Interactions between a collagen-binding adhesive and dental substrate

The adhesion between polymer adhesives and dentin involves the removal of minerals, by acid etching the dentin surface, to allow for monomer infiltration among collagen fibrils. However, instability within this hybrid layer has been observed, which may partially be attributed to a slow degradation of the collagen not protected by the adhesive. The objective of this work was to improve the stability of the hybrid layer by increasing the interactions between adhesives and collagen through the incorporation of a monomer that behaves reactively toward collagen in the adhesive. In this work, a control adhesive was prepared based on a chemical formulation containing Bis-GMA and HEMA, and was modified by incorporating different concentrations (5, 10, and 20%) of NSA (N-acryloxysuccinimide), which contains an ester group capable of interacting with primary amine. These experimental adhesives were applied to bovine dentin for the in vitro production of the interfacial layer, which was analyzed by Raman spectroscopy and scanning electron microscopy. The obtained results showed that it was possible to incorporate the NSA monomer into the adhesive up to a maximum concentration of 10%. The presence of amide bonds in the Raman spectra, as well as the presence of a large amount of experimental adhesive within the interfacial layer, as indicated in the scanning electron microscopy images, may suggest the occurrence of chemical interactions between polymers and dentin collagen fibrils. These interfacial chemical interactions involving dental adhesives and dentin can be an important tool in protecting the hybrid layer from degradation.     

Monomers for adhesive polymers: 11. Structure–adhesive properties relationships of new hydrolytically stable acidic monomers

The synthesis of six new hydrolytically stable acidic monomers is described. Those monomers are N,N‐disubstituted acrylamides bearing either a phosphonic acid group or a diphosphonic acid group. They were fully characterized using ¹H NMR, ¹³C NMR and ³¹P NMR spectroscopy and high‐resolution mass spectrometry. The copolymerization of each acidic monomer with N,N′‐diethyl‐1,3‐bis(acrylamido)propane was investigated using photo‐differential scanning calorimetry. Self‐etching enamel–dentin adhesives were formulated and evaluated in terms of both dentin and enamel adhesion. The influence of the monomer structure (nature of either the spacer or the acidic group, nature of the acrylamide substitution) on the adhesive properties is discussed. The adhesives based on 10‐(N‐ethylacrylamido)decylphosphonic acid and 10‐(N‐methylacrylamido)decylbisphosphonic acid are able to achieve a strong bond between a dental composite and both dentin and enamel. © 2013 Society of Chemical Industry     

Engineered Peptide Repairs Defective Adhesive–Dentin Interface

Failure of dental composite restorations is primarily due to recurrent decay at the tooth–composite interface. At this interface, the adhesive and its bond with dentin is the barrier between the restored tooth and the oral environment. In vivo degradation of the bond formed at the adhesive/dentin (a/d) interface follows a cascade of events leading to weakening of the composite restoration. Here, a peptide‐based approach is developed to mineralize deficient dentin matrices at the a/d interface. Peptides that have an inherent capacity to self‐assemble on dentin and to induce calcium–phosphate remineralization are anchored at the interface. Distribution of adhesive, collagen, and mineral is analyzed using micro‐Raman spectroscopy and fluorescence microscopy. The analysis demonstrates remineralization of the deficient dentin matrices achieved throughout the interface with homogeneous distribution of mineral. The peptide‐based remineralization demonstrated here can be an enabling technology to design integrated biomaterial–tissue interfaces.

     

Adhesive monomers to dental ceramics. III. Influence of surface treatment on effective adhesion of calcium metaphosphate ceramic with N-(vinylbenzyl)iminodiacetic acid

Influence of surface treatment of calcium metaphosphate ceramic was analyzed in detail to achieve high adhesion in an aqueous environment with N-(vinylbenzyl)iminodiacetic acid as a novel dental adhesive monomer. The adhesion strength was enhanced greatly by alkali etching of the ceramic surface, although the adhesion profile varied with etching conditions. Scanning electron microscopy, electron probe microanalysis, and roughness evaluation indicated that high adhesion was closely associated with the formation of fine irregularity on the surface that was rich in Ca. N-(Vinylbenzyl)iminodiacetic acid was thus confirmed to be a suitable adhesive monomer for the ceramic in dentistry in terms of strength and durability when the ceramic surface was properly etched. © 1996 John Wiley & Sons, Inc.     

Effect of a Self-Etching Adhesive System Containing a Novel Antimicrobial Polymer (QAMP) on Inhibiting Carious Lesions by Evaluating the Mechanical Properties of the Resin–Dentin Interface

The objective of this study was to assess the in vitro effect of a quaternary ammonium methacrylate polymer (QAMP) incorporated into a self-etching adhesive system on inhibiting caries by evaluating the mechanical properties of the adhesive interface. Twenty-four human third molars were distributed into: Clearfil? SE Bond containing 5% QAMP (experimental group), Clearfil? Protect Bond (positive control), and Clearfil? SE Bond (negative control). Teeth of each group were divided according to the method for producing artificial caries lesions: pH-cycling or microbiological assay. All samples were sectioned and polished in order to obtain hardness (H) and Young's modulus (E) values by nanoindentation test in the hybrid layer and dentin. Data were analyzed by ANOVA and Games Howell's post hoc test (α = 0.05). Regarding the hybrid layer, Clearfil? SE Bond containing QAMP demonstrated H and E values statistically higher than Clearfil? SE Bond in both pH-cycling and microbiological experiments. Considering dentin, Clearfil? SE Bond containing QAMP showed H and E values statistically higher than Clearfil? Protect Bond and Clearfil? SE Bond in the pH-cycling method and then Clearfil? SE Bond concerning the microbiological method. In general, Clearfil? SE Bond containing QAMP provided better mechanical properties for the resin–dentin interface after cariogenic challenges.     

Preparation, characterization, and surface and biological properties of N-stearoyl amino acids

Several lipoamino acids were synthesized, in which n-octadecanoic acid (stearic acid) was coupled with the α-amino group of an amino acid. The products were characterized and their identities confirmed by advanced analytical techniques like Fourier transform infrared ¹H nuclear magnentic resonance spectroscopy, and differential scanning, calorimetry. Their surface properties, such as critical micelle concentration (CMC) and foaming properties, biodegradability, and antimicrobial activity were also evaluated. The N-stearoyl amino acids (NSA) had low CMC values, and some of them showed good foaming properties. They were screened for antimicrobial activity against the gram-positive bacteria Staphylococcus aureus, Micrococcus luteus, and Bacillus cerceus, the gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, and the yeast Candida albicans. All the compounds inhibited at least one of these organisms. N-Stearoyl proline was the most effective, the order of antimicrobial activity being aromatic NSA> acidic NSA>basic NSA. However, the effective inhibition by all the compounds indicates the desirability of more thorough investigation and suggests that some of these compounds may have potential utility as biostatic additives in commercial products. All NSA are highly biodegradable and can readily be removed under conditions of normal secondary sewage treatment.     

An overview of solvents in resin–dentin bonding

Resin bonding to dentin is less durable than bonding to enamel. Bonding to dentin had been a great challenge till date. Though the current dental adhesive systems have tremendously improved the complex dentin bonding, there are still challenges that need to be addressed. Improper handling of the dental adhesive systems is one of the several reasons for the decrease in durability of resin–dentin bonds over time. Improper handling includes inappropriate storage and inaccurate method(s) of application. Solvents incorporated in the dental adhesive systems are known to dissolve methacrylate monomer/co-monomer blends and the initiator/co-initiator systems. These solvents are volatile and they play several important roles in achieving successful and durable bond to dentin. Lack of knowledge about the role of solvents used in dental adhesives could be one of the reasons for improper handling of the dental adhesive systems. This overview discusses the solvent aspects of current dental adhesive systems and their applications in bonding. The overview consists of published literature retrieved from “Pubmed”, by using specific key words “solvents”, “resin adhesives”, “dentin”, “bonding”. The relevant literature was retrieved after screening the titles and the abstracts. Further relevant articles that were included for the overview were retrieved from the reference lists of the initially retrieved articles. The literature seems to indicate that solvent type, solvent content and other factors, like storage of the adhesives and methods of application play a major role in dentin bonding. The knowledge acquired on the solvents and their roles in dentin bonding would enable the users of the dental adhesives to handle them appropriately and consequently achieve strong and durable resin–dentin bonds.     

Microscopic evaluation of the thickness and structure of the cement and cement–dentin interdiffusion zone after luting posts with three different luting cements

Clinical studies report that failures of fiber post cementation occur mainly at the cement–dentin interface. The aim of this in vitro study is to compare the scanning electron microscopic (SEM) evaluations of the cement thicknesses in the root canals and the thickness of cement–dentin interface zones obtained after luting standardized glass-fiber posts with three different types of luting cements. Thirty single-rooted mandibular premolars of similar sizes were prepared for post insertion after biomechanical preparation and obturation. They were divided into three groups containing 10 samples each. Standardized glass-fiber posts were cemented with zinc phosphate cement for ZNP group, with conventional adhesive resin cement for CAR group, and with self-adhesive resin cement for SAR group. The formation and thickness of cement and cement–dentin interface zone were evaluated by stereomicroscope and SEM using ×800 magnification, and the data were analyzed. There was no significant difference between groups in terms of cement thickness (p = 0.835); however, there were significant differences among the cement layer thicknesses measured at the three examined levels of the root canals (p = 0.000). The groups using conventional adhesive resin cement presented longer micromechanical interlocking while the groups using self-adhesive resin cement showed wide gaps and zinc phosphate cement showed no bonding between cement–dentin interdiffusion zones along the root canal. As a clinical consequence, the use of zinc phosphate cement may not provide strong bond between dentin–cement interface. Conventional adhesive resin cements showed reliable bond to dentin when compared to zinc phosphate and self-adhesive resin cement.     

The synthesis of hyperbranched poly (amine-ester) and study on the properties of its UV-curing film

Firstly, the monomer of N, N-diethylol-3-amine methylpropionate was obtained via Michael addition of methyl acrylate and diethanolamine. Then the hyperbranched poly (amine-ester) (HBPE) was synthesized through pentaerythritol as core molecules and monomer as AB₂. HBPE was characterized by Fourier transform-infrared spectroscopy, hydrogen nuclear magnetic resonance (¹H-NMR) and elemental analysis. Methyl tetrahydrophthalic anhydride (MTHPA) is grafted to the hydroxyl groups of HBPE and then glycidyl methacrylate (GMA) is introduced to the structure of HBPE, which is obtained by the UV-curable hyperbranched prepolymer (HBPE-MTHPA-GMA). Ultraviolet-differential scanning calorimeter showed that the HBPE-MTHPA-GMA has high photocuring speed under photoinitiator. Furthermore, the films also show good impact strength, outstanding adhesive force and primary thermal stability.     

Effects of a new 4-acryloxyethyltrimellitic acid in a visible light-cured dental adhesive on adhesion and polymerization reactivity

A new adhesive-promoting monomer, 4-acryloxyethyltrimellitic acid (4-AET), was synthesized. The effects on the adhesion to bovine dentin and the polymerization reactivity [the inclusion varying from 0 to 10 wt % 4-AET of the experimental light-cured dental bonding resins (adhesive), wherein the adhesives were aged artificially at 50°C over 2 weeks] were investigated, using tensile and shear bond testing, a differential scanning calorimeter (DSC), and a scanning electron microscope (SEM). Tensile and shear bond strengths to ground dentin were not significantly decreased in 4-AET content over 2 weeks of aging, and the optimum concentration of 4-AET was found to be 5 wt %. The correlation between the tensile and shear bond strengths to the dentin was highly positive (r = 0.8517–0.9329) during the 2 weeks. The maximum temperature (T_max) of the polymerization in DSC was affected by the 4-AET content in the positive correlation. The correlation between the T_max and the bond strength to dentin was highly positive (r = 0.8995–0.9644). The SEM study showed that the bonding resin appeared to adhere strongly to ground dentin without the formation of resin-tags in the dentinal tubules. It was suggested that the bonding strength was attributable to the degree of penetration of the 4-AET/HEMA primer into the dentin and the polymerization reactivity of the bonding resin comprising 4-AET. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1057–1069, 1998     

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.     

Effect of saliva contamination on shear bond strength and microleakage of one-bottle etch-and-rinse and self-etch adhesives: scanning electron and confocal laser microscopic analyses

Purpose: To evaluate the effect of saliva contamination on shear bond strength, microleakage, and microstructure of the adhesive interface in two different adhesive systems by using scanning electron microscopy (SEM) and confocal laser microscopy (CLSM). Materials and methods: Randomly, 228 third molars were allocated to six groups for an etch-and-rinse adhesive One-Step Plus (Bisco Inc.) and a self-etch adhesive G Bond (GC Corp.): Group 1 – manufacturer’s instructions were followed; Group 2 – involved contamination and drying before adhesive application; Group 3 – involved contamination, washing, and blot drying before adhesive application; Group 4 – involved contamination, etching, washing, and blot drying before adhesive application; Group 5 – involved contamination and drying after adhesive application, followed by adhesive reapplication; Group 6 – involved contamination and washing after adhesive application, followed by adhesive reapplication. Shear bond strength was tested after specimens were stored in distilled water at 37?°C for 24?h. Specimens were evaluated under a stereomicroscope for microleakage. Dentin–resin interfaces were evaluated by SEM and CLSM. Results: Group 2 for One-Step Plus and Group 3 for G Bond showed significantly lower bond strengths than control groups. Microleakage values were significantly greater at dentin than at enamel margins for all groups. In Group 2, for both adhesive systems, the highest microleakage was observed at dentin margins. Further, dentin–adhesive interfaces were not uniform and gaps were found by SEM and CLSM. Conclusions: The SEM and CLSM images demonstrated high variability of dentin–resin interfaces among saliva-contaminated groups. Rinsing the saliva and re-applying adhesive might be the best way to reduce the effect of saliva contamination on bond strength and microleakage.     

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.     

Influence of the preheating of bonding agents on the degree of conversion and bond durability in tridimensional dentin cavities

Objectives: The aim of this study was to evaluate the degree of conversion (DC) of dental bonding agents at different temperatures and the bond durability of restorations bonded with preheated dental bonding agents. Materials and methods: Three multistep adhesive systems, including one 3-step etch-and-rinse (Adper Scotchbond Multipurpose Plus) and two 2-step self-etching systems (Clearfil SE Bond; Filtek Low-Shrinkage Adhesive System), were evaluated. Dental bonding agents were preheated at 25, 37, and 60?°C. Bar-shaped specimens (n?=?5) were prepared for DC analysis. Fourier Transform Infrared/Attenuated Total Fluorescence spectra were obtained, and the DC was calculated by comparing the aliphatic bonds/reference peaks of nonpolymerized and polymerized materials. For bond durability analysis, tridimensional dentin cavities were prepared in 180 bovine incisors, which were then restored. Samples were stored in water for 24?h, and half of them were subjected to additional degradation with 10% NaOCl for 5?h. The push-out bond strength test was performed in a universal testing machine until failure. Failure modes were analyzed by scanning electron microscopy. Data were analyzed by analysis of variance (ANOVA) and Tukey’s tests (p?<?0.05). Results: Dental bonding agents preheated at 60?°C showed higher DC values than those preheated at 25 and 37?°C. The temperature of the dental bonding agent did not influence the bond durability, although fewer adhesive failures were observed in restorations bonded with dental bonding agents at 60?°C. Conclusion: Although the preheating of dental bonding agents can increase the DC, it may not improve the bond durability of dentin restorations.     

Morphology transition control of polyaniline from nanotubes to nanospheres in a soft template method

A soft template route is reported for the fabrication of polyaniline nanospheres via the oxidative polymerization of aniline in the presence of β‐naphthalenesulfonic acid (β‐NSA) as both surfactqant and dopant, and ammonium persulfate as oxidant at 2–5 °C. Control over the morphology and size of the nanoparticles was achieved by changing the reaction medium via addition of an organic cosolvent (i.e. ethanol or ethylene glycol) and by controlling the concentrations of aniline and β‐NSA and the molar ratio of β‐NSA to aniline. By this means the size of the β‐NSA–aniline micelles and the way that aniline monomer interacts with the micelles were controlled. In fact the lower dielectric constant of organic cosolvent, due to reduction of the possibility of dissociation of ionic species, causes the monomer to exist mostly as neutral aniline molecules rather than as anilinium cations. The neutral aniline molecules form aniline‐filled micelles with β‐NSA, which act as soft templates for the formation of polyaniline nanospheres. Scanning and transmission electron microscopies, dynamic light scattering, and Fourier transform infrared and UV‐visible spectroscopies were used to characterize the products. The mechanism of morphology transition from nanotubes to nanoparticles is discussed based on the experimental observations. © 2014 Society of Chemical Industry     

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.     

Zwitterionic sulfobetaine‐modified non‐woven fabric for blood filtration

Blood filtration requires a high removal ratio of leukocytes and with simultaneous high recovery ratio of platelets and other beneficial components. Problems are often encountered with blood filter materials in terms of high platelet loss. Zwitterions such as phosphorylcholine, sulfobetaine and carboxybetaine show effective resistance against protein adsorption and platelet adhesion. The study reported was aimed at achieving surface modification of poly(butylene terephthalate) non‐woven fabric (PBTNF) using UV radiation‐induced graft copolymerization of a zwitterionic sulfobetaine, N‐(3‐sulfopropyl)‐N‐methacroyloxyethyl‐N,N‐dimethylammonium betaine (SMDB), in order to improve the wettability and platelet recovery ratio of the PBTNF. Attenuated total reflection Fourier transform infrared and X‐ray photoelectron spectroscopy results showed that SMDB was successfully grafted onto the PBTNF. Photoinitiator concentration, monomer concentration and UV irradiation time affected markedly the degree of grafting. Critical wetting surface tension, water wetting time and hemolysis tests showed an improvement in wettability and blood compatibility as a result of graft copolymerization of SMDB. A blood filter material composed of SMDB‐modified PBTNF reduced platelet adhesion and had higher platelet recovery compared to poly(acrylic acid)‐modified PBTNF. It was found that SMDB monomer was successfully grafted onto PBTNF using UV radiation. The degree of grafting of SMDB could be controlled by varying the photoinitiator concentration, monomer concentration and UV irradiation time. SMDB‐modified PBTNF showed significant improvement in wettability and blood compatibility. The zwitterionic structure of SMDB is resistant to platelet adhesion. The SMDB‐modified PBTNF could be a candidate for a blood filter material and in other medical applications. Copyright © 2010 Society of Chemical Industry     

Effect of an Er,Cr:YSGG laser preparation on dentin bond strength of a universal adhesive

The aim of this study was to evaluate the bond strength of a universal adhesive system to dentin prepared with SiC paper or an Er,Cr:YSGG laser using different bonding strategies (etch-and-rinse versus self-etch mode). Ninety-six extracted caries-free, sound human molars were used. The teeth were longitudinally sectioned in the mesiodistal direction and were wet polished with 600-grit SiC paper to obtain a standardized flat dentin surface. All prepared teeth were randomly divided into two groups, according to the surface preparation method: GroupI:an erbium, chromium:yttrium,scandium, gallium, garnet laser; Group II: silicon carbide paper[SiC] (n = 48). Each group was then assigned into three subgroups according to the universal adhesive’s (Single Bond Universal) bonding strategies: (a) etch-and-rinse mode with phosphoric acid, (b) etch-and-rinse mode with a laser, (c) self-etch mode (n = 16). For surface preparation, the Er,Cr:YSGG laser was used at 3 W, 30 Hz with 140 μs pulse duration for 25 s. For etching mode, the laser was used at 1.5 W (60% air, 70% water). Cylinders of composite were fabricated on the bonding area and shear bond strength was determined using a universal testing machine. Failure modes were evaluated using a stereomicroscope. The data were analyzed using two-way ANOVA followed by the Bonferroni test (p < 0.05). Bonding strategies showed statistically significant differences in both the SiC-and laser-prepared groups (p < 0.05).Universal adhesive used in etch-and-rinse mode with acid showed significantly higher bond strength values than in self-etch mode (p < 0.05). The bond strength values did not differ according to the surface preparation method (p > 0.05). Irrespective of preparation method, using universal adhesive in etch-and-rinse mode with acid might improve dentin bond strength. Laser preparation did not affect the bond strength of the universal adhesive tested.     

Airborne-particle abrasion with niobium phosphate bioactive glass on caries-affected dentin: effect on the microtensile bond strength

This study evaluated the effect of airborne-particle abrasion with niobium phosphate bioglass (NbG) microparticles on the bond strength (μTBS) and longevity of an adhesive system to different dentin substrates. In this study, 18 Caries-free molars were used, of which 12 were microbiologically processed for caries induction. The dentin surfaces were evaluated in three groups: (1) Control – Healthy Dentin; (2) Partial removal of carious tissue; (3) complete removal of carious tissue. Half the teeth in each group were submitted to airborne-particle abrasion with NbG microparticles (15 s/1 cm/5 bar). After this, the adhesive Clearfil S³ was applied and composite buildups were constructed incrementally; and specimens were longitudinally sectioned to obtain bonded sticks (1.0 mm²) to be tested in tension (0.5 mm/min) immediately or after 6 months of storage in water. The fracture patterns were evaluated by stereomicroscope (40×) and then by scanning electron microscopy. The data were analyzed by the Kruskal-Wallis (post hoc Dunn) and Mann-Whitney tests (α = 0.05). Healthy dentin showed the highest bond strength (μTBS). Airborne-particle abrasion with NbG increased the μTBS values in the Group with complete caries removal. The bond strength values in the 24-h period were higher than those at 6 months. In the majority of the specimens the fracture mode was adhesive/mixed. The authors concluded that airborne-particle abrasion on dentin with NbG particles increased the μTBS in the group in which carious dentin was completely removed.     

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.