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Purpose: The aim of this study was to evaluate the tensile bond strength (TBS) of repairs in recent fillings of methacrylate- (MBC) or silorane-based composites (SBC) subsequent to different surface treatments. Materials and Methods: Fifty slabs of Filtek P60 (3M ESPE, St Paul, USA) and Filtek P90 (3M ESPE) were stored for 10 days in distilled water at 37°C. The surface of adhesion was abraded with a 600-grit silicone paper and repaired using each respective composite: G1, no treatment (control); G2, application of adhesive; G3, application of silane and adhesive; G4, sandblasting (Al2O3) and adhesive; and G5, sandblasting (Al2O3), silane, and adhesive. Further 10 slabs of each composite were also evaluated for cohesive strength (G6). After 30 days immersion in distilled water at 37°C, the TBS was determined. Results: TBS results were higher for MBC than for SBC (P = 0.00012). The experimental groups were similar for SBC and the TBS was 27% of its cohesive strength. For P60, sandblasting significantly improved the TBS compared to other groups. With MBC, G4 and G5, the TBS was approximately 47% of its cohesive strength. Conclusion: Sandblasting (Al2O3) improves the repair-strength of MBC, whilst for the SBC all treatments succeed. MBC presents higher repair strength than SBC. [ABSTRACT FROM AUTHOR]

There are few studies that fully characterize the effect of the filler size on the surface, optical and mechanical properties of resin composites. Aim: To determine the influence of the filler size content on surface, optical and mechanical properties before and after accelerated aging. Methods: Seven resin composites were investigated: Filtek Supreme® (3M/ESPE), Estelite Σ Quick® (Tokuyama), Evolu-X® (Dentsply), Esthet-X HD® (Dentsply), Opallis® (FGM), Herculite XRV Ultra® (Kerr) and Filtek Z250® (3M/ESPE). Elastic modulus (EM) and flexural strength (FS) were determined by three-point bending of specimens immersed or not in absolute ethanol for seven days. Roughness (Ra) and gloss (G.U.) analyses were determined before and after ethanol storage for seven days and CIELAB color change (ΔE*) was obtained with a spectrophotometer. Results were analyzed by two-way ANOVA (general linear model) for EM and FS, with repeated measures for roughness and gloss, and one-way ANOVA for ΔE*. All comparisons were performed by Tukey's test (5%). Pearsons' correlation test was performed to determine the correlation between EM, FS, roughness, gloss, and ΔE* with the mean filler sizes. Results: Mechanical properties decreased for all materials when submitted to immersion in ethanol. Increasing filler size gradually increased EM, FS and roughness values; gloss values decreased and didn't significantly affects ΔE*. Nanofiller composites presented higher gloss values than the others. Conclusions: It was possible to determine that the average filler size is a good predictor just for FS and gloss retention. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: The purpose of this study was to evaluate the reactivity and polymerization kinetics behavior of a model dental adhesive resin with water-soluble initiator systems. Methods: A monomer blend based on Bis-GMA, TEGDMA and HEMA was used as a model dental adhesive resin, which was polymerized using a thioxanthone type (QTX) as a photoinitiator. Binary and ternary photoinitiator systems were formulated using 1mol% of each initiator. The co-initiators used in this study were ethyl 4-dimethylaminobenzoate (EDAB), diphenyliodonium hexafluorophosphate (DPIHFP), 1,3-diethyl-2-thiobarbituric acid (BARB), p-toluenesulfinic acid and sodium salt hydrate (SULF). Absorption spectra of the initiators were measured using a UV–Vis spectrophotometer, and the photon absorption energy (PAE) was calculated. The binary system camphorquinone (CQ)/amine was used as a reference group (control). Twelve groups were tested in triplicate. Fourier-transform infrared spectroscopy (FTIR) was used to investigate the polymerization reaction during the photoactivation period to obtain the degree of conversion (DC) and maximum polymerization rate (R p max) profile of the model resin. Results: In the analyzed absorption profiles, the absorption spectrum of QTX is almost entirely localized in the UV region, whereas that of CQ is in the visible range. With respect to binary systems, CQ+EDAB exhibited higher DC and values. In formulations that contained ternary initiator systems, the group CQ+QTX+EDAB was the only one of the investigated experimental groups that exhibited an value greater than that of CQ+EDAB. The groups QTX+EDAB+DPIHFP and QTX+DPIHFP+SULF exhibited values similar to those of CQ+EDAB with respect to the final DC; however, they also exhibited lower reactivity. Significance: Water-soluble initiator systems should be considered as alternatives to the widely used CQ/amine system in dentin adhesive formulations. [Copyright &y& Elsevier]

Abstract: Objectives: Since photoinitiator systems for dental resins based on camphorquinone (CQ) present color disadvantages, trimethylbenzoyl-diphenyl-phosphine oxide (TPO) has been proposed as an alternative. However, there are remaining considerations about its curing efficiency. The aims of the present investigation were: to characterize the relationship between the photoinitiator absorption spectra and the light spectrum emitted from a QTH light (absorbed power density, PDabs); to evaluate the kinetics of polymerization, and the depth of cure for filled dimethacrylate resins formulated with different photoinitiator systems. Methods: CQ+EDMAB (control); TPO and TPO+EDMAB were used in 50:50 Bis-GMA/TEGDMA resins. Photoinitiator absorption and QTH-light emission were evaluated using a spectrophotometer and kinetics of polymerization with differential scanning calorimetry (DSC) (n =3). Depth of cure was analyzed by the scraping method (n =5), as recommended by ISO4049. One-way ANOVA/Tukey''s (p <0.05) was used to analyze the results. Results: CQ presented higher PDabs than TPO (364 and 223mW/cm3, respectively). The DSC revealed that TPO and TPO+EDMAB produced a faster reaction than CQ+EDMAB. Composite formulated with CQ+EDMAB produced higher depth of cure (6.3±0.4mm) than those with TPO (4.3±0.1) or TPO+EDMAB (4.2±0.3). Significance: Although CQ presented higher PDabs than TPO, formulations containing TPO exhibited higher reactivity than that with CQ. On the other hand, materials formulated with TPO demonstrated lower depth of cure than that with CQ. Therefore, its use as an alternative photoinitiator requires further investigation, with higher concentrations. [Copyright &y& Elsevier]

Many developments have been made in the field of resin composites for dental applications. However, the manifestation of shrinkage due to the polymerization process continues to be a major problem. The material's shrinkage, associated with dynamic development of elastic modulus, creates stresses within the material and its interface with the tooth structure. As a consequence, marginal failure and subsequent secondary caries, marginal staining, restoration displacement, tooth fracture, and/or postoperative sensitivity are clinical drawbacks of resin-composite applications. The aim of the current paper is to present an overview about the shrinkage stresses created during resin-composite applications, consequences, and advances. The paper is based on results of many researches that are available in the literature. [ABSTRACT FROM AUTHOR]

Though many advances have been made in the development of dental adhesives, the immediate, or short-term, disruption created by stress — due to polymerization of resin composite restorative materials within dental cavities — is still a challenge yet to be completely solved in restorative dentistry. Therefore, the aim of this paper is to present a general overview of the subject, concerning resin composite formulations, origins of stress, clinical consequences of stress development, in vitro methods used for its measurement and methods used to reduce stress magnitudes and rates of development. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To evaluate the effect of amine ratio (ethyl 4-dimethylaminobenzoate, EDMAB) on the maximum rate of polymerization (), degree of conversion (DC), Knoop hardness (KH), water sorption (Wsp), water solubility (Wsl) and color changes (ΔE) over time of resin composites formulated with the photoinitiators camphorquinone (CQ), phenylpropanedione (PPD) and CQ-PPD in combination. Materials and methods: Experimental resin composites were made with photoinitiator:amine ratios of 2:1, 1:1, 1:1.5 and 1:2 by weight. was evaluated with differential scanning calorimetry (DSC), DC with DSC and Fourier transformed infrared (FTIR) spectroscopy, KH with Knoop indentation, Wsp and Wsl adapted from ISO 4049; and color with a chromameter. The results were analyzed with two-way ANOVA/Tukey’s multiple comparison test (p <0.05). Results: The higher the amine ratio in the composite, the higher was DC, , and KH, and the lower was Wsl, regardless of the photoinitiator type. The use of PPD alone resulted in poorer properties than CQ and CQ-PPD. Many factors seem to affect the color changes and the b-axis data revealed that the higher the amine ratio, the higher was the +b value (yellowing) for CQ and CQ-PPD formulations. Conclusions: Higher amine ratios led to improved polymer properties, but also produced more yellowing in resin composites with CQ and CQ-PPD. The use of PPD alone was not advantageous for producing good final properties when compared to CQ and CQ-PPD. [Copyright &y& Elsevier]

Abstract: Objectives: To evaluate (1) the influence of fluoride-containing adhesive on microtensile bond strength (μTBS) and (2) in vitro secondary caries inhibition at the resin–dentin interface after 24h and 3 months water-storage and (3) the degree of conversion of different adhesives after 24h 1 month. Methods: Flat surfaces of human teeth were ground and randomly assigned to six groups: (SBMP-24) Scotchbond Multi-Purpose control [SBMP], 24h; (SE-24) SBMP etch and primer+Clearfil SE Bond adhesive [SE], 24h; (PB-24) SBMP etch and primer+Clearfil Protect Bond adhesive [PB], 24h; (SBMP-3) SBMP, 3 months; (SE-3) SBMP+SE, 3 months; and (PB-3) SBMP+PB, 3 months. To evaluate the effect of the adhesive resin alone, all teeth were etched with 35% phosphoric acid and primed with SBMP primer prior to applying the adhesive resin. Bonded assemblies were prepared for μTBS and stored in distilled water at 37°C for 24h and 3 months. Sections of restored teeth of each group were exposed to an acid challenge. The specimens were sectioned, polished, and then observed with polarized light microscopy (PLM). Also, the degree of conversion (DC) of the adhesives was measured using Fourier Transform-Infrared spectroscopy (FTIR) at 24h and 1 month, after polymerization. Results: μTBS values obtained in MPa (24h/3m) were: (MP) 61.5±10.5/52.9±8.9, (SE) 55.5±11.8/55.6±13, and (PB) 50.3±9.9/61.0±13.6. For interface analysis by PLM, an inhibition zone (IZ) adjacent to the hybrid layer was created only when the fluoride-containing adhesive (PB) was used. The DC in percentage (24h, 1 month) were: (MP) 60.5±2.8/61.3±0.6, (SE) 69.6±1.3/70.7±0.05, and (PB) 53.1±0.4/58.3±1.6. Significance: The fluoride-containing adhesive demonstrated significant increase of bond strength values after water-storage. This material was also able to create an acid inhibition zone in dentin. There was a significant increase of degree of conversion after 1 month only for PB. [Copyright &y& Elsevier]

Abstract: Objective: To evaluate the influence of tetrahydrofuran (THF) on the resin-to-dentin microtensile bond strength (μTBS) after water storage, for 24h and 6 months, and to compare its behavior with that of traditional solvents. Methods: Seven versions of monomer/solvent mixtures (primers) were prepared using the following solvent and water combinations: (1) THF, (2) acetone, (3) ethanol, (4) water, (5) THF/water, (6) acetone/water and (7) ethanol/water. An experimental adhesive resin was also synthesized to compare adhesive systems with the different primers. Forty-two bovine incisors, randomly separated into seven groups, had their superficial coronal dentin exposed. After acid-etching and rinsing, the excess water was removed from the surface with absorbent paper. Each experimental primer was applied with agitation (30s) followed by a mild air stream (10s). The experimental adhesive resin was applied and light-activated (20s). Resin composite restorations were constructed incrementally. Restored teeth were stored in distilled water at 37°C (24h) and sectioned to obtain sticks with an area of 0.5mm2. Half the specimens were subjected to the μTBS test immediately after being cut and the other half were tested after 6 months of water storage. Data (MPa) were analyzed by two-way ANOVA (solvent type and storage time as factors) and Tukey–Kramer''s test at α =0.05. Results: Factors and interaction showed a statistical effect. After 6 months storage, acetone groups and primers containing THF showed similar μTBS to initial means. Significance: THF seems to be a promising solvent for use in dental adhesive systems, maintaining bond strength on dentin substrate after storage. [Copyright &y& Elsevier]