erosive properties of VA‐filled polyphenylene sulfide (PPS) composites. Composite samples containing VA particles at various concentrations (0, 2.5, 5, 10, 15, and 20 wt%) were manufactured by twin screw extruder and injection molding machine. Thermal properties were investigated by thermogravimetric and dynamic mechanical analysis methods. Erosive wear properties were investigated by performing solid particle erosion tests at 30º and 90º impingement angles. The mechanical properties such as flexural strength and modulus of uneroded samples and residual flexural strength and modulus of eroded composite samples were determined by three‐point bending tests. Results show that thermal, mechanical, and residual mechanical properties of the PPS composite were significantly improved by adding VA, although erosion resistance was decreased markedly. It was concluded that VA can be used as a reinforcement in PPS composites to improve thermal and mechanical properties and to reduce the cost of the PPS composites. POLYM. COMPOS., 35:1826–1833, 2014. © 2014 Society of Plastics Engineers