Three-step Adhesive System Research Articles

Development of experimental HEMA-free three-step adhesive system

Objective To evaluate the influence of Bis-EMA 30 on the resin-to-dentin microtensile bond strength (μTBS) and structural reliability of the experimental three-step etch-and-rinse adhesive systems. Methods Five experimental primers containing different dimethacrylate monomer concentrations (0, 10, 20, 40, 60 wt% of the Bis-EMA 30, P0.P60) added to acid monomer and solvents (ethanol/water), and a resin bond (Bis-GMA/TEGDMA, 50/50 wt%) were formulated. The adhesive system Scotchbond™ MultiPurpose (SBMP, 3M ESPE) was tested as commercial reference. Sixty bovine incisors were randomly separated into six groups, and their superficial coronal dentin was exposed. After acid etching and rinsing, the excess water was removed from the surface with absorbent paper. Each experimental primer was actively applied (30 s), followed by a mild air stream (10 s). The experimental adhesive resin was applied and light activated for 20 s. Resin composite restorations were incrementally built up. The restored teeth were stored in distilled water at 37 °C for 24 h, and then sectioned to obtain sticks with a cross-sectional area of approximately 0.5 mm 2, after which 24 specimens per group were subjected to the μTBS test. Data (MPa) were analyzed by One-way ANOVA, Tukey test ( α = 0.05) and Weibull analysis. Results The P40 group showed μTBS means similar to those of the control (SBMP), whereas both had statistically higher values when compared with the other groups ( p < 0.001). Moreover, P40 showed higher structural reliability, represented by the high Weibull modulus and characteristic strength values. The lowest μTBS was observed in the P0, P10 and P20 groups, which also had low structural reliability. Significance Bis-EMA 30 is a promising monomer to be considered as a substitute for HEMA in adhesive system compositions.

Effect of adhesive system type and tooth region on the bond strength to dentin.

This study evaluated the bond strength of two etch-and-rinse adhesive systems (two- and three-step) and a self-etching system to coronal and root canal dentin. The root canals of 30 human incisors and canines were instrumented and prepared with burs. The posts used for luting were duplicated with dual resin cement (Duo-link) inside Aestheti Plus #2 molds. Thus, three groups were formed (n = 10) according to the adhesive system employed: All-Bond 2 (TE3) + resin cement post (rcp) + Duo-link (Dl); One-Step Plus (TE2) + rcp + Dl; Tyrian/One-Step Plus (SE) + rcp + Dl. Afterwards, 8 transverse sections (1.5 mm) were cut from 4 mm above the CEJ up to 4 mm short of the root canal apex, comprising coronal and root canal dentin. The sections were submitted to push-out testing in a universal testing machine EMIC (1 mm/min). Bond strength data were analyzed with two-way repeated measures ANOVA and Tukey's test (p < 0.05). The relationship between the adhesives was not the same in the different regions (p < 0.05). Comparison of the means achieved with the adhesives in each region (Tukey; p < 0.05) revealed that TE3 (mean +/- standard deviation: 5.22 +/- 1.70) was higher than TE2 (2.60 +/- 1.74) and SE (1.68 +/- 1.85). Under the experimental conditions, better bonding to dentin was achieved using the three-step etch-and-rinse system, especially in the coronal region. Therefore, the traditional etch-and-rinse three-step adhesive system seems to be the best choice for teeth needing adhesive endodontic restorations.

Microtensile bond strength of fiber-reinforced composite with semi-interpenetrating polymer matrix to dentin using various bonding systems

This study investigated the microtensile bond strength (microTBS) of fiber-reinforced composite (FRC) to dentin using various adhesive systems. Forty eight (n = 8/group) human molars were flattened to expose dentin. A layer of preimpregnated unidirectional FRC (everStick) was applied on the dentin surface after treatment with either a single-step self-etching adhesive, two-step self-etching system, or a conventional three-step adhesive system. For the control, particulate filler composite (PFC) (Filtek Z250) layering without FRC was used. After 24-hour water storage at 37 degrees C, the specimens were sectioned, further water-stored at 37 degrees C for 30 days and then tested. Data were analyzed using ANOVA and Tukey's test, and reliability was analyzed with Weibull distribution. microTBS values differed significantly according to the adhesive material used (p < 0.05). Single-step self-etching adhesive showed the lowest bond reliability and microTBS values with both FRC and PFC, whereas conventional three-step and two-step self-etching systems showed higher bond reliability and microTBS with both materials.

The application of hydrogen peroxide in composite repair

This study examined the influence of different surface conditioning methods on composite-to-composite microtensile bond strength. Thirty two-year old composite resin discs were randomly divided into three groups according to the different mechanical/chemical surface pretreatment tested: (1) 38% hydrogen peroxide (H(2)O(2))-treatment; (2) 50-microm aluminum oxide sandblasting; (3) no treatment. Depending on the intermediate agent applied, two subgroups were created: (A) three-step adhesive system; (B) prehydrolyzed silane coupling agent + three-step adhesive system. Microtensile bond strength measurements were performed and the data were statistically analyzed with Kruskall-Wallis Analysis of Variance and Dunn's multiple range test for post hoc comparisons (p < 0.05). Failure mode was evaluated with a scanning electron microscope. Changes in composite surface topography after H(2)O(2) treatment were also investigated. Composite repair strength did not benefit from H(2)O(2) treatment and adhesive application. Preliminary sandblasting significantly improved interfacial bond strength regardless of the intermediate agent applied. No changes in surface texture were produced after H(2)O(2) treatment. An atypical fracture pattern was detected at the interfacial level between H(2)O(2)-treated composite surfaces and the overlying adhesive and composite. H(2)O(2) treatment affected the composite-to-composite repair strength: a compromised resin polymerization may occur, resulting in a poor interfacial quality and a weak bond. Sandblasting still remains a reliable technique for composite repair.

Microleakage of class V resin composite restorations after conventional and Er:YAG laser preparation

This in vitro study compared the microleakage of Class V resin composite restorations at bevelled enamel/composite and dentin/composite interfaces following Er:YAG laser (pre-treatment modalities: laser-etching and/or acid-etching) or conventional preparation and acid-etch, in association with two resin composite formulations and their three-step adhesive system. Class V cavities with conventional bevel produced on the lingual and buccal surfaces of eighty extracted caries- and restoration-free human teeth, were assigned to eight groups: cavities were or Er:YAG-lased and acid-etched (groups 1 and 5); or Er:YAG-lased, laser-etched and acid-etched (groups 2 and 6); or Er:YAG-lased and only laser-etched (groups 3 and 7); or cut by dental drill at high-speed and acid-etched (groups 4 and 8). The specimens were restored with Optibond FL+Herculite XRV (groups 1, 2, 3 and 4) or with Scotchbond MP+Z 100 (groups 5, 6, 7 and 8), stored in distilled water at 37 degrees C for 24 h, thermocycled 1500 times between 5 and 55 degrees C, placed in a 2% aqueous solution of methylene blue for 24 h at 37 degrees C, embedded in resin and sectioned. Microleakage was assessed according to the depth of dye penetration along the restoration. There were statistically significant differences between occlusal and cervical regions for all groups (P<0.01) except for groups 3 and 7. Pair-wise comparison of groups showed that acid-etch is advocated when using resin composite in Er:YAG-lased Class V cavities; the seal at enamel margins in Er:YAG-lased and laser-etched cavities depended on the resin composite formulation and corresponding adhesive (P<0.05).

Adverse effects of human pulps after direct pulp capping with the different components from a total-etch, three-step adhesive system

The objective was to evaluate the response of human pulps capped with different components from a total-etch three-step adhesive system. Direct pulp capping was performed in 25 caries-free human premolars scheduled for extraction due to orthodontic treatment. The teeth were randomly divided in five groups, and capped with the following materials: Group 1-acid+primer+adhesive were used as recommended; Group 2-only primer was applied; Group 3-only bonding resin (light-cured for 10s); Group 4-only composite resin (light-cured for 40s); Group 5-calcium hydroxide. After capping, all teeth were restored with ScotchBond Multi Purpose Plus and Z-100 was placed incrementally. After 60 days, the teeth were extracted and processed for light microscopic examination (H/E) according to a histological score system. These were subjected to non-parametric tests (alpha<0.05). Overall, the histological features showed that groups 1-4 were quite similar and inferior to group 5. In groups 1-4 the pulp response varied from acute inflammatory cell infiltrate with varying degrees to necrosis. The groups 3 and 4 showed a trend towards better pulp response, since a normal connective tissue could be observed in more than half of the sample. All teeth from group 5 showed normal connective tissue below an amorphous dentin bridge. Adhesive components (primer or adhesive) as well as a composite should be avoided for pulp capping. Ca(OH)(2) should be the first choice for pulp capping.

Rewetting effect of water-based primer on the air-dried dentin

The purpose of this study was to evaluate the rewetting effect of water-based primer on the air-dried dentin. In this in vitro study, freshly extracted non-caries human molars and three-step adhesive system(SBMP) were used. Freshly extracted non-caries human molars and three-step adhesive system(SBMP) were used. Flat occlusal dentin surface were prepared using low-speed diamond saw. Prepared teeth were randomly divided into three groups. Group 1.(W); etched(35% phosphoric acid for 15s) and blot-dried, Group 2.(5D); 5s airdried, Group 3.(30D); 30s air-dried. To obtain color contrast in CLSM observation, primer was mixed with rhodamine B and bonding resin was mixed with fluorescein. Microscopic sample of each group were obtained after longitudinal section. Morphological investigation of resin-dentin interface and thickness of hybrid layer measurement using CLSM were done. Microtensile bond strength for each specimen was measured. Specimen were observed under microscope to examine the failure patterns of interface between resin and dentin. The results of this study were as follows: 1. The results(mean) of Thickness of hybrid layer were W;19.67, 5D;20.9, 30D;10㎛. Only 30D had statistically significant differences to W and 5D(P<0.05). 2. The results(mean) of Microtensile bond strength were W;16.02, 5D;14.69, 30D;11.14MPa. Only 30D had statistically significant differences to W and 5D(P<0.05). 3. There were positive correlation between Thickness of hybrid layer and microtensile bond strength(P<0.05).

Morphology and thickness of the diffusion of resin through demineralized or unconditioned dentinal matrix.

The formation of a hybrid layer is the main bonding mechanism of current dentin-bonding systems. This study evaluated the morphology and thickness of the resin-infiltrated dentinal layer after the application of adhesive systems. The dentin-bonding agents were evaluated on flat dentinal preparations confected on the occlusal surfaces of human teeth. The test specimens were prepared and inspected under scanning electron microscopy at a magnification of X 2,000. The adhesive systems were responsible for different hybrid layer thicknesses (p < 0.05), and the mean values were: for Scotchbond MP Plus (SM), 7.41 +/- 1.24 micrometer for Single Bond (SB), 5.55 +/- 0.82 micrometer for Etch & Prime 3.0 (EP), 3.86 +/- 1.17 micrometer and for Clearfil SE Bond (CB), 1.22 +/- 0.45 micrometer. The results suggest that the conventional three-step adhesive system (SM) was responsible for the thickest hybrid layer, followed by the one-bottle adhesive (SB). The self-etching adhesives, EP and CB, produced the formation of the thinnest hybrid layers.