The Journal of Adhesive Dentistry, 04/2015

Purpose: To evaluate the influence of different processing techniques, ceramic thicknesses, and cooling rate protocols on the μTBS of a veneering ceramic to zirconia (Y-TZP). Materials and Methods: Eighty Y-TZP ceramic blocks (VITA In-Ceram 2000) with dimensions of 10 x 7 x 5 mm were obtained. The blocks were sintered in a special furnace at 1500° for 2 h, wet ground, and divided into 8 groups according to the factors "processing technique" (P: pressed/veneering ceramic PM9; or V: layered/ veneering ceramic VM9), "thickness" (2 mm and 4 mm), and "cooling protocol" (S: slow [10°C/s]; F: fast [50°C/s]). The Y-TZP/veneering ceramic blocks were sectioned to produce non-trimmed bar specimens (bonded area: 1 ± 0.1 mm2), which were submitted to 1200 thermal cycles (5°C and 55°C, 30-s dwell time) and stored for 1 week in distilled water (37°C) before microtensile testing in a universal test machine (EMIC, 1 mm/min). The data in MPa were analyzed statistically using three-way ANOVA and Tukey's test. Results: ANOVA revealed that only the factor processing technique was significant (p = 0.015), unlike the factors thickness (p = 0.111) and cooling protocol (p = 0.202). The majority of the failures were classified as adhesive. Conclusion: Layered application of a thin veneering ceramic using a fast cooling rate resulted in improved bonding between veneering ceramic and zirconia. Keywords: zirconia, all-ceramics, microtensile, bond strength, pressed ceramics

Purpose: To evaluate the effect of different concentrations of hydrofluoric acid (HF) on the contact angle and the resin bond strength durability to feldspathic ceramic. Materials and Methods: To evaluate the contact angles of distilled water on etched feldspathic ceramic, 25 specimens (12 × 10 × 2.4 mm) of VitaBlocks Mark II were used, divided into 5 groups (n = 5): one unconditioned control (UC) group with no ceramic surface treatment, and 4 other groups that were etched for 60 s with different concentrations of HF: 1% (HF1), 3% (HF3), 5% (HF5) and 10% (HF10). The bond testing utilized 40 ceramic blocks (12 × 10 × 4 mm) that were fabricated and subjected to the same surface treatments as previously mentioned (excluding the control). The etched surfaces were silanized and resin cement was applied. After 24 h, the blocks were sectioned to produce bar specimens that were divided into two groups, non-aged (immediate testing) and aged (storage for 230 days + 12,000 thermocycles at 5°C and 55°C), and subjected to microtensile testing (μTBS). Micromorphogical analysis of the treated surfaces was also performed (atomic force and scanning electron microscopy). One-way ANOVA and Tukey's tests were applied for data analysis. Results: UC had the highest contact angle (61.4°), whereas HF10 showed the lowest contact angle (17.5°). In non-aged conditions, different acids promoted statistically similar bond strengths (14.2 to 15.7 MPa) (p > 0.05); in terms of bond durability, only the bond strength of the HF1 group presented a statistically significant decrease comparing before and after aging (14.5 to 10.2 MPa). Conclusion: When etched with 3%, 5%, or 10% hydrofluoric acid, the ceramic tested showed stable resin adhesion after long-term aging. Keywords: acid etching, porcelain, microtensile bond strength, topographical changes, wettability, contact angle

Purpose: This study evaluated the effect of aging solutions on the durability of resin-dentin bonds by means of microtensile bond strength (μTBS) and nanoleakage (NL) tests. Materials and Methods: The adhesive system Adper Single Bond 2 (3M ESPE) was applied according to the manufacturer's instructions to the flattened occlusal surface of 40 extracted human molars. After bonding, teeth were sectioned to obtain bonded sticks (0.8 mm2 area) which were tested in tension immediately or after different storage periods (1 week, 1 month, or 6 months). Bonded sticks were kept immersed in 5 different solutions: 1) distilled water (DW); 2) 99.9% propionic acid (PA); 3) 99% acetic acid (AA); 4) 75% ethanol (ET), and 5) mineral oil (MO). To determine NL, bonded sticks from each experimental condition were immersed in silver nitrate and analyzed by SEM. Data were analyzed by two-way repeated measure ANOVA and Tukey's test (α = 0.05). Results: Faster degradation of bond strength (1 week) could be seen for AA and ET (p 0.05) in comparison with DW. Specimens stored in PA and DW showed bond strengths significantly reduced after one and six months, respectively (p 0.05). No degradation of the resin-dentin bond strengths was observed for specimens stored in MO (p > 0.05). Nanoleakage increased for all groups except MO after storage. Conclusion: Propionic acid, acetic acid, and ethanol can be used as alternative aging solutions to more quickly obtain results on the bond resistance to degradation. Keywords: adhesive system, microtensile bond strength, degradation, silver nitrate uptake, dentin, oral simulating fluids

Purpose: To investigate the effects of placement technique and adhesive material on adaptation of composites before and after light curing. Materials and Methods: Cylindrical cavities (3 mm diameter, 1.7 mm depth) in extracted human molars were restored in 6 groups (n = 5) using 2 adhesives - two-step self-etching Clearfil SE Bond 2 (SE2) and all-in-one Clearfil Tri-S Bond Plus (TSP) (Kuraray Noritake Dental) - and 2 composites - Estelite Sigma Quick (ESQ) and Estelite Flow Quick (FLQ) (Tokuyama Dental) - placed with three different techniques: ESQ bulk placed, FLQ lining followed by ESQ and FLQ bulk placed. Specimens were scanned twice using swept-source optical coherence tomography (SS-OCT) before and after photopolymerization of the composite. Gap formation during polymerization or the difference in floor interface (DFI%) and final unsealed interface (USI%) were measured by image coregistration and subtraction on 6 diametrical planes across each scan. Results: Two-way ANOVA suggested that both factors (adhesive and filling technique) and their interaction were significant (p 0.001). SE2 showed significantly lower DFI% than did TSP when the composites were placed in bulk, but no difference was found when flowable lining was applied (p 0.05). Within TSP, all filling techniques were significantly different and the lining group showed the lowest values, followed by ESQ-bulk. Overall, SE2 always showed lower UFI% than did TSP, while there was no difference among different techniques within SE2. Conclusion: SS-OCT is a unique method to observe the pre-existing interfacial defects and gaps developed during polymerization, which were found to depend on both placement technique and applied adhesive. Keywords: swept-source optical coherence tomography, gap formation, image subtraction, two-step self-etching adhesive, all-in-one adhesive, lining

Purpose: This study evaluated (1) the dentin bond strength of fluoridated restorative systems following aging and (2) the enamel/dentin microhardness around restorations after a pH-cycling regimen. Materials and Methods: Sixty-four human third molars and four restorative systems were used. A resin-modified glass ionomer (GC Fuji II LC) was used as a fluoride-containing material in the positive control group, while Adper Easy Bond adhesive and Filtek Z350 XT composite resin, which are not fluoridated, were used together in the negative control group. Beautifil II composite resin and FL-Bond II adhesive, both fluoride-containing materials, were compared to Bond Force and Estelite Sigma Quick restorative system, which only contain fluoride in the adhesive. For dentin bond strengths, specimens of each material were fabricated for two test groups (n = 8): group 1: tested after 24 h; group 2: tested after 1 year of storage in artificial saliva. Both groups were tested using a microtensile method. For the cross-sectional microhardness test, standardized Class V cavities were prepared and filled with the different restorative systems. After experiencing repeated thermocycling and being subjected to pH-cycling, the teeth were sectioned. The microhardness was measured in enamel and dentin at 50 μm from the cavity wall and at six depths in relation to the surface subjected to pH cycling. Results: None of the restorative systems showed decreased bond strength after storage for one year in artificial saliva. No significant differences in microhardness were observed among the restorative materials on enamel and dentin. Conclusion: All the restorative systems evaluated presented stable bond strength after one year of storage. The pH cycling caused a reduction in the superficial enamel microhardness close to the cavity wall. In dentin, the demineralization affected the superficial and sub-surface areas. Keywords: adhesive system, fluoride, bond strength, microhardness, enamel, dentin

Purpose: This study examined the effects of matrix metalloproteinase-inhibiting solutions and aging methods on the bond strength between resin composite and human dentin. Materials and Methods: Crown segments of 105 human non-carious molars were bonded using simulated pulpal pressure at 20 cm water pressure. The teeth were randomly split into 5 groups according to the solution applied: CG (control, no solution), CHX (0.2% chlorhexidine), EPE (10% ethanolic propolis extract), APE (aqueous propolis extract), and E (70% ethanol). Each solution was left on the acid-etched dentin for 1 min. Adper Single Bond 2 and resin composite (Filtek Z350 XT) were applied to all specimens. The 5 groups were subdivided according to the aging method: SI (sectioned immediately); S (storage in artificial saliva for 6 months); and T (thermomechanical aging with 240,000 mechanical cycles and 1000 thermal cycles). Specimens were sectioned into sticks and subjected to microtensile testing. Bond strength data were analyzed by two-factor ANOVA followed by a post-hoc Tukey's test (α = 0.05). Results: For the factor "solution", there was no significant difference among the groups (p = 0.32). For the factor "aging method", significant differences were found (p 0.001), with the following mean bond strengths (MPa): SI: 31.1; S: 24.4; T: 26.8. Conclusions: The use of matrix metalloproteinase-inhibiting solutions on dentin as an adjunct to the application of an etch-and-rinse adhesive does not prevent the loss of bond strength after aging. Nevertheless, these solutions have no adverse effect on adhesion to tooth structure. Keywords: aging, matrix metalloproteinase, resin composite, tensile strength

Purpose: This laboratory study evaluated the short-term adhesive properties of one 10-MDP-containing and two MDP-free resin composite cements, using two types of zirconia surface pretreatments. Materials and Methods: Eighteen sintered zirconia disks (Procera, Nobel Biocare) were randomly divided into three study groups according to their surface treatment: (a) polished surface (control group); (b) airborne-particle abraded (grit blasted) with 50-μm aluminum trioxide (APA); and (c) selective infiltration etching (SIE). The zirconia disks were then bonded to 180 pre-aged composite resin disks (0.9 mm × 0.7 mm) using three different resin composite cements (Panavia F2.0, Esthetic, and Aegis). Resin-zirconia adhesion strength was evaluated using the microshear bond strength test (μSBS) after 24 h (baseline) and 2 weeks of storage in deionized water at 37°C. Three-way ANOVA, one-way ANOVA, and Scheffé's post-hoc tests were used to analyze the data (p = 0.05). Results: Surface treatments significantly influenced the μSBS (p 0.001). The highest mean μSBS values were recorded with the MDP-containing resin composite cement (Panavia F2.0) in both SIE (32.4 ± 5.3 MPa) and APA (28.6 ± 8.8 MPa) groups. Water storage significantly reduced the bond strength obtained with the MDP-free cements (Esthetic and Aegis) and in the control group, while the bond strength in SIE and APA groups using the 10- MDP-containing resin composite cement exhibited relatively unchanged values. Conclusion: SIE and APA in combination with the 10-MDP-containing resin composite cement established a strong, durable bond to zirconia substrates under short-term aging conditions. The cement containing amorphous calcium phosphate (Aegis) did not bond to zirconia surfaces. During the observation period, μSBS decreased significantly due to hydrolytic degradation, except when the 10-MDP-containing resin composite cement (Panavia F2.0) was used in the SIE and APA groups. Keywords: adhesive strength, microshear bond strength, resin composite cement, surface treatment, zirconia, MDP monomer

Purpose: The aim of this randomized, controlled, single-center, split-mouth clinical trial was to evaluate the clinical performance of a self-adhesive flowable composite resin (SAFC) in noncarious cervical lesions in comparison with a nanohybrid composite applied with a three-step etch-and-rinse adhesive system (E&Ra/nanoC). Materials and Methods: Eighty noncarious cervical lesions were included and assigned to one of two groups according to the split-mouth design. The cervical lesions in the experimental group were restored with an SAFC (Fusio Liquid Dentin), while a nanohybrid composite (G-aenial) applied with a three-step etch-and-rinse adhesive system (Optibond FL) was used for the control group. Clinical evaluation was performed after 1 week and again at 6 months according to FDI criteria. Data were analyzed using Wilcoxon Signed Rank and Mann-Whitney U-tests (α = 0.05). Results: After 6 months, 27 of the 40 SAFC restorations were in clinically unacceptable condition due to retention failure; this corresponded to a success rate of 33% compared to the success rate of 100% for the E&Ra/ nanoC restorations (p 0.05). For other criteria examined, the difference between the two groups was only statistically significant for color and translucency (p 0.05). Conclusion: The clinical performance of the SAFC was found to be unacceptable after 6 months of clinical use. Keywords: self-adhesive flowable composite, noncarious cervical lesions, nanohybrid composite