The Journal of Adhesive Dentistry, 04/2007

Purpose: Using an optical sensor, to automatically evaluate the marginal seal of restorations placed with 21 adhesive systems of all four adhesive categories in cylindrical cavities of bovine dentin applying different outcome variables, and to evaluate their discriminatory power. Materials and Methods: Twenty-one adhesive systems were evaluated: three 3-step etch-and-rinse systems, three 2-step etch-and-rinse systems, five 2-step self-etching systems, and ten 1-step self-etching systems. All adhesives were applied in cylindrical cavities in bovine dentin together with Tetric Ceram (n=8). In the control group, no adhesive system was used. After 24 h of storage in water at 37°C, the surface was polished with 4000-grit SiC paper, and epoxy resin replicas were produced. An optical sensor (FRT MicroProf) created 100 profiles of the restoration margin, and an algorithm detected gaps and calculated their depths and widths. The following evaluation criteria were used: percentage of specimens without gaps, the percentage of gap-free profiles in relation to all profiles per specimen, mean gap width, mean gap depth, largest gap, modified marginal integrity index MI. The statistical analysis was carried out on log-transformed data for all variables with ANOVA and post-hoc Tukey's test for multiple comparisons. The correlation between the variables was tested with regression analysis, and the pooled data according to the four adhesive categories were compared by applying the Mann-Whitney nonparametric test (p 0.05). Results: For all the variables that characterized the marginal adaptation, there was a great variation from material to material. In general, the etch-and-rinse adhesive systems demonstrated the best marginal adaptation, followed by the 2-step self-etching and the 1-step self-etching adhesives; the latter showed the highest variability in test results between materials and within the same material. The only exception to this rule was Xeno IV, which showed a marginal adaptation that was comparable to that of the best 3-step etch-and-rinse systems. Except for the variables "largest gap" and "mean gap depth", all the other variables had a similar ability to discriminate between materials. Pooled data according to the four adhesive categories revealed statistically significant differences between the one-step self-etching systems and the other three systems as well as between two-step self-etching and three-step etch-and-rinse systems. Conclusions:With one exception, the one-step self-etching systems yielded the poorest marginal adaptation results and the highest variability between materials and within the same material. Except for the variable "largest gap", the percentage of continuous margin, mean gap width, mean gap depth, and the marginal integrity index MI were closely related to one another and showed - with the exception of "mean gap depth" - similar discriminatory power. Keywords: automated marginal analysis, optical sensor, adhesive systems, gap width, gap depth, MI index

Purpose: To determine the effect of thorough air drying on the static and dynamic bonding effectiveness of a HEMAfree all-in-one adhesive bonded to Class-I cavity-bottom dentin. Materials and Methods: G-Bond (GC, Japan) was applied to standard occlusal Class I cavities following either a gentle (1 bar) or strong (4 bar) air-drying technique. After restoring the cavity using a composite resin (Gradia Anterior, GC), microspecimens were prepared that were loaded until failure or inserted in a microrotary fatigue testing device. Results: Strong air drying had no effect on the static (39.1 vs 38.4 MPa) or the dynamic (19.0 vs 18.6 MPa) strength of the interface complex. Conclusion: Strong air drying did not improve the static or the dynamic bonding effectiveness, although a very thorough (4 bar) and long air-drying procedure was employed. SEM analysis revealed that even when the adhesive was strongly air dried, droplets originating from phase separations could still be observed, albeit to a reduced extent. Ineffective drying and pooling of the adhesive in a narrow cavity diminished the effect of strong air drying of the all-in-one adhesive. Keywords: adhesion, dental adhesive, fatigue, enamel, dentin

Purpose: Air-polishing is routinely used for professional tooth cleaning. Therefore, the aim of this in vitro study was to evaluate the influence of different air-polishing powders on dentin bonding. Materials and Methods: Dentin bond strengths of a resin composite (Clearfil AP-X) bonded with different classes of adhesives (4-step etch-and-rinse: Syntac; 3-step etch-and-rinse: OptiBond FL; 2-step etch-and-rinse: Single Bond Plus; 2-step self-etching: AdheSE, Clearfil SE Bond, Clearfil Protect Bond, One Coat Self-Etch Bond; all-in-one/mix: Xeno III; all-in-one/no mix: Clearfil S3 Bond, G-Bond) were measured on flattened dentin surfaces. In test groups, specimens were air polished with Prophypearls (calcium carbonate) or ClinPro Prophypowder (glycine) prior to bonding. Microtensile bond strengths were evaluated after 24 h of storage at 37°C in water. Surfaces and resin-dentin interfaces were observed by SEM, TEM, and CLSM. Results: Mean bond strengths varied from 18 to 73 MPa in control groups. Calcium carbonate air polishing generally caused significantly reduced dentin bond strengths (p 0.05). TEM exhibited severe nanoleakage after calcium carbonate air polishing. Glycine did not affect dentin bonding performance of the adhesives under investigation. Conclusion: Calcium carbonate air polishing should be avoided when dentin-bonded restorations are applied. Glycine powder is an alternative. Keywords: air polishing, dentin bonding, resin composites, calcium carbonate, glycine

Purpose: To evaluate the effect of different silane agents and air-drying temperatures on the repair strength of a microfilled hybrid composite. Materials and Methods: Composite cylinders (8 x 4 mm) of Gradia Direct Anterior (GC, N = 36), stored in a saline solution at 37°C for 1 month, were sandblasted (50-µm aluminium oxide), cleaned (35% phosphoric acid) and randomly divided into six groups (n = 6). Two prehydrolyzed silane primers (Monobond-S, Ivoclar-Vivadent, Porcelain Primer, Bisco), a non prehydrolyzed silane primer (Porcelain Liner M, Sun Medical) and three silane/adhesive coupling agents (Porcelain Bond Activator-PBA/Clearfil New Bond, PBA/Clearfil SE Bond, PBA/Clearfil Tri-S Bond, Kuraray) were investigated. Silane-coated surfaces were air dried at two different temperatures (23°C and 38°C) and repairs (8 x 8mm) were fabricated (Gradia Direct Anterior). Unrepaired composite cylinders (8 x 8 mm, n = 6) were used as control to evaluate the cohesive strength of the material. Microtensile bond strength measurements (µTBS) were performed. Results: The silane agent applied (p 0.001), the airdrying temperature (p 0.001) and their interaction (p 0.001) were significant factors (two-way ANOVA, Tukey test; p 0.05). Silane primers achieved inferior µTBS when air dried at 23°C as compared to silane/adhesive blends. Warm air-drying was significantly beneficial to composite repairs mediated by silane primers. Comparable results were achieved by silane/adhesive couplings at 23°C and 38°C. At 38°C all the intermediate agents resulted in repair µTBS that were comparable to the 24-h cohesive strength of the composite (one-way ANOVA, Dunnett t-tests; p 0.05). Conclusion: The chemical interactions between silane primers and compozite substrate may be optimized through warm airdrying. Silane/adhesive couplings were not influenced by the air drying temperature. Keywords: silane, adhesive resin, warm air drying, composite repair, microtensile bond strength

Purpose: This study evaluated the effect of different physicochemical aging methods and surface conditioning techniques on the repair bond strength of composite. It was hypothesized that the aging conditions would decrease the repair bond strength and surface conditioning methods would perform similarly for the repair of resin composites. Materials and Methods: Disk-shaped resin composite specimens (Clearfil Photo Bright, Kuraray) were randomly assigned to one of the three aging conditions (N = 120, n = 12/per group): (1) immersion in deionized water (37°C, 1 week), (2) immersion in citric acid (pH: 3.0, 1 week), (3) boiling in water (8 h), (4) thermocycling (5000 times, 5°C to 55°C), (5) immersion in water (37°C, 2 months). After aging procedures, the specimens were subjected to one of the following surface conditioning methods: (1) chairside silica coating (30-µm SiOx) (CoJet, 3M ESPE) + silane (ESPE-Sil) (SC method), (2) silane (Clearfil SE Bond Primer and Clearfil Porcelain Bond Activator) + bonding agent (Clearfil SE Bond) (SB method). The fresh and aged composite surfaces were also examined using SEM (n = 6, 1/group). Resin composite (Quadrant Anterior Shine) was bonded to the conditioned substrates using polyethylene molds and then light polymerized. Shear force was applied to the adhesive interface in a universal testing machine (1 mm/min). The failure types were categorized as: A) cohesive in the substrate, B) adhesive at the interface, or C) cohesive in the adherend. Bond strength values were statistically analyzed using two-way ANOVA and Tukey's test (α = 0.05). Results: A significant influence of the conditioning method (p 0.0001) and aging method was observed (p 0.01) (two-way ANOVA, Tukey-Kramer). The SC method showed significantly higher bond values (7.8 ± 1.2 to 11.6 ± 5 MPa) than those of SB method (4.6 ± 2.3 to 7.6 ± 3.9 MPa) in all groups (p 0.0001). While the SC method showed 96% cohesive (A type), the SB method demonstrated 92% adhesive failures (B type). SEM images showed distinct pattern of microcracks in the boiled specimens and filler dissolution with disorganized matrix resin in the other aged specimens. Aging the composite substrates through water storage for 2 months produced significantly lower bond strengths than those of water or acid storage for 1 week (p = 0.011). Conclusion: Chairside silica coating and silanization provided the highest bond strength values with almost exclusively cohesive failures on aged composites. Aging methods showed significant differences on the composite-composite repair strength. Keywords: physicochemical aging, repair, resin composite, silica coating, surface conditioning

Purpose: The aim of the present study was to evaluate the crystalline phase and microstructure of 4 commercial machinable ceramic blocks - Cerec Vitablocs Mark II (Vita), ProCAD (Ivoclar/Vivadent), GN-I (GC), and GNCeram (GC) - and compare flexural strength and shear bond strength between a dual-curing resin luting agent and the ceramics treated with a silane coupling agent. Materials and Methods: Specimens were examined using scanning electron microscopy/energy-dispersive x-ray spectroscopy, and x-ray diffractometry. Three-point bending tests were performed with polished specimens 20 mm long, 4 mm wide, and 1.2 mm thick. Two differently shaped specimens for each of the 4 machinable ceramics were treated with a silane coupling agent. The specimens were then cemented together with a dual-curing resin luting agent. Half of the specimens were stored in water at 37°C for 24 h and the other half were thermocycled 20,000 times. Results: Chemical composition, crystalline phase, and crystallinity were significantly different between brands. The Vitablocs Mark II material had the significantly lowest flexural strength (101.7 ± 15.3 MPa), while the GNCeram material had the highest (174.8 ± 10.3 MPa). The use of a silane coupling agent yielded high shear bond strength after 20,000 thermocycles (Vitablocs Mark II: 37.7 ± 3.7 MPa, ProCAD: 41.2 ± 3.1 MPa, GNCeram: 50.2 ± 2.1 MPa), except with the GN-I material (23.9 ± 4.4 MPa). Conclusion: It appeared that crystal distribution and particle size of leucite crystal, not crystallinity, in the feldspar glass matrix of silica-based machinable ceramics might influence the flexural strength and efficacy of a silane coupling agent in bonding between a dual-curing resin luting agent and machinable ceramics. Keywords: machinable ceramic, flexural strength, bond strength, dual-curing resin luting agent, surface characteristics