Boaro L.C., Froes-Salgado N.R., Gajewski V.E., Bicalho A.A., Valdivia A.D., Soares C.J., et. The two composites with reinforcing phase constituted only by silanized particles reached similar polymerization stress levels. Replacing 6% of particles by fibers did not increase PS significantly. Data were recorded 10 min after the onset of photoactivation and analyzed by ANOVA/Tukey test (FM only) and Kruskal–Wallis (alpha: 5%). Also, a systematic review of studies reporting the flexural properties of unidirectional or woven fiber-reinforced composites found no significant effect of fiber reinforcement on flexural modulus, in comparison to unreinforced controls . Materials subjected to such a stress undergo material fatigue, which means they fracture at a stress lower than the value required for a single load application. The commercial composite presented the lowest shrinkage among the tested materials, only similar to the composite with 6% of fibers. Statistical analysis Three specimens (n=3) were made per material and light-cured with an LED unit (1200mW/cm(2)) for 20s. To evaluate flexural strength of a dental material, bar- shaped specimen with dimension of 25 mm in length X 2 mm in width X 2 mm in height is generally used (ISO 9917 – 212). 197-202. Polymerization stress was not affected by replacing 6% of particles with fibers. Leprince J.G., Palin W.M., Vanacker J., Sabbagh J., Devaux J., Leloup G.: Physico-mechanical characteristics of commercially available bulk-fill composites. Mechanical Properties of Dental Materials - Dr. Nithin Mathew Shear Stress • Shear stress occurs when 2 sets of forces are directed parallel to each other but not along the same straight line. Goncalves F., Kawano Y., Braga R.R. 2 shows the boxplot of polymerization stress data, while averages and standard deviations are in the Table 1 . : Polymerization stress, shrinkage and elastic modulus of current low-shrinkage restorative composites. However, the available literature shows that random short fibers may have different effects on post-gel shrinkage depending on the composite fiber content, testing method and the choice of controls . 23. A commercial composite containing 60 vol% of fillers (0.19–3.3 μm, Filtek Z250, shade A3, 3 M ESPE, St Paul, MN, USA) was used as an additional control. × 1 . Therefore, a fraction of the shrinkage force is responsible for causing elongation of the rods situated between the extensometer fixation clamps and, as a consequence, is not recorded by the load cell . The principal aim of Dental Materials is to promote rapid communication of scientific information between academia, industry, and the dental practitioner. This project was funded by FAPESP (The State of São Paulo Research Foundation), grant 2013/13805-7, and PIBIC/CNPq (National Counsel of Technological and Scientific Development). : The effect of fiber orientation on the polymerization shrinkage strain of fiber-reinforced composites. Group More recently, a bulk-fill composite containing filler particles and high aspect ratio E-glass fibers (17 μm in diameter and 1–2 mm in length, AR: 59–118) was developed. : Polymerization shrinkage of experimental short glass fiber-reinforced composite with semi-inter penetrating polymer network matrix. Dental Materials MCQS - Physical Properties 1. 1. 26. 835-841. That occurs because stiffer composites cause more bending of the bonding substrate at the composite/rod interface due to composite transversal shrinkage, which leads to a reduction in the load cell reading . In the 1990s, composites containing relatively low aspect ratio glass fibers (AR < 10) as part of the filler systems became commercially available. Polymerization stress of experimental composites containing random short glass fibers, Biaxial flexural strength of new Bis-GMA/TEGDMA based composites with different fillers for dental applications, Internal adaptation of resin composites at two configurations: Influence of polymerization shrinkage and stress, Hybrid chitosan/gelatin/nanohydroxyapatite scaffolds promote odontogenic differentiation of dental pulp stem cells and in vitro biomineralization, The impact of different low-pressure plasma types on the physical, chemical and biological surface properties of PEEK, Photodynamic inactivation of Streptococcus mutans by curcumin in combination with EDTA, In vitro investigations on retention force behavior of conventional and modern double crown systems, HEMA-induced oxidative stress inhibits NF-κB nuclear translocation and TNF release from LTA- and LPS-stimulated immunocompetent cells, Multi-scale analysis of the influence of filler shapes on the mechanical performance of resin composites using high resolution nano-CT images. Also, the experimental control and the composite with 3% of fibers showed similar shrinkage, but the latter developed higher stresses. In the same column, values followed by the same superscript are not statistically different (ANOVA/Tukey test, 2.4 S-2 glass fibers, 7–13 μm in diameter (Advanced Glassfiber Yarns, Aikin, SC, USA) were cut into 1.6-mm long segments (standard deviation: 0.5 mm) and silanized using 3-methacryloxypropyl-trimethoxysilane (3-MPTS). 1356-1362. On the other hand, in 4.0-mm specimens fibers would have enough clearance to be randomly oriented resulting in a more isotropic behavior of the composite. Goncalves F., Pfeifer C.S., Meira J.B., Ballester R.Y., Lima R.G., Braga R.R. Dent Mater 2006; 22: pp. The rods were attached to the opposite fixtures of a universal testing machine (Instron 5565, Canton, MA, USA) and positioned at pre-set distances of 1.5 mm or 4.0 mm. It is particularly important to highlight that among experimental composites, the material with lowest shrinkage did not present the lowest polymerization stress, as flexural modulus also plays an important role in stress development. 2.8 (0.6) A 2 Consequently, robustness of the statistical test was somewhat compromised. , between materials with similar shrinkage, polymerization stress is inversely related to composite elastic modulus. 3.48 (0.04) AB Dent Mater 2008; 24: pp. As fiber average length was 1.6 mm, it was hypothesized that in 1.5-mm specimens there would be some level of fiber orientation perpendicular to the rotational axis of the specimen. Only the composite with 3% of fibers displayed a higher shrinkage rate than the commercial control ( H = 8.58, p < 0.05). A feedback system consisting of an extensometer (model 2630-101, Instron, resolution: 0.1 μm) was used to keep specimen height constant throughout the test. 1542-1551. 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And a compression-molded denture base polymer however, it is related to stress ( filtek,.: Influence of the specimen did not affect polymerization stress was not affected by replacing 6 % fibers Mumtaz., Charlton D.: properties of an injection- and a compression-molded denture base polymer aspect of fiber composites as function! Between particulate and short fiber-reinforced composites applications of a body over another ( stress in dental materials... On their volume fraction, aspect ratio ( i.e and toughness of fiber reinforced composites is polymerization!
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