The Journal of Adhesive Dentistry, 01/2019

Purpose: To evaluate through a systematic review and meta-analysis whether the immediate and long-term bonding performance of universal adhesives would be improved by prior acid etching. Materials and Methods: Two reviewers performed a literature search up to April 2018 in eight databases: PubMed, Web of Science, Cochrane Library, SciELO, Scopus, LILACS, IBECS, and BBO. Only studies that evaluated the dentin or enamel bond strength of universal adhesives using a self-etch or etch-and-rinse strategy were included. Analyses were carried out using RevMan 5.3.5 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark). A global analysis comparing self-etch or etch-and-rinse strategies and the influence of aging on bonding performance was performed with random-effects models at a significance level of p 0.05. Results: A total of 59 in vitro studies were included in the meta-analysis. The enamel bond strength of universal adhesives was improved by the etch-and-rinse approach (p 0.05). In dentin, this effect was observed for ultra-mild and intermediately strong universal adhesives (p 0.05). Irrespective of the strategy employed, intermediately strong adhesives showed a decrease in bond strength after all types of aging. This effect was also observed for ultra--mild universal adhesives used in the etch-and-rinse approach (p 0.05). Mild universal adhesives showed bond strength stability in both strategies (p > 0.05). Conclusions: The in vitro evidence suggests that bonding performance of mild universal adhesives can be improved by using the selective enamel-etch strategy. Mild universal adhesives seem to be the more stable materials, in both etch-and-rinse or self-etch strategies. Keywords: adhesive, dental bonding, dental materials, universal adhesives, systematic review

Purpose: To evaluate the effect of ethanol-wet/hydrophobic resin bonding (EWB) in a simplified dehydration protocol with ultrasonic agitation (UA) of etch-and-rinse adhesives on the bonding quality in root canals. Materials and Methods: 56 extracted human maxillary central incisors were divided into 4 groups (n = 14) according to the procedures of bonding fiber posts in root canals: A: conventional etch-and-rinse adhesive as control (All-Bond 3, Bisco); B: EWB in a simplified dehydration protocol, ie, after 100% ethanol dehydration (30 s, 3 times), ethanol/hydrophobic resin (50% bis-GMA + TEG-DMA, 50% ethanol) was applied into the root canal as a primer, followed by applying pure co-monomer adhesive; C: EWB in a standard dehydration protocol, ie, ascending concentrations of ethanol (50%, 70%, 80%, 90%) for 30 s and 100% ethanol (30 s, 3 times) for dehydration, with the remaining procedure conducted as in group B; D: EWB in a simplified dehydration protocol under ultrasonic agitation (UA), ie, 100% ethanol under ultrasonic agitation for 30 s, ethanol/hydrophobic resin as a primer applied under UA for 60 s, followed by the application of pure co-monomer adhesive. All the specimens were cemented with Duo-Link (Bisco) and immersed in artificial saliva for 24 h or thermocycled for 10,000 times. Bond strength, failure mode, and nanoleakage were evaluated. Hybrid layer and resin tags were also observed with SEM. Data were analyzed with two-way ANOVA (bond strength) and Kruskal-Wallis analysis (nanoleakage, resin tag score) (α = 0.05). Results: Significant differences existed in bond strength (p = 0.02) and nanoleakage (p = 0.02) among groups. After 24 h and after thermocycling, group D exhibited higher bond strengths than did group B (p = 0.02 after 24 h, p = 0.03 after aging) and group A (p = 0.06 after 24 h, p = 0.04 after aging). Bond strength and nanoleakage showed no significant difference after aging (p > 0.05). There was no significant difference in resin tag scores between any of the groups, but the apical third of the roots exhibited the lowest score (p = 0.001). Conclusion: The synergistic effects of the two pretreatment strategies (EWB in a simplified dehydration protocol and UA) improved the bonding quality. UA had a positive effect on the adhesion of the etch-and-rinse adhesives, when EWB in a simplified procedure was applied into the root canal. Keywords: adhesion to dentin, adhesive bond strength, fiber post, ultrasound

Purpose: To evaluate the method of resin cement mixing and insertion into the root canal on resin cement porosity and fiberglass-post push-out bond strength (PBS). Materials and Methods: One hundred twenty human single-rooted teeth were sectioned to a length of 15 mm, en-do-dontically filled, and received a fiberglass post cemented with 3 self-adhesive resin cements (RelyX U200, seT, Panavia SA) using 4 mixing methods/insertion techniques (handmix/endodontic file, handmix/Centrix syringe, automix/conventional tip, automix/endo tip). The samples were scanned using micro-CT. Two slices from the cervical, middle, and apical thirds were submitted to push-out bond strength (PBS) testing, and failure modes were classified. The PBS, volume of resin cement, and porosity data were analyzed using ANOVA and Tukey's test. Results: The porosity was lowest in the cervical third and highest in the apical third, irrespective of the resin cement. The porosity was lower in the the automix/endo tip group compared to the handmix/endodontic file group. The use of Centrix or endo tip reduced the porosity and increased the PBS in the apical third compared with the use of endodontic files. The root canal depth reduced the PBS for U200 and seT when handmix/endodontic files were used. U200 and seT using the automix method increased the PBS, thus eliminating the effect of root region, irrespective of the insertion technique. In general, U200 showed higher PBS and Panavia lower PBS. Adhesive failure between root dentin and resin cement was predominant. Conclusions: Automixing the cement and using an endo tip produces fewer voids and increased the bond strengths. Keywords: fiber post, insertion technique, micro-CT, porosity, root canal, resin cement

Purpose: To investigate the efficacy of different ceramic surface cleaning methods after saliva contamination on the resin bond strength to lithium disilicate ceramics. Materials and Methods: 300 e.max CAD blocks (Ivoclar Vivadent) were polished with 600-grit silicon carbide paper and divided into five groups with or without human saliva contamination and according to the surface treatment performed (n = 10); control: no pretreatment; MP: Monobond Plus; PA+MP: 37% phosphoric acid (PA) followed by MP; HF+MP: 5% hydrofluoric acid (HF) followed by MP; MEP: Monobond Etch & Prime. The specimens were bonded with one of three resin cements: Variolink Esthetic DC (VE), Multilink Automix (MA) and Speed CEM (SC). After 24-h water storage, tensile bond strength (TBS) was measured. The ceramic surfaces after pretreatment were analyzed using x-ray photoelectron spectroscopy (XPS). Results: XPS analysis showed similar elemental distributions between saliva contamination vs no saliva in PA, HF, and MEP. The TBSs were significantly influenced by surface treatments (p 0.05). HF+MP and MEP showed statistically non-significantly different bond strengths to saliva-contaminated HF+MP and MEP, but were different from MP and saliva-contaminated MP. The TBSs after 24 h were significantly higher in HF+MP and MEP groups with VE. HF+MP and MEP did not show statistically significant differences among any groups with or without saliva contamination. Conclusion: Surface treatments with PA or HF followed by silane or by MEP alone were effective in removing saliva contamination and enhancing the resin bond strength. Keywords: lithium disilicate ceramics, saliva-contaminated, tensile bond strength

Purpose: To evaluate the effects of double application of self-etch adhesives on their microtensile bond strength (μTBS) to dentin, as well as the hardness (H) of resin-dentin interfacial structures. Materials and Methods: Midcoronal dentin surfaces (n = 45) were polished with 180-grit SiC paper and randomly allocated to 9 groups based on three adhesives - Scotchbond Universal Adhesive (SB), G Premio Bond (GP), and Clearfil Megabond 2 (MB) - and three application modes: single application (S), double application with light curing after each application (DL), and double application with light curing only at the end (D). Following composite-resin build up and water storage (37°C; 24 h), μTBS were obtained. The hardness of adhesive, resin-dentin interface and dentin were evaluated by nanoindentation. The μTBS and H data were analyzed by two-way ANOVA to demonstrate the effects of adhesive and application mode as well as their interaction, followed by Tukey's test (α = 0.05). Fracture modes were determined using a stereomicroscope. Results: μTBS and H were significantly affected by the adhesives and their application modes (p ˂ 0.001). Double application significantly increased the µTBS and H of adhesive and resin-dentin interface (p ˂ 0.05). SB and MB showed significantly higher µTBS than GP (p ˂ 0.05). Conclusion: Double applications during bonding of dentin having clinically relevant smear layers were beneficial for three contemporary self-etch adhesives. The improvement in bonding performance is believed to be the result of increased chemical interaction, better solvent removal, and improved resin infiltration, leading to improved mechanical properties of the resin-dentin interface or thicker adhesive layers providing improved stress distribution. Keywords: clinically relevant smear layer, dentin bonding, double application, hardness, microtensile bond strength, self-etch adhesive, single application

Purpose: To evaluate the light transmittance of ceramic veneers of different thicknesses and verify their influence on the degree of conversion, color stability, and dentin bond strength of light-curing resin cements containing different photoinitiator systems. Materials and Methods: Experimental resin cements were fabricated containing camphorquinone and amine (CQ-amine), TPO, Ivocerin (IVO), or TPO and Ivocerin (TPO-IVO). All photoinitiators were characterized by UV-Vis spectrophotometry. Disk-shaped lithium disilicate ceramic specimens that were 0.4, 0.7, and 1.5 mm in thickness were prepared using IPS e.max Press (Ivoclar Vivadent, shade LT/A2). Light transmittance through each specimen was measured using spectrophotometry. Specimens of each cement (n = 10) were made in a custom-designed mold and were light cured through each glass-ceramic disk using a multiwave LED (Bluephase G2, Ivoclar Vivadent). CS was evaluated using spectrophotometry before and after artificial aging with UV light. DC was evaluated using FTIR-spectroscopy. Dentin µSBS was evaluated using 0.75-mm-thick specimens that were light cured under the same protocol (n = 10). All data were submitted to two-way ANOVA and Tukey's test (α = 0.05; β = 0.2). Results: CQ-amine cements showed the highest color changes (p 0.05) due to increased yellowing when compared to the amine-free cements (p 0.05). However, all cements showed a significant color change after aging when cured through ceramics up to 1.5 mm thick (p 0.05). The TPO-IVO cement showed the highest DC and the IVO cement showed a similar DC when compared to the CQ-amine cement. The TPO cement presented the lowest DC (p = 0.0377). No differences in mean dentin µSBS were found among the cements, except for the TPO cement, which presented a lower mean dentin µSBS (p = 0.0277). Conclusion: Amine-free cements containing Ivocerin and TPO seem to be a better alternative to CQ-amine cements, while not reducing either DC or dentin µSBS of amine-free cements. However, CQ-amine and amine-free cements still seem to change color over time. Keywords: dental photoinitiators, ceramics, dental cements

Purpose: To investigate the effect of different etching products used prior to the application of universal self-etching adhesive on dentin bonding. Materials and Methods: The etching products Multi Etchant (ME), Enamel Conditioner (EC), and K-etchant GEL (KE) were used as pre-treatments prior to the application of the one-bottle self-etching adhesive Adhese Universal (AU). Ground human dentin surfaces were randomly divided into four treatment groups: 1. control (CT; AU without con-ditioner); 2. ME; 3. EC; 4. KE. Microtensile bond strength (µTBS) tests with a thermocycling challenge (0-TC or 10,000-TC) were carried out and the morphological attributes of the adhesive-dentin interface were observed after an acid-base challenge using SEM to observe the acid-base resistant zone (ABRZ). Results: The KE group had a statistically significantly lower µTBS than did the ME and EC groups at 0-TC, and than the CT, ME, and EC groups at 10,000-TC (p 0.05). An ABRZ was observed in all groups but had partially disappeared in KE. A funnel-shaped area of erosion was also observed at the junction of the dentin and bonding layer in the CT, ME, and EC groups, while the hybrid layer was thicker in the KE group with no evidence of erosion. Conclusion: The application of ME or EC did not reduce the microtensile bond strength and resulted in ABRZ formation, while the ABRZ was partially reduced in the KE group. Keywords: dentin, selective enamel-etch, acid-base resistant zone, microtensile bond strength test, thermal cycling test

Purpose: The purpose of this in vitro study was to compare the shear bond strength of different universal adhesives to enamel and dentin with and without additional phosphoric acid etching before and after thermocycling (TC). Materials and Methods: The mesial, distal, lingual, and buccal surfaces of the teeth were ground flat to expose two enamel areas and two dentin areas. Specimens were randomly divided into 36 groups (n = 10). Four adhesives were tested: Scotchbond Universal (SBU), Prime & Bond Elect (PBE), All-Bond Universal (ABU), and iBond Universal (IBU). The application was performed in the self-etch mode (SE) or in the etch-and-rinse mode (ER). Optibond FL (OFL) was used as an etch-and-rinse control. After composite buildups were made, half of the groups were tested before and the other half after TC. The failure mode was evaluated using a light microscope. Results: In enamel, mean bond strengths ranged from 13.4 to 21.9 MPa in the SE mode before TC. When used as an ER adhesive, mean bond strengths exceeded 30 MPa. TC did not influence the mean bond strengths in either application mode. Regarding dentin, significant differences in the SE mode were adhesive dependent. Differences were only detected between SBU and IBU before TC and were not present after TC. When SBU, PBE, and ABU were used as ER adhesives, no differences were detected before TC. TC only affected IBU when compared to the other adhesives. Conclusion: Universal adhesives benefit from phosphoric acid etching, as bond strengths increased especially at enamel surfaces. Keywords: universal adhesives, shear bond strength, self-etch, etch-and-rinse, enamel, dentin