Comparison of a new bisphenol-a-glycidyl dimethacrylate-based cortical bone void filler with polymethyl methacrylate.
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A newly formulated and reinforced bisphenol-a-glycidyl dimethacrylate (bis-GMA) resin (Cortoss/Orthovita, Malvern, Pa.) was compared with Simplex P polymethyl methacrylate (Stryker Howmedica Osteonics, East Rutherford, N.J.) in rabbits for up to 52 weeks and in sheep for up to 78 weeks. As seen in scanning electron microscopy and histology examinations, both implant materials were surrounded by bone at late time periods, with fibrous layers of connective tissue seen in half the Simplex P specimens. No clinically significant safety differences between implant materials were apparent. Interfacial bond strengths between the implant and bone generally increased with time, but were 4.5-fold greater with Cortoss than Simplex P at 24 weeks, and 100-fold greater at 52 weeks. Forces required to displace 316SS rods held in place with Cortoss were consistently greater than forces to displace rods held in place with Simplex P. No statistically significant differences in displacement forces were found between rods held in place with Cortoss polymerized in situ and rods held with prepolymerized Cortoss. Interfacial bond strengths were greater for Simplex P that was polymerized in situ than for prepolymerized polymethyl methacrylate specimens. Cortoss synthetic cortical bone void filler is a good candidate material to fix implants in bone. It has characteristics consistent with long-term safety and has a better ability to bond to bone than Simplex P. (+info)
Does single versus stepped curing of composite resins affect their shear bond strength?
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BACKGROUND: Shrinkage occurs during polymerization of all resin composites, affecting not only the physical properties of the composites but also the marginal integrity of the restoration. Stepped photo-polymerization, in contrast to single-cure photo-polymerization, is said to minimize this shrinkage. The thickness of the increments of resin composite being cured may also be a factor in final shear bond strength. This study compared the shear bond strength resulting from these two curing methods with resin composites of various thicknesses. METHODS: Resin composite in increments of 1.5, 3 and 4.5 mm thickness, cured by stepped or single-cure photo-polymerization, was bonded to human third molar dentin with either the Scotchbond Multipurpose adhesive system or the Singlebond adhesive system. Each experimental group consisted of 12 specimens. After 7 days of storage in water, shear bond strength was tested to failure, and the mode of failure was recorded. RESULTS: The thickness of the resin composite and the method of curing had no significant effect on shear bond strength for bonds mediated by Scotchbond Multipurpose adhesive, but significantly lower shear bond strength was recorded for bonds mediated by Singlebond adhesive for resin composite 4.5 mm in thickness. With thicker resin composite, there was a tendency toward a greater proportion of adhesive cohesive bond failures. CLINICAL SIGNIFICANCE: The stepped photo-polymerization system of curing appears to offer no advantages over single-cure photo-polymerization, except that the former reportedly improves marginal adaptation and reduces marginal leakage. These results suggest that increments of resin composite to be cured by either method should be no thicker than 2 mm, particularly when the bond is mediated by a single-bottle adhesive. (+info)
Polymer properties on resins composed of UDMA and methacrylates with the carboxyl group.
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The properties of dental matrix resins have been improved by synthesis of new monomers. However, except for improvements in water-resistance, monomers with better mechanical properties than Bis-GMA and UDMA could not being synthesized. Changing the point of emphasis, we tried to improve the mechanical properties controlling the matrix resin higher structure using noncovalent bonds. We prepared a matrix resin structured by UDMA, which is a high viscosity base monomer with imino groups, and by a low viscosity acidic monomer with carboxyl groups, which permits noncovalent bonds such as hydrogen bonds or electrostatic interaction with imino groups. The maximal mechanical strength for matrix resins structured by UDMA and an acidic monomer was obtained with a composition of imino groups and carboxyl groups at a ratio of 1:1. This mechanical strength value was higher than those obtained with UDMA resin or with a Bis-GMA/TEGDMA/UDMA resin with typical composition. The improvement in mechanical properties may be due to the complex based on noncovalent bonds, between the imino groups of UDMA and the carboxyl groups of the acidic monomers. (+info)
Fracture aspects of resin-dentin bonding in non-trimming microtensile test.
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Comparative studies on resin-dentin bond strength and failure mode were performed between the conventional tensile test and the microtensile test with non-trimming small specimens, 1 x 1 mm in cross-section, for two brands of dentin bonding systems. The fracture surface of the conventional large specimen showed a catastrophic cohesive failure in dentin at its center and a lesser adhesive failure, suggesting that the whole failure was due to the development of some major cracks. The non-trimming microtensile test showed significantly larger average bond strength with markedly larger standard deviation and significantly larger fraction of adhesive failure than the conventional test. Some small specimens were extremely strong and some were weak according to the heterogeneous distribution of tight bonding and defective or deficient bonding over the whole dentin surface. These results suggest that the non-trimming microtensile test may potentially provide more realistic aspects of resin-dentin bonding than the conventional bulk specimen. (+info)
A study of cavity preparation by Er:YAG laser. Effects on the marginal leakage of composite resin restoration.
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The purpose of this study was to evaluate marginal leakage of composite resin restoration from cavities prepared by Er:YAG laser. The observation of the dentin surface after the application of laser irradiation was performed by LSM, the cutting surface showed a rough surface similar to scales, and exposed dentinal tubules were observed without striations or a smeared layer formation that were observed when using a rotary cutting device. Leakage tests revealed no significant differences in the marginal seal for both enamel and dentin between cavities prepared by Er:YAG laser irradiation and when using an air-turbine. In this study, the usefulness of cavity preparation by Er:YAG laser irradiation in composite resin restoration was suggested. (+info)
Polymerization with a micro-xenon light of a resin-modified glass ionomer: a shear bond strength study 15 minutes after bonding.
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The purpose of this study was to evaluate the initial shear bond strength (15 minutes after bonding) of a resin-modified glass ionomer (RMGIC, Fuji Ortho LC) cured with two different light-curing units: a conventional visible light (Ortholux XT) and a microxenon light (Aurys). Seventy-five freshly extracted bovine permanent mandibular incisors were randomly assigned to one of five groups; each group consisted of 15 specimens. Group A (Transbond XT) and group B (Fuji Ortho LC) were exposed to the visible light for 20 and 40 seconds, respectively, and used as controls. The remaining three groups (C, D, and E) were bonded with Fuji Ortho LC and cured with Aurys for 10, 5, and 2 seconds, respectively. All samples were tested in a shear mode on an Instron universal testing machine 15 minutes after bonding. The shear bond strength of the control group bonded with Transbond XT was significantly higher (P = 0.000) than those of all the other groups tested. Regarding Fuji Ortho LC, no statistically significant differences were found between the bond strength of the control group cured with Ortholux XT, and those of the groups cured with Aurys for 2, 5, and 10 seconds. The present findings indicate that, compared with visible light-curing, the micro-xenon light enables the clinician to significantly reduce the curing time of RMGICs, without affecting their initial shear bond strengths. (+info)
Effect of fluoride mouth rinse on fluoride releasing and recharging from aesthetic dental materials.
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This study evaluated fluoride-release and recharging with the fluoride mouth rinsing technique on fluoridated materials. Three fluoride containing materials and one non-fluoride containing composite resin were used for this study. Samples for each material consisted of 15 discs, 9 mm diameter with a thickness of 1 mm. Initial fluoride release was assessed over a 60-day period. After that, 15 discs for each material were divided into 3 groups: distilled water group, 450-ppm and 900-ppm mouth rinsing groups. Fluoride release increased in combination with fluoride mouth rinse, and fluoride was higher in the 900-ppm group than the 450-ppm group. Moreover, S-PRG or F-PRG fillers materials released fluoride in higher than fluoroaluminosilicate glass fillers materials. In addition fluoride release from control samples was not observed. Therefore, only fluoride release material takes up fluoride. The findings of the present investigation suggest that the rate of fluoride release was different for each material, because they contained different function fillers. The results showed the importance of the fluoride mouth rinsing technique for fluoride-releasing restorative materials for the prevention of secondary caries. (+info)
Effect of presilanization filler decontamination on aesthetics and degradation resistance of resin composites.
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Filler-matrix coupling determines, to a large extent, the mechanical strength and clinical longevity of dental composites. The aim of this study was to examine how far a methodology to decontaminate filler prior to silanization may improve aesthetic performance in addition to physico-mechanical properties such as degradation resistance. It was reported that filler particles are surrounded and wrapped by a film that consists of multiple layers of silane molecules. X-ray photoelectron spectroscopy, however, revealed that silanization of filler particles largely depended upon siloxane bridge (Si-O-Si) formation between the silica surface and the silane molecule rather than on intermolecular bonding between adjacent silane molecules. In this study, we showed that filler decontamination resulted in a higher translucency, thereby providing a better aesthetic potential. In addition, experimental composites produced following presilanization decontamination of filler revealed a higher Vickers hardness value and a diametral tensile strength that was resistant to degradation by thermo-cycling. (+info)