The Journal of Adhesive Dentistry, 02/2003

As adhesives containing hydrophilic/acidic resin components are vulnerable to water movement after polymerization, this study tested the hypothesis that coupling of a single-bottle adhesive (OptiBond Solo Plus) to self/dual-cured composites is compromised by adhesive permeability, even with the adjunctive use of chemical co-initiators. Two versions of chemical co-initiators (activators) were investigated: the proprietary resin-containing OptiBond Solo Plus Activator (A), and a resin-free solution of 2% benzene sulphinic acid sodium salt in ethanol (B). For microtensile bond testing, hydrated (H) or dehydrated (D) bonded human dentin were coupled to a dual-cured composite (Bis-Core) under light- (L) or self-activation (C) mode. A delayed light-activation mode (DL) was also employed to simulate the slower rate of polymerization of self-cured composites but without the influence from adverse chemical interaction. Nine groups were tested: 1) L-H (control); 2) DL-H; 3) DL-D; 4) C-H; 5) C-D; 6) CA-H; 7) CA-D; 8) CB-H; and 9) CB-D. For transmission electron microscopy, a light-cured and an experimental self-cured composite of the same composition were used for the nine groups. Only the bond strength results of the experimental groups DL-D (Group 3) and CB-D (Group 9) were not significantly different from the control group L-H (p > 0.05). TEM revealed the presence of discrete silver-filled water blisters along the adhesive-composite interface in groups 2, 6, and 8, and within the composite in group 4. Adverse chemical interaction in groups 4 and 5 resulted in the observation of a line of silver deposits along the adhesive composite interface. The coupling of composites after prolonged contact with hydrated dentin bonded with OptiBond Solo Plus is affected by the intrinsic permeability of the adhesive. The adjunctive use of the Activator is only slightly effective in improving the coupling of this adhesive with self/dual-cured composites. Although the use of resin-free benzene sulphinic acid sodium salt solution completely eliminates the adverse chemical interaction, the inherent permeability of the polymerized adhesive precludes optimal coupling of self/dual-cured composites to bonded hydrated dentin.

To evaluate enamel bond strengths of self-etching primer systems with and without the use of phosphoric acid etching. The enamel of sixteen bovine incisors was ground with wet 600-grit SiC paper, and specimens were divided into seven groups. Group SE and group ABF were bonded with Clearfil SE Bond (Kuraray) and an experimental self-etching primer system ABF (Kuraray) in accordance with the manufacturer's instructions. The enamel of groups SE+AC and ABF+AC was acid-etched (AC) prior to application of the primers. The enamel of groups AC+SE-P and AC+ABF-P was acid-etched and the bonding resin was applied without primer. All of these groups were restored with Clearfil AP-X (Kuraray). For the control group (SB), enamel was etched and bonded with Single Bond (3M) according to manufacturer's instructions and restored with Z-250 (3M). After 24 h of water storage, the teeth were sectioned into 0.7-mm-thick slabs, trimmed for microtensile bond testing and subjected to tensile forces at a crosshead speed of 1 mm/min. After testing, all samples were analyzed with SEM. Data were evaluated by one-way ANOVA and Fisher's PLSD (α = 0.05). Acid etching prior to application of the self-etching primer produced higher bond strengths to enamel than self-etching priming only. Omission of the primer step provided bond strengths similar to the other acid-etched groups. SEM analysis revealed that when the acid was applied prior to the self-etching primers, an increase in failure within enamel occurred. Since high bond strength to enamel is critical for good margins and seal of the restorations, applying the etching step should be considered in case of restorations that rely mainly on enamel bonding.

The effect of self-etching primer on the adhesion of tri-n-butylborane (TBB)-initiated resin to enamel has not been fully determined. We prepared a self-etching primer containing amino acid methacrylate, and evaluated the effectiveness of the self-etching primer for the adhesion of TBB-initiated 4-methacryloxyethyl trimellitate anhydride (4-META)/methyl methacrylate (MMA) resin to ground enamel. Methacryloyloxy tyrosine (MTY) was prepared by reacting methacryloyl chloride and L-tyrosine in trifluoroacetic acid. An original self-etching primer containing an aqueous mixture of MTY, 35 wt% 2-hydroxyethyl methacrylate (HEMA), and 3 wt% ferric chloride was designed. Three strengths of MTY (5%, 10%, and 20%) were tested. The bovine enamel surface was treated with the self-etching primer for 30 s. After drying, a stainless steel rod was bonded to the enamel using TBB-initiated 4-META/MMA resin. The tensile bond strength was measured after 1-day immersion in water at 37°C. The self-etching primer containing 20 wt% MTY (20MTY) yielded a significantly higher bond strength of 13.2 ± 2.8 MPa than the self-etching primer containing 5 wt% and 10 wt% MTY. This value was not significantly different from that with phosphoric acid etching. Field-emission scanning electron microscopy revealed that 20MTY treatment produced no distinct dissolution pattern on enamel. Tight bonding between the resin and enamel was clearly observed. Our original self-etching primer containing 20 wt% MTY, 35 wt% HEMA, and 3 wt% ferric chloride was effective for obtaining strong adhesion of 4-META/MMA-TBB resin to enamel compatible with phosphoric acid etching.

To evaluate the bond strength of a self-etching (Clearfil SE Bond) and a single-bottle (Excite) adhesive system using two cavity configurations (C-factors 5 and 1). Class I cavities (3 x 4 x 2.5 mm) were prepared in 28 extracted human molars using diamond burs under water cooling. Teeth were divided into 4 groups: G1: Excite, C-factor 5; G2: Excite, C-factor 1; G3: Clearfil, C-factor 5; G4: Clearfil, C-factor 1. To determine C-factor 5, systems were applied to all cavity walls according to the manufacturers' instructions (5 bonded, 1 unbonded). For C-factor 1, lateral walls were isolated using nail varnish, and adhesive systems were only applied to the pulpal floor (5 unbonded, 1 bonded). Cavities were restored using Tetric Ceram composite resin (Ivoclar/Vivadent), and bulk light cured for 40 s (500 mW/cm2). Teeth were stored in distilled water for 24 h at 37°C, and then sectioned using a diamond disk, yielding stick-shaped specimens with a bonded area of approximately 0.8 mm2. Specimens were submitted to the microtensile bond test at a rate of 1 mm/min speed in a universal testing machine. Resin-dentin bond strengths (MPa) were submitted to ANOVA and Tukey's tests (p 0.05) [number of specimens]: G1 = 35.8b [43]; G2 = 48.9a [55]; G3 = 45.9a [60]; G4 = 49.0a [53]. There was no statistically significant difference between adhesive systems for C-factor 1. For C-factor 5, Clearfil SE Bond produced higher values when compared to the other group. Changes in C-factor only affected the total-etch adhesive system tested. This may be a result of the different filler volume in the self-etching system, and not of the bonding technique itself.

To evaluate the effect of 2% chlorhexidine on the microtensile bond strength of composite resin to dentin treated with three dentin bonding systems. Flat dentinal surfaces were prepared in 24 extracted human third molars. Teeth were randomly divided into 8 distinct experimental groups according to the adhesive applied (Prime & Bond NT, Single Bond and Clearfil SE Bond), the application (yes/no) of chlorhexidine, and the time point at which it was applied (before or after acid etching the dentin). Composite resin blocks were built up over treated surfaces, and teeth were then stored in water at 37°C for 24 h. Samples were thermocycled, stored under the same conditions, and then vertically sectioned, thus obtaining specimens with 1.0 ± 0.1 mm2 cross-sectional area. Specimens were stressed in tension at 0.5 mm/min crosshead speed. Bond strength results were evaluated using a one-way ANOVA (p 0.05). The modes of failures were verified using optical microscopy. Dentin disks were obtained from 3 additional teeth treated in the same manner for observation under SEM. The most representative samples of fractured specimens were also observed under SEM. No statistically significant differences of bond strength values were found between any groups. Failures occurred mainly within the bond; exclusively adhesive fractures (adhesive-dentin) were not observed. The 2% chlorhexidine solution, applied before or after acid etching of the dentin, did not interfere with the microtensile bond strength of composite resin to the dentin treated with Prime & Bond NT, Single Bond, or Clearfil SE Bond bonding systems.

To evaluate the cavity sealing obtained after thermocycling with five adhesive systems in which one all-in-one adhesive was compared to three one-bottle adhesives, and to observe the effect of a low-charged resin layer added to a one-bottle adhesive. Twenty-five recently extracted teeth were randomly allocated to five experimental adhesive systems (n = 5 each): Optibond Solo (OS), Scotchbond 1 (SB1), PQ 1, Prompt-L-Pop (PLP), SB1+Revolution (R). On each tooth, two rectangular cavities at the cementoenamel junction were filled with a microhybrid composite (Z100) and the tested adhesives. Teeth were thermocycled and stained with AgNO3 + vitamin C. Leakage was evaluated on a 6-point (0-5) severity scale and the highest score was selected for each restoration. Results were treated by ordinal logistic regression and considered to be significant at p 0.05. No significant difference was found between leakage values for enamel and dentin interfaces. Leakage scores never exceeded 2 for OS, SB1 and SB1+R, while they reached a maximum of 5 in 20% of PLP cases. OS was significantly better than the other adhesive systems, which were statistically equivalent. The addition of a flowable composite layer on SB1 did not yield a significant difference, but tended to give better results mainly at the dentin interface. The all-in-one adhesive PLP, because of quite variable results, seems less reliable than the one-bottle adhesives, of which OS provides significantly the best results. Addition of a flowable composite on SB1 appears to yield slightly better results.

The purpose of this study was to evaluate the sealing ability of single-unit all-ceramic and gold-electroformed crowns luted with a resin cement under laboratory conditions. Thirty extracted maxillary premolars were selected. Standardized abutments were prepared for full-crown restorations with cervical margins located 1 mm below the cementoenamel junction. Samples were divided into two groups (n = 15) based on type of restorative system: Group 1: a heat-pressed all-ceramic system (IPS Empress 2, Ivoclar-Vivadent); Group 2: a gold-electroformed porcelain-fused-to-metal system (Gramm Technik). Crowns were luted with Excite DSC bonding system (Ivoclar-Vivadent) and Variolink II resin cement (Ivoclar-Vivadent) following manufacturer's instructions. After luting procedures and 700 thermal cycles (5°C and 55°C, 1 min dwell time), 20 specimens (n = 10 per group) were randomly selected and processed for microleakage evaluation at cervical sites. The remaining specimens (n = 5 per group) were prepared for SEM investigation on film thickness. Microleakage and film thickness data were statistically evaluated using the Mann-Whitney U-test (p 0.05). Fifty percent of group 1 and 60% of group 2 samples showed leakage. For group 1, dye penetration was mostly observed between metal and resin material, while group 2 specimens showed leakage mainly between ceramic margins and resin cement. Samples from group 1 showed a cement thickness of 82 µm, while 71 µm was found for group 2. Statistically significant differences were not found between samples from the two groups. Regarding microleakage and film thickness, both restorative systems evaluated in this study performed similarly.

To determine the effect of surface treatments on bond strength of two resin cements (ParaPost Cement and Panavia F) to posts of titanium alloy (ParaPost XH), glass fiber (ParaPost Fiber White), and zirconia (Cerapost), and to dentin. After embedding, planar surfaces of posts (n = 9 to 14) and human dentin (n = 10) were obtained by grinding. The posts received one of three surface treatments: 1. roughening (sandblasting, hydrofluoric acid etching), 2. application of primer (Alloy Primer, Metalprimer II, silane), or 3. roughening followed by application of primer (sandblasting or etching followed by primer, Cojet treatment). ParaPost Cement and Panavia F were bonded to the post and dentin specimens, and the bonded specimens were placed in water at 37°C for 7 days. The specimens were debonded in shear. Panavia F had significantly higher bond strength to ground ParaPost XH, Cerapost, and dentin than did ParaPost Cement. Most surface treatments resulted in an improved bond strength of resin cements to the posts. Compared to the ground control, Cojet treatment and sandblasting were the most effective treatments. Etching of Cerapost with hydrofluoric acid with and without silane treatment significantly decreased the bond strength of Panavia F to the post. The bond strength of resin cements to the posts was affected by the material of the post, the surface treatment of the post, and by the type of resin cement. The bond strength of resin cement to dentin was influenced by the type of resin cement.