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 1,275 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study evaluated the influence of the method and period of storage on the adhesive bond strength of indirect composite resin to bovine dentin. Ninety bovine incisors were stored in three different solutions: 0.2% thymol, 10% formalin, and 0.2% sodium azide, during 3 periods of storage: 7 days, 30 days and 6 months, resulting in 9 groups (n = 10). The roots were cut off and the buccal surface was ground with #600-grit silicon carbide paper. The surface was conditioned with 37% phosphoric acid for 15 s and a composite resin restoration (TPH Spectrum) was fixed using a one-bottle adhesive system (Adper Single Bond) and a dual-cured resinous cement (Rely X ARC) under a load of 500 g for 5 minutes. The samples were serially cut perpendicular to the bonded interface to obtain slices of 1.2 mm in thickness. Each slab was trimmed with a cylindrical diamond bur resulting in an hourglass shape with a cross-sectional area of approximately 1 mm(2). The microtensile bond strength (microTBS) testing was performed in a testing machine (EMIC 2000 DL) at a 0.5 mm/minute crosshead-speed until failure. After fracture, the specimens were examined under SEM to analyze the mode of fracture. muTBS Means were expressed in MPa and the data were analyzed by two-way ANOVA (3X3) and the Tukey test (alpha = 0.05). The storage times of 7 and 30 days produced no significant difference irrespective of the solution type. The formalin and thymol solutions, however, did have a negative influence on bond strength when the teeth were stored for 6 months.
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PMID:Influence of method and period of storage on the microtensile bond strength of indirect composite resin restorations to dentine. 1914 92

Color characteristics of the shades for different filler type resin composites were compared in the reflectance and transmittance modes, and specular component included (SCI) and specular component excluded (SCE) geometries for reflectance mode. Resin composites and shades used in this study were submicron filled Estelite Sigma (Sigma: Inc, A2, A3, B3, C2, OA2, OA3) and nanofilled Filtek(TM) Supreme XT (XT: Clear, A2E, A2B, A3B, C2B, A2D, A3D). Resin disks of 2 mm in thickness and final polish with 2,400-grit silicon carbide paper were kept in 100% humidity. One week after curing, color of the resin disks were measured with a spectrophotometer. Both for Sigma and XT, reflectance of each of all shades measured with SCI were significantly higher than those with SCE. Compared to the values with SCI and SCE, the L with SCI were significantly higher for all shades of Sigma and XT, however, a and b were depended with brands and shades. Different filler type resin composites showed different color characteristics, reflectance, transmittance and L a b distribution. In some shades, color difference between the measurement with SCI and SCE was visually perceptible level. It would be concluded that the color of resin composite measured with the SCI and SCE geometries differed.
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PMID:Color characteristics of resin composites in different color modes and geometries. 1932 9

Nanocrystalline diamond (NCD) coatings offer an excellent alternative for tribological applications, preserving most of the intrinsic mechanical properties of polycrystalline CVD diamond and adding to it an extreme surface smoothness. Silicon nitride (Si3N4) ceramics are reported to guarantee high adhesion levels to CVD microcrystalline diamond coatings, but the NCD adhesion to Si3N4 is not yet well established. Micro-abrasion tests are appropriate for evaluating the abrasive wear resistance of a given surface, but they also provide information on thin film/substrate interfacial resistance, i.e., film adhesion. In this study, a comparison is made between the behaviour of NCD films deposited by hot-filament chemical vapour deposition (HFCVD) and microwave plasma assisted chemical vapour deposition (MPCVD) techniques. Silicon nitride (Si3N4) ceramic discs were selected as substrates. The NCD depositions by HFCVD and MPCVD were carried out using H2-CH4 and H2-CH4-N2 gas mixtures, respectively. An adequate set of growth parameters was chosen for each CVD technique, resulting in NCD films having a final thickness of 5 microm. A micro-abrasion tribometer was used, with 3 microm diamond grit as the abrasive slurry element. Experiments were carried out at a constant rotational speed (80 r.p.m.) and by varying the applied load in the range of 0.25-0.75 N. The wear rate for MPCVD NCD (3.7 +/- 0.8 x 10(-5) mm3 N(-1) m(-1)) is compatible with those reported for microcrystalline CVD diamond. The HFCVD films displayed poorer adhesion to the Si3N4 ceramic substrates than the MPCVD ones. However, the HFCVD films show better wear resistance as a result of their higher crystallinity according to the UV Raman data, despite evidencing premature adhesion failure.
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PMID:Adhesion and wear behaviour of NCD coatings on Si3N4 by micro-abrasion tests. 1950 45

The objective of this study was to test the hypothesis that thermal cycling weakens the flexural strength of porcelain. Specimens of Deguceram Gold and Vita Omega 900 were tested in four groups of 30 specimens each: in the original glazed condition versus being ground with 1000-grit, 600-grit, and 100-grit silicon carbide abrasives. Corresponding to these four types of surface treatments, four groups of 30 specimens per group received 5,000 times of thermal cycling. Flexural strength was measured using a four-point flexural test, and Weibull modulus was calculated. Within each type of surface treatment, the thermal cycling treatment did not result in any decrease in flexural strength although it caused the Weibull modulus to become smaller - except for the control and thermal-cycled groups of 600-grit surface treatment.
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PMID:Effects of thermal cycling and surface roughness on the Weibull distribution of porcelain strength. 1972 Dec 80

To determine the shear bond strength of 10 self-etching adhesive systems to dentin and enamel, flat bonding sites were prepared on 216 extracted human molar teeth, using 600-grit silicon carbide paper to expose dentin or enamel. Following the application of each adhesive system, bonded assemblies of Spectrum TPH were prepared using a gelatin capsule matrix (n = 24). After 24 hours of storage in water at 37 degrees C, 12 specimens from each enamel and dentin group were debonded. This was followed by thermocycling for 6,000 cycles between water baths at 5 degrees C and 55 degrees C, with a dwell time of 20 seconds in each bath. Specimens were loaded to failure in a testing machine with a crosshead speed of 5 mm/minute. Statistical analysis included a one-way ANOVA and least square difference post hoc test. There were significant differences in shear bond strength for both enamel and dentin among the materials tested (p < 0.05).
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PMID:Bond strength of composite to dentin and enamel using self-etching adhesive systems. 1981 15

The purpose of this study was to investigate the influence of chlorhexidine (CHX) concentration on the microtensile bond strength (muTBS) of contemporary adhesive systems. Eighty bovine central incisors were used in this study. The facial enamel surface of the crowns was abraded with 600-grit silicon carbide paper to expose flat, mid-coronal dentin surfaces. The tested materials were Scotchbond Multipurpose (SMP), Single-Bond (SB), Clearfil SE Bond (CSEB) and Clearfil Tri S Bond (CTSB). All the materials were applied according to manufacturer's instructions and followed by composite application (Z250). The teeth were randomly divided into 16 groups: for the etch-and-rinse adhesives (SMP and SB), 0.12% or 2% CHX was applied prior to or after the acid etching procedure. For the self-etch adhesives (CSEB and CTSB) 0.12% or 2% CHX was applied prior to the primer. Control groups for each one of the adhesive systems were also set up. The specimens were immediately submitted to muTBS testing and the data were analyzed using Analysis of Variance and the Tukey post hoc test (alpha = .01). The failure patterns of the specimens were observed using scanning electron microscopy. The effects of 2% CHX were statistically significant (p < 0.01) for the self-etch adhesives but were not significant for the etch-and-rinse adhesive systems. Analysis of the data demonstrated no statistical difference between the etch-and-rinse adhesive systems. CHX-based cavity disinfectants in concentrations higher than 0.12% should be avoided prior to the self-etch adhesive systems evaluated in this study to diminish the possibilities of reduction in bond strength.
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PMID:Influence of chlorhexidine concentration on microtensile bond strength of contemporary adhesive systems. 1989 72

This study examined the relationship between the adhesive application time and enamel bond strength of several single-step self-etch adhesive systems. The adhesives used were: Bond Force (BF, Tokuyama Dental Corporation, Tokyo, Japan), Clearfil tri-S Bond (CT, Kuraray Medical Inc, Tokyo, Japan), iBond Self-Etch (IB, Heraeus Kulzer, Armonk, NY) and OptiBond All-in-One (OB, sds Kerr). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600-grit silicon carbide paper to expose labial enamel. Adhesives were applied for 10, 20 or 40 seconds and the resin composites were condensed into a mold (phi4 x 2 mm) on the enamel and light irradiated. Ten samples per test group were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/minute. One-way ANOVA and the Tukey HSD test (alpha = 0.05) were performed within each adhesive system. The enamel surfaces after adhesive application were also observed in a Field Emission Electron Probe Surface Roughness Analyzer and the Ra value was calculated. The enamel bond strength ranged from 13.6 to 17.8 MPa for BF, 13.6 to 15.9 MPa for CT, 14.3 to 16.2 MPa for IB and 13.4 to 19.8 MPa for OB. Significant increases in bond strength were found for the 40-second application groups, except for IB. No changes in Ra value were found for BF and IB, while significant decreases in Ra value were recorded with 40-second application for CT and OB. The data suggested that the duration of the single-step self-etch adhesive application was a crucial factor for determining the enamel bond strengths of some of the single-step self-etch adhesives employed in the current study.
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PMID:Influence of adhesive application time on enamel bond strength of single-step self-etch adhesive systems. 2016 14

We determine the backscatter reflectance (more properly the bidirectional reflectance distribution function at a 45 degrees angle of incidence and observation) for circularly polarized radiation of lambda = 10.6 microm for 120-grit aluminum oxide sandcloth (1.5 x 10(-2) sr(-1)) and 400-grit silicon carbide sandpaper (1.1 x 10(-2) sr(-1)) with respect to sublimed flowers of sulfur (1.8 x 10(-1) sr(-1)). The effect of range and the atmospheric effect of turbulence-induced beam wander are discussed for both rotating disks and linearly translated belts. The advantages of large slowly rotating disks for field calibrations are presented.
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PMID:Calibration of coherent lidar targets. 2023 13

Gold-plated sandpaper was investigated for use as a Lambertian standard reference reflector for the IR spectrum. Various grit sizes from 3 to 400 microm and material types (i.e., silicon carbide and aluminum oxide) were studied. The different gold-plated sandpaper grit sizes were measured in the same way using three laser wavelengths (0.6328, 3.39, and 10.6 microm) at five angles of incidence of the source (0, 10, 20, 30, and 60 degrees ). All the scattering measurements were performed in the plane of incidence. The best choices of sandpaper grit sizes were 9-microm A1(2)O(3) for 0.6328- and 3.39-microm radiation and 600 grit by Armak Co. for 10.6-microm radiation. These choices were compared with other commonly used reflectors such as magnesium oxide, halon, sintered bronze, and flowers of sulfur. An attempt was made to correlate surface roughness (size of grit) to the degree of approximation to a good Lambertian reflector, but it was found that grit size is not as important as the filling factor, or density of particles, over a given area. It was found that fairly good approximations to Lambertian behavior result when the angle of incidence is small but not when the angle of incidence is as large as 60 degrees .
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PMID:Bidirectional reflectance distribution function of gold-plated sandpaper. 2033 13

The purpose of the present study was to test the hypothesis that glazing will affect the Weibull modulus or the mean flexural strength of dental porcelain. Four groups (n = 30) of specimens were prepared from feldspathic body porcelain (Vita VMK 68). The specimens were tested in groups: original glazed condition (control), and after grinding separately with 1,000-grit, 600-grit, and 100-grit silicon carbide abrasive. A three-point flexure test was undertaken for each specimen. The flexural strength of porcelain and the Weibull modulus were then obtained using a computer program and load-to-failure data. Flexural strength decreased as surface roughness increased, and the differences were significant (p < 0.05), as determined by Tukey's multiple range test, except between the 600-grit group and the 100-grit group. The Weibull modulus of the glazed group was the largest (16.3), and the surface roughness was found to influence the Weibull modulus.
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PMID:The effect of surface roughness on the Weibull distribution of porcelain strength. 2037 9


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