Search

Three types of metal specimens (ring-shaped, plate-shaped, and a simulated anterior arch) for distortion observations were made from Au-Ag-Pd-Cu alloy. Distortion due to polymerization shrinkage and thermal contraction of a heat-curing acrylic resin containing 4-META (4-methacryloyloxyethyl trimellitate anhydride, 4-META resin) could be visualized for the ring-shaped specimen, which showed increasing distortion of the metal frame upon adhesion of the resin to the outer metal surface. Distortion of the plateshaped specimen adhering to 4-META resin decreased with increasing thickness of the cured resin. The distortion of the metal frame simulating an anterior arch of a six-unit bridge with a facing composite resin showed that the curvature of the metal frame was larger after curing of the facing composite resin. However, it recovered most of its original curvature with an associated increase in the number of cracks between the crowns after trimming the resin to a tooth profile. [ABSTRACT FROM AUTHOR]

Summary: Resin–dentin bonding was first achieved through mechanical hybridization between resin and collagen fibrils using a functional monomer containing resin system. In the last decade, new adhesive resin systems were frequently released onto the market within a short-period of time. Before and after commercialization, the bond integrity has been tested by bond tests, and leakage evaluation by researchers, but it is very difficult for clinicians to obtain a comprehensive, up-to-date understanding of their nature and degradation. Although newly developed adhesive resins have attempted to improve the bond strength at least in the first 24h after bonding, the long-term durability of the bonds has not yet been established analytically. However, numerous recent studies have shown micromorphological evidence of biodegradation of resin–dentin bonds, due to hydrolysis of the resin and collagen fibrils within the bonds. This review mainly summarizes the most recent work in biodegradation of resin–dentin bonds based on micromorphological analyses of data obtained by scanning and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

Hashimoto M, Fujita S, Nagano F, Ohno H, Endo K. Ten-years degradation of resin–dentin bonds. Eur J Oral Sci 2010; 118: 404–410. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The purpose of this study was to evaluate the durability of resin–dentin bonds in 10-yr water-storage testing. Resin–dentin bonded bulk specimens were prepared using six commercially available resin adhesives. The resin–dentin bonded specimens were stored in water for 24 h (control group) or for 10 yr (experimental groups). After each storage period, the specimens were sectioned to make specimen beams and then subjected to a microtensile bond test. After the bond test, fractured surfaces were examined by scanning electron microscopy (SEM). In addition, interfacial observation of silver nanoleakage was performed using the backscatter electron mode of SEM. The bond strengths of four of the six adhesive systems tested decreased significantly after 10 yr. However, no significant bond-strength reduction was recorded for the other two systems. The interfacial observations showed water tree propagation in the bonding resin layer as a typical morphological change after aging for five of the six adhesives tested. Water tree propagation may be a symptom of degradation in the resin bonding layer of resin–dentin bonds. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the durability of one-bottle self-etching adhesive during long-term water-storage testing. Resin–dentin bonded specimens were prepared using four commercially available one-bottle self-etching adhesives. The specimens were sectioned perpendicular to the adhesive interface to produce beam-shaped specimens that were stored in water for 24 h (control group) and 100, 200, and 300 d (experimental groups). After each storage period, the beams were subjected to a microtensile bond test. After the bond test, fractured surfaces were examined using a scanning electron microscope. In addition, interfacial observations of the silver tracer were performed using the secondary and back-scatter modes of the scanning electron microscope. The bond strength of all tested adhesives decreased significantly after 100 or more days in water. The interfacial observations showed an oxygen-inhibition zone as electron lucent in the adhesive–composite border in control specimens, displaying silver impregnation with breakage after aging. The deterioration of the oxygen-inhibition zone in the adhesive–resin composite junction resulted in a decrease in bond strength after 100 d in water for one-bottle self-etching adhesives. [ABSTRACT FROM AUTHOR]