Influence of self-etching primer preapplication on the dentin-titanium shear bond strength mediated by a resin-modified glass-lonomer cement.

PURPOSE: The aims of this study were to evaluate the in vitro shear bond strength of the dentin-titanium interface mediated by Fuji Plus, a resin-modified glass-ionomer cement, applied in combination with several self-etching bonding systems, and to compare the values obtained with those of SuperBond, chosen as a reference luting agent. MATERIALS AND METHODS: The self-etching bonding systems used in combination with Fuji Plus were AdheSE, Xeno III, Clearfil SEBond, Unifil Bond, and an experimental self-etching bonding system comprising the sequential application of Xeno III and the bonding component of SE Bond. Two control groups were also tested: a negative control with Fuji Plus along with its conditioner (10% ferric chloride, 2% citric acid solution); and a positive control with the resin cement SuperBond. One hundred five human molars were used to prepare seven groups of fifteen samples each. The samples were tested in shear after 7-day storage at 100% relative humidity and 37 degrees C. RESULTS AND CONCLUSION: Three of the tested combinations of self-etching bonding systems with Fuji Plus significantly improved in comparison with the negative control group, from 9% to 44%. The self-etching bonding systems obtained using Fuji Plus in combination with Clearfil SEBond, Unifil Bond, and the experimental system were not different from those obtained with SuperBond.

Self-etching adhesives improve the shear bond strength of a resin-modified glass-ionomer cement to dentin.

PURPOSE: Despite the improvements of resin-modified glass-ionomer cements, the dentin bond strength of these materials remains inferior to that provided by "bonding system/composite" combinations and limits the clinical use of RMGIC. The objective of this in vitro study was to investigate the effect of new self-etching bonding systems on the adhesion to dentin of Fuji II LC. MATERIALS AND METHODS: Seven recent self-etching systems were studied (Clearfil SE Bond = CSE, Optibond Solo Plus Self-Etching Primer = OSP, One Up Bond F = OUP, Mac Bond II = MB2, Xeno III = XB3, ADPER Prompt-L-Pop = ADP, Unifil Bond = UB) and compared with Cavity Conditioner (C). After the bonding procedure, a resin-modified glass-ionomer cylinder (Fuji II LC) was bonded to the surface using a Teflon mold (diameter: 3 mm; height: 5 mm). The different specimens were tested in a shear bond mode (0.5 mm/min). Statistical analyses were performed with one-way ANOVA and Fischer PLSD test (p < 0.05). RESULTS: The one-way ANOVA revealed a significant influence of the surface treatment parameter (p < 0.0001). The lowest shear bond strength values were obtained with Cavity Conditioner. The highest values were obtained with MB2. The multiple comparisons revealed that ADP = OBP = XB3 = OUB = UB = CSE and that UB = CSE = MB2. CONCLUSION: The application of the 7 self-etching adhesives tested in this study improves the dentin shear bond strengths of Fuji II LC. This increase depended on the adhesive system and ranged from 50% for ADP up to 130% for MB2.

Effect of a LED versus halogen light cure polymerization on the curing characteristics of three composite resins.

PURPOSE: To evaluate the effect, in vitro, of a LED (GC E Light) versus an halogen (Astralis 7) polymerization on the mechanical properties of three commercially available microhybrid composite resins. METHODS: Three commercially available composite resins (Tetric Ceram, Charisma, and Z100), and six modes of polymerization were evaluated (one mode for Astralis (AST): HIP 40 seconds and five modes for the GC E Light (GCE): standard 40 seconds, fast cure 6 seconds, fast cure 12 seconds, soft cure A 39 seconds, and turbo 10 seconds) in terms of top surface and bottom surface (2 mm-depth) microhardness, and flexural strength. Five specimens of each composite resin were made for the two mechanical properties tested. Five hardness values were recorded on each side for each sample with a Vickers diamond indenter. A three point bending test was performed at a crosshead speed of 1 mm/minute. Statistical comparisons were made using a two-way ANOVA (composite resin, polymerization mode) and a Fisher's test (P < 0.05). RESULTS: Z100 presented highest properties for both tests. Top surface microhardness: for Tetric Ceram and Charisma, the longer the exposure time, the higher the results, with no difference between AST mode and the longer GCE modes. For Z100, the highest values were obtained with AST. Whichever the material, short times (fast cure 6 seconds and turbo) exhibited poor results. Bottom surface microhardness: the samples cured with AST presented higher results but quite similar mechanical properties were achieved with the fast cure 12 GCE mode of the LED LCU. Fast cure 6 seconds and turbo obtained the lowest results. Flexural strength: the results were comparable with those obtained in bottom microhardness.

Simulated oral environment and microleakage of Class II resin-based composite and sandwich restorations.

PURPOSE: To evaluate the influence of the simulation of intra-oral conditions on the interfacial microleakage of Class II composite restorations. MATERIALS AND METHODS: 40 Class II cavities were prepared on freshly extracted human third molars and filled with a direct resin composite technique (SBMP+ + Z100) or open sandwich technique (Fuji II LC + SBMP+ + Z100). Extreme intra-oral conditions were simulated (35 degrees C/95% of relative humidity) and compared with ambient conditions (20 degrees C/40% RH). After thermocycling (2,000 cycles--5 and 55 degrees C), 2 hours immersion in silver nitrate aqueous solution and embedding into epoxy resin, samples were longitudinally sectioned. The extent of microleakage was expressed as a percentage of silver penetration of enamel and dentin interfaces. The influences of environmental conditions and restorative technique were evaluated by a two-way ANOVA and the comparison between the different groups with a Fisher PLSD test. RESULTS: In comparison with values obtained in ambient conditions, the simulation of extreme environmental conditions resulted in increased silver penetration percentages for direct resin composite restorations. On the contrary, the open sandwich technique, using resin-modified glass-ionomer cements, did not seem sensitive to excessive "temperature/relative humidity" parameters. Restorations made with resin-modified glass-ionomer cements used in the open sandwich technique appear to be more tolerant towards "temperature/relative humidity" parameters, which simulated intra-oral conditions, compared with modern adhesive systems.

Influence of new light curing units and bonding agents on the microleakage of Class V composite resin restorations.

PURPOSE: To evaluate the influence of four light curing units on the stress induced by polymerization of two dentin bonding systems and a composite resin. METHODS: Standardized kidney-shaped Class V cavities were prepared on the buccal and lingual surfaces at approximately 1 mm below the cemento-enamel junction (2 mm deep, 6-7 mm wide and 2 mm high). Two dentin bonding systems (DBS), Single Bond (SB), Optibond Solo Plus (OS+), and four light curing units (LCU): Astralis 7 (mode HIP 40 seconds), Elipar Highlight (soft start polymerization 40 seconds), GC e Light (8 mm tip) (fast cure of 12 seconds), and Optilux 501 (turbo tip) (fast cure of 10 seconds) were tested. The preparations were restored using the same microfilled composite (Filtek A110, shade A3). The teeth were thermocycled, immersed in a dye solution and sectioned. The enamel failures and the occlusal and cervical dentin microleakages were measured. RESULTS: No enamel and occlusal dentin microleakage was found. Concerning cervical dentin microleakage, with Single Bond, no significant difference was noted for all the light curing units (P< 0.05). With OptiBond Solo Plus, the filled adhesive, only two, the LCU Elipar and GC e Light, presented no statistical difference when all of the others exhibited statistical differences among themselves. The light intensity, the exposure duration, and the light source of the LCU are important parameters. When comparing the influence of the dentin adhesive, OS+ presented results significantly greater than SB, depending upon which lights were used. The Optilux 501 showed no significant difference. To act as a shock absorber, the adhesive needs to have time to compensate for the polymerization shrinkage.

Influence of a simulated oral environment on microleakage of two adhesive systems in Class II composite restorations.

OBJECTIVES: The aim of this in vitro study was to evaluate the influence of a simulation of intra-oral conditions on the microleakage of two adhesive systems (Scotchbond MultiPurpose Plus=SBMP+ and Clearfil SE Bond=SE Bond). For SBMP+, the influence of bonding procedure (comparison between manufacturer's protocol and an experimental procedure) was also studied. METHODS: Sixty Class II cavities with cervical margins 1mm below the cemento-enamel junction were prepared in the mesial/distal surfaces of recently extracted human molars. For the 3 groups (n=10), the adhesive system was applied under ambient conditions (20 degrees C/40% of relative humidity (RH)) for the mesial cavity and under extreme conditions (35 degrees C/95% RH) for the distal cavity. SBMP+ and SE Bond were applied strictly according to manufacturer's instructions. SBMP+ was also used according to an experimental procedure (intensive evaporation of the primer solvent). Cavities were restored with Z 100. After polishing, the specimens were thermocycled (2000 cycles, 5-55 degrees C). Teeth were coated with nail varnish, immersed in silver nitrate and sectioned longitudinally. The extent of microleakage was measured in percentage of dye penetration. Statistical analysis was performed using a 2 way ANOVA and a Fischer's PLSD test. RESULTS: Microleakage was dependent on the environmental conditions. In '35 degrees C/95% RH' conditions, dye penetration significantly increased for the 3 groups. For SE Bond, the microleakage percentages were the lowest, both in ambient and extreme conditions. For SBMP+, the experimental procedure allowed a decrease in microleakage, but only in ambient conditions. CONCLUSIONS: The simulation of intra-oral conditions caused a large increase in microleakage in the 3 groups tested. The self-etching primer presented the best behavior towards the 'temperature/RH' parameters simulated in this study.