The Journal of Adhesive Dentistry, 02/2020

Purpose: To evaluate the clinical performance of direct posterior composite restorations with and without short glass-fiber (SGF) reinforced composite in endodontically treated teeth. Materials and Methods: Twenty-four patients (mean age 32.5 years) were included in the study and two molars of each patient received endodontic treatment. After endodontic treatment, one tooth was restored with G-aenial Bond/fiber-reinforced composite (everX Posterior GC) using a microhybrid composite (G-aenial Posterior), and the other tooth was restored with G-aenial Bond/microhybrid composite (G-aenial Posterior). The modified USPHS criteria were used to evaluate the restorations at baseline, 1-, 2-, and 3-year follow-ups. Results: The success rate of the everX Posterior and G-aenial Posterior restorations after 3 years was 78.3% and 91.3%, respectively. Five everX Posterior restorations and two G-aenial Posterior restorations failed. Based on the criteria used in this study, no significant differences between the two restorations were found at any evaluation time. Conclusion: All restorations showed acceptable clinical performance regarding all evaluation criteria, apart from the failed restorations. The main cause of restoration failure was restoration fracture. The failure rate of everX Posterior restorations was higher than G-aenial Posterior restorations. Keywords: glass-fiber–reinforced composite, microhybrid composite, self-etching adhesive, direct posterior composite, endodontically treated teeth, clinical study, clinical performance

Purpose: To evaluate the degree of conversion (DC%), water sorption (Sp), solubility (Sl), dentin bond strength (μTBS) (immediate and after 12 months of storage), and the antibacterial effect of an experimental adhesive containing different concentrations (%) of proanthocyanidin (PA): 0, 1%, 2%, 4.5%, and 6% (PA0, PA1%, PA2%, PA4.5% and PA6%, respectively). Materials and Methods: DC% was measured by FT-IR and the Sp and Sl were determined based on the ISO 4049 specification. For μTBS, resin composite buildups were constructed incrementally and specimens (n = 8) were sectioned to obtain sticks (1 mm2). The μTBS was evaluated after 24 h and 12 months of water storage at 37°C. The failure mode was analyzed. The antibacterial effects were evaluated by analyzing the bacterial growth (S. mutans) (n = 5) and antibiofilm activity (n = 5) of the adhesives by spectrophotometry. Results: The incorporation of PA did not affect the Sp, Sl, or DC%. Immediate μTBS was similar for all groups. After 12 months, PA4.5% presented significantly higher μTBS than PA0, while the other groups did not differ from PA0 and PA4.5%. Groups PA0 and PA1% underwent significant reduction in μTBS. In the experimental groups PA2%, PA4.5% and PA6%, μTBS was maintained after storage. All groups showed antibacterial activity. Conclusion: Incorporation of 2%, 4.5%, and 6% PA maintained the dentin μTBS after 12-month storage, without affecting the Sp, Sl, or DC% of experimental adhesives. PA4.5% presented higher μTBS values than PA0 after 12 months. The adhesive presented antibacterial effect irrespective of PA concentration. Keywords: dentin bonding agents, cross linker, antimicrobial, bond strength

Purpose: To evaluate the influence of new air-abrasion powders with different silica concentrations (silica-coated aluminum oxide) and aging on the bond strength between composite cement and Y-TZP ceramic. Materials and Methods: Ceramic slices (7 x 6.3 x 2 mm3) were randomly allocated into 8 groups (n = 20) considering different surface treatments (SiC: silica-coated aluminum oxide particles; AlOx: aluminum oxide particles; 7% Si and 20% Si: experimental powders consisting of 7% and 20% silica-coated of AlOx respectively) and aging (baseline: 24 h at 37°C in water; aged: 90 days at 37°C in water + 12,000 thermal cycles). A blinded researcher performed the air-abrasion procedure for 10 s (identical parameters for all groups). Composite resin cylinders (Ø = 3 mm) were cemented onto the silanized ceramic surfaces, light cured, and subjected to shear bond-strength testing (wire loop Ø = 0.5 mm). The topography of the powders and air-abraded surfaces was analyzed using SEM and atomic force microscopy (AFM). The elemental composition of the powders and air-abraded surfaces was analyzed with energy dispersive spectroscopy (EDS), and surface wetting of the air-abraded surfaces was also determined by contact-angle measurements. Results: Under baseline conditions, all groups presented similar bond strengths, but only SiC and 7% Si yielded unaltered bond strength after aging. SiC and 7% Si presented lower contact angles. All groups presented similar surface topographies. The silica content was also similar among groups, except for AlOx. Conclusion: 7% Si and SiC presented similar bond strength and better bonding performance after aging than AlOx and 20% Si. A higher silica concentration was not able to promote stable adhesion of composite cement after aging. Keywords: air abrasion, silica concentration, surface treatments, shear bond strength, yttrium-stabilized zirconium oxide

Purpose: To evaluate 1. the microtensile bond strength (µTBS) and in situ degree of conversion (DC) of adhesives applied using two bonding strategies after silver diamine fluoride (diamine) application on carious dentinal lesions, and 2. dentin etching patterns using SEM and energy dispersive x-ray spectroscopy. Materials and Methods: Human molars were randomly divided into 12 experimental groups according to: 1. application of a silver diamine fluoride solution (carious dentinal lesion without silver diamine fluoride treatment [control], with 12% silver diamine fluoride [diamine 12%] or 38% silver diamine fluoride [diamine 38%]); 2. adhesives (Clearfil Universal Bond Quick [CUQ] and Scotchbond Universal [SBU]); 3. adhesive strategy (etch-and-rinse [ER] and self-etch [SE]). After restoration, the specimens were sectioned and submitted to µTBS testing. Sticks from each tooth were used for DC evaluation. To examine the changes induced by diamine before and after phosphoric acid treatment, SEM/EDX analysis was performed. Data from the µTBS and DC tests were analyzed using three-way ANOVA and Tukey's test (α = 0.05). Results: Both concentrations of diamine resulted in a statistically significantly higher mean µTBS compared to the control (p < 0.0001). Diamine 38% showed a statistically significantly higher mean µTBS for both adhesives in SE mode compared to diamine 12% (p < 0.0001). The application of diamine to carious dentinal lesions did not significantly influence the mean DC values for either adhesive (p = 0.72). SBU showed a higher mean DC compared to CUQ (p = 0.03). After diamine treatment, there was an increase in the Ca peak intensity and the presence of residual silver ions mainly when diamine 38% was applied along with the SE approach. Conclusion: Independent of the adhesive application approach, the use of diamine may be a promising alternative to increase µTBS without jeopardizing the DC of the two adhesives in carious dentinal lesions. Keywords: silver diamine fluoride, adhesives, microtensile bond strength, dental caries, micro-Raman spectroscopy, SEM

Purpose: To evaluate the influence of hydrofluoric acid (HF) concentration and etching time on the microshear bond strength (µSBS) of RelyX Unicem 2 (3M Oral Care) to VITA Suprinity (Vita Zahnfabrik; zirconia-reinforced lithium-silicate glass ceramic: ZLS) and IPS e.max CAD (Ivoclar Vivadent; lithium-disilicate glass ceramic: LD). Materials and Methods: Forty-eight bars each were fabricated of ZLS and LD with Cerec InLab MC-XL. For each material, 8 groups were formed with respect to etching time (20, 40, 60, 120 s) and HF concentration (4.9% and 9.5%). In each group, after etching and silanization, 15 cylindrical specimens of RelyX Unicem 2 were built up for µSBS testing with a special device. Data were analyzed using three-way ANOVA. Failure modes were assessed using an optical stereomicroscope, classified as adhesive, cohesive in resin or ceramic, or mixed. Failure modes were statistically analyzed using Fisher's Exact Test. One bar per group was prepared for SEM observation of the etched surface. Results: ZLS showed significantly higher bond strengths than LD (p < 0.001). Etchant concentration was an influential factor with superior strengths after 4.9% HF etching (p = 0.009). Etching time did not significantly affect adhesion (p = 0.066). The material-etching interaction was statistically significant (p = 0.004). Particularly for ZLS, 4.9% HF etching obtained significantly higher bond strengths than did 9.5%. By using 4.9% HF, adhesion was significantly higher on ZLS than on LD. Conclusion: Material and HF concentration influenced the adhesion between RelyX Unicem 2 composite cement and lithium-silicate glass ceramics. Etching time was not an influential factor. The use of 4.9% HF for 20 s proved to be the most effective etching treatment of the intaglio surface. Keywords: CAD-CAM, hydrofluoric acid, IPS e.max CAD, microshear bond strength, VITA Suprinity

Purpose: To determine the effect of Weibull analysis with censoring of cohesive failures on the evaluation of the effect of surface treatment and adhesive on the microtensile composite-composite bond strength. Materials and Methods: Surfaces of Filtek Z250 (3M Oral Care) specimens aged in distilled water for five months at 37°C were ground with SiC paper P320 or air abraded with Al2O3 and built up with the same composite using Optibond FL (OPF, Kerr), Clearfil SE Bond (CSE, Kuraray Noritake) and Gluma Comfort Bond (GLU, Kulzer) adhesives. After sectioning and trimming, the specimens were stored at 37°C in distilled water for 24 h and then tested in a microtensile bond strength setup. Complete datasets of all strength data and adhesive datasets containing adhesively failed specimens were analyzed with a one-way Welch ANOVA at α = 0.05 and compared with the results of Weibull analysis applied on complete and adhesive datasets as well as complete datasets right censored for cohesive failures. Weibull shape (m) and scale (σo) parameters were estimated using the maximum likelihood method and used to calculate bond strength (σ0.10) at 10% probability of failure as a measure of system performance. The surface morphology was studied using light and scanning electron microscopy. Results: While ANOVA indicated a significant effect of surface treatment and non-significant effect of the adhesive, the Weibull analysis results depended on bond strength characteristics and censoring. The scale parameter of the complete dataset indicating a significant effect of surface treatment for all adhesives became statistically non-significant for CSE after censoring. When this effect was evaluated by σ0.10, the non-significant effect of surface treatment for OPF and GLU became statistically significant due to censoring. The effect of the adhesive evaluated by the scale parameter was non-significant both for surfaces as well as complete and censored datasets. On the other hand, s0.10 suggested significant differences between adhesives on the ground surface for complete datasets which became statistically non-significant for the censored datasets. Conclusion: This study indicates that the results of statistical evaluation of bond strength can be affected not only by the experimental set-up and statistical model but also the bond strength characteristics and the manner in which the strengths of cohesively failed specimens are included in calculations. Keywords: microtensile bond strength, Weibull analysis, cohesive failures, censoring

Purpose: To evaluate the effect of surface treatments and aging on the bond strength of composite cement to a novel CAD/CAM nanohybrid composite. Materials and Methods: Microtensile bond strength (µTBS) of a dual-curing composite cement (Bifix QM; BQ) to three CAD/CAM restorative materials (Grandio [GR], Vita Enamic [VE], and Lava Ultimate [LU]) was evaluated after different surface treatments. The surfaces of specimens received the following treatments: control (no treatment), sandblasting (SB), SB + silane (Ceramic Bond; CB), hydrofluoric acid (HF), HF + CB, TiF4 2 wt/v%, TiF4 2 wt/v% + CB, TiF4 4 wt/v%, and TiF4 4 wt/v% + CB. Half of the specimens in each group were aged. Surface topography and surface roughness were evaluated. Statistical analysis was conducted using ANOVA and Tukey's test. The Weibull analysis was conducted on µTBS data of aged groups. Results: The µTBS was significantly affected by the type of CAD/CAM material, type of treatment, and aging (p < 0.001). Silane application significantly improved the µTBS (p < 0.05). The µTBS decreased significantly with aging (5000 thermocycles) (p < 0.05). BQ cement resulted in the highest μTBS to GR treated with TiF4 2% wt/v + CB compared to the other groups (p < 0.05). Aged GR/BQ treated with TiF4 2% wt/v + CB had the highest predicted µTBS (19 MPa). Conclusion: TiF4 2% wt/v followed by silane application enhanced the adhesion of GR/BQ and LU/BQ systems. On the other hand, HF surface treatment followed by silane application improved the adhesion of the VE/BQ system. Keywords: bond strength, composite cement, nanohybrid CAD/CAM, polymer-infiltrated ceramic, resin nanoceramic, surface roughness, surface treatments

Purpose: To synthesize tantalum oxide quantum dots (Ta2O5QDs) using an imidazolium ionic liquid as a precursor and evaluate the effect of its addition to an experimental adhesive resin on the degree of conversion (DC) and antibacterial activity. Materials and Methods: Ta2O5QDs was synthesized from the hydrolysis of an imidazolium ionic liquid (1-n-decyl-3-methylimidazolium hexachlorotantalate [DMI.TaCl6]) and evaluated by transmission electron microscopy (TEM). The adhesive was formulated with 66.7 wt% bisphenol A-glycidyl methacrylate (bis-GMA), 33.3 wt% 2-hydroxyethyl methacrylate (HEMA) with a photoinitiator/co-initiator system. In one group, Ta2O5QDS was added to the adhesive at 1 wt% Ta2O5QDs) and one group remained without Ta2O5QDS as control (CTRL). The adhesives were evaluated for DC by Fourier Transform Infrared spectroscopy. Direct contact inhibition assay was used to evaluate the antibacterial activity of the experimental adhesive resins against biofilm formation and planktonic bacteria. Results: Ta2O5QDs had a particle size distribution of 1.52 ± 0.73 nm. DC was 50.91 ± 4.94% for CTRL and 55.4 ± 4.58% for Ta2O5QDs (p = 0.310). Ta2O5QDs showed less Streptococcus mutans biofilm formation on adhesive surfaces (p = 0.013). There was no statistically significant difference in terms of antibacterial activity against planktonic bacteria (p = 0.079). Conclusion: Non-agglomerated Ta2O5QDs synthesized from an imidazolium ionic liquid provided antibacterial activity to the experimental adhesive resin against biofilm formation of Streptococcus mutans. Keywords: antibacterial adhesive, dental caries, dentin bonding agent, polymerization

Purpose: To evaluate interfacial gap and fracture resistance of endodontically treated maxillary premolars, restored with different glass-fiber reinforced materials. Materials and Methods: Eighty-four extracted intact premolars were endodontically treated and MOD cavities prepared. Specimens were divided into 7 groups (n = 12 for each) as follows: sound teeth (G1); no restoration (G2); direct composite restoration with fiber-reinforced composite (everX Posterior GC) (G3); direct composite restoration (Filtek Supreme XTE, 3M Oral Care; "FSXTE") (G4); a horizontal layer of high-viscosity flowable composite (G-ænial Flow, GC) was placed on the pulp chamber floor, 10 mm x 3 mm glass fibers (everStick NET, GC) were inserted into the cavity (G5); same procedure as in group 5 except the direct restoration was made incrementally with FSXTE (3M Oral Care) (G6); composite overlays were placed (G7). Specimens were scanned with micro-CT to evaluate 3D interfacial gaps before and after chewing simulation using Mimics software to calculate voids between restoration and tooth (dentin and enamel). These data (in mm3) were collected for statistical analysis. Thereafter, specimens were loaded to fracture using a universal testing machine. Maximum breaking loads were recorded in Newton (N). The data obtained were analyzed using two-way ANOVA and post-hoc Tukey's test (p < 0.05). Results: ANOVA showed that horizontal glass-fiber insertions statistically significantly reduced interfacial gaps after chewing simulation. No differences in fracture resistance were found between Filtek Supreme XTE and everX Posterior; moreover, glass-fiber insertion did not significantly improve fracture resistance in either case. Composite overlays achieved significantly better fracture toughness than did direct restorations. Conclusions: For the direct restoration of endodontically treated premolars, the insertion of glass fibers into direct composite restorations was unable to guarantee a significant increase in the fracture resistance or a significant change in the fracture pattern. However, it significantly reduced interfacial gap volume after cycling fatigue. Keywords: 3D gap, endodontically treated teeth, fiber, fracture resistance, micro-CT