The Journal of Adhesive Dentistry, 05/2018

Purpose: To evaluate the morphological properties, phase transformation, and microshear bond strength of composite cement to bioglass-coated zirconia surfaces treated with Nd:YAG laser. Materials and Methods: Seventy-five zirconia disks were divided into five groups (n = 15). Group C received no surface treatment (control). Group S was subjected to sandblasting with 50-μm aluminum oxide particles. Group B samples were coated with bioglass 45S5. Groups BL9 and BL5 received bioglass coating and laser irradiation with 9 J/cm2 and 5 J/cm2 energy density. Morphological assessment was done using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Zirconia phase transformation was assessed by XRD. Microhear bond strength testing was performed using a modified microtensile tester. The data were analyzed using the Welch test and the Games-Howell test (p 0.05). Results: The sandblasted and bioglass-coated groups showed the highest bond strengths compared to other groups (p 0.05). Group S showed the highest surface roughness and the highest frequency of cohesive failure. In all samples, the tetragonal phase decreased after surface treatment. Groups BL9 and BL5 showed some levels of tetragonal to cubic phase transformation. Conclusion: Bioglass coating of zirconia surfaces (using the slurry method) can increase its microshear bond strength comparable to that of sandblasting. Surface roughness of sandblasted zirconia was the highest among all methods. Irradiation of Nd:YAG laser on bioglass-coated zirconia surfaces is not effective and decreases its bond strength compared to sandblasting and bioglass coating. Increasing the Nd:YAG laser energy density cannot increase the surface roughness of bioglass-coated zirconia surfaces. Bioglass coating results in transformation of the tetragonal to the cubic phase. Keywords: Nd:YAG laser, bioglass, zirconia surface, bond strength, phase transformation

Purpose: To evaluate the influence of recycling a pressed ceramic material on surface properties, color stability and bond strength to composite cement. Materials and Methods: Forty-eight (48) ingots from a heat-pressed ceramic (PM9, Vita Zahnfabrik) were fabricated through the lost-wax technique and then polished with SiC sandpaper to standardize the dimensions (diameter: 12 mm; length: 4 mm). Leftover material from processing the pressed groups was retrieved and used to repeat heat pressing for the re-pressed groups. The ingots were randomly divided into 3 groups according to the number of injections - one, two, or three times. Ra, Rz, and RSm surface roughness parameters were evaluated through a contact rugosimeter. Topography was analyzed using SEM and the chemical constituents using EDS (energy dispersive spectroscopy). Color stability was evaluated according to CIE-Lab parameters to determine color variation (∆E). Composite ingots with the same dimensions were cemented over each ceramic, then this set was cut into sticks with a 1-mm2 cross-sectional area. Half of the sticks were submitted to microtensile bond strength (µTBS) testing after 24 h. The other half was tested after thermocycling (5000 cycles, 5°C-55°C) and storage in water at 37°C for 6 months. Results: One-way ANOVA showed that the number of injections influenced both Rz and RSm roughness parameters (p = 0.00), but not Ra (p = 0.97). One injection exhibited higher (Rz) and grooves with less space between them (RSm) compared to the other groups. For color stability, the values of L*, a*, and b* were influenced by the number of injections (p = 0.00). ∆E = 5 was found for 2 injections and ∆E = 3 for 3 injections, using a control group as reference. One-way ANOVA showed that the number of injections significantly influenced wettability values: 1inj (63 ± 5.3)A > 2inj (49 ± 8.2)B > 3inj (45.8 ± 15.8)B. However, the evaluated factor did not influence the bond strength of non-aged groups. Furthermore, aged groups showed that 1inj (21 ± 37)a presented higher mean values than 2inj (10 ± 8)b or 3inj (12 ± 10.)b. Conclusion: Re-pressing the evaluated ceramic improves roughness and wettability, but compromises the color stability and decreases bond strengths after long-term aging. Keywords: ceramic, mechanical properties, microstructure, repeated heat-pressing, leucite-reinforced glass-ceramics

Purpose: To evaluate the immediate and 12-month microtensile bond strength (μTBS) of two self-etch adhesives on sclerotic dentin with or without previous EDTA conditioning. The conditioning pattern and the relative area of open dentinal tubules were also evaluated. Materials and Methods: Twenty-eight bovine incisors with naturally exposed sclerotic dentin were used. For μTBS testing, 20 teeth were divided into 4 groups (n = 5) according to the combination of the main factors: 1. adhesive (Clearfil SE Bond [CSE, Kuraray] and Adper SE Plus [ADSE, 3M Oral Care]); 2. surface treatment (previous conditioning with EDTA and previous conditioning with distilled water [DW]). The sclerotic surfaces were conditioned with either 17% EDTA or DW for 2 min prior to adhesive application. Composite buildups were constructed. Specimens were sectioned to obtain composite-dentin sticks (0.8 mm2) to be tested immediately or after 12 months (distilled water at 37°C) in tensile mode (0.5 mm/min). The conditioning pattern and the relative area of open dentinal tubules (OT) were evaluated in the remaining eight teeth. After adhesive application, the surfaces were rinsed off with acetone and ethanol. Then the surface was evaluated by SEM with image software. Data from μTBS and OT were submitted to three-way repeated measures ANOVA and data from OT were submitted to one-way repeated measures ANOVA. After, for both tests, Tukey's post-hoc test was applied (α = 0.05). Results: For both adhesives, EDTA resulted in the highest mean immediate μTBS (p = 0.002), which remained stable after 12 months of water storage (p 0.38). CSE showed higher μTBS when compared to ADSE (p = 0.001). Degradation of the mean μTBS was observed for both adhesives only in the DW groups. Adhesive application plus with EDTA conditioning increased the OT area in comparison with only adhesive application (p 0.001). Conclusion: EDTA conditioning increased the immediate microtensile bond strength in sclerotic dentin substrate and prevented degradation when associated with a self-etch adhesive. Keywords: sclerotic dentin, scanning electron microscopy, self-etch adhesives, EDTA, microtensile bond strength

Purpose: To evaluate the effect of selective phosphoric acid etching on enamel using "no-wait" self-etching adhesives. Materials and Methods: Clearfil Universal Bond Quick (UBQ, Kuraray Noritake) or G-Premio BOND (GPB, GC) was applied to ground human enamel surfaces. The adhesives were used in 3 modes: no-waiting self-etching mode (UBQ-0 or GPB-0), 10-s self-etching mode (UBQ-10 or GPB-10), and the selective-etch mode with phosphoric acid etching (UBQ-PA or GPB-PA). After an acid-base challenge, the morphological attributes of the interface were examined using scanning electron microscopy (SEM) to characterize the acid-base resistant zone (ABRZ). Microshear bond strength (µSBS) testing to enamel and ultimate tensile strength (UTS) of the adhesive resin were carried out. Results: ABRZ formation was confirmed in all groups. UBQ-PA and GPB-PA created thicker ABRZ with no funnel-shaped erosion beneath the adhesive-enamel interface. µSBS of UBQ-PA was significantly higher than UBQ-0 and UBQ-10 (p 0.05). However, there were no statistically signficant differences in µSBS among GPB-0, GPB-10, and GPB-PA. For the UTS, UBQ was significantly higher than GPB. Conclusion: Selective phosphoric acid etching created a stable adhesive-enamel interface. The no-waiting self-etching concept adhesive led to a thinner ABRZ. The results of µSBS suggest that phosphoric acid etching effects on enamel are material dependent. Keywords: enamel, multimode, no-waiting self-etching concept, phosphoric acid, acid-base resistant zone, microshear bond strength test

Purpose: The present study investigated the creep of adhesive resin under constant loading at the orthodontic bracket/enamel interface with an orthodontic bracket-tooth model (shear creep) and three-point bending test (bending creep). Materials and Methods: For the bracket-tooth model, sixty premolars were assigned to 4 groups (n = 15). Orthodontic brackets were bonded onto the enamel surface using four different bonding agents: conventional, homogeneous Transbond XT orthodontic composite (group 1/TBC); Transbond XT composite reinforced with photopolymerized glass-fiber-reinforced composite (FRC with bidirectional fibers) (group 2/TBE); Transbond XT reinforced with FRC of vertically oriented unidirectional fibers (group 3/TBV); and Transbond XT reinforced with FRC of horizontally oriented fibers (group 4/TBH). Load was applied at the bracket/tooth interface and from the bracket wire slot. In the three-point bending test, the creep and recovery of the rectangular interface materials were tested by a dynamic mechanical analyzer. The data obtained were statistically analyzed with ANOVA and a post-hoc test using SPSS v20 statistical software. Results: The groups exhibited significant differences in strain % and time for bracket deflection at the interface (p 0.05). The interface loading with unidirectional fibers (groups TBV and TBH) were statistically significantly different compared to the interface with bidirectional fibers and control group (groups TBE and TBC). The three-point test showed the least creep compliance (ie, creep deformation occurring at each time point [J]) with group TBC, followed by groups TBV and TBE. Group TBC showed the highest nanohardness and elastic modulus; the lowest values were seen in group TBE, reflecting differences in polymer matrix composition. Conclusion: The creep and time for debonding the bracket increased with incorporation of glass fibers at the interface between bracket and enamel. Keywords: adhesive resin, fiber reinforced composites, interpenetrating polymer network, cross linking, creep, recovery

Purpose: To evaluate the effect of water aging of adherend composite on repair bond strength to nanofilled composites with specific fillers using different bonding agents. Materials and Methods: Three nanofilled composites - Beautifil II with S-PRG filler (BE) / Filtek Supreme ultra with nanocluster filler (SP) / Estelite Σ Quick (ES) - and one microhybrid composite, Clearfil APX (AP), were used in this study. The composite disks were immersed in water for different durations (immediate, 1 week, 2 weeks or 1 month), and then the polished surfaces were treated with one of three bonding agents - no treatment (control), application of Clearfil SE One (SE), application of Clearfil SE One plus Clearfil Porcelain Bond Activator (PB) - then filled with a repair composite. The bonded composite disks were subjected to the microshear bond strength (µSBS) test. Additionally, water sorption (W_sp) and solubility (W_sl) of the resin composite were measured. The µSBS data were was statistically analyzed using a three-way ANOVA and t-test with Bonferroni correction for multiple comparisons. Results: Water aging of adherend composite affected the repair bond strength (p 0.05). For BE, SP, and ES, application of an adhesive agent improved repair bond strengths to water-aged composites (p 0.05), but adding a silane coupling agent could not (p > 0.05). For AP, the µSBS significantly increased, with control group SE group PB group (p 0.05). Conclusion: Microhybrid composite was a more suitable material for composite repair than nanofilled composite, due to adhesion to exposed, larger silica fillers. S-PRG filler and nanocluster filler in the nanofilled composites played a slight role in improving their repair bonding performances with the bonding agents tested. Keywords: bond strength, dental materials, resin composite repair, surface treatments, water solubility, water sorption

Purpose: To compare the the loss of retention and color match of glass-ionomer cements (GIC) and resin-based composites (RC) in noncarious cervical lesions. Other secondary outcomes (surface texture, marginal adaptation, marginal discoloration, and secondary caries) were evaluated in a systematic review and meta-analysis. Materials and Methods: A comprehensive search was performed in PubMed, Scopus, Web of Science, LILACS, BBO, and Cochrane. We included only randomized clinical trials. The quality of the evidence for each outcome was assessed using the GRADE tool. Results: A total of 1530 articles were identified, but only 19 reports remained for analysis, all of which were judged to possess "unclear" risk of bias. GIC showed higher retention rates in all follow-ups (1 to 3 years, p 0.0001; at 5 years, p 0.00001). No difference was observed for marginal discoloration, marginal adaptation and secondary caries in all follow-ups (p > 0.05). RC showed better color match than GIC only at 2 years (p = 0.03). Higher roughness was observed in GIC in all follow-ups (at 1 year p = 0.0003; at 3 years p = 0.0004). Quality of evidence was graded as moderate or low due to unclear risk of bias and imprecision in some outcomes. Conclusion: The loss of retention of RMGIC/GIC was inferior to that of RC, but a higher roughness was observed in the RMGIC/GIC when compared to RC in all follow-ups of the clinical studies evaluated. In addition, the color match was better with RC only in the 2-year follow-up when compared to GIC. The quality of evidence was judged as moderate to low in these two outcomes. Keywords: glass-ionomer cement, noncarious cervical lesions, resin composite, adhesives, systematic review, clinical evaluation

Purpose: To evaluate the bonding efficacy of 4-META/MMA-TBB resin to highly translucent zirconia subjected to various surface treatments. Materials and Methods: Highly translucent zirconia specimens (Zpex Smile, Tosoh; 11.5 mm diameter, 5.0 mm thick) were mechanically pre-treated to improve micromechanical interlocking either by sandblasting with 50-µm Al2O3 particles (Kulzer Japan) or subjecting the specimens to a low-pressure plasma treatment (PM100, Yamato), or evaluated using the as-sintered surfaces as controls. Next, specimens from each condition were primed with an MDP-containing primer (PZ Primer, Sun Medical), while some remained unprimed. All specimens were bonded to stainless rods using 4-META/MMA-TBB resin (Super-Bond, Sun Medical). The specimens were stored in ultrapure water at 37°C for 24 h, after which a portion were subjected to 10,000 thermocycles. For all specimens (n=10/group) the tensile bond strength (TBS) was determined with a universal testing machine. The measured values were statistically analyzed using Weibull analysis. Fractographic analysis was performed using a light microscope and an SEM. Results: After aging, Weibull analysis revealed significantly lower bond strengths for both as-sintered and plasma-treated zirconia without a primer treatment. The fractographic analysis showed that these two conditions resulted in a higher frequency of adhesive failure. Conclusion: Chemical pre-treatment with an MDP-containing primer improved bonding efficacy of 4-META/MMA-TBB resin to highly translucent zirconia. In addition, Al2O3 sandblasting resulted in durable bonding of 4-META/MMA-TBB resin to highly translucent zirconia, regardless of chemical pre-treatment. Keywords: highly translucent zirconia, alumina sandblasting, 4-META/MMA-TBB resin, Weibull analysis, MDP primer, tensile bond strength