One-year bonding performance of one-bottle etch-and-rinse adhesives to dentin at different moisture conditions

Abstract

This study aimed to investigate the one-year bond strengths to dentin of one-bottle etch-and-rinse adhesive systems applied under different moisture conditions. Class V cavities were prepared in bovine incisors and randomly allocated (n?=?8) according to the type of adhesive system used – SB (Adper? Single Bond 2); PB (Prime & Bond 2.1); and XPB (XP Bond) – and the moisture condition kept in the cavity – moist, over-wet, and over-dry. Filtek? Z250 was used for teeth restoration. Specimens for microtensile bond strength (µTBS) test were obtained and stored in water for 24?h or 1?year, and submitted to mechanical testing. Data were analyzed using t-tests, ANOVA and the Holm–Sidak post hoc test (α?=?0.05). Weibull analysis was used to verify the reliability of specimens. The type of adhesive and the moisture condition of the substrate affected the µTBS. At 24?h, SB performed better under the moist and over-wet conditions. At 1?year, SB, PB, and XPB showed the greatest percentage reduction at the moist (～38%), over-wet (100%), and over-dry (100%) conditions, respectively. The reliability of adhesives was affected by the variable factors tested. In conclusion, the solvent composition of adhesives and the moisture condition of the substrate play an important role in the bond strength and bonding stability of resin-based restorations, as well as on the reliability of the adhesive interfaces over time.     

Incorporation of inorganic fillers into experimental resin adhesives: Effects on physical properties and bond strength to dentin

This study investigated the effect of different monomeric systems and inorganic fillers on the physical properties of experimental resin adhesives and on the immediate and 6-month bond strength to dentin. Two, 2-step self-etch adhesive systems were prepared: two primers (constituted of GDMA-P, ethanol, water, and HEMA or PEG(400)-UDMA) and two adhesives (constituted of Bis-GMA, TEGDMA, and HEMA or PEG(400)-UDMA). Next, the adhesives were allocated into three groups according to filler incorporated: unfilled (control), silica (SiO₂), or ytterbium trifluoride (YbF₃). Degree of conversion (DC, after 30 and 60 s of light-activation), water sorption (WS) and solubility (SL), and flexural strength (σ) and modulus (E_f) tests were performed for all adhesives. A microtensile bond strength (µTBS) test to dentin was evaluated after 24 h (immediate) and 6 months (6-month) of water storage using a universal testing machine (DL500, EMIC). Data were analyzed using statistical tests (α=5%). The adhesives showed similar DC at a same light exposure time, although light-activation for 60 s improved conversion of monomers. The unfilled HEMA-containing adhesive showed higher WS, SL, σ and E_f compared to others. The incorporation of fillers into the adhesives did not affect negatively the immediate µTBS results; however, after 6 months the presence of SiO₂ impaired in complete premature failures, and the presence of YbF₃ reduced the µTBS in the PEG(400)-UDMA-based group. The unfilled HEMA-containing group also reduced bond strength after 6 months of water storage. In conclusion, depending on the resin matrix composition, YbF₃ seems to be a good option for reinforcing adhesive systems.     

Effects of simulated pulpal pressure,mechanical and thermocycling challenge on the microtensile bond strength of resin luting cements

This study aimed at comparing the microtensile bond strength (µTBS) of three simplified luting strategies after different aging processes. Sixty human molars were prepared to expose flat middle dentin surfaces which received the following luting procedures: (i) SB+ARC – two-step etch-and-rinse adhesive+conventional resin cement (Adper Singlebond 2+RelyX ARC, 3M-ESPE); (ii) S3+PAN – one-step self-etch adhesive+conventional resin cement (Clearfil S3+Panavia F2.0, Kuraray Medical); (iii) U200 – self-adhesive resin cement (RelyX U200,3M-ESPE). The specimens were finally restored by indirect resin composite procedures (Filtek Z100,3M-ESPE). The aging regimens were water storage at 37 °C for one week (control), one week of 20 cm H₂O simulated pulpal pressure (SPP), 200,000 mechanical loading (ML) cycles, or 5000 thermal cycles (TC). The µTBS data was analyzed by two-way ANOVA and Tukey's test (α=0.05). SB+ARC showed significantly higher µTBS for control and all aging processes (p<0.001). Nevertheless, TC had no effect on the bond strength of SB+ARC. No difference in µTBS was observed between S3+PAN and U200 after SPP (p=0.251), but significant lower values were found for U200 after ML (p=0.010) besides being superior in the control groups (p<0.001). For U200, all ageing regimens induced significant reductions in the bond strength (p<0.001) with a more pronounced negative effect after ML. S3+PAN showed significant lower bond strength (p=0.010) only after ML aging. Two-step etch-and-rinse adhesive associated with dual-curing conventional resin cement may present the highest overall µTBS. However, the use of S3 one-step self-etch adhesive along with conventional resin cements may provide the most stable luting performance under the tested aging strategy.     

Bond durability of contemporary universal adhesives: effect of dentin treatments and aging

The aim of this in vitro investigation was to evaluate the effects of different dentin treatments on µTBS values of three different universal adhesives. Sixty extracted bovine incisors were used. The teeth were horizontally sectioned from the enamel-cement junction and embedded in an acrylic resin. Enamel was removed with 180-grit SiC paper to expose dentin. The exposed dentin surfaces were further polished with 600-grit SiC paper to provide a standardized smear layer. Teeth were randomly divided into three groups, according to the universal adhesives: All-Bond Universal, Single Bond Universal, and G-Bond Plus. Each group was then assigned into four subgroups, according to the dentin treatments: etch-and-rinse mode (ER), ER + 2% chlorhexidine (CHX), ER + %2.5 genipin (GE), and self-etch mode (SE). Samples were longitudinally sectioned across the bonded-interfaces to obtain resin-dentin beams. Beams were prepared from the same teeth were randomly and equally divided into two groups: immediate µTBS testing and µTBS testing after 6-month. The failure loads were recorded in MPa, and failure modes were evaluated at 30× magnification. The data were analyzed using a two-way ANOVA, to determine the effects of dentin treatment and storage time, and the interaction of these two factors on the µTBS of universal adhesives. Dentin treatments were showed significant differences (p?<?0.05). ER mode exhibited higher µTBS than SE mode. However, universal adhesives were more durable in the SE mode than ER mode. Also, chlorhexidine treatment significantly improved adhesive performance of all universal adhesives, while no significant improvement was detected with genipin treatment.     

Assessment of the initial and aged dentin bond strength of universal adhesives

This study evaluated the effect of mechanical loading on microtensile bond strengths (μTBS) of universal adhesives to dentin and quantified adhesive dentin penetration using micro-Raman spectroscopy. Human molars had occlusal dentin exposed and were allocated into eight groups: All-Bond Universal and Scotchbond Universal using etch-and-rinse and self-etch approaches, Adper Prompt L-Pop, Adper Single Bond Plus, Clearfil SE Bond, and Optibond FL. Following bonding procedures and build-ups, specimens were either stored in water at 37 °C for 24 h or mechanically loaded (50,000 cycles, 50 N) prior to μTBS test. Additional teeth were prepared for micro-Raman analysis of adhesive penetration and FE-SEM. Data were analyzed by two-way ANOVA and Tukey׳s post hoc test (P<0.05). Mechanical loading had no deleterious effect on μTBS with the exception of Adper Prompt L-Pop. Incomplete infiltration of the demineralized dentin was noticed for adhesives using the etch-and-rinse approach and for Scotchbond Universal in the self-etch approach.     

The effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramics to dentin

This study evaluated the effect of different cementing strategies and adhesive interface aging on microtensile bond strength (μTBS) of lithium disilicate ceramic (IPS e.max CAD) to dentin. Forty coronal dentin fragments were randomly assigned to four groups according to the cementing strategy used to bond lithium disilicate ceramic to coronal dentin surface (n = 10): U200 (self-adhesive resin cement (RC) RelyX U200®/3 M ESPE), SBU (single-step self-etching adhesive system (AS) Single Bond Universal®/3 M ESPE + RelyX ARC®/3 M ESPE RC), AdperSB (two-step etch-and-rinse AS Single Bond 2®/3 M + RelyX ARC®/3 M ESPE RC) and Scotchbond (three-step etch-and-rinse AS Scotchbond Multi-Purpose®/3 M + RelyX ARC®/3 M RC). After 48 h, the ceramic-tooth blocks were sectioned perpendicular to the adhesive interface in the form of sticks and randomly subdivided into two groups according to when they were to be submitted to μTBS testing: immediately or 6 months after storage in water. Some sticks were kept for analysis of the adhesive interface by scanning electron microscopy (SEM). The μTBS test was performed in a universal testing machine (0.5 mm/min). The data (MPa) were analyzed using split-plot ANOVA and Tukey’s test (α = 0.05). Water storage decreased μTBS in all cementing strategies. The μTBS was greatest in the Scotchbond group and lowest in the U200 group, at both storage times. No signs of interface degradation were detected under SEM after water storage. In conclusion, water storage decreased bond strength, regardless of the adhesive cementation strategy, and that the three-step adhesive system/dual-cure resin cement ultimately performed better in terms of bond strength.     

Effect of irradiation source on the dentin bond strength of a one-bottle universal adhesive containing an amide monomer

One-bottle universal adhesives have been widely used because of their simplicity of bonding procedures for various dental materials. The present study evaluated the effect of the polymerization light source on the micro-tensile bond strengths of a universal adhesive (Clearfil Universal Bond Quick) to dentin in comparison with a one-bottle self-etch adhesive (Clearfil S³ Bond Plus) and two 2-step self-etch adhesives (Clearfil SE Bond and Clearfil SE Bond 2). The adhesives were applied to extracted human dentin according to the manufacturer’s instructions and irradiated using either a quartz-tungsten-halogen (QTH) or blue light-emitting diode (LED). Subsequently, a resin composite was incrementally built on each adhesive and light-cured using the QTH. The bonded specimens were sectioned and subjected to micro-tensile bond strength tests. Both the type of adhesive and the light source were found to statistically affect the bond strength, with no interactions. The LED gave greater bond strength than the QTH. The bond strengths of the two-step adhesives were significantly higher than those of the one-bottle products, irrespective of the light source. The Clearfil Universal Bond Quick exhibited significantly higher bond strength than the Clearfil S³ Bond Plus. LED curing improved the performance of Clearfil Universal Bond Quick, and this product generated bond strength superior to that of the existing one-bottle adhesive Clearfil S³ Bond Plus.     

Development of a simplified etch-and-rinse adhesive containing niobiophosphate bioactive glass

PurposeThe aim of this study was to evaluate radiopacity, degree of conversion (DC), Knoop hardness (KHN), ultimate tensile strength (UTS) and microtensile bond strength (µTBS) to dentin of an experimental adhesive containing micro-filler of niobium–phosphate bioactive glass (NPG).Materials and methodsThe NPG glass was produced by fusion of NbO₅, Na₂CO₃, CaO, (NH₄)₂HPO₄ at 1400 °C. After cooling, the glass was ground to a mean particle size<25 µm, and either added (40 wt%) to an experimental adhesive resin mix containing monomers and solvent, or not. The DC of the adhesives was evaluated by Fourier transform infrared spectroscopy. Flat dentin surfaces were obtained from 16 molar teeth, and prepared for use to evaluate µTBS (n=8). An hourglass-shaped matrix (UTS and KHN) or disk-shaped matrix (radiopacity) was filled with adhesive and light-polymerized. The data from each test were analyzed by appropriate statistical methods.ResultsThe presence of glass particles made the adhesive system radiopaque. Addition of bioactive NPG glass particles to the adhesive system prevented decreases in bond strength; reduced the UTS and increased DC and KHN. All groups showed predominance of adhesive failure mode.ConclusionAddition of 40% NPG glass may be an alternative to obtain an adhesive system with adequate mechanical and bond strength to dentin properties.     

The sonic application of universal adhesives in self-etch mode improves their performance on enamel

The objective of this study was to evaluate the effect of sonic application of universal adhesives on the enamel microshear bond strengths (µSBS), in situ degree of conversion (DC) and etching pattern. Ninety-six extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 12 groups, according to the combination of 1) adhesive system (All-Bond Universal [ABU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and 2) adhesive application mode (manual active etch-and-rinse [M-ER], manual active self-etch [M-SE], and sonic vibration self-etch [S-SE]). Specimens were stored in water at 37 °C during 24 h and tested at 1.0 mm/min (µSBS). DC was evaluated in the enamel-resin interfaces using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field- emission scanning electron microscope. Data were analyzed with two-way ANOVA and Tukey's test (α = 0.05). S-SE application increased µSBS and DC for all universal adhesives when compared to M-SE (p < 0.05). S-SE application resulted in mean bond strengths that were statistically similar to those obtained with the respective ER application mode (p > 0.05). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. An improvement in etching ability was observed in S-SE application compared to M-SE application. In light of the improved performance of universal adhesives when applied sonically in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel. The sonic application of universal adhesives in self-etch mode may be a practical alternative to enamel etching.     

Effect of Different Application Techniques of All-in-One Adhesives on Microtensile Bond Strength to Sound and Caries-Affected Dentin

The aim of this study was to evaluate the microtensile bond strength of two all-in-one self-etch adhesives applied to sound and caries-affected dentin with four different application techniques. Forty extracted third molars with occlusal caries were randomly divided into four groups for G-Aenial Bond and S3 Bond: (1) according to manufacturer's instructions; (2) with acid etching before applying adhesives; (3) doubling adhesive application time; and (4) doubling adhesive coating. Teeth were sectioned to obtain 1-mm- ± 0.2-mm-thick dentin sticks and subjected to a tensile force. For G-Aenial Bond, doubling the time and application of two consecutive coats produced significantly higher strength than that obtained by following manufacturers' instructions and acid etching application to sound dentin. Prior acid etching and application of two consecutive coats to caries-affected dentin generated significantly higher bond strength than that using other techniques. For S3 Bond, there was no significant difference between application techniques in caries-affected dentin. For sound dentin, double-time application of S3 Bond produced significantly higher strength than application according to the manufacturers' instructions. Compared to the application according to manufacturer's instructions, acid etching before applying adhesives, doubling application time, and doubling the coating had a positive effect on bond strength to caries-affected dentin for all-in-one adhesives.     

Deproteinization stabilises dentin bonding of self-adhesive resin cements after thermocycling

This study examined the effect of deproteinization on the microtensile dentin bond strength (µTBS) and nanoleakage (NL) of conventional and self-adhesive resin cements after 24 h or after 20,000 thermocycles. Occlusal dentin of thirty-two human molars were distributed into four groups according to the type of cement used: conventional or self-adhesive; and the strategy of luting: RelyX ARC/Single Bond 2 (RAc) following the manufacturer׳s instructions (control), RelyX ARC/Single Bond 2 (RAd) applied after dentin deproteinization; RelyX U200 (RUc) following the manufacturer´s instructions (control); RelyX U200 (RUd) applied after dentin deproteinization. The specimens were cut into non-trimmed dentin–composite sticks and the half sticks of each group were subdivided into two subgroups: 24 h water storage and after 20,000 thermal cycles, before microtensile bond test. For NL, 5 bonded sticks from each subgroup were prepared and analyzed under SEM. Three-way ANOVA showed that the dentin deproteinization increased the µTBS of both cements, although the RAd group showed a decrease on the µTBS after thermocycling. Chi-square test showed significant loss of specimens by premature failure for the groups after thermocycling, except for the RUd group. The dentin deproteinization improved the initial µTBS and decreases the NL of both cements tested, but, after thermocycling, this technique is only effective for RelyX U200.     

Biodegradation of caries-affected dentin bonding interface of fluoride and MDPB-containing adhesive system

The aim of this study was to evaluate the effect of a fluoride/MDPB (12-methacryloyloxydodecylpyridinium bromide)-containing adhesive system on the durability of a bond to permanent artificially induced caries-affected dentin (CAD) exposed to Streptococcus mutans culture and water storage. Twelve third molars were selected. Flat dentin surfaces were submitted to artificial caries development in S. mutans and Broth heart infusion (BHI). Caries-infected dentin was removed with burs according to clinical criteria and CAD cavities were restored with Adper Scotchbond Multi-Purpose (SBM) and Clearfil Protect Bond (CPB). Nontrimmed resin–dentin bonded interfaces (1 mm²) were stored in S. mutans+BHI for 3 days, in deionized water for 3 months, and afterwards subjected to microtensile bond strength test (μTBS). The control group was not submitted to storage and immediate μTBS testing was performed. Fractographic analysis was performed after μTBS testing. Four molars were restored as described, and morphological evaluation hybrid layer (HL) was performed by scanning electron microscopy (SEM). Two-way ANOVA with split-plot design and Tukey′s tests were performed. No difference was found between μTBS values of SBM and CPB irrespective of groups. Significant decrease was observed in μTBS values after S. mutans culture and water storage, but without difference between them. CPB had more homogenous hybrid layer than SBM. Fluoride/MDPB-containing adhesive system did not prevent degradation of CAD bond strength in both degradation methods.     

Effect of adhesive air-drying time on bond strength to dentin: A systematic review and meta-analysis

ObjectiveThe objective of this review was to evaluate the effect of air-drying time on the adhesion (bond) strength of adhesives to dentin in previously published studies and to conduct a meta-analysis to quantify the differences in the bond strength obtained after the different air-drying times.MethodsAn electronic search was performed using the Medline, Cochrane library, and Scopus databases. The included studies were laboratory studies that investigated the effect of adhesive air-drying time on adhesion (bond) strength of resin-based adhesives to coronal dentin. Studies which evaluated the effect of adhesives air-drying time on physical and mechanical properties of adhesives, interfacial properties, bond strength to root dentin, enamel, or bond strength of indirect composite restoration or orthodontic bracket, were excluded. The methodological quality of included studies was assessed. Meta-analysis was performed using Comprehensive Meta-Analysis software, version 2.0 (Biostat, Englewood, NJ, USA). The results of the meta-analysis were subjected to a further one-way analysis of variance, followed by the Tukey post hoc multiple comparison using R-software, version 3.4.3 (R Foundation for Statistical Computing, Vienna, Austria).ResultsThirteen studies fulfilled the inclusion criteria of this review, while only five studies were included in meta-analysis. The effect of adhesive air-drying time on the bond strength was significant in eight studies (61.5%), material-dependent in four studies (30.8%), and not significant in one study (7.7%). Eight studies (61.54%) presented a medium-risk of bias, three studies (23.08%) presented a low-risk of bias, and two studies (15.38%) presented a high-risk of bias. The analysis of micro-tensile bond strength (μTBS) of adhesives showed statistically significant difference between different air-drying times (p<0.05). The highest mean μTBS values were: 52.9 ± 11.38 MPa (obtained after air-drying of adhesives for 30 s), followed by 48.26 ± 9.77 MPa (15 s), and 37.76 ± 1.45 (25 s), while the lowest mean μTBS was 33.98 ± 2.30 MPa and 35.79 ± 6.63 MPa (5 s) obtained after 10 s and 5 s respectively.ConclusionThe air-drying time of adhesives is crucial to the adhesion strength to coronal dentin. Adhesive air-drying for shorter durations (5–10 s) may be insufficient to obtain adequately durable bonding to dentin, instead, Air-drying should be performed for longer durations (15–30 s), considering the pressure and distance of air-drying source.     

Effect of a Novel Quaternary Ammonium Methacrylate Polymer (QAMP) on Adhesion and Antibacterial Properties of Dental Adhesives

This study investigated the resin–dentin bond strength (μTBS), degree of conversion (DC), and antibacterial potential of an innovative adhesive system containing a quaternary ammonium methacrylate polymer (QAMP) using in situ and in vitro assays. Forty-two human third molars were flattened until the dentin was exposed and were randomly distributed into three groups of self-etching adhesive systems: Clearfil™ SE Bond containing 5% QAMP (experimental group), Clearfil™ Protect Bond (positive control) and Clearfil™ SE Bond (negative control). After light curing, three 1 mm-increments of composite resin were bonded to each dentin surface. A total of thirty of these bonded teeth (10 teeth per group) was sectioned to obtain stick-shaped specimens and tested under tensile stress immediately, and after 6 and 12 months of storage in distilled water. Twelve bonded teeth (4 teeth per group) were longitudinally sectioned in a mesio-to-distal direction to obtain resin-bonded dentin slabs. In situ DC was evaluated by micro-Raman spectroscopy. In vitro DC of thin films of each adhesive system was measured using Fourier transform infrared spectroscopy. In vitro susceptibility tests of these three adhesive systems were performed by the minimum inhibitory/minimum bactericidal concentration (MIC/MBC) assays against Streptococcus mutans, Lactobacillus casei, and Actinomyces naeslundii. No statistically significant difference in μTBS was observed between Clearfil™ SE Bond containing 5% QAMP and Clearfil™ SE Bond (p > 0.05) immediately, and after 6 and 12 months of water storage. However Clearfil™ Protect Bond showed a significant reduction of μTBS after 12 months of storage (p = 0.039). In addition, QAMP provided no significant change in DC after incorporating into Clearfil™ SE Bond (p > 0.05). Clearfil™ SE Bond containing 5% QAMP demonstrated MIC/MBC values similar to the positive control against L. casei and A. naeslundii and higher than the negative control for all evaluated bacterial strains. The use of QAMP in an adhesive system demonstrated effective bond strength, a suitable degree of conversion, and adequate antibacterial effects against oral bacteria, and may be useful as a new approach to provide long-lasting results for dental adhesives.     

Efficacy of different surface treatments and universal adhesives on the microtensile bond strength of bulk-fill composite repair

Abstract

The purpose of this in vitro study was to evaluate the influence of different surface treatments and aging on the microtensile bond strength (μTBS) of bulk-fill composite resins. Bulk-fill composites (Filtek One; 3M ESPE) randomly received five different surface treatments: (1) no treatment, control, (2) 37% phosphoric acid etching (PA), (3) 9% hydrofluoric acid etching (HF), (4) air-borne particle abrasion with 50-μm alumina particles (Al₂O₃), (5) tribochemical silica coating (CoJet). Following, the specimens were divided into three subgroups according to universal adhesive applied: Clearfil Universal Bond (CU; Kuraray), Prime&Bond Universal (PBU; Dentsply Sirona), or Single Bond Universal (SBU; 3M ESPE). A nanofill composite (Filtek Ultimate; 3M ESPE) was employed as a repair. Bonded specimens were stored in water for 24?h at 37?°C or thermal aged, then subjected to the μTBS test. Additionally, specimens were analyzed with a contact profilometer and were evaluated with scanning electron microscopy. Control and PA treatments were showed the lowest µTBS (p?<?0.05), and there was no significant difference between these two groups (p?>?0.05). Al₂O₃ and CoJet treatments generally exhibited a similar influence on µTBS values. In addition, a correlation was found between surface roughness and bond strength (r?=?0.831). CoJet resulted in significantly higher repair µTBS values when compared to the other surface treatments. In addition, the use of silane-containing universal adhesive was increased the cohesive failure rate and maintained the repair µTBS values after thermocycling.     

Efficacy of multi-mode adhesive systems on dentin wettability and microtensile bond strength of resin composite

Purpose: To evaluate the wetting ability and the microtensile bond strength of adhesive systems in various depths of dentin. Materials and Method: 48 extracted human molars cut in half in buccolingual direction. Buccal and lingual surfaces were used to obtain deep (n = 48) and superficial (n = 48) dentin. Groups were divided into 4 subgroups: Self-etch (CSE), etch&rinse (SB), multi-mode self-etch (SAU) and multimode etch&rinse (EAU) adhesive systems. 3 consecutive contact-angle measurements were obtained: T0- 3 μl drop of distilled water on dentin; T1-Droplet of the adhesive; T2- Distilled water after polymerization of the adhesive. After composite build-ups, microtensile measurements were performed. Contact angle data were analysed with analysis of variance for repeated measures. Bond strength data were analyzed by repeated measures analysis of variance, comparisons were made according to the logarithmic values (p < 0.05). Results: The difference between groups was not significant regardless of dentin depth for all measurements (p < 0.05). All groups except CSE enhanced the wetting ability of the adhesive but reduced the wetting ability of distilled water after application of the adhesive (p < 0.05). Regarding adhesive systems, the groups showed no significant difference between bond strengths to various depths of dentin except SAU (p > 0.05); in SAU, bond strength to deep dentine were significantly higher than superficial dentin (p < 0.05). Regarding adhesives’ bond strength, CSE showed significantly greater values than the other groups (p < 0.05). Conclusion: The cavity depth does not affect the bonding ability for all adhesive systems; self-etch adhesive systems might be a better choice since different adhesives may influence the wetting ability and microtensile bond strength of the dentin substrates.     

Effect of epigallocatechin gallate,green tea extract and chlorhexidine application on long-term bond strength of self-etch adhesive to dentin

This study evaluated the effect of dentin pretreatment with metalloproteinase inhibitors on long-term microtensile bond strength (μTBS) of self-etch adhesive (SEA) to dentin. Thirty-two dentin fragments received pretreatments (n=8): C: control (not treated); GT: 2% green tea extract; CLX: 2% chlorhexidine; EGCG: 2% epigallocatechin gallate. SEAs (Clearfil SE Bond) and resin composite were applied to dentin surface. After 24 h, resin-blocks were cut into sticks submitted to μTBS testing immediately or after 6 months of storage in water. Two-way ANOVA and Tukey test (α=5%) indicated that CLX group showed μTBS values statistically superior to the other groups at immediate testing, whereas those of EGCG group were the lowest (p=0.018). After 6 months, a significant increase in μTBS values was observed for all groups, except for CLX (p=0.018). In conclusion, μTBS increased in dentin pretreatment with EGCG and green tea groups, and in the non-treated group.     

Effect of zinc chloride added to self-etching primer on bond strength to caries-affected dentin and chemical-physical-mechanical properties of adhesives

The aim of this in vitro study was to evaluate the effect over time of zinc chloride (ZnCl₂) incorporated into the primer of a two-step self-etching adhesive system (Clearfil SE Bond, Kuraray - SE) on long-term microtensile bond strength (μTBS) to caries-affected dentin (CAD), and on flexural strength (FS) and conversion degree (CD) of the adhesive. First, the CD of SE with and without 2% (wt) ZnCl₂ solution was evaluated by Fourier transform infrared spectroscopy (FTIR). Then, beam-shaped samples (7 mm × 2 mm x 1 mm) were prepared with the SE primer containing the ZnCl₂ solution, to perform flexural strength (FS) tests. For μTBS testing purposes, CAD surfaces were randomly divided into two groups, according to the presence of ZnCl₂ powder (2 wt%) incorporated into the adhesive system (ZnCl₂), or its absence (NT). An additional group consisting of dentin pretreated with a 2% chlorhexidine digluconate (CHX) solution was proposed as a positive control (n = 10). A two-step self-etching system (SE) was applied following the manufacturer's instructions, and restorations of composite resin were built up on the dentin. After 24 h, the resin-dentin blocks were sectioned into specimens that were submitted to μTBS testing immediately following, or after 12 months of water storage (WS). Both μTBS and FS tests were performed using a universal testing machine (0.5 mm/min). FS and CD data were submitted to the Student t-test, and μTBS data were submitted to two-way ANOVA and Tukey's test (α = 0.05). ZnCl₂ incorporation had no statistically significant influence on flexural strength (p = 0.88) or conversion degree (p = 566). Regarding μTBS, no significant effect of the double interaction of “dentin treatment” versus “WS period” (p = 0.546) was observed. The bond strength was not affected by the WS period (p = 0.805). The highest mean bond strength was observed for the NT group, which did not differ from the ZnCl₂ group. The lowest mean bond strength was observed for the CHX group, which differed statistically from the NT group (p = 0.053). It was concluded that incorporation of ZnCl₂ into the SE self-etching primer did not interfere in the bond strength of caries-affected dentin, in regard to failure mode, flexural strength or CD, and had no other beneficial effects.     

Effect of 2% chlorhexidine digluconate application and water storage on the bond strength to superficial and deep dentin

The aim of the present in vitro study was to evaluate the effect of chlorhexidine, applied before a self-etching adhesive system (Clearfil SE Bond) on microtensile bond strength to superficial and deep dentin (DD), immediately and after six months of water storage (WS). Forty dentin specimens were divided into two groups according to dentin depth: superficial and deep. The specimens were then divided according to the solution to be applied (n = 10): CLX: 2% chlorhexidine (passively applied for 60 s) and NT (no treatment). A self-etching adhesive system was applied according to the manufactures instructions, with composite restorative placed on the dentin surface. After 24 h, dentin–resin blocks were sectioned into beam-shaped specimens that were submitted to microtensile bond strength testing either immediately or after six months of WS. Data were submitted to three-way ANOVA (α = 0.05). Bond strength values for the deep dentin group were significantly lower than those observed for superficial dentin (SD) (p = 0.002), whether chlorhexidine solution had been applied or not. There was no statistical difference in bond strength for specimens tested after 24 h and 6 months of WS. The application of chlorhexidine did not affect immediate and long-term bond strength to dentin. Bond strength in deep dentin was lower than in SD.     

Improvement of the Molar Tube Bond Durability with Preheated Orthodontic Adhesive

This study aimed to evaluate the effect of preheated orthodontic adhesives and thermal cycling on the bond strength of molar tubes. One hundred sixty molar tubes were bonded to acid-etched bovine incisors using a conventional orthodontic adhesive (Transbond XT), two microhybrid (Wave and Permaflo), and a nanofilled (Filtek Z350) flowable composite resins, at room temperature or preheated at 60°C. Transbond XT primer and Single Bond 2 adhesive system were used in association with Transbond XT and the flowable composites, respectively. The specimens were stored in water (37°C) for 24 h, and half of the sample was subjected to thermal cycling for 6000 cycles. Ashear bond strength (SBS) test was performed, followed by the appraisal of the adhesive Remnant Index (ARI). Three-way analysis of variance (ANOVA) and the Tukey test were performed at a significance level of 95% (P < .05). Samples bonded with preheated adhesives showed higher SBS regardless of the aging method. Only samples bonded with preheated conventional orthodontic adhesive maintained their bond strength after thermal cycling for 6000 cycles. Preheating orthodontic adhesives improved the bond strength of molar tubes, but only the preheated conventional orthodontic adhesive was capable of maintaining bond strength after thermal cycling.