Effects of Potassium Oxalate on Knoop Hardness of Etch-and-Rinse Adhesives

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The objective of this study was to determine whether the hardness of etch-and-rinse adhesives may be affected by the pretreatment of acid-etched dentin with potassium oxalate desensitizer. Unerupted human third molars were cut into crown segments by removing the occlusal enamel and roots. The pulp chamber of these crown segments was connected to a syringe barrel filled with phosphate-buffered saline so that the moisture of dentin was maintained during the bonding procedures. Three etch-and-rinse adhesives-two two-step systems (Adper Single Bond 2 [SB], One-Step [OS]) and one three-step system (Adper Scotchbond Multi-Purpose [MP])-were applied to acid-etched dentin that had been treated (experimental groups) or not (control groups) with potassium oxalate (BisBlock). The Knoop hardness (KHN) of adhesives was taken at different sites of the outer surface of the adhesive-bonded dentin. The KHN of the three tested adhesives applied to acid-etched dentin treated with potassium oxalate was significantly lower than that exhibited by the respective controls (not treated with oxalate; p<0.05). Regardless of the adhesive, the treatment with potassium oxalate reduced the adhesives' KHN (p<0.05), with the OS system exhibiting the lowest KHN compared with the MP and SB systems.374356362Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [300615/2007-8, 473164/2007-8

Effects of ethanol addition on the water sorption/solubility and percent conversion of comonomers in model dental adhesives.

Objectives. This study evaluated the kinetics of water uptake and percent conversion in neat versus ethanol-solvated resins that were formulated to be used as dental bonding agents. Methods. Five methacrylate-based resins of known and increasing hydrophilicities (R1, R2, R3, R4 and R5) were used as reference materials. Resins were evaluated as neat bonding agents (100% resin) or they were solvated with absolute ethanol (95% resin/5% ethanol or 85% resin/15% ethanol). Specimens were prepared by dispensing the uncured resin into a circular mold (5.8mm 70.8 mm). Photo-activation was performed for 80 s. The water sorption/ diffusion/solubility was gravimetrically evaluated, while the degree of conversion (DC) was calculated by Fourier-transform infrared spectroscopy. Results. Water sorption increased with the hydrophilicity of the resin blends. In general, the solvated resins exhibited significantly higher water sorption, solubility and water diffusion coefficients when compared to their corresponding neat versions (p < 0.05). The only exception was resin R1, the least hydrophilic resin, in which neat and solvated versions exhibited similar water sorption (p > 0.05). Addition of ethanol increased the DC of all resins tested, especially of the least hydrophilic, R1 and R2 (p < 0.05). Despite the increased DC of ethanol\u2013solvated methacrylate-based resins, it occurs at the expense of an increase in their water sorption/diffusion and solubility values. Significance. Negative effects of residual ethanol on water sorption/solubility appeared to be greater as the hydrophilicity of the resin blends increased. That is, the use of less hydrophilic resins in dental adhesives may create more reliable and durable bonds to dentin

Effects of ethanol addition on the water sorption/solubility and percent conversion of comonomers in model dental adhesives

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Objectives. This study evaluated the kinetics of water uptake and percent conversion in neat versus ethanol-solvated resins that were formulated to be used as dental bonding agents. Methods. Five methacrylate-based resins of known and increasing hydrophilicities (R1, R2, R3, R4 and R5) were used as reference materials. Resins were evaluated as neat bonding agents (100% resin) or they were solvated with absolute ethanol (95% resin/5% ethanol or 85% resin/15% ethanol). Specimens were prepared by dispensing the uncured resin into a circular mold (5.8 mm x 0.8 mm). Photo-activation was performed for 80 s. The water sorption/diffusion/solubility was gravimetrically evaluated, while the degree of conversion (DC) was calculated by Fourier-transform infrared spectroscopy. Results. Water sorption increased with the hydrophilicity of the resin blends. In general, the solvated resins exhibited significantly higher water sorption, solubility and water diffusion coefficients when compared to their corresponding neat versions (p < 0.05). The only exception was resin R1, the least hydrophilic resin, in which neat and solvated versions exhibited similar water sorption (p > 0.05). Addition of ethanol increased the DC of all resins tested, especially of the least hydrophilic, R1 and R2 (p < 0.05). Despite the increased DC of ethanol-solvated methacrylate-based resins, it occurs at the expense of an increase in their water sorption/diffusion and solubility values. Significance. Negative effects of residual ethanol on water sorption/solubility appeared to be greater as the hydrophilicity of the resin blends increased. That is, the use of less hydrophilic resins in dental adhesives may create more reliable and durable bonds to dentin. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.251012751284Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)NIDCR [R01-DE-014911]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [07/54618-4]CNPq [300615/2007-8, 473164/2007-8]NIDCR [R01-DE-014911

Effect of air-drying on the solvent evaporation, degree of conversion and water sorption/solubility of dental adhesive models

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)This study evaluated protocols to eliminate acetone from dental adhesives and their effect on the kinetic of water sorption and percent of conversion of these adhesives. Experimental methacrylate-based adhesives with increasing hydrophilicity (R2, R3, R5) were used as reference materials. Primer-like solutions were prepared by addition of 50 wt% acetone. Acetone elimination was measured gravimetrically before and after: a spontaneous evaporation, an application of air-drying at room temperature or application of 40 degrees C air-drying. Protocols were performed from 15 to 60 s. Specimens of adhesive/acetone mixtures were photo-activated and tested for degree of conversion, water sorption and solubility. Data were analyzed by ANOVA and Bonferroni's tests (alpha = 0.05). Complete acetone elimination was never achieved, but it was significantly greater after the 40 degrees C air-drying application. Higher acetone elimination was observed for the least hydrophilic adhesive. Longer periods for acetone evaporation and heated air-stream can optimize polymerization and reduce the water sorption/solubility of adhesive system models.233629638Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)NIDCR [R01-DE-015306]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)CNPq [306100/2010-0]FAPESP [07/54618-4]NIDCR [R01-DE-015306