Adhesion of resin composite core materials to dentin.

PURPOSE: This study determined (1) the effect of polymerization mode of resin composite core materials and dental adhesives on the bond strength to dentin, and (2) if dental adhesives perform as well to dentin etched with phosphoric acid as to dentin etched with self-etching primer. MATERIALS AND METHODS: Human third molars were sectioned 2 mm from the highest pulp horn and polished. Three core materials (Fluorocore [dual cured], Core Paste [self-cured], and Clearfil Photo Core [light cured]) and two adhesives (Prime & Bond NT Dual Cure and Clearfil SE Bond [light cured]) were bonded to dentin using two dentin etching conditions. After storage, specimens were debonded in microtension and bond strengths were calculated. Scanning electron micrographs of representative bonding interfaces were analyzed. RESULTS: Analysis showed differences among core materials, adhesives, and etching conditions. Among core materials, dual-cured Fluorocore had the highest bond strengths. There were incompatibilities between self-cured Core Paste and Prime & Bond NT in both etched (0 MPa) and nonetched (3.0 MPa) dentin. Among adhesives, in most cases Clearfil SE Bond had higher bond strengths than Prime & Bond NT and bond strengths were higher to self-etched than to phosphoric acid-etched dentin. Scanning electron micrographs did not show a relationship between resin tags and bond strengths. CONCLUSION: There were incompatibilities between a self-cured core material and a dual-cured adhesive. All other combinations of core materials and adhesives produced strong in vitro bond strengths both in the self-etched and phosphoric acid-etched conditions.

In vitro tensile bond strength of adhesive cements to new post materials.

PURPOSE: The purpose of this study was to measure the in vitro tensile bond strength of 3 types of adhesive resin cements to stainless steel, titanium, carbon fiber-reinforced resin, and zirconium oxide post materials. MATERIALS AND METHODS: Disks of post materials were polished to 600 grit, air abraded, and ultrasonically cleaned. Zirconium oxide bonding surfaces were pretreated with hydrofluoric acid and silanated. Bis-Core, C&B Metabond, and Panavia cements were bonded to the post specimens and placed in a humidor for 24 hours. Post specimens were debonded in tension. Means and standard deviations (n = 5) were analyzed by 2-way analysis of variance. Tukey-Kramer intervals at the 0.05 significance level were calculated. Failure modes were observed. RESULTS: Panavia 21 provided the highest bond strengths for all types of post materials, ranging from 22 MPa (zirconium oxide) to 37 MPa (titanium). C&B Metabond bonded significantly more strongly to stainless steel (27 MPa) and titanium (22 MPa) than to zirconium oxide (7 MPa). Bis-Core results were the lowest, ranging from 16 MPa (stainless steel) to 8 MPa (zirconium oxide). In most cases, bonds to carbon fiber post materials were weaker than to stainless steel and titanium, but stronger than to zirconium oxide. In general, higher bond strengths resulted in a higher percentage of cohesive failures within the cement. CONCLUSION: Panavia 21 provided the highest bond strengths to all post materials, followed by C&B Metabond. In most cases, adhesive resins had higher bond strengths to stainless steel, titanium, and carbon fiber than to zirconium oxide.

Color accuracy of resin cements and try-in pastes.

The color accuracy of resin composite cements and their corresponding try-in pastes was assessed. Three shades of three brands were compared using the cements alone and in contact with a standard porcelain disk. There were significant differences in color between resin cements and their corresponding try-in pastes. The addition of a 1-mm-thick porcelain disk greatly reduced the apparent color differences. The color of resin cements changed over time, but not significantly. Baseline measurements of resin cement colors were compared and measurements made after 24 hours of storage. Color changes were statistically significant but not perceptible, and all samples became slightly darker with age.

Bond strength of orthodontic composite cement to treated porcelain.

A porcelain-fused-to-metal ceramic was prepared for bonding by five treatments: sandblasting, sandblasting and silanating, hydrofluoric acid etching, hydrofluoric acid etching and silanating, and 600-grit polishing and silanating. Two commercial, all-purpose bonding agents were used to bond a composite cement to the porcelain samples. In vitro tensile bond strengths were compared with samples for which no bonding agent was used. Highest bond strengths (22 to 41 MPa) were obtained, with one exception, when the porcelain surface was silanated; however, the use of silane increased the occurrence of porcelain fracture on debonding. Composite cement bonded without bonding agent to nonsilanated porcelain prepared by sandblasting or etching with hydrofluoric acid had bond strengths of 6.5 MPa and 18 MPa, respectively, with all bond failures at the bracket/composite interface. The use of all-purpose bonding agents and silanating agents may not be necessary for adequate orthodontic direct bonding.

Color stability of resin cements after accelerated aging.

The color stability of both light- and dual-polymerized samples of three shades of three commercial resin cements was measured using a reflection spectrophotometer after accelerated aging over a period of 179 hours. Porcelite cement was the most color stable, followed by Optec and then 3M. The Optec and Porcelite cements changed color after accelerated aging, but with one exception the changes were not perceptible. Five of six 3M cements had perceptible color changes after accelerated aging, becoming darker and more yellow. The two lighter shades of Optec and 3M changed color more than the darker shade. Most differences between light- and dual-polymerized samples were significant but none was perceptible.

Effect of R59022, an inhibitor of diacylglycerol kinase, on IgE-mediated histamine release from human lung mast cells and basophils.

We have examined the effect of the diacylglycerol kinase inhibitor R59022 on histamine release from human lung mast cells and basophils. At 1 microM the drug increased the IgE-dependent release of histamine from human basophils from 19 +/- 5% to 60 +/- 13% (n = 5, p < 0.01). The increase in histamine release was dose dependent with maximum enhancement between 1 and 10 microM. 1 microM R59022 also increased f-met peptide-induced histamine release from 18 +/- 4% to 55 +/- 11% (n = 5, p < 0.05). However, the drug did not significantly increase the release of histamine when the non-physiologic stimulus PMA was used to initiate release. The effect of the drug on anti-IgE-induced release was most marked at lower concentrations of anti-IgE and declined when superoptimal concentrations of anti-IgE were used. As anticipated there was a strong negative correlation (r = 0.764, p < 0.05) between anti-IgE-induced histamine release and the percentage enhancement in the presence of 10 microM R59022. In contrast, to these potent effects on the human basophil the drug failed to affect the anti-IgE-induced release of histamine from human lung mast cells. The data suggest that the R59022 increases the release of histamine induced by anti-IgE in human basophils but not in human lung mast cells. Furthermore, the ability of R59022 to potentiate basophil histamine release is restricted to receptor-mediated stimuli such as anti-IgE and does not extend to non-physiologic stimuli such as the phorbol ester PMA.

Effect of dissolution on color of extrinsic porcelain colorants.

The effect of in vitro dissolution in acidulated phosphate-fluoride gel on the color of metal ceramic samples having surface metal oxide colorants was determined. Three different colorants were applied using two techniques at two different firing temperatures. The color difference was most apparent when the colorant and glaze were combined with only one firing cycle. All colorants increased in value, but changes in color difference were most evident with the blue colorant. It was concluded that dissolution in acidulated phosphate-fluoride gel does affect the color of extrinsic metallic oxide colorants.

Bond strength of composite to etched and sandblasted porcelain.

In vitro tensile bond strengths of composite to porcelain treated by acid etching or sandblasting were measured. A 9.5% HF gel was applied for 30, 60, 150, or 300 seconds at 23 degrees C. Al2O3 particles were applied as wet-10.2, dry-33.5, dry-48.0, or dry-78.0 microns. Average roughness (Ra) was measured by profilometry before and after each treatment. Both longer etching time and sandblasting using Al2O3 with larger particle sizes produced increased surface roughness of porcelain. Etching with 9.5% hydrofluoric acid gel produced higher bond strengths than sandblasting with a series of Al2O3 particles. Etching longer than 60 seconds produced increased cohesive failures in porcelain, whereas most failures observed with sandblasted surfaces were adhesive.

In vitro bond strength of silica-coated metal posts in roots of teeth.

This study determined the in-vitro bond strength of abrasive-sprayed and silica-coated Ni-Cr-Be posts to roots of extracted teeth using three resin cements (Panavia EX [P], Super-Bond C&B [SB], Prisma Universal Bond 2-Dicor [PUB-D]) and zinc phosphate cement (ZP). There were no significant differences among bond strengths of resin cements (8.8 to 10.8 MPa) bonded to abrasive-sprayed posts, but the bonds were stronger than those obtained using zinc phosphate cement (4.4 MPa). With the silica-coated posts, Super-Bond C&B produced the highest bond strength (14.5 MPa), followed by PUB-D (10.9 MPa), P (7.5 MPa), and ZP (5.4 MPa).

Bond strength of composite to porcelain treated with new porcelain repair agents.

In vitro tensile bond strengths of composite to porcelain were evaluated using three pretreatments (HF etching, sandblasting, diamond abrasion) of the porcelain, four bonding agents (Clearfil Porcelain Bond, Porcelain Liner M, Porcelain Liner M with Super-Bond C&B, and Scotchprime) and two storage conditions (24 h and thermocycling). The overall coefficient of variation was 27%. Significant differences among bond strengths were observed, with storage condition being the most important factor, followed by bonding agent and then pretreatment. Thermocycling decreased the bond strength of all samples, but samples treated with Scotchprime were affected least. For 24 h storage, Clearfil Porcelain Bond and Scotchprime had bond strengths above 23 MN/m2 to sandblasted porcelain.

Variables affecting the spectral transmittance of light through porcelain veneer samples.

The spectral transmittance of porcelain laminate veneers was measured at three different thicknesses (0.50, 0.75, and 1 mm) and three different opacities (25%, 75%, and 100%). The results indicated that the thickness of the porcelain veneer was the primary factor affecting light transmission and not the opacity. The measured values of transmittance were then used to estimate the setting time for light-cured luting agents of a porcelain veneer.

Color and shade matching: the weak link in esthetic dentistry.

While esthetics has always been important, the introduction of new esthetic products, simplified techniques, and increased patient awareness have expanded the public demand for esthetic dentistry. This article will present information on three components necessary to obtain an accurate shade match.