The Journal of Adhesive Dentistry, 03/2016

Purpose: To evaluate the effect of a novel surface treatment intended to improve bond strength to high-translucency zirconia. Materials and Methods: Fully sintered high-translucency zirconia disks (Incoris TZI) were divided into four groups according to the surface treatment received: modified fusion sputtering technique, selective infiltration etching, low pressure particle abrasion using 30-μm alumina particles, while 50-μm particle abrasion served as control. Surface roughness was evaluated quantitatively using a contact profilometer. The disks were bonded to pre-aged composite resin disks using a light-polymerized adhesive resin (RelyX ultimate). The bilayered disks were sectioned into microbars and zirconia-resin bond strength was evaluated using the microtensile bond strength test (MTBS). The test was repeated after 3 months of water storage (37°C). Scanning electron microscopic examination of the zirconia resin interface was performed at different magnifications. A repeated measures ANOVA and Bonferroni post-hoc test were used to analyze the data (n = 20, α = 0.05). Results: One-way ANOVA revealed significant differences in average surface roughness (Ra) between the tested groups (p 0.001). The highest Ra value was recorded for fusion sputtering (12.23 ± 0.11 μm), followed by 50-μm particle abrasion (6.400 ± 0.887), then low pressure 30-μm particle abrasion (2.4 ± 0.15 μm), while the lowest surface roughness was recorded for the selective infiltration group (0.368 ± 0.04 μm). Modified fusion sputtering and selective infiltration etching produced significantly higher MTBS values at each of the tested intervals (p 0.001) compared to particle abrasion using different particle sizes. Water storage resulted in reduction in the bond strength of 30-μm abraded specimens, which was attributed to structural defects observed at the zirconia/ resin interface. Scanning electron microscopic examination revealed a nanoporous surface characteristic of selective etching surface treatment, and modified fusion sputtering resulted in the creation of surface-fused microbeads. Conclusion: Within the limitations of this study, selective infiltration etching and modified fusion sputtering techniques established a strong, stable, durable bond to high-translucency zirconia. Keywords: high-translucency zirconia, microtensile bond, surface treatment, selective etching, fusion sputtering

Purpose: To evaluate the effect of a scrubbing technique with one-step self-etching adhesives on bond strengths and nanoleakage expression at the resin/dentin interface. Materials and Methods: Flat human dentin surfaces bonded with one of two mild self-etching adhesives, SE One (SE) or Scotchbond Universal (SU) applied either with scrubbing or without scrubbing technique, were prepared (n = 5). The microtensile bond strengths (μTBS), SE micrographs of morphological changes on treated dentin surfaces, and expression of nanoleakage along the bonded dentin interfaces as shown with TEM were evaluated. μTBS data were analyzed using two-way ANOVA and the post-hoc t-test at the significance level of 0.05. Results: The scrubbing technique had a significant positive effect on the μTBS of SU (p 0.05), while it produced no significant difference for SE (p > 0.05). Morphological evaluation of the treated dentin surfaces demonstrated that SU with scrubbing showed the highest etching ability, followed by scrubbing SE > nonscrubbing SE > nonscrubbing SU. In the nonscrubbing groups, nanoleakage formation using SU exhibited a reticular pattern throughout the hybridized complex, whereas with SE, water-tree nanoleakage was only found in the adhesive layer at dentinal tubule orifices. The scrubbing groups of both adhesives did not exhibit any nanoleakage expression. Conclusion: Using a scrubbing technique when applying mild self-etching adhesives could improve resin monomer infiltration into dentin, chase water on adhesive surfaces, and facilitate smear layer removal. Keywords: scrubbing, one-step self-etching adhesive, dentin, bond strength, nanoleakage, smear layer, water chasing

Purpose: To investigate the effects of an experimental 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-based one-step self-etching adhesive (EX adhesive) applied to enamel and dentin on the production of calcium salt of MDP (MDP-Ca salt) and dicalcium phosphate dehydrate (DCPD) at various periods. Materials and Methods: The EX adhesive was prepared. Bovine enamel and dentin reactants were prepared by varying the application period of the EX adhesive: 0.5, 1, 5, 30, 60 and 1440 min. Enamel and dentin reactants were analyzed using x-ray diffraction and solid-state phosphorus-31 nuclear magnetic resonance (31P NMR). Curvefitting analyses of corresponding 31P NMR spectra were performed. Results: Enamel and dentin developed several types of MDP-Ca salts and DCPDs with amorphous and crystalline phases throughout the application period. The predominant molecular species of MDP-Ca salt was determined as the monocalcium salt of the MDP monomer. Dentin showed a faster production rate and greater produced amounts of MDP-Ca salt than did enamel, since enamel showed a knee-point in the production rate of the MDP-Ca salt at the application period of 5 min. In contrast, enamel developed greater amounts of DCPD than did dentin and two types of DCPDs with different crystalline phases at application periods > 30 min. The amounts of MDP-Ca salt developed during the 30-s application of the EX adhesive on enamel and dentin were 7.3 times and 21.2 times greater than DCPD, respectively. Conclusion: The MDP-based one-step adhesive yielded several types of MDP-Ca salts and DCPD with an amorphous phase during the 30-s application period on enamel and dentin. Keywords: one-step self-etching adhesive, MDP, calcium salt of MDP, nuclear magnetic resonance, x-ray diffraction

Purpose: To investigate the influence of atmospheric pressure plasma (APP) treatment on the microtensile dentin bond strength of two etch-and-rinse adhesive systems, after one week and one year of water storage, and additionally to observe the micromorphology of resin/dentin interfaces under scanning electronic microscopy (SEM). Materials and Methods: The occlusal enamel was removed from third human molars to expose a flat dentin surface. The teeth were then randomly divided into six groups (n = 7), according to two adhesives (Optibond FL and XP-Bond) and three APP treatments (untreated dentin [control], APP application before or after acid etching). After performing the composite resin buildup on bonded dentin, the teeth were sectioned perpendicularly to the bonded interface to obtain beam-shaped specimens (cross-sectional area of ~0.9 mm2). The specimens were tested in tension until failure after one week and one year of water storage (1.0 mm/min rate). Bond strength data were analyzed by three-way ANOVA and Tukey's post-hoc test (α = 0.05%). Bonded beam specimens from each tooth were also prepared for interfacial SEM investigation. Results: At one week, APP treatment applied after acid etching increased the dentin bond strength for XP Bond, while no effect was observed for Optibond FL. After one year, the bond strength of XP Bond decreased in groups where APP was applied after etching. The evaluation time did not influence the bond strength for Optibond FL. Conclusion: One-year evaluation did not show any sign of degradation of interfacial structures in any group. Application of APP to etched dentin combined with a two-step etch-and-rinse adhesive significantly increased bond strength at one week, but the effect was not stable after one year and was adhesive dependent. Keywords: plasma, microtensile, dentin adhesion

Purpose: To evaluate the acid-base resistant zone (ABRZ) at the adhesive/enamel interface of self-etching adhesives with or without prior phosphoric acid etching. Materials and Methods: Four adhesives were used in 8 groups: Clearfil SE Bond (SEB), Optibond XTR (XTR), Scotchbond Universal Adhesive (SBU), and Clearfil BOND SE ONE (ONE) without prior phosphoric-acid etching, and each adhesive with phosphoric acid etching for 10 s (P-SEB, P-XTR, P-SBU and P-ONE, respectively). After application of self-etching adhesives on ground enamel surfaces of human teeth, a flowable composite was placed. For observation of the acid-base resistant zone (ABRZ), the bonded interface was exposed to demineralizing solution (pH 4.5) for 4.5 h, followed by 5% NaOCl with ultrasonication for 20 min. After the acid-base challenge, morphological attributes of the interface were observed using SEM. Results: ABRZ formation was confirmed in all groups. The funnel-shaped erosion beneath the interface was present in SBU and ONE, where nearly 10 to 15 μm of enamel was dissolved. With phosphoric acid etching, the ABRZs were obviously thicker compared with no phosphoric acid etching. Conclusion: Enamel beneath the bonding interface was more susceptible to acid dissolution in SBU and ONE. In the case of the one-bottle self-etching adhesives and universal adhesives that intrinsically have higher pH values, enamel etching should be recommended to improve the interfacial quality. Keywords: enamel, multimode, selective-acid etching, acid-base resistant zone, self-etching

Purpose: To evaluate the microshear bond strength of tri-calcium silicate-based materials to different restorative materials. Materials and Methods: Thirty-five disks of TheraCal LC and Biodentine were fabricated using teflon molds according to manufacturers' instructions. Then the specimens were randomly divided into 7 groups according to the materials applied: Fuji IX, Fuji II, Equia Fil, Vertise Flow, Filtek Bulk Fill Posterior Restorative, Filtek Z250 with Prime&Bond NT and with Clearfil SE Bond. All restorative materials were placed onto the disks using tygon tubes. Following a storage period, the specimens underwent microshear bond strength testing in a universal testing machine, and fracture modes were analyzed. Data were analyzed using one-way ANOVA and Tukey's post-hoc test. Results: For all restorative materials, TheraCal LC showed significantly higher μSBS values compared to Biodentine. GIC based materials showed the lowest μSBS for TheraCal and Biodentine. For Biodentine, Filtek Z250 applied with Prime&Bond NT and Filtek Bulk Fill Posterior Restorative applied with Scotchbond Universal Adhesive exhibited the highest μSBS, while Filtek Z250 applied with Clearfil SE Bond revealed the highest bond strength to TheraCal LC. Conclusion: For all restorative materials tested in this study, TheraCal LC showed higher μSBS compared to Biodentine. For both TheraCal LC and Biodentine, the placement of GIC-based materials prior to composite resin restorations might decrease the bond strength. Composite resins applied with self-etching adhesives increased the bond strength of TheraCal LC; however, for Biodentine, application of etch-and-rinse adhesives may improve the adhesion of composite resins. Keywords: TheraCal LC, Biodentine, microshear bond strength, tri-calcium based cements, restorative materials

Purpose: To evaluate the effect of different bonding strategies on short- and long-term bis-GMA-based resin cement bond strengths to zirconia. Materials and Methods: One hundred twenty samples of fully-sintered zirconia (Prettau Zirconia) were sandblasted and randomly distributed into 5 groups (n = 24): UA: Scotchbond Universal Adhesive; SZP: Signum Zirconia Bond I + II; ZPP: Z-Prime Plus; EXP: MZ experimental primer; CO: no primer application (control). After performing these surface treatments, translucent tubes (0.8 mm diameter and 1.0 mm height) were placed on the zirconia specimens, and bis-GMA-based cement (Duo-Link) was injected into them and light cured. Specimens were tested for microshear bond strength either 24 h or 6 months (m) after water storage (37°C) and surfaces were characterized by SEM and EDX. Two-way ANOVA and Tukey's post-hoc test (p 0.05) were used to evaluate bond strength results. Results: The mean bond strengths (MPa ± SD) were: UA=14.6 ± 4.7^a (24 h); 16.0 ± 4.8^a (6 m); SZP = 14.0 ± 5.4^ab (24 h); 11.9 ± 2.6^ab (6 m); ZPP=8.0 ± 1.8^b (24 h); 8.6 ± 3.3^b (6 m); EXP = 1.2 ± 0.5^c (24 h); 0.6 ± 0.7^c (6 m); CO=1.0 ± 1.2^c (24 h); 1.3 ± 1.2^c (6 m). Bonding strategy significantly influenced bond strength (p = 0.0001), but storage time did not (p = 0.841). Groups UA and SZP showed a homogeneous layer covering the zirconia surface. In these groups, EDX demonstrated the presence of phosphorus. Group ZPP resulted in a nonhomogeneous layer, exposing the zirconia substrate underneath. EXP application resulted in an undetectable layer. Conclusion: Water storage did not affect resin cement bond strengths to zirconia irrespective of the surface treatment. Bis-GMA-based resin cement bond strengths to zirconia are affected by specific bonding strategies. Keywords: dental ceramic, zirconia primers, microshear bond strength, energy dispersive x-ray spectroscopy, resin cement, multimode adhesive

Purpose: Pull-out testing was used to determine the tensile load (TL) and tensile strength (TS) of five different fiber post systems bonded to human intracanal dentin. Materials and Methods: 120 caries-free premolars, canines, and maxillary central incisors were divided into 5 different groups for 5 fiber post systems (n = 24): 1. RelyX Fiber Post 3D (RX3D); 2. RelyX Fiber Post (RX); 3. Luxa- Post (LP); 4. FibreKleer 4X Tapered Post (FK); 5. ParaPost Taper Lux (PP). The teeth were prepared and posts inserted. Core buildups were performed with the corresponding product's resin composite. All specimens were stored in water for 24 h at 37°C. TL and TS were tested on half of the specimens (n = 12/group). The remaining samples were thermocycled (10,000 x 5°C/55°C) before testing. TL was directly measured and TS was calculated using the bonding surface. Failure modes were identified using a stereomicroscope. Data were analyzed using twoway ANOVA with the post-hoc Scheffé test, as well as the chi-squared test (p 0.05). Results: FK and LP resulted in the lowest mean TL but were not significantly different from those of RX and RX3D. The highest mean TL and TS were observed for PP. Nevertheless, PP fell within the same statistical subset as RX3D and RX. Thermocycling showed no impact on the results. RX3D predominantly showed debonding of the post plus core buildup from the tooth; all other systems mainly demonstrated detachment of the core from the posts. Conclusion: PP, RX, and RX3D together with an adhesive core buildup yielded the highest bond strength to human dentin. Parameters TL and TS showed the same tendencies and statistical evidence. Keywords: fiber post, retention load, retention strength

Purpose: To evaluate the chemical interaction between synthetic hydroxyapatite (HAp) and polyalkenoic acid copolymer- based (also known as Vitrebond copolymer [VCP]) adhesives. Materials and Methods: Six dentin adhesive formulations were used: 1) Adper Single Bond Plus (SB); 2) SB formulation without VCP (SBnoVCP); 3) Adper Easy Bond (EB); 4) EB formulation without VCP (EBnoVCP); 5) Scotchbond Universal adhesive (SBU); 6) SBU formulation without VCP (SBUnoVCP). Each adhesive was mixed with HAp, polymerized, and analyzed using FTIR and 13C/31P NMR spectroscopy. Results: The FTIR spectra of SB+HAp indicated that the carbonyl group changed absorption wavenumber compared to that of SBnoVCP+HAp. 13C NMR analysis showed that the presence of methacrylated phosphoric esters in the EB and SBU formulations led to similar carbonyl resonance with or without VCP. 31P NMR revealed a resonance shift at 0.5 ppm for SB+HAp, EB+HAp and SBU+HAp spectra. In comparison with EB+HAp and SBU+HAp, a slight fade-out of the same resonance shift for EBnoVCP+HAp and SBUnoVCP+HAp was observed without completely disappearing, respectively, meaning that VCP might induce a modification of phosphorus moieties in addition to the ionic interaction between phosphate ester groups and HAp. Conclusion: Our data suggests that a chemical interaction occurred between VCP-containing adhesives and synthetic HAp. Keywords: dentin-bonding agents, glass-ionomer cements, hydroxyapatites, spectroscopy, Fourier Transform Infrared