The Journal of Adhesive Dentistry, 04/2017

Purpose: To evaluate in a randomized clinical evaluation the 3-year clinical durability of a one-step universal adhesive and compare it intraindividually with a 2-step self-etch adhesive in Class II restorations. Materials and Methods: Each of 57 participants (mean age 58.3 years) received at least two extended Class II restorations that were as similar as possible. The cavities in each of the 60 individual pairs of cavities were randomly distributed to the 1-step universal adhesive (All-Bond Universal: AU) and the control 2-step self-etch adhesive (Optibond XTR: OX). A low shrinkage composite (Aelite LS) was used for all restorations, which were evaluated using slightly modified USPHS criteria at baseline and 1, 2, and 3 years. Results: 114 Class II restorations were evaluated at three years. Eight restorations, 3 AU and 5 OX, failed during the follow-up, resulting in 94.7% (AU) and 91.2% (OX) success rates (p > 0.05). Annual failure rates were 1.8% and 2.9%, respectively.The main reason for failure was composite fracture. Conclusion: Class II composite restorations placed with a 1-step universal adhesive showed good short-term efficacy. Keywords: adhesive, clinical, posterior, composite, self etch, universal

Purpose: To evaluate the effect of sonic application of 5 different self-etch adhesives on the push-out bond strength of fiber posts in root canals. Materials and Methods: In a preliminary test, 24 teeth were treated with manual and sonically assisted bonding, then a composite cylinder was built up to test the shear bond strength as a proof of principle. In the main test, 120 root canals were endodontically prepared and divided into 10 groups: 5 self-etch adhesives (Futurabond DC, Futurabond M, Futurabond U, Optibond XTR, Universalbond), each applied under manual and sonic application modes. After insertion of the fiber posts using the specific adhesive and a dual-curing composite, the teeth were sectioned and the push-out test was performed. The specimens were analyzed by light and scanning electron microscopy. Statistical analysis was performed using the Shapiro-Wilk test, one-way ANOVA and the Tamhane test. Results: Sonic application of self-etch adhesive systems did not increase the bond strength of fiber posts in root canals. In general, the bond strength decreased from the coronal to the apical part of the root canal, irrespective of the applied method. The best post retention was achieved with Futurabond U and Optibond XTR. Conclusion: Sonic application of self-etch adhesives did not improve the fiber post retention in the root canal and can therefore not be recommended. Nevertheless, sonic application of etch-and-rinse adhesives can increase the bond strength to coronal dentin. Keywords: sonic application, fiber posts, self-etch adhesives, bond strength, failure mode, post retention, coronal dentin

Purpose: To study the influence of a polyalkenoate copolymer (VCP) on the immediate (24 h) and 6-month dentin bonding stability of VCP-based adhesives, using microtensile bond strength (μTBS), nanoleakage (NL), and ultramorphological analyses (FE-SEM). Materials and Methods: Eighty-four caries-free molars were randomly assigned to seven adhesives: Clearfil SE Bond (CSE, Kuraray Noritake); Adper Single Bond Plus (SB, 3M ESPE); SB without VCP (SBnoVCP, 3M ESPE); Scotchbond Universal Adhesive applied as a etch-and-rinse adhesive (SBU_ER); SBU without VCP applied as an etch-and-rinse adhesive (SBUnoVCP_ER); SBU applied as a self-etch adhesive (SBU_SE, 3M ESPE); SBU without VCP applied as a self-etch adhesive (SBUnoVCP_SE, 3M ESPE). Half of the beams were tested after 24 h, and the other half was aged in water for 6 months prior to testing. For each tooth/evaluation time, two beams were randomly selected for NL analysis. Statistical analyses of µTBS results were performed using two-way ANOVA, Tukey's post-hoc tests, and Student's t-test for paired data (α = 0.05). Nanoleakage was statistically analyzed using the Kruskal-Wallis and Mann-Whitney tests, with Wilcoxon's test for paired data. For FE-SEM, four caries-free molars were assigned to each of the seven groups. Dentin disks were restored and cross sectioned into halves. One half was observed at 24 h, and the other at 6 months. Results: The highest 6-month mean μTBS was obtained with SBU_SE/SBUnoVCP_SE and SBUnoVCP_ER. SBUnoVCP_SE resulted in greater silver deposition at 6 months. FE-SEM observations showed that CSE and SBU_SE specimens resulted in a submicron hybrid layer without signs of degradation at 6 months. Conclusions: VCP may contribute to the long-term bonding stability of VCP-based adhesives. Keywords: dental materials, dentin bonding, tensile strength, microscopy

Purpose: To evaluate the bonding performance of a universal adhesive to sound and artificially-created caries-affected dentin, using either the etch-and-rinse or self-etch strategy. Materials and Methods: Flat midcoronal dentin surfaces from 48 third molars were randomly assigned to eight groups according to the substrate (sound dentin and artificially-created caries-affected dentin [pH cycling for 14 days]) and the adhesive or application mode (Scotchbond Universal: self-etch or etch-and-rinse strategies; Adper Single Bond 2 and Clearfil SE Bond, a two-step etch-and-rinse adhesive and a two-step self-etch adhesive as controls, respectively). Then, composite blocks were constructed, the specimens were further stored in water for 24 h, and composite-dentin sticks were prepared (0.8 mm2) and tested under tension at 1.0 mm/min. Data were analyzed with two-way ANOVA and Tukey's test (α = 0.05). Results: All adhesives tested on artificially-created caries-affected dentin presented similar μTBS (p > 0.05), and inferior bonding performance when compared to sound dentin (p = 0.000). On sound dentin, Scotchbond Universal presented higher bond strengths when applied in the etch-and-rinse than self-etch mode, but comparable bond strength in each application mode in relation to the respective control adhesive (p = 0.04). Conclusion: Scotchbond Universal can be used in different application modes when bonded to artificially-created caries-affected dentin; however, the etch-and-rinse strategy improves its bonding ability to sound dentin. Moreover, Adper Single Bond 2 and Clearfil SE Bond presented similar bond strengths, regardless of the dentin condition and comparable performance in relation to each strategy of Scotchbond Universal. Keywords: dentin, pH cycling, caries-affected dentin, microtensile, universal adhesives

Purpose: To evaluate the efficacy of different surface treatments on the repair of veneered zirconia ceramics. Materials and Methods: Forty-eight zirconia disks were divided into three groups according to the method of surface treatment: polished surface, air abraded, or ground using a special silicon carbide bur (SiC Grinding Bur). All specimens were primed using a primer containing MDP (Cimara Zircon, Voco) and then bonded to composite in Plexiglas tubes using dual-curing adhesive resin (Bifix QM, Voco). Each of the three groups was further divided into two subgroups (n = 8) stored either in water at 37°C for 3 days without thermocycling or stored in water at 37°C for 150 days with an additional 37,500 thermocycles between 5°C and 55°C. After storage, tensile bond strength (TBS) was measured in a universal testing machine. Results: After 3 days of storage, silicon carbide bur and air-abraded groups showed high TBS that ranged from 32.7 to 41.0 MPa (p ≤ 0.05). After 150 days of storage with thermocycling, the air-abraded group showed the most durable TBS (34.8 MPa), while the silicon carbide bur group showed a significant reduction in TBS (21.2 MPa); in the polished control group, specimens all debonded spontaneously during storage (p ≤ 0.05). Conclusion: Repair of zirconia ceramic after chipping of its veneers showed durable TBS when surface conditioning with air abrasion or roughening of the zirconia surface with a silicon carbide bur was provided. Keywords: intraoral ceramic repair, zirconia repair, silicon carbide grinding bur, tensile bond strength, primer, zirconia framework, all-ceramic restorations

Purpose: To investigate the impact of pretreatment and conditioning on bonding behavior of polyetherketoneketone (PEKK) to methylmethacrylate(MMA)- and dimethacrylate(DMA)-based polymers. Materials and Methods: 1200 PEKK substrates (Pekkton ivory) were fabricated, air abraded (110 µm, Al2O3) and divided into 8 pretreatment groups as follows: 1. Visio.link (VL); 2. VL+ opaquer; 3. Pekk Bond (PB); 4. PB + opaquer; 5. plasma; 6. plasma + opaquer; 7. plasma + VL+ opaquer; 8. plasma + PB + opaquer. A low-density cold oxygen plasma was used to treat specimens in groups 5-8. All pretreated PEKK substrates were bonded with either MMA-based polymers (denture acrylic: "Anaxdent acryline") or DMA-based polymers (veneering composites: flowable "Anaxdent dentin flow" or packable "Anaxdent dentin paste"). On denture acrylic, the anaxgum opaquer paste was applied, and on veneering composites, the anaxblend opaquer paste. All specimens were stored in water for 24 h at 37°C, and 20 specimens of each subgroup were additionally thermocycled (5°C/55°C, 10,000x). Tensile bond strength (TBS) was measured and analyzed with the general linear model analysis, Kaplan-Meier survival estimates, and Breslow-Gehan tests. Results: The combination of plasma and VL showed the highest TBS results, followed by VL and the combination of plasma and PB. The lowest TBS was observed among PEKK specimens treated with plasma and without pretreatment, followed by specimens conditioned with PB. The application of an opaquer layer increased the TBS. Bonding to PEKK with MMA-based polymers showed higher TBS results than with DMA-based polymers. Among DMA-based polymers, the flowable polymer bonded significantly better to PEKK compared to paste polymer. After thermocycling, the TBS decreased. Conclusion: Sufficient bonding to PEKK is possible when plasma treatment is used in combination with the tested adhesives and an opaquer layer. Keywords: PEKK, bonding, tensile bond strength, air abrasion, plasma treatment, opaquer

Purpose: To examine the effect of CHX pre-treatment on long-term bond strength of fiber posts luted with self-adhesive resin cements. Materials and Methods: Seventy-two single-rooted teeth were selected for root canal treatment and post space preparation. The tested self-adhesive cement/post combinations were (N = 36): 1. RelyX Fiber-Posts luted with RelyX Unicem; 2. Rebilda Posts luted with Bifix SE Cement. For both self-adhesive cements, half of the specimens (experimental groups) were luted after the application of a solution of 2% CHX, while no CHX application was performed for the remaining specimens (control groups). Luted specimens were cut and used for push-out bond strength evaluation immediately, and after storage in artificial saliva for 6 months or 1 year. Additional specimens were processed for quantitative interfacial nanoleakage analysis. Results: ANOVA showed that the variable times of storage had a significant influence on the results (p 0.05), while no influence of the luting procedure (cements with or without CHX) on the final outcome (p > 0.05) was found. Tukey's pairwise post-hoc test showed that the radicular bond strength decreased with time of storage. In particular, a significant difference was found between T0 and T1y, but not between T0 and T6m. In contrast, in terms of pretreatment, no significant reduction in push-out bond strength was observed, irrespective of the aging time. Conclusion: CHX pretreatment did not prevent bond strength degradation of fiber posts luted with self-adhesive cements. Keywords: chlorhexidine, dentin bonding agents, fiber posts, nanoleakage analysis, push out, self-adhesive cements

Purpose: To test the hypothesis that the concentration of 10-methacryloxydecyl dihydrogen phosphate (MDP) in zirconia primers has no effect on the chemical bonding efficacy of methacrylate resins to yttria-stabilized tetragonal zirconia (Y-TZP). Materials and Methods: Shear bond strength testing was performed to evaluate the efficacy of experimental primers containing 5, 10, 15, 20 or 30 wt% MDP (5M, 10M, 15M, 20M, 30M) in improving composite-zirconia bond strength. Bonding without use of MDP-containing primer served as the negative control (Ctr0). Bonding with a commercially available MDP-containing primer served as the positive control (CtrM). Thermogravimetric analysis (TGA), inductively coupled plasma-mass spectrometry (ICP-MS), x-ray photoelectron spectroscopy (XPS), Fourier transform-infrared spectroscopy (FT-IR), and computational simulation of infrared spectra were used to confirm the formation of Zr-O-P bond between MDP and Y-TZP. Results: Results derived from TGA, ICP-MS, XPS, and FT-IR suggested that MDP chemically bonded with Y-TZP. Simulation of IR data supported the FT-IR results. There was a higher concentration of phosphorus on the 10M-conditioned Y-TZP surface when compared with the other groups, suggesting bettter formation of Zr-O-P bond in the 10M group. Shear bond strengths were significantly lower for group 5M (p 0.05), compared to groups 10M to 30M, which were not significantly different from one another (p > 0.05). Conclusions: MDP improves resin bonding of zirconia through the formation of Zr-O-P bonds with zirconia. 10 wt% MDP appears to be the most optimal concentration for synthesizing zirconia primers for resin bonding. Keywords: adhesion, bond strength, MDP, phosphate ester monomer, surface treatment, yttria-stabilized tetragonal zirconia

Purpose: To evaluate dentin sealing (DS), micropermeability (MP), and dentin bond strength (BS) of HEMA-free adhesives after 24 h and one year of artificial saliva storage. Materials and Methods: Two HEMA-free (G-ænial Bond and BeautiBond) and All-Bond 3 (the bottle of resin is HEMA-free) adhesives were tested. Adper Single Bond 2, a HEMA-containing adhesive, served as the control. All adhesives were applied according to the manufacturers' instructions and teeth were prepared for DS (n = 5), MP (n = 5), and BS testing (n = 10). DS under a pulpal pressure of 10 psi was performed at 4 time points (when smear layer was present, after EDTA treatment, after adhesive application, and after 1 year). MP was assessed using pulpal pressure of a 20-cm aqueous dye-solution column and confocal laser scanning microscopy. DS, MP, and BS were performed after 24 h or one-year storage. BS and DS data were statistically analyzed using two-way ANOVA, the Tukey-Kramer test (for BS) and Tukey's post-hoc test (for DS) (a = 0.05). A qualitative MP assessment was performed by comparing the accumulation of yellow dye within the resin-dentin interface. Results: Adper Single Bond 2 and All-Bond 3 completely sealed the dentin at 24 h and one year. G-ænial Bond showed statistically significant DS reduction of approximately 15% after one year. BeautiBond showed no DS reduction after one year. The resin-dentin interface created using Adper Single Bond 2 and GA showed dye accumulation primarily after one year. The mean BS of All-Bond 3 was statistically significantly higher than that of other adhesives, while G-ænial Bond and BeautiBond showed statistically significantly lower mean bond strengths than did Adper Single Bond 2 and All-Bond 3. After one-year storage, the mean BS was statistically significantly lower only for G-ænial Bond. Conclusion: DS, MP, and BS were not influenced by the absence of HEMA in the tested adhesives. Keywords: dentin, dentin bonding agents, bond strength, permeability, HEMA