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chemical cleaning agents and bonding to glass-fiber posts0 تومان
The inﬂuence of chemical cleaning agents on the bond strength between resin cement and glass-fber posts was investigated. The treatments included 10% hydroﬂuoric acid, 35% phosphoric acid, 50% hydrogen peroxide, acetone, dichloromethane, ethanol, isopropanol, and tetrahydrofuran. Flat glass-fber epoxy substrates were exposed to the cleaners for 60 s. Resin cement cylinders were formed on the surfaces and tested in shear. All treatments provided increased bond strength compared to untreated control specimens. All failures were interfacial. Although all agents improved the bond strength, dichloromethane and isopropanol were particularly effective.
Comparison of shear bond strength of aesthetic restorative materials0 تومان
Aim: The present study was conducted to determine and compare the shear bond strengths of Conventional glass ionomer; Resin-modified glass ionomer; Polyacid-modified composite and Composite Resin, and to assess and determine the mode of failure (adhesive, cohesive, mixed). Materials and Methods: Occlusal dentin of 40 extracted human teeth were randomly divided into four groups of ten teeth, each based on the restorative materials tested as follows: Group I: Conventional Glass Ionomer Cement (Control); Group II: Resin-modified Glass Ionomer Cement; Group III: Polyacid-modified Composite Resin; Group IV: Hybrid Composite Resin. The bonded materials were subjected to shear bond strength (SBS) testing in a Instron Universal Testing Machine (UTM) at a crosshead speed of 0.5 mm/min. The bond failure location was examined by the use of a stereomicroscope at 10× magnification. The mean SBS of Groups I–IV obtained was 3.81, 9.71, 11.96 and 18.16 MPa, respectively. Comparison of mean shear bond strengths of all groups was done by one way ANOVA test and comparison of means in between groups by the Student’s t test. Conclusion: It is concluded that the compomer restorative materials show higher shear bond strength than conventional glass-ionomer and resin-modified glass-ionomer, but less than composite resin.
Composite materials: Composition, properties and clinical applications0 تومان
Various composite materials are available today for direct restorative techniques. The most well-known materials are the hybrid composites. This technology, based on methacrylates and different types of filler coupled with silanes, has been continuously improved. Disadvantages such as polymerisation shrinkage, bacterial adhesion and side effects due to monomer release still remain. The aim of material development is to eliminate or at least reduce these negative factors by adapting the individual components of the material. With ormocers, the methacrylate has been partially replaced by an inorganic network. According to recent studies, the biocompatibility was not improved in all cases. The development of compomer was an attempt to combine the positive properties of glassionomers with composite technology. This has only partially succeeded, because the fluoride release is low. In an in-situ study, a caries protective effect could be shown at least in the first days following filling placement with concurrent extra-oral demineralisation. By replacing the chain-monomers in the composite matrix by ring-shaped molecules, a new approach to reduce polymerisation shrinkage was investigated. A new group of materials, the siloranes, has been developed. Siloranes are hydrophobic and need to be bonded to the dental hard tissue using a special adhesive system. Longterm clinical studies are still needed to provethe superiority of this new group of materials over modern hybrid composites.
Effects of External Bleaching on Restorative Materials: A Review0 تومان
With the increasingly commercial emphasis on dental esthetics, patients have become more interested in improving the appearance of their smile. For many ,whiter teeth is their chief goal. However, when considering dental bleaching, practitioners need to take certain precautions. Over the past decade, multiple studies have evaluated the effects of bleaching agents on restorative materials. This article reviews their conclusions, focusing mainly on the clinical impact these agents can have on amalgam, porcelain, ormocer, glass ionomer, compomer and composite resin restorations. lar bleaching products, can change the physical properties of dental restorations such as their colour, surface roughness, hardness and ion leakage. In this article, we put these changes in restorative materials into clinical perspective and provide practitioners with the evidence to properly answer patients’ questions.
Newer Root Canal Irrigants in Horizon: A Review0 تومان
Sodium hypochloride is the most commonly used endodontic irrigant, despite limitations. None of the presently available root canal irrigants satisfy the requirements of ideal root canal irrigant. Newer root canal irrigants are studied for potential replacement of sodium hypochloride. This article reviews the potential irrigants with their advantages and limitations with their future in endodontic irrigation.