Ethanol wet-bonding technique sensitivity assessed by AFM

The effect of ethanol wet bonding technique on postoperative hypersensitivity of Class II composite restorations: A randomized trial

Background

To evaluate the effect of Ethanol Wet Bonding Technique (EWBT) on postoperative hypersensitivity (POH) of composite restorations in premolar teeth.

Materials and Methods

In this randomized trial, 24 patients with at least three proximal carious lesions with similar axial depth and position of gingival floor in their premolars were enrolled. Following cavity preparation, the teeth were randomly assigned to one of three groups: (1) Class II resin-based composite (RBC) restoration using an etch-and-rinse adhesive + wet bonding technique (Control); (2) RBC restoration using EWBT + hydrophobic adhesive; and (3) RBC restoration using EWBT + hydrophilic adhesive. Tooth hypersensitivity was evaluated before and 1, 3, 7, 14 and 30 days after treatment according to the Visual Analog Scale. Data were analyzed statistically with Kruskal-Wallis and Friedman tests (P = 0.05).

Results

All teeth showed similar levels of hypersensitivity after treatment (both P > 0.05). Furthermore, there was no difference between POH levels of the test and control groups at any control period (P < 0.05). Friedman test indicated that the POH significantly reduced within time in all groups (P < 0.05).

Conclusion

Application of ethanol-wet bonding technique, either with hydrophobic or hydrophilic adhesives did not affect the POH of Class II composite restorations in premolars.

The pursuit of resin-dentin bond durability: Simultaneous enhancement of collagen structure and polymer network formation in hybrid layers

OBJECTIVE

Imperfect polymer formation as well as collagen's susceptibility to enzymatic degradation increase the vulnerability of hybrid layers over time. This study investigated the effect of new dimethyl sulfoxide (DMSO)-containing pretreatments on long-term bond strength, hybrid layer quality, monomer conversion and collagen structure.

METHODS

H₃PO₄-etched mid-coronal dentin surfaces from extracted human molars (n = 8) were randomly treated with aqueous and ethanolic DMSO solutions or following the ethanol-wet bonding technique. Dentin bonding was performed with a three-step etch-and-rinse adhesive. Resin-dentin beams (0.8 mm²) were stored in artificial saliva at 37 °C for 24 h and 2.5 years, submitted to microtensile bond strength testing at 0.5 mm/min and semi-quantitative SEM nanoleakage analysis (n = 8). Micro-Raman spectroscopy was used to determine the degree of conversion at different depths in the hybrid layer (n = 6). Changes in the apparent modulus of elasticity of demineralized collagen beams measuring 0.5 × 1.7 × 7 mm (n = 10) and loss of dry mass (n = 10) after 30 days were calculated via three-point bending and precision weighing, respectively.

RESULTS

DMSO-containing pretreatments produced higher bond strengths, which did not change significantly over time presenting lower incidence of water-filled zones. Higher uniformity in monomer conversion across the hybrid layer occurred for all pretreatments. DMSO-induced collagen stiffening was reversible in water, but with lower peptide solubilization.

SIGNIFICANCE

Improved polymer formation and higher stability of the collagen-structure can be attributed to DMSO's unique ability to simultaneously modify both biological and resin components within the hybrid layer. Pretreatments composed of DMSO/ethanol may be a viable-effective alternative to extend the longevity of resin-dentin bonds.

A novel dentin bonding scheme based on extrafibrillar demineralization combined with covalent adhesion using a dry-bonding technique

Dentin bonding is a dynamic process that involves the penetration of adhesive resin monomers into the extrafibrillar and intrafibrillar demineralized collagen matrix using a wet-bonding technique. However, adhesive resin monomers lack the capacity to infiltrate the intrafibrillar space, and the excess water that is introduced by the wet-bonding technique remains at the bonding interface. This imperfectly bonded interface is inclined to hydrolytic degradation, severely jeopardizing the longevity of bonded clinical restorations. The present study introduces a dentin bonding scheme based on a dry-bonding technique, combined with the use of extrafibrillar demineralization and a collagen-reactive monomer (CRM)-based adhesive (CBA). Selective extrafibrillar demineralization was achieved using 1-wt% high-molecular weight (MW) carboxymethyl chitosan (CMCS) within a clinically acceptable timeframe to create a less aggressive bonding substance for dentin bonding due to its selectively extrafibrillar demineralization capacity. CMCS demineralization decreased the activation of in situ collagenase, improved the shrinking resistance of demineralized collagen, and thus provided stronger and more durable bonding than traditional phosphoric acid etching. The new dentin bonding scheme that contained CMCS and CBA and used a dry-bonding technique achieved an encouraging dentin bonding strength and durability with low technical sensitivity. This bonding scheme can be used to improve the stability of the resin-dentin interface and foster the longevity of bonded clinical restorations.

Review of nano-technology applications in resin-based restorative materials

OBJECTIVE

Nanotechnology has progressed significantly and particles as small as 3 nm are being employed in resin-based restorative materials to improve clinical performance. The goal of this review is to report the progress of nanotechnology in Restorative Dentistry by reviewing the advantages, limitations, and applications of resin-based restorative materials with nanoparticles.

MATERIALS AND METHODS

A literature review was conducted using PubMed/Medline, Scopus and Embase databases. In vitro, in vivo and in situ research studies published in English between 1999 and 2020, and which focused on the analysis of resin-based restorative materials containing nanoparticles were included.

RESULTS

A total of 140 studies were included in this review. Studies reported the effect of incorporating different types of nanoparticles on adhesive systems or resin composites. Mechanical, physical, and anti-bacterial properties were described. The clinical performance of resin-based restorative materials with nanoparticles was also reported.

CONCLUSIONS

The high surface area of nanoparticles exponentially increases the bioactivity of materials using bioactive nanofillers. However, the tendency of nanoparticles to agglomerate, the chemical instability of the developed materials and the decline of rheological properties when high ratios of nanoparticles are employed are some of the obstacles to overcome in the near future.

CLINICAL SIGNIFICANCE

In spite of the recent advancements of nanotechnology in resin-based restorative materials, some challenges need to be overcome before new nano-based restorative materials are considered permanent solutions to clinical problems.

Bond strengths of three-step etch-and-rinse adhesives to silane contaminated dentin

This study aimed to evaluate the effect of silane coupling agent contamination on the microtensile bond strength (µTBS) of 3-step etch-and-rinse adhesives on dentin. Flat occlusal dentin surfaces were prepared and randomly divided into 8 groups (n=20) based on the tested adhesives; Scotchbond Multi-purpose or Optibond FL, with contamination of an experimental silane (2 vol% of 3-m ethacryloxypropyltrimethoxysilane at pH 4.5) before acid-etching, after-etching or after-priming; while the groups without silane contamination served as controls. µTBS data were analyzed by two-way ANOVA and Tukey's HSD tests at a significance level of 0.05. Additional specimens of contaminated dentin were used to analyze changes in the organic molecules by Fourier transform infrared spectroscopy (FTIR). Silane contamination before acid-etching did not significantly change µTBS (p>0.05), but contamination after-etching and after-priming significantly decreased µTBS of both adhesives (p<0.05). Silane contamination had an adverse effect on the dentin bond strength of 3-step etch-and-rinse adhesives especially after-priming.

Influence of proanthocyanidins combined with ethanol-wet bonding on the bonding quality of fibre posts to root dentine

This study evaluated the influence of a bonding approach using proanthocyanidins (PAs) combined with ethanol-wet bonding (EWB) and a hydrophobic adhesive on the bonding quality of fibre posts. After endodontic treatment and post-space preparation, 72 single-rooted extracted human teeth were etched, thoroughly rinsed, and then treated using the following procedures (n = 24 teeth per group): group 1, no pretreatment; group 2, pretreatment with absolute ethanol three times, for 30 s each time; or group 3, pretreatment with absolute ethanol solution containing 5% PAs three times, for 30 s each time. Six teeth per group were dried according to a dry and a wet drying protocol and then observed using field emission-scanning electron microscopy. The remaining 18 teeth in each group were cemented with fibre posts: All-Bond 3 and Duo-Link cement were used for group 1; and hydrophobic adhesive and Duo-Link cement were used for groups 2 and 3. Push-out bond strength, failure mode, and nanoleakage were evaluated immediately and after collagenase treatment. Higher push-out bond strength and less nanoleakage were observed in the two ethanol-pretreatment groups, regardless of storage conditions. Teeth pretreated with PAs + ethanol exhibited significantly higher push-out bond strength after collagenase treatment than did teeth pretreated with ethanol alone. Within the limits of this study, the bonding approach of PAs combined with EWB and a hydrophobic adhesive synergistically improved the durability of fibre post bonds.

Six-month performance of restorations produced with the ethanol-wet-bonding technique: a randomized trial

This double-blind randomized controlled clinical trial evaluated the effectiveness of dentin pretreatment with 100% ethanol (EWBT - ethanol wet bonding technique) and different adhesive protocols in noncarious cervical lesions (NCCL) after 6 months. Patients presenting at least one NCCL were included. NCCLs (n=148) were randomly assigned to 4 groups: NE (Non-EWBT + three-step etch-and-rinse (Scotchbond Multi Purpose, 3M ESPE [MP]), E (EWBT + MP); EB (EWBT + [Bond - third step of MP]), and EU (EWBT + universal adhesive (Single Bond Universal, 3M ESPE). Conventional acid-etching (Condac 37%, FGM) and nanohybrid resin composite (Z350, 3M ESPE) were used. Trained and calibrated examiners (Kappa = 0.61) evaluated the restorations at baseline (7 days) and 6-month recall using the USPHS modified criteria. Data were subjected to Chi square (α = 0.05). Differences in the success rate were found for the treatments (p = 0.003). EB presented the lowest success rate compared with the other groups (p < 0.02). No significant differences were detected among NE, E, and EU (p > 0.49). The survival rates were 97.23%, 97.30%, 78.95%, and 97.30% for NE, E, EB, and EU, respectively. Regarding postoperative sensitivity, a significant reduction was found for groups E (p = 0.027) and EU (p < 0.01) after 6 months. After 6 months, EWBT associated to the hydrophobic adhesive system had the highest failure rate.

Hydrophobic and antimicrobial dentin: A peptide-based 2-tier protective system for dental resin composite restorations

Dental caries, i.e., tooth decay mediated by bacterial activity, is the most widespread chronic disease worldwide. Carious lesions are commonly treated using dental resin composite restorations. However, resin composite restorations are prone to recurrent caries, i.e., reinfection of the surrounding dental hard tissues. Recurrent caries is mainly a consequence of waterborne and/or biofilm-mediated degradation of the tooth-restoration interface through hydrolytic, acidic and/or enzymatic challenges. Here we use amphipathic antimicrobial peptides to directly coat dentin to provide resin composite restorations with a 2-tier protective system, simultaneously exploiting the physicochemical and biological properties of these peptides. Our peptide coatings modulate dentin's hydrophobicity, impermeabilize it, and are active against multispecies biofilms derived from caries-active individuals. Therefore, the coatings hinder water penetration along the otherwise vulnerable dentin/restoration interface, even after in vitro aging, and increase its resistance against degradation by water, acids, and saliva. Moreover, they do not weaken the resin composite restorations mechanically. The peptide-coated highly-hydrophobic dentin is expected to notably improve the service life of resin composite restorations and to enable the development of entirely hydrophobic restorative systems. The peptide coatings were also antimicrobial and thus, they provide a second tier of protection preventing re-infection of tissues in contact with restorations. STATEMENT OF SIGNIFICANCE: We present a technology using designer peptides to treat the most prevalent chronic disease worldwide; dental caries. Specifically, we used antimicrobial amphipathic peptides to coat dentin with the goal of increasing the service life of the restorative materials used to treat dental caries, which is nowadays 5 years on average. Water and waterborne agents (enzymes, acids) degrade restorative materials and enable re-infection at the dentin/restoration interface. Our peptide coatings will hinder degradation of the restoration as they produced highly hydrophobic and antimicrobial dentin/material interfaces. We anticipate a high technological and economic impact of our technology as it can notably reduce the lifelong dental bill of patients worldwide. Our findings can enable the development of restorations with all-hydrophobic and so, more protective components.

Influence of ethanol-wet dentin, adhesive mode of application, and aging on bond strength of universal adhesive

The aim of this study was to evaluate the effect of ethanol on the bond longevity of a universal adhesive system to bovine dentin, under different modes of adhesive application and artificial aging. Bovine dentin was exposed, and the smear layer was standardized by sandpaper polishing. Specimens were randomly divided into 2 groups: ethanol (E) and non-ethanol (N). Groups were subdivided according to adhesive mode of application into etch-and-rinse (Er) and self-etching (S). Resin blocks were built onto the treated surface, and the specimens were stored in deionized water at 37°C for 48 h. Half of the specimens (n = 10) were subjected to thermomechanical aging (A for aged and Na for non-aged). Resin/dentin beams were obtained and subjected to microtensile test in a universal testing machine. Data were analyzed using a three-way ANOVA and Tukey's tests (α = 5%). There was interaction among the three factors (p=0.0003). The use of ethanol resulted in higher values, except for the Er and Na groups (E_Er_Na = N_Er_Na). The mode of application was similar, except for the N and A groups (N_S_A > N_Er_A). For the A groups, the values were lower, except in the cases using ethanol, in which the results were not affected. The study concluded that the use of ethanol resulted in higher microtensile bond strength values, even after aging. The mode of adhesive application did not influence the results.

Extrafibrillar collagen demineralization-based chelate-and-rinse technique bridges the gap between wet and dry dentin bonding

Limitations associated with wet-bonding led to the recent development of a selective demineralization strategy in which dentin was etched with a reduced concentration of phosphoric acid to create exclusive extrafibrillar demineralization of the collagen matrix. However, the use of acidic conditioners removes calcium via diffusion of very small hydronium ions into the intrafibrillar collagen water compartments. This defeats the purpose of limiting the conditioner to the extrafibrillar space to create a collagen matrix containing only intrafibrillar minerals to prevent collapse of the collagen matrix. The present work examined the use of polymeric chelators (the sodium salt of polyacrylic acid) of different molecular weights to selectively demineralize extrafibrillar dentin. These polymeric chelators exhibit different affinities for calcium ions (isothermal titration calorimetry), penetrated intrafibrillar dentin collagen to different extents based on their molecular sizes (modified size-exclusion chromatography), and preserve the dynamic mechanical properties of mineralized dentin more favorably compared with completely demineralized phosphoric acid-etched dentin (nanoscopical dynamic mechanical analysis). Scanning and transmission electron microscopy provided evidence for retention of intrafibrillar minerals in dentin surfaces conditioned with polymeric chelators. Microtensile bond strengths to wet-bonded and dry-bonded dentin conditioned with these polymeric chelators showed that the use of sodium salts of polyacrylic acid for chelating dentin prior to bonding did not result in significant decline in resin-dentin bond strength. Taken together, the findings led to the conclusion that a chelate-and-rinse conditioning technique based on extrafibrillar collagen demineralization bridges the gap between wet and dry dentin bonding.

STATEMENT OF SIGNIFICANCE

The chelate-and-rinse dental adhesive bonding concept differentiates from previous research in that it is based on the size-exclusion characteristics of fibrillar collagen; molecules larger than 40kDa are prevented from accessing the intrafibrillar water compartments of the collagen fibrils. Using this chelate-and-rinse extrafibrillar calcium chelation concept, collagen fibrils with retained intrafibrillar minerals will not collapse upon air-drying. This enables adhesive infiltration into the mineral-depleted extrafibrillar spaces without relying on wet-bonding. By bridging the gap between wet and dry dentine bonding, the chelate-and-rinse concept introduces additional insight to the field by preventing exposure of endogenous proteases via preservation of the intrafibrillar minerals within a collagen matrix. If successfully validated, this should help prevent degradation of resin-dentine bonds by collagenolytic enzymes.

Novel potential scaffold for periodontal tissue engineering

OBJECTIVE

The objective of the study is characterization of novel calcium and zinc-loaded electrospun matrices to be used for periodontal regeneration.

MATERIALS AND METHODS

A polymethylmetacrylate-based membrane was calcium or zinc loaded. Matrices were characterized morphologically by atomic force and scanning electron microscopy and mechanically probed by a nanoindenter. Biomimetic calcium phosphate precipitation on polymeric tissues was assessed. Cell viability tests were performed using oral mucosa fibroblasts. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests or by ANOVA and Student-Newman-Keuls multiple comparisons.

RESULTS

Zinc and calcium loading on matrices did not modify their morphology but increased nanomechanical properties and decreased nanoroughness. Precipitation of calcium and phosphate on the matrix surfaces was observed in zinc-loaded specimens. Matrices were found to be non-toxic to cells in all the assays. Calcium- and zinc-loaded scaffolds presented a very low cytotoxic effect.

CONCLUSIONS

Zinc-loaded membranes permit cell viability and promoted mineral precipitation in physiological conditions. Based on the tested nanomechanical properties and scaffold architecture, the proposed membranes may be suitable for cell proliferation.

CLINICAL RELEVANCE

The ability of zinc-loaded matrices to promote precipitation of calcium phosphate deposits, together with their observed non-toxicity and its surface chemistry allowing covalent binding of proteins, may offer new strategies for periodontal regeneration.

The effects of chlorhexidine and ethanol on push-out bond strength of fiber posts

CONTEXT

Irrigation of root canals with chlorhexidine (CHX) and ethanol is common practice to prevent root canal infection during postplacement. However, pretreatment with these solvents may interfere with the bond strength of posts.

AIMS

This study aimed to evaluate if root dentin pretreatment using CHX and/or ethanol influences the push-out bond strength of fiber-reinforced composite resin (FRCR) posts.

MATERIALS AND METHODS

Fifty space posts prepared in endodontically treated extracted human canine roots were randomly divided into five groups (n = 10) according to the dentin pretreatment: Distilled water (W); 1% CHX diacetate solution (1C); CHX diacetate + 99% ethanol (1CE); 99% ethanol (E); and 2% CHX digluconate solution (2C). After pretreatment, the adhesive system (Peak Universal Bond; Ultradent, South Jordan, UT, USA) was applied in the root dentin and the FRCR was cemented with resin cement. Then, horizontal slices of 2 mm were obtained from each root third and the push-out bond strength was assessed. Statistical analysis was done using analysis of variance (ANOVA) and Tukey's tests (P = 0.05).

RESULTS

At all thirds, 1CE and E groups presented similar push-out bond strength values (P > 0.05), which were higher than the other groups (P < 0.05). W, 1C, and 2C groups were similar (P > 0.05).

CONCLUSION

The root dentin pretreatment with ethanol, alone or mixed with CHX diacetate increased the bond strength of FRCR luted with resin cement.

Resin bond strength to water versus ethanol-saturated human dentin pretreated with three different cross-linking agents

Context:

Resin-dentin bonds are unstable owing to hydrolytic and enzymatic degradation. Several approaches such as collagen cross-linking and ethanol-wet bonding (EWB) have been developed to overcome this problem. Collagen cross-linking improves the intrinsic properties of the collagen matrix. However, it leaves a water-rich collagen matrix with incomplete resin infiltration making it susceptible to fatigue degradation. Since EWB is expected to overcome the drawbacks of water-wet bonding (WWB), a combination of collagen cross-linking with EWB was tested.

Aim:

The aim of this study was to compare the effect of pretreatment with different cross-linking agents such as ultraviolet A (UVA)-activated 0.1% riboflavin, 1 M carbodiimide, and 6.5 wt% proanthocyanidin on the immediate and long-term bond strengths of an etch and rinse adhesive system to water- versus ethanol-saturated dentin within clinically relevant application time periods.

Settings and Design:

Long-term in vitro study evaluating the microtensile bond strength of adhesive-dentin interface after different surface pretreatments.

Subjects and Methods:

Eighty freshly extracted human molars were prepared to expose dentin, etched with 37% phosphoric acid for 15 s rinsed, and grouped randomly. They were blot-dried and pretreated with different cross-linkers: 0.1% riboflavin for 2 min followed by UVA activation for 2 min; 1 M carbodiimide for 2 min; 6.5 wt% proanthocyanidin for 2 min and rinsed. They were then bonded with Adper Single Bond Adhesive (3M ESPE), by either WWB or EWB, followed by resin composite build-ups (Filtek Z350, 3M ESPE). Bonded specimens in each group were then sectioned and divided into two halves. Microtensile bond strength was tested in one half after 24 h and the other after 6 months storage in artificial saliva.

Statistical Analysis Used:

Analysis was done using SPSS version 18 software (SPSS Inc., Chicago, IL, USA). Intergroup comparison of bond strength was done using ANOVA with post hoc Tukey's test, and intragroup comparison was done using paired t-test.

Results:

The microtensile bond strength of cross-linked groups was higher compared to control group (P < 0.001). EWB showed much higher bond strength values on cross-linked dentin compared to noncross-linked dentin. UVA-activated riboflavin group exhibited highest bond strengths followed by carbodiimide and proanthocyanidin groups, respectively, on both water- as well as ethanol-saturated dentin. Even after 6 months storage, cross-linked groups showed significantly higher values compared to initial bond strength values of control group (P < 0.001).

Conclusions:

0.1% riboflavin pretreatment of dentin followed by UVA activation for 2 min exhibited highest increase in bond strength values at 24 h and least reduction in bond strength values after 6 months storage compared to other groups. Biomodification of dentin using collagen cross-linking followed by EWB exhibited a synergistic effect in improving the resin-dentin bond durability.

Effect of simplified ethanol-wet bonding on dentin bonding durability of etchand-rinse adhesives

This in vitro study evaluated the effects of simplified ethanol-wet bonding technique on dentin bonding durability of two etchand-rinse adhesives to bovine dentin. Sixteen freshly extracted bovine incisors were divided into four groups according to bonding technique (water-wet or ethanol-wet bonding) and adhesive (Single Bond 2 or Prime & Bond NT). After etching and rinsing, dentin surfaces were left either water-moist or immersed in ethanol. Following adhesive application and composite build-up, bonded teeth were sectioned into sticks for microtensile bond strength (µTBS) testing conducted after 24-h and 12-month water storage. There were no significant differences in bond strength among the groups at 24 h. At 12 months, the bond strengths of adhesives to dentin were significantly decreased (p<0.05). Simplified ethanol-wet bonding did not improve the resin-dentin bonding durability of tested etch-and-rinse adhesives.

Letter to the Editor regarding "Depletion of water molecules during ethanol wet-bonding with etch and rinse dental adhesives"

I would like to comment on the above titled paper that recently published in Materials Science and Engineering C 33:21-27 (2013). I mentioned potential deficiencies in the study design. Then, I argued some statements made in the paper about interactions between bounded water around collagen molecules and resin infiltration, hence longevity of resin bonding. It is important to highlight these concerns regarding this paper so that readers are provided with another view of the ethanol wet-bonding concept.

In vitro evaluation of casein phosphopeptide-amorphous calcium phosphate effect on the shear bond strength of dental adhesives to enamel

BACKGROUND

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is applied for remineralization of early caries lesions or tooth sensitivity conditions and may affect subsequent resin bonding. This in vitro study investigated the effect of CPP-ACP on the shear bond strength of dental adhesives to enamel.

MATERIALS AND METHODS

Sixty extracted human molar teeth were selected and randomly divided into three groups and six subgroups. Buccal or lingual surfaces of teeth were prepared to create a flat enamel surface. Adhesives used were Tetric N-Bond, AdheSE and AdheSE One F. In three subgroups, before applying adhesives, enamel surfaces were treated with Tooth Mousse CPP-ACP for one hour, rinsed and stored in 37°C temperature with 100% humidity. This procedure was repeated for 5 days and then adhesives were applied and Tetric N-Ceram composite was adhered to the enamel. This procedure was also fulfilled for the other three subgroups without CPP-ACP treatment. After 24 hour water storage, samples were tested for shear bond strength test in a universal testing machine. Failure modes were determined by stereomicroscope. Data were analyzed by t-test and one-way analysis of variance with P < 0.05 as the level of significance.

RESULTS

In comparison between applied and non-applied CPP-ACP subgroups, there was no significant decrease in the shear bond strength to enamel only in Tetric N-Bond (P > 0.05). In non-applied CPP-ACP subgroups, there were statistically significant differences among all subgroups. Tetric N-Bond had the highest and AdheSE One F had the lowest shear bond strength.

CONCLUSION

CPP-ACP application reduces the shear bond strength of AdheSE and AdheSE One F to enamel but not Tetric N-Bond.

Adjunctive application of chlorhexidine and ethanol-wet bonding on durability of bonds to sound and caries-affected dentine

OBJECTIVES

To examine the effect of adjunctive application of chlorhexidine (CHX) and ethanol-wet bonding (EWB) on bond durability and nanoleakage of hydrophobic adhesive to sound (SD) and caries-affected dentine (CAD).

METHODS

Dentine surfaces of molars were etched after caries removal and randomly allocated to four groups (n=12). In Groups 1 and 2, dentine surfaces were saturated with either 2 ml of 100% ethanol or 2 ml of ethanol with 2% CHX for 60s. In Groups 3 and 4, dentine surfaces were saturated with either 15 μL of distilled water or 15 μL of distilled water with 2% CHX for 60s. Two coats of primer, followed by neat resin were applied and light-cured for 40s. Resin composite build-ups were placed and bonded specimens were sectioned for bond strength testing after 24 h and 12 months' storage in artificial saliva. Bond strength data were analyzed using 3-way ANOVA and SNK tests. Interfacial nanoleakage was evaluated after 24 h and 12 months using a field-emission scanning electron microscopy and data were analyzed using Kruskal-Wallis test.

RESULTS

Significant differences were observed for the three factors: "substrate" (p<0.001), "rewetting agents" (p<0.001) and "time" (p<0.001) on bond strength. Incorporation of 2% CHX to EWB preserved bond strength to SD and CAD and reduced interfacial nanoleakage after 12 months. Incorporation of 2% CHX to WWB also preserved bond strength to SD after ageing.

CONCLUSIONS

Incorporation of chlorhexidine to ethanol-wet bonding has an interaction effect on preservation of bond durability to sound and caries-affected dentine.

CLINICAL SIGNIFICANCE

Incorporation of chlorhexidine to ethanol-wet bonding with hydrophobic adhesive enhances the success rate of aesthetic bonded restorations.

Bond strength of composite resin to enamel: assessment of two ethanol wet-bonding techniques

OBJECTIVE

Ethanol wet-bonding (EWB) technique has been stated to decrease degradation of resin-dentin bond. This study evaluated the effect of two EWB techniques on composite resin-to-enamel bond strength.

MATERIALS AND METHODS

Silicon carbide papers were used to produce flat enamel surfaces on the buccal faces of forty-five molars. OptiBond FL (OFL) adhesive was applied on enamel surfaces in three groups of 15 namely: Enamel surface and OFL (control);Protocol 1 of the EWB technique: absolute ethanol was applied to water-saturated acid-etched enamel surfaces for 1 minute before the application of ethanol-solvated hydrophobic adhesive resin of OFL 3 times;Protocol 2: progressive ethanol replacement; water was gradually removed from the enamel matrix using ascending ethanol concentrations before OFL application. Composite build-ups were made and the specimens were stored for 24 hours at 37°C and 100% relative humidity. Shear bond strength test was performed using a universal testing machine at 1 mm/min crosshead speed. Fracture patterns were evaluated microscopically. Data were analyzed with one-way ANOVA and Fisher's exact test (α=0.05).

RESULTS

There were no significant differences in bond strength between the groups (P=0.73). However, regarding failure patterns, the highest cohesive enamel fractures were recorded in groups 2 and 3.

CONCLUSION

In this study, although both methods of EWB did not influence immediate bond strength of composite resin to enamel, the majority of failure patterns occurred cohesively in enamel.

Effect of chlorhexidine and ethanol-wet bonding with a hydrophobic adhesive to intraradicular dentine

PURPOSE

To evaluate the effect of adjunctive application of ethanol-wet bonding and chlorhexidine (CHX) with a hydrophobic adhesive on bond durability of fibre posts to intraradicular dentine.

METHODS

Ninety-six extracted human teeth with a single root and root canal were prepared for post placement after endodontic treatment. The teeth were randomly divided into four groups (n=24) after etching and rinsing for rewetting: Group 1: water-wet bonding, Group 2: water-wet bonding with CHX, Group 3: ethanol-wet bonding and Group 4: ethanol-wet bonding with CHX. Teeth in Groups 1 and 2 were treated with either distilled water or distilled water with 2% CHX for 60 s; while teeth in Groups 3 and 4 were treated with either 100% ethanol or 100% ethanol with 2% CHX. Two coats of primer, followed by neat resin were applied and light-cured for 40 s. Fibre posts were luted to bonded root dentine using dual-cure resin cement. Bonded roots were subjected to push-out bond strength testing and interfacial nanoleakage evaluation after 24 h, 6 and 12 months of storage. Data were analyzed using 3-way ANOVA (rewetting solutions, time and post space regions) and SNK tests.

RESULTS

Groups 3 and 4 showed significantly (p<0.05) higher bond strengths and lower nanoleakage than Groups 1 and 2 after 12 months of ageing. Addition of 2% chlorhexidine to ethanol-wet bonding with a hydrophobic adhesive did not further improve the bonding of a fibre post to intraradicular dentine, when compared to ethanol-wet bonding alone after 12 months of ageing.

CLINICAL SIGNIFICANCE

Ethanol-wet bonding with a hydrophobic adhesive alone could improve the bond durability of fibre post to intraradicular dentine and therefore would increase the success rate of post and core restorations of endodontically treated teeth.

Overview of Clinical Alternatives to Minimize the Degradation of the Resin-dentin Bonds

The incorporation of hydrophilic and acidic resin monomers substantially improved the initial bonding of contemporary etch-and-rinse (ER) and self-etch (SE) adhesives to intrinsically wet dental substrates, providing quite favorable immediate results, regardless of the bonding approach used. However, in the long term, the bonding effectiveness of most simplified ER and SE adhesives drop dramatically. This review examines the fundamental processes that are responsible for the aging mechanisms involved in the degradation of the resin-bonded interfaces and some possible clinical approaches that have been effective in minimizing or even preventing the degradation of the adhesive interfaces produced with simplified adhesives. The incorporation of some of the feasible approaches - described in this review - may improve the quality of the adhesive restorations performed in clinical practice, while manufacturers develop bonding materials that are less susceptible to the aging mechanisms present in the oral environment.

One-Year Evaluation of a Simplified Ethanol-Wet Bonding Technique: A Randomized Clinical Trial

The objective of this randomized clinical trial was to evaluate the clinical performance of adhesive restorations using a three-step etch-and-rinse adhesive (TSER), a one-step self-etching adhesive (OSSE), and a simplified ethanol-wet bonding technique (EWBT) prior to the application of a composite resin in non-carious cervical lesions. Ninety-three restorations (31 for each group) were placed in 17 patients by a single operator. No cavity preparation was performed. After 6 and 12 months, the restorations were assessed by two previously trained examiners using modified Ryge criteria for retention (kappa=1.00) and marginal adaptation/staining (kappa=0.81), and the results were analyzed by Fisher's exact and Kruskal-Wallis tests, respectively. No significant differences were observed among groups at the 6- and 12-month time points for any of the assessed criteria (p≥0.05). The intra-group analysis performed by Cochran's test (for retention) and Wilcoxon test (for marginal adaptation/staining) revealed significant differences between the baseline/12-month time intervals in marginal adaptation in OSSE (p=0.0180) and in marginal staining in TSER (p=0.0117). The survival analysis for retention criteria performed using a log-rank test did not show significant differences (p>0.05). The restorations placed using the simplified EWBT performed equally well as the other adhesive strategies employed.

A randomized clinical trial evaluating the success rate of ethanol wet bonding technique and two adhesives

BACKGROUND

Composite resin restorations may have a short lifespan due to the degradation of resin-dentin interface. Ethanol wet bonding technique may extend the longevity of resin-dentin bond. The purpose of this one year randomized clinical trial was to compare clinical performance of two adhesives with ethanol wet bonding technique.

MATERIALS AND METHODS

This randomized clinical trial was performed on 36 non-carious cervical lesions in 12 patients restored with composite resin using one of the following approaches: 1. OptiBond FL (Kerr, USA); 2. Clearfil SE Bond (Kuraray, Japan) with enamel etching and 3. Ethanol wet bonding technique with the part of adhesive of OptiBond FL. The clinical success rate was assessed after 24 h, 6, 9 and 12 months according to the United States Public Health Service (USPHS) criteria: Marginal discoloration, marginal defect, retention rate, caries occurrence, and postoperative sensitivity. The tooth vitality was also assessed.

RESULTS

The retention rate was 100% at baseline and at 6 months follow up for all types of bonding protocols and was 91.67% at 9 and 12 months follow up for ethanol wet bonding group. None of the restorations in three groups showed marginal defects, marginal discoloration or caries occurrence and were vital after 12 months. There was no statistically significant difference between three groups after 12 months follow up (p value = 0.358).

CONCLUSIONS

Composite restorations placed using ethanol wet bonding technique presented equal performance to the other groups.

Bond durability of self-etch adhesive to ethanol-based chlorhexidine pretreated dentin after storage in artificial saliva and under intrapulpal pressure simulation

OBJECTIVE

To evaluate the bond strength durability of a single-step self-etch adhesive to dentin pretreated with either ethanol-based chlorhexidine (ECHX) or water-based chlorhexidine (WCHX) after storage in artificial saliva and under intrapulpal pressure simulation (IPPS).

METHODS

The occlusal enamel of 30 freshly extracted premolars was trimmed to expose midcoronal dentin. Roots were sectioned to expose the pulp chamber. Specimens were distributed over three groups (n=10) according to the dentin pretreatment used. In the first group, Adper Easy One (3M ESPE) was applied to the dentin surfaces according to the manufacturer's instructions (control group). In the second group, dentin was pretreated before bonding with 1 mL of 2% CHX diacetate dissolved in 100% ethanol (ECHX). The third group received the same pretreatment; however, CHX was dissolved in distilled water (WCHX). Pretreatment and bonding were carried out while the specimens were subjected to IPPS. Resin composite (Valux Plus, 3MESPE) buildups were made. After curing, specimens were stored in artificial saliva and under IPPS at 37°C in a specially constructed incubator (n=5/group) either for 24 hours or six months prior to testing. Thereafter, bonded specimens were sectioned into sticks with a cross section of 0.9 ± 0.01 mm(2) and subjected to microtensile bond strength (μTBS) testing (n=25/subgroup) using a universal testing machine. Data were statistically analyzed using two-way analysis of variance (ANOVA) with repeated measures, one-way ANOVA , and Bonferroni post hoc tests (p≤0.05). Failure modes were determined using a scanning electron microscope.

RESULTS

After 24 hours of storage, control and WCHX groups revealed significantly higher μTBS than the ECHX group. After six-month storage in artificial saliva and IPPS, only the WCHX group maintained its μTBS value. The predominant mode of failure was the mixed type, except for the ECHX group, which was mostly adhesive.

CONCLUSION

Pretreatment of the dentin with ECHX had a negative effect on bonding of the tested single-step self-etch adhesive; however, WCHX showed bond stability under IPPS.

Interaction morphology and bond strength of nanofilled simplified-step adhesives to acid etched dentin

OBJECTIVE

To evaluate the effect of nanofillers incorporated into adhesives on the microtensile bond strength (μ-TBS) and interfacial micromorphology to dentin.

METHODS

The occlusal enamel of 5 human molars was removed and each tooth sectioned into four quarters. The exposed dentin was treated with one of the following adhesives: Adper Single Bond (SB-unfilled), OptiBond Solo Plus (OS-barium aluminoborosilicate, 400nm Ø), Prime & Bond NT (NT-colloidal silica, 7-40 nm Ø) and Adper Single Bond 2 (SB2-colloidal silica, 5nm Ø). Cylinders of resin-based composite were constructed on the adhesive layers. After 24-hour storage, the restored tooth-quadrants were sectioned to obtain stick-shaped specimens (0.8 mm2, cross-sectional area) and submitted to μ-TBS at a cross-speed of 0.5 mm/min. Data were analyzed using one-way ANOVA and Tukey's test (alpha = .05). Twenty-eight additional teeth were used for interfacial micro-morphologic analysis by SEM (16-teeth) and TEM (12-teeth). The dentin surfaces of 32 discs were treated with the adhesives (8 discs for adhesive) and laminated to form disc-pairs using a flowable resin composite for SEM/EDS analysis. For TEM, 90nm-thick nondemineralized unstained sections were processed.

RESULTS

SB2 showed significant higher bond strength than SB, OS and NT. The SEM/EDS and TEM analysis revealed nanofillers infiltrated within the interfibrillar spaces of the SB2-hybrid layer. Fillers were concentrated around patent tubular orifices and in the adhesive layer for OS and NT.

CONCLUSION

The presence of nanofillers within the interfibrillar spaces of the SB2-hybrid layer suggests its importance in the improvement of the μ-TBS.

Characterization of micro- and nanophase separation of dentin bonding agents by stereoscopy and atomic force microscopy

The aim was to study the effect of solvents on the phase separation of four commercial dental adhesives. Four materials were tested: Clearfil™ SE Bond (CSE), Clearfil Protect Bond (CPB), Clearfil S3 Bond (CS3), and One-Up Bond F Plus (OUB). Distilled water or ethanol was used as a solvent (30 vol%) for microphase separation studies, by stereoscopy. For nanophase images, the mixtures were formulated with two different solvent concentrations (2.5 versus 5 vol%) and observed by atomic force microscopy. Images were analyzed by using MacBiophotonics ImageJ to measure the area of bright domains. Macrophase separations, identified as a loss of clarity, were only observed after mixing the adhesives with water. Nanophase separations were detected with all adhesive combinations. The area of bright domains ranged from 132 to 1,145 nm² for CSE, from 15 to 285 nm² for CPB, from 149 to 380 nm² for CS3, and from 26 to 157 nm² for OUB. In water-resins mixtures, CPB was the most homogeneous and OUB showed the most heterogeneous phase formation. In ethanol-resin mixtures, CSE attained the most homogeneous structure and OUB showed the most heterogeneous phase. Addition of 5 vol% ethanol to resins decreased the nanophase separation when compared with the control materials.

Ethanol-wet bonding may improve root dentine bonding performance of hydrophobic adhesive

OBJECTIVES

The current study aimed to assess ethanol-wet dentine surfaces by atomic force microscopy (AFM), and to evaluate the efficacy of ethanol-wet bonding on root dentine by determining the shear bond strength (SBS) and interfacial nanoleakage expression.

METHODS

Flat dentine slices from human premolar roots were randomly grouped into five. All specimens were acid-etched, rinsed, and left moist. They were then treated with 100% ethanol for 0s (control group), 20s (Group 1), 60s (Group 2), three 60s periods (Group 3), or stepwise ethanol application (Group 4). After treatment, each group was bonded either with Adper™ Scotchbond™ Multi-Purpose (Scotchbond) or experimental hydrophobic adhesive. Nano-scale adhesion forces (Fad) were probed by AFM and analysed using one-way ANOVA. The SBS results were analysed using two-way ANOVA. Tukey's test was employed for multiple comparisons.

RESULTS

Ethanol-wet protocols significantly decreased the value of Fad (p<0.001). When bonded with Scotchbond, ethanol treatment did not affect the bond strength (p>0.05), but decreased the interfacial nanoleakage. The SBS values of the groups bonded with hydrophobic adhesive varied with different ethanol-wet protocols (p<0.05). Decreased nanoleakage was manifested in all experimental groups, except Group 1. Compared with the classical water-wet bonding with Scotchbond in the control group, Group 4 bonded with hydrophobic adhesive exhibited a significantly higher bond strength (p<0.05).

CONCLUSIONS

Ethanol-wet bonding using a stepwise ethanol application protocol may have potential benefits in the root dentine bonding of hydrophobic adhesive.

Limitations in bonding to dentin and experimental strategies to prevent bond degradation

The limited durability of resin-dentin bonds severely compromises the lifetime of tooth-colored restorations. Bond degradation occurs via hydrolysis of suboptimally polymerized hydrophilic resin components and degradation of water-rich, resin-sparse collagen matrices by matrix metalloproteinases (MMPs) and cysteine cathepsins. This review examined data generated over the past three years on five experimental strategies developed by different research groups for extending the longevity of resin-dentin bonds. They include: (1) increasing the degree of conversion and esterase resistance of hydrophilic adhesives; (2) the use of broad-spectrum inhibitors of collagenolytic enzymes, including novel inhibitor functional groups grafted to methacrylate resins monomers to produce anti-MMP adhesives; (3) the use of cross-linking agents for silencing the activities of MMP and cathepsins that irreversibly alter the 3-D structures of their catalytic/allosteric domains; (4) ethanol wet-bonding with hydrophobic resins to completely replace water from the extrafibrillar and intrafibrillar collagen compartments and immobilize the collagenolytic enzymes; and (5) biomimetic remineralization of the water-filled collagen matrix using analogs of matrix proteins to progressively replace water with intrafibrillar and extrafibrillar apatites to exclude exogenous collagenolytic enzymes and fossilize endogenous collagenolytic enzymes. A combination of several of these strategies should result in overcoming the critical barriers to progress currently encountered in dentin bonding.