The Journal of Adhesive Dentistry, 04/2002

Single-step adhesives which etch and prime simultaneously and are not rinsed should not exhibit areas of incomplete infiltration within hybrid layers produced in sound dentin. This study examined the extent of silver uptake using ammoniacal silver nitrate in three two-step, self-etching primers (Imperva Fluoro Bond, Shofu; UniFil Bond, GC, ABF system, Kuraray) and one single-step, self-etching adhesive (AQ Bond, Sun Medical) bonded to dentin and four poly(HEMA) resins used as controls. Flat dentin surfaces were bonded with these adhesives and sectioned into 0.8-mm-thick slabs that were then coated with nail varnish except for the bonded interfaces and immersed in AgNO3 for 24 h. Four types of poly(HEMA) resins were made: 100% HEMA; 90% HEMA-10% water; 75% HEMA-10% water, all polymerized with TBBO at 50°C for 6 h; 100% HEMA polymerized at 25°C for 30 min. After developing, undemineralized, unstained, epoxy resin-embedded sections were prepared for TEM. Nanoleakage patterns were observed in all bonded specimens. Fine segregated silver particles and reticular silver-staining patterns were found within the thin hybrid layers created by the three self-etching primers. For the single-step, self-etching adhesive, heavy silver deposits were identified within the hybridized complex formed by this adhesive within the smear layer, the underlying intact dentin, and in the adhesive layer. Increasing amounts of silver uptake were observed in poly(HEMA) specimens containing more water or that were polymerized at 25°C for a short time instead of 50°C for 6 h. Silver uptake in hybrid layers formed by self-etching adhesives in sound dentin is not necessarily caused by disparities between the depths of demineralization and resin infiltration. They represent areas of increased permeability within a polymerized resin matrix in which water is incompletely removed resulting in regions of incomplete polymerization and/or hydrogel formation.

The objective of this in vitro study was to evaluate the bonding compatibility between different adhesives and a dual-cured resin cement, using a conventional tensile bond test. The adhesives used were: Prime & Bond (PB) (Dentsply) (PB), Scotchbond Multi Purpose (SB) (3M), and the activator Self Cure (SC) (Dentsply). The dual-curing resin cement used was Enforce (EF) (Dentsply). Six groups with five specimens in each were tested: G1: EF/PB/EF (light cured); G2: EF/SB/EF (light cured); G3: EF/PB+SC/EF (light cured); G4: EF/PB+SC/EF (only chemically cured); G5: EF/EF (light cured); G6: EF/EF (only chemically cured). The resin cement was applied in two stainless steel molds with a cone-shaped perforation measuring 4 mm in diameter and 1 mm in thickness, and the adhesive was applied between them. Ten minutes after specimens were cured, the tensile strength was measured in a universal testing machine at a crosshead speed of 0.5 mm/min. The mean values (MPa) ± SD obtained in each experimental group were: G1: 1.4 ± 0.2; G2: 1.3 ± 0.2; G3: 1.2 ± 0.4; G4: 0.8 ± 0.2; G5: 1.2 ± 0.1; G6: 0.7 ± 0.1. The results were statistically evaluated using nonparametric Kruskal-Wallis and Dunn tests (p = 0.05). Statistically significant differences among groups were found only between G1 and G4, and G1 and G6. There was no incompatibility among the different adhesives used with dual-cured resin cement. The lowest tensile bond strength values occurred in the absence of photoactivation.

The aim of the study was to investigate the effect of the relative humidity of the ambient air on the dentin bonding efficiency of four self-etching primer adhesives. Three commercially available self-etching primer adhesives, AQ Bond, Fluorobond, One-Up Bond F, and one experimental all-in-one adhesive, AC-Bond, were selected. Peripheral plane dentin surfaces of human molars were prepared with wet SiC paper. Eight specimens were prepared for each of the adhesives and each of the following six conditions prior to application of the bonding agents and a hybrid-type resin composite material: air dried, wet, or stored for 1 h at 33%, 50%, 75%, and 100% relative humidity (RH). Shear bond strength (SBS) was determined after 24 h of storage in water at 37°C. None of the adhesives showed statistically significant differences in SBS between the experimental conditions. AC Bond, AQ Bond, and Fluorobond were equally effective with an average SBS of 19.0 MPa, whereas One-Up Bond F showed a significantly lower mean SBS of 11.5 MPa. The self-etching primer adhesives tested are unaffected by the degree of dentin wetness or ambient air humidity exposure prior to application. Unless considered necessary for other clinical reasons, use of rubber-dam is not compulsory.

The aim of this study was to investigate the effect of dentin smear-layer thickness on the bond strength of three all-in-one adhesives of different acidity. Peripheral dentin was prepared by wet grinding on SiC papers (80-, 180-, 240-, 320-, 400-, 600-, 4000-grit), and by turbine cutting with supercoarse, coarse, medium, fine, or extrafine diamond burs. The smear layer thickness (SLT) was measured microscopically. The relationship between SLT and average grain size of the abrasives used to prepare the dentin surface was described by regression analysis. Shear bond strength (SBS) was determined for the following adhesives: AC Bond, pH 2.1 (experimental, Heraeus); AQ Bond, pH 2.5 (Sun Medical); and Prompt L-Pop, pH 1.1 (3M-Espe). Six specimens were tested for each adhesive on dentin ground with each of the seven SiC grit sizes. The mode of failure was inspected by SEM. SBS data were analyzed by one-way ANOVA and Fisher's PLSD test at p 0.05. A logarithmic relationship between SLT and grain size of the abrasives was established. The coefficient of determination R2 for the regression line was 0.803. Shear bond strengths for the individual adhesives did not differ significantly by SiC grit size. SBS of AC Bond (18.3 MPa) was greater than the SBS of AQ Bond and Prompt L-Pop (16.9 MPa). Cohesive failures were consistently found in resin composite or adhesive. Smear layer thickness increased with decreasing SiC grit numbers and increasing diamond bur roughness. In spite of the widely differing acidity, all three adhesives tested were equally effective over the range of SLT from 2.6 µm through 0.9 µm.

To evaluate the bond strength of a self-etching primer (SE, Clearfil SE Bond) and a one-bottle adhesive system (EX, Excite) on enamel and dentin. Twenty-eight sound human molars were used. The teeth were randomly divided into four groups (n = 7): SE applied to enamel (SE-E); SE applied to dentin (SE-D); EX applied to enamel (EX-E); EX applied to dentin (EX-D). A resin (Tetric Ceram) block of approximately 5 x 5 x 5 mm was built up on the tooth and cured for 40 s. After 24 h, samples were obtained by cutting along the x and y axis of the tooth. Stick-shaped samples of approximately 0.8 mm2 cross-sectional area were obtained. The sticks underwent microtensile testing. The tensile bond strength (MPa) values of the test groups were: SE-E, 38.9 (± 4.8); SE-D, 44.5 (± 7.7); EX-E, 45.8 (± 4.7); EX-D, 42.9 (± 7.1). These values were not statistically significantly different. The null hypothesis was accepted that there is no difference between the self-etching primer and the one-bottle adhesive tested here. In addition, the bonding conditions provided by either bonding material on enamel were not significantly more favorable than on dentin. The majority of the specimens failed adhesively under load.

Evaluation of a new surface treatment method to obtain a good bond strength between a luting composite and (1) a light-cured, (2) a heat-cured and (3) a thermoplastic resin. Specimens were prepared and tests conducted according to ISO 10477, Amend. 1. The surfaces of Targis (light cured), SR Isosit (heat cured), and Dental D (thermoplastic) were ground under water cooling with 400-grit grinding paper, polished with 800-grit paper and air dried. Each resin material was divided into 3 groups of 10 specimens each. Group 1 was flame treated with a PyrosilPen for 5 s/2 cm2, group 2 for 10 s/2 cm2, and group 3 for 20 s/2 cm2. Subsequently, a methacryl silane was applied, followed by a luting composite. Prior to measuring shear bond strength, the specimens were thermocycled 5000 times in a water bath between 5°C and 55°C. SEM, FTIR investigations, and fracture analysis were also done. Etched and silanized Empress II - the gold standard - was used as a control. The following shear bond strengths were found: treatment time 5 s/2 cm2, Targis 25 (12) MPa, SR Isosit 17 (11) MPa; treatment time 10 s/2 cm2, Targis 23 (12) MPa, SR Isosit 26 (8) MPa; treatment time 20 s/2 cm2, Targis 29 (5) MPa, SR Isosit 26 (9) MPa. All Dental D specimens failed completely so that shear bond strength could not be measured. The control achieved 27 (6) MPa. No significant differences were found between the materials or the flaming times. On all flamed surfaces, Si was detected by FTIR. SEM showed that no heat destruction occurred at a flaming time of 5 s/2 cm2, a slight change at 10 s/2 cm2, and a significant change at 20 s/2 cm2. This new bonding technology is an effective method for surface-treating polymerized composite resin materials to obtain good bonding to luting composites. The method fails on thermoplastic resins.

The aim of this study was to evaluate the influence of four different types of temporary cements, Tempbond (Kerr), Tempbond NE (Kerr), Improv (Sterioss), and Dycal (Dentsply/Caulk), on the marginal adaptation and tensile strength of prosthetic specimens cemented on replicas of CeraOne abutments. Four test groups were formed: Group 1 (G-1), Tempbond (Kerr); Group 2 (G-2), Tempbond NE (Kerr); Group 3 (G-3), Improv (Sterioss); Group 4 (G-4), Dycal (Dentsply/Caulk). For the specimens, gold cylinders (DCB 160, Nobel Biocare) adapted to stainless steel replicas of CeraOne abutments (Nobel Biocare) were utilized. The replicas on a stainless steel base were made in a special machine for implant components. The cement thicknesses for each luting agent were measured using a Measurement Comparative Microscope (Mitutoyo). The readings obtained before cementation were used as the controls (G-0). Following each group's cementation, the specimens were submitted to tensile strength tests with a Universal Testing Machine (Kratus). The results of the marginal adaptation test as reflected by cement thicknesses were: G-0 = 11.7 µm, G-1 = 35.7 µm (± 8.8), G-2 = 41.7 µm (± 9.0), G-3 = 32.6 µm (± 9.7) and G-4 = 38.2 µm (± 6.7). The tensile strength tests yielded the following values: G-1 = 58.5 N (± 14.8), G-2 = 51 N (± 8.2), G-3 = 61.8 N (± 17.1) and G-4 = 71.8 N (± 9.3). The four temporary cements tested all provided similar marginal adaptation. G-4 (Dycal) showed a higher tensile strength than G-2 (Tempbond NE).

This study evaluated the effect of nonvital tooth bleaching on shear bond strength (SBS) of the composite resin/bovine enamel interface at different periods of time after bleaching. Three hundred twenty teeth were randomly divided into four groups according to bleaching agent: SPH: sodium perborate and 30% hydrogen peroxide; SPW: sodium perborate and distilled water; CP: 37% carbamide peroxide; and PLA: distilled water (placebo). The bleaching agents in the pulp chambers were replaced every 7 days for 4 weeks. For SBS testing, each of these groups was randomly divided into four subgroups (n = 20) according to the postbleaching periods of time: 0 (baseline), 7, 14, and 21 days. At the respective time, enamel slabs were embedded in polyester resin and flattened. Composite resin cylinders (Z100/Single bond, 3M) were bonded to the enamel surface and subjected to the SBS test using a universal testing machine. The ANOVA and Tukey's test (α = 0.05) showed statistically significant differences (expressed by different letters) among the bleaching agents only at follows: PLA (a), CP (ab), SPW (ab), and SPH (b). The SPH group, showing the lowest mean value, differed significantly from the control group. At 7, 14, and 21 days, no significant differences were observed. Nonvital tooth bleaching affected the resin/enamel SBS values when sodium perborate mixed with 30% hydrogen peroxide was used.