The Journal of Adhesive Dentistry, 06/2019

Purpose: This meta-analysis investigated the influence of different acid etching times on the retention rate of pit-and-fissure sealants based on clinical trials with a minimum duration of two years. Materials and Methods: A literature search was carried out in electronic databases along with hand searching to identify clinical trials that evaluated pit-and-fissure sealants in permanent molars. From 1280 identified abstracts, 195 studies were selected for full-text analysis, and 28 studies with 36 test groups were included in this meta-analysis. Test groups with etching times of 15 (n = 3), 20 (n = 2), 30 (n = 10), 40 (n = 1) and 60 s (n = 20) were found. Incidence rates of pit-and-fissure sealant losses were modelled using negative binomial regression. Results: The regression analysis did not reveal a significant influence of etching time on the survival of pit-and-fissure sealants based on the identified and included clinical trials. Conclusions: Due to the limited number of clinical data for 15 and 20 s, conclusions regarding very short acid etching times were not possible. On the basis of regression analysis, a minimum of 30-s acid etching might be sufficient prior to fissure sealing. Keywords: acid etching, caries prevention, clinical studies, enamel pretreatment, meta-analysis, pit-and-fissure sealants, systematic review

Purpose: To compare the retention rates of non-carious cervical restorations (NCCLs) constructed using the sandwich technique (a lining of glass-ionomer cement [GIC] or resin-modified glass-ionomer cement [RMGIC] and composite resin [CR]) with CR-only restorations. Materials and Methods: The search was performed in various databases, including the Cochrane Library, PubMed, Scopus, and Web of Science. Gray literature was inspected, as were ongoing and unpublished abstracts from the IADR (1990-2017). Study quality was evaluated using the Cochrane Collaboration bias risk tool. Data from primary and secondary outcomes were meta-analyzed at 1-, 2- and 3-year follow-ups using the random effects model. The quality of the body of evidence was assessed using the GRADE approach. Results: Initially, a total of 3645 articles were selected. After selection by titles, abstracts, and full texts, 6 articles were retrieved, but three were follow-ups of the same RCT. Therefore, a total of four studies remained for analysis. All studies were at unclear risk for bias. Among all outcomes, only loss of retention was lower for the sandwich technique at the 3-year follow-up (risk ratio [RR]: 7.5; 95% CI: 2.1 to 27.2; p = 0.002). Conclusions: Based on the limited number of available studies, higher retention rates in NCCL restorations were observed with the sandwich technique compared to CR-only restorations at the 3-year follow-up. Secondary outcomes were not influenced by the restorative technique. Except for retention rates, which were of moderate quality, the evidence quality of all secondary outcomes was low. Keywords: glass-ionomer cements, permanent, dental restoration, dental materials, meta-analysis

Purpose: This study examined the influence of different monomer systems on the tensile bond strength between a resin composite and a polymerized fiber-reinforced composite (FRC). The influence of the age (shelf-life) of the FRC prepreg (reinforcing fiber pre-impregnated with a resin system) before preparing the FRC substrate for the bonding test was also assessed. Materials and Methods: Semi-interpenetrating polymer network (semi-IPN)-based glass FRC prepregs were aged for various durations (1, 1.5, and 3 years) at 4°C before being used to prepare FRC substrates via light polymerization. Four groups of aged prepregs were prepared through different treatments with: 1. no primer; 2. a dimethacrylate-based adhesive primer; 3. a universal primer; and 4. a specific composite primer. Subsequently, a resin composite luting cement was applied on the treated FRC substrates and cured with light. The water sorption of the FRC-composite specimens was determined. Then, the differences in the tensile bond strength were evaluated using ANOVA (p ≤ 0.05). Results: There were significant differences in the tensile bond strength between the composite cement and the FRC according to the primer used (p < 0.001), aging time (p < 0.001), and their interactive effect (p < 0.001). Conclusion: The monomers of the universal primer demonstrated the best ability to diffuse into the semi-IPN structure of the polymer matrix of FRC. This improved the interfacial bond strength between the composite cement and the FRC substrate. Keywords: adhesive interface, fiber-reinforced composite, poly(methyl methacrylate), primer, semi-interpenetrating polymer network, tensile bond strength

Purpose: The aim of the present study was to measure the bond strength of adhesively luted glass-fiber bundles inside the root canal with respect to the application procedure in comparison to conventional solid glass-fiber posts. Materials and Methods: 104 human anterior teeth were endodontically treated, root filled and divided into 8 groups (n = 13). After post space preparation, fiber bundles consisting of 6 and 12 glass fibers, respectively, were luted adhesively with a multi-mode adhesive (Futurabond U; Voco, Cuxhaven, Germany) and a dual-curing composite (Rebilda DC, Voco) with the following application modes into the root canal: (1) direct application with tweezers, (2) distribution of the fibers using a spreader, (3) application of ultrasound after insertion of fibers. Two different solid posts (Rebilda DC, Voco; and DentinPost, Komet, Lemgo, Germany) were used as controls. Roots were sectioned into 6 slices per root (thickness 1 mm). Bond strengths were measured using thin-slice push-out tests for 3 slices 24 h after post insertion and for 3 slices per sample following thermocycling (TC) for 6000 cycles and storage in 0.9% NaCl for 6 months. Homogeneity of the slices was analyzed using a stereomicroscope and, for representative samples, micro-computed tomography (µCT). Results: Mean push-out bond strengths (MPa) were significantly affected by post system (p < 0.0005) and location inside the root canal (p = 0.004) but not by application mode (p = 0.544) or TC (p = 0.098; repeated measurement ANOVA). Fiber bundles consisting of 6 (13.2 ± 4.7) and 12 fibers (14.5 ± 4.3) revealed bond strength comparable to that of Rebilda Post (13.67 ± 3.2) but significantly higher than that of Dentin Posts (8.7 ± 3.02). Inhomogeneities were detected among 35.5% to 43.1% of the fiber-bundle samples, irrespective of number of fibers and application mode, and among 24.4% to 27.3% of the solid posts (p = 0.010; chi-squared test). µCT revealed voids inside the composite bulk between the fibers as well as between composite and dentin of adhesively luted fiber bundles. Conclusion: Adhesively luted fiber bundles achieved bond strengths comparable to those of solid fiber posts for one investigated post type, and even higher values compared to another post type. Inhomogeneities were frequently detected irrespective of application mode. Keywords: root canal dentin, fiber post, fiber bundles, aging, adhesive luting

Purpose: To compare the adhesive-enamel microshear bond strength (µSBS), in situ degree of conversion (DC), and the enamel-etching pattern of universal adhesives when applied for a prolonged period in the self-etch vs the etch-and-rinse mode in fluorotic enamel. Materials and Methods: Ninety-six human molars (48 with a Thylstrup and Fejerskov index [TFI] score of 0 and 48 with TFI score of 4) were sectioned into four parts and divided into 24 experimental groups based on enamel surface (sound enamel or fluorotic enamel), adhesive (Clearfil Universal Bond, Futurabond U, iBond Universal, or Scotchbond Universal), and enamel treatment/application time (etch-and-rinse mode [ER] or self-etch mode with application times of 20 s [20SE] and 40 s [40SE]). The specimens were stored for 24 h and tested in shear at 1.0 mm/min (μSBS). Adhesive-enamel interfaces were evaluated for DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated using SEM. For each adhesive, data from µSBS and DC were analyzed separately using two-way ANOVA and Tukey's post-hoc test at α = 0.05. Results: On sound enamel, 40SE usually resulted in statistically similar mean µSBS (p > 0.52) and statistically significantly improved mean DC values (p < 0.001) compared with the ER mode. Moreover, significantly improved mean µSBS and DC values were obtained compared with 20SE (p < 0.01). On fluorotic enamel, there was no statistically significant difference in µSBS between the experimental groups (p > 0.76). However, for each applied adhesive, 40SE resulted in improved mean DC values compared with 20SE or ER (p < 0.001). The deepest enamel-etching pattern was obtained in ER mode, followed by 40SE in sound and fluorotic enamel. Conclusion: Compared with ER mode, the prolonged application time of universal adhesives in SE mode in fluorotic enamel increased the DC, enhanced enamel-etching pattern and promoted similar results in terms of adhesive-enamel bond strength. Keywords: adhesive bond strength, dental fluorosis, micro-Raman spectroscopy, scanning electron microscopy, universal adhesive

Purpose: To evaluate the effect of different irrigation solutions on the bonding of self-adhesive composite cements to the root canal during fiber-post cementation. Materials and Methods: One hundred twenty single-rooted human teeth were endodontically treated. The post spaces were prepared and specimens were randomly divided into ten groups, according to the combination of the factors: post space irrigation (distilled water, 2.5% NaOCl, 17% EDTA, 26% polyacrylic acid, and 17% EDTA + 2.5% NaOCl) and self-adhesive composite cement (RelyX U200 [3M Oral Care] and Multilink Speed [Ivoclar Vivadent]). The proportion of open dentinal tubules was evaluated by SEM. After fiber post cementation, six slices were obtained from each root (coronal, middle, and apical thirds) for evaluation of push-out bond strength (BS), nanoleakage (NL), and Vickers microhardness (VHN) of the composite cement. Data from open dentinal tubules were submitted to Kruskal-Wallis and Student-Newman-Keuls tests (α = 0.05). Data from BS, NL, and VHN were evaluated by two-way ANOVA and Tukey's test (α = 0.05). Results: Irrigation with EDTA, polyacrylic acid, and EDTA + NaOCl increased the proportion of open dentinal tubules. For RelyX U200, NaOCl, distilled water and EDTA resulted in the highest BS and VHN values, while for Multi- link Speed, these values were higher only for distilled water. Both composite cements presented lower BS and VHN with polyacrylic acid. NL did not differ between experimental groups (p > 0.05). Conclusion: For both composite cements tested, distilled water showed better results in push-out and microhardness tests. Keywords: adhesive cementation, bond strength, endodontic fiber posts, indentation, nanoleakage, self-adhesive luting

Purpose: To evaluate the effect of axial wall height (AWH) on failure resistance of CAD-CAM adhesively-bonded, all-ceramic crowns on molar preparations with a conservative total occlusal convergence (TOC). Materials and Methods: 60 newly extracted maxillary third molars were divided into 5 groups (n = 12) and prepared for all-ceramic crowns with occlusal cervical AWH of 0, 1, 2, 3, and 4 mm, all containing a conservative 10-degree TOC. Scanned preparations were fitted with lithium-disilicate glass-ceramic crowns using a self-adhesive resin-composite luting agent after intaglio surface preparation with hydrofluoric acid and silane. Specimens were stored at 37°C/98% humidity for 24 h and tested to failure at a 45-degree angle applied to the palatal cusp on a universal testing machine. Mean results were analyzed using ANOVA and Tukey's test (p = 0.05). Results: Preparations containing 2, 3, and 4 mm AWH demonstrated similar and higher failure resistance than the 0- and 1-mm axial wall height groups. Conclusions: Under the conditions of this study, evidence is presented that under certain conditions CAD-CAM adhesive technology may compensate for less than optimal AWH. Based on both failure load results and failure mode analysis, adhesively-luted maxillary molar CAD-CAM crowns based on a preparation containing 10-degree TOC require at least 2 mm AWH for adequate resistance and retention. However, adoption of these findings is cautioned until both fatigue analysis and appropriate clinical evidence has been provided. Keywords: CAD-CAM, adhesion, lithium disilicate, failure load, axial wall height, total occlusal convergence

Purpose: To evaluate shear bond strength (SBS), adhesive remnant index (ARI), and orthodontic bracket base after debonding of orthodontic brackets bonded using two different adhesives. Materials and Methods: Ninety sound human premolars were divided into three groups of n = 30. 1. Transbond, where brackets were bonded with Transbond XT (3M Unitek); 2. Multilink, where brackets were bonded with Multilink Speed (Ivoclar Vivadent); 3. Multilink+etch, where brackets were bonded using Multilink Speed after etching enamel. ARI scores were obtained using a stereomicroscope. SEM was used to evaluate the treated enamel surfaces and the base of the brackets. One-way ANOVA was performed to statistically analyze SBS. The Kruskal-Wallis test was conducted to investigate ARI scores, followed by multiple comparison tests (p < 0.05). Results: SBS was significantly lower in the Multilink group compared to the other groups (p < 0.05). SEM evaluation revealed minimum penetration of resin tags within the enamel and that most of the resin was attached to the base of the brackets in the Multilink group compared to the other two groups (p < 0.05). Conclusion: Application of Multilink Speed on nonetched enamel provides acceptable SBS of orthodontic brackets bonded to enamel with minimum penetration of resin tags into enamel and less residual resin on tooth surfaces. Keywords: orthodontic bracket bonding, SBS, self-adhesive resin cement, SEM, EDS

Purpose: To investigate the micro push-out bond strength of individually formed (everStick Post) and prefabricated (GC Fiber Post) fiber-reinforced composite (FRC) posts cemented with three different types of self-adhesive composite cements. Materials and Methods: Forty-two single-rooted human teeth were decoronated, endodontically treated, and had post spaces prepared for everStick Post (n = 21) or GC Fiber Post (n = 21). The teeth were randomly divided into three subgroups (n = 7), and posts were cemented either with G-CEM LinkAce (GC), SpeedCEM (Ivoclar Vivadent) or RelyX U200 (3M Oral Care). Specimens were then perpendicularly sectioned and divided at the cementoenamel junction into two root levels: coronal or apical. A micro push-out test was performed using an 0.8-mm-wide stainless steel plunger. Bond strength was calculated in MPa by dividing the fracture load (N) by the bonded surface area (mm2). Log-transformed data was statistically analyzed using factorial ANOVA and Tukey's post-hoc test (α < 0.05). Fracture modes were determined employing a stereomicroscope, and differences were evaluated using a likelihood ratio test and Pearson's chi-squared test. Specimens were also observed using SEM. Results: Bond strengths were significantly affected by both post type and root level (p < 0.05), but not by self-adhesive cement (p > 0.05). Fracture types showed a significantly higher prevalence of adhesive fractures at the apical level, with all fractures starting at the cement-dentin interface. Conclusion: Individually formed FRC posts demonstrated greater bond strength than their prefabricated FRC counterparts. The apical level of the luted posts yielded lower bond strengths than the coronal level. Failures were predominantly adhesive at the cement-dentin interface. Keywords: fiber post, push-out, self-adhesive cement, semi-interpenetrating polymer network

Purpose: To determine the effects of ceramic-surface conditioning and aging on the bond strength between composite cement and zirconia-reinforced lithium-silicate glass-ceramics (ZLS) under simulated clinical conditions. Materials and Methods: ZLS disks (Celtra Duo, Dentsply Sirona, n = 110 test group n = 10, diameter: 8.3 mm, height: 3.4 mm) were assigned to four surface-conditioning groups: (I) 30 s of ~5% hydrofluoric-acid etching (Vita Ceramics Etch, Vita; HF), silanization (Calibra Silane; SIL); (II) successive contamination with saliva and silicone (CONT), HF, SIL; (III) CONT, tribochemical silicatization (CoJet), SIL; (IV) HF, SIL, application and light polymerization of an adhesive (Prime&Bond Active), CONT, reapplication and light polymerization of the adhesive. The ZLS disks were bonded to composite-resin cylinders in acrylic tubes (inner diameter: 3.3 mm) using self-adhesive composite cement (Calibra Universal). The tensile-bond strength (TBS) was measured after both 24 h and 6 months of water storage (WS). Additional aging protocols were tested for group I (3-day WS; 30-day WS including 7500 thermocycles between 6.5 and 60°C; 150-day WS including 37,500 thermocycles). Results: After 24 h, the mean TBS ranged between 21 MPa (group III) and 30-35 MPa (remaining groups). With the exception of 3-day WS, TBS was statistically significantly reduced by aging. The greatest reduction was observed for silicatized specimens (group III, mean TBS after aging: 9.8 MPa). Conclusion: Both ceramic surface conditioning and aging had a statistically significant effect on the bond strength between composite cement and ZLS. A treatment protocol based on tribochemical silicatization cannot be recommended for the adhesive cementation of ZLS. Keywords: acid etching, adhesive cementation, aging, air abrasion, all-ceramic, bond durability, composite cement, tensile bond strength