Fiber which can not chemically bond to

Fiber posts have more esthetic then metallic post because of their tranclucency, but their bond strength to the composite core is a concern.

Hence some chemical surface pretreatments have been suggested to increase their adhesive properties.(5)Fiber posts are composed of different types of fibers embaded in a a matrix resin. The matrix resin of glass fiber posts is epoxy which can not chemically bond to the compoite core due its high degree of conversion.

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Therefore, to increase the bond strength some investigators propose using silane coupling agent on the fiber post surface (2).Silane enhances surface wettability and by its bifunctional properties, a chemical covalent bond could be achieved between the silane the exposed glass fibers or filler particles of the post(2).Goracci-etal (2005) stated that silanization can increase the bond strength between different types of fiber posts and flowable composites (6). But MPS (3-trimethoxy silylpropylmethacrylate) silane can not bond adequetly with the epoxy matrix, therefore, a weak bond strength between resin phase of the fiber posts and the methacrylate-based resin composite is existed(5).

Hydrogen peroxide (H2O2) can selectively dissolve the epoxy matrix without damaging the glass fibers and this procedure can bring the glass fibers in better contact with silane coupling agent. Mosharraf et al (2013) study showed that using 20%H2O2 before silanization can significantly improve the TBS(2).The etching effect of Hydrogen-peroxide depends on its capability to dissolve the resin matrix partially, thereby breaking the epoxy resin bonds through the mechanism of substrate oxidation. The same etching procedure is employed to improve the micro-mechanical retention between the epoxy resin matrix of fiber post and methacrylate-based resin composites.By removing the superficial layer of epoxy resin through chemical treatment more surface area of exposed quartz fibers becomes available for reacting with the molecules of silane. Thus after etching and rinsing of post surface, large active surface of exposed quartz fibers is available for both chemical and micro-mechanical retention(5,7) Studies performed by Sumitha et al (2011),Francesca Monticellietal(2006),Heidari et al(2013) and Yenisey et al (2008)(14) using 10% Hydrogen Peroxide showed increased micro-tensile bond strength(7,8,9,10).

Similar studies performed by M de Souza et al (2011) using 24% and 50% Hydrogen Peroxide showed increased surface roughness of fiber posts (11).


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