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Várzea Grande, Brazil

Munchow E.A.,Federal University of Pelotas | Valente L.L.,Federal University of Pelotas | Peralta S.L.,Federal University of Pelotas | Fernandez M.R.,Federal University of Pelotas | And 4 more authors.
Journal of Biomedical Materials Research - Part B Applied Biomaterials

The ethyl-4-dimethylaminobenzoate (EDAB) is widely used as a coinitiator of the camphorquinone (CQ), but in acidic circumstances it might present some instability, reducing the polymerization efficiency of the material. Considering this, new coinitiators are being evaluated. Hence, this study evaluated the kinetic of polymerization (KP), the degree of conversion (DC), and the rate of polymerization (RP) of experimental resin adhesives containing 1,3-diethyl-2-thiobarbituric acid (TBA) as a coinitiator of the CQ. The experimental monomeric blend was prepared with bisphenol A glycidyl dimethacrylate, 2-hydroxyethyl methacrylate, and acidic monomers. CQ was added at 1 mol % as photoinitiator. Six groups were formulated: four containing concentrations of 0.1, 0.5, 1, and 2 mol % of TBA, one without coinitiator, and the last one containing 1 mol % of EDAB (control group). The KP and the R P were performed using real-time Fourier Transform infrared spectroscopy. The group without coinitiator has not formed a polymer, whereas the addition of TBA resulted in the conversion of monomers in polymer. The DC of the adhesives was as higher as the increase in the TBA content. The group with 2 mol % of TBA presented improved DC and reactivity (RP) than the other groups and the control one. Hence, the TBA has performed as a coinitiator of the CQ for the radical polymerization of methacrylate resin adhesives and it has improved the DC and the reactivity of the materials. Thus, it is a potential coinitiator for the photopolymerization of dental materials. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1217-1221, 2013. Copyright © 2013 Wiley Periodicals, Inc., a Wiley Company. Source

Da Silveira Lima G.,University of Varzea Grande | Ogliari F.A.,Federal University of Pelotas | Souza E Silva M.G.,Federal University of Pelotas | Munchow E.A.,Federal University of Pelotas | And 2 more authors.
Journal of Applied Polymer Science

This study evaluated the effectiveness of benzodioxole derivatives as coinitiators of radical polymerization in a model-dental adhesive resin. To compose the adhesive resin, a monomer mixture based on 50 wt % of Bis-GMA, 25 wt % of TEGDMA, and 25 wt % of HEMA was used. Camphorquinone (CQ) 1 mol % was used as a photoinitiator to initiate polymerization. 1,3-Benzodioxole (BDO) and piperonyl alcohol (PA) were used as coinitiators at 0.25, 0.5, 1, 2, 4, 8, and 16 mol % level. In addition, tertiary amine, ethyl 4-dimethylamino benzoate (EDAB) was used as coinitiator in the control group. Some physical, chemical, and mechanical properties of the polymer formed in the experimental adhesives were evaluated using the kinetics of polymerization, sorption and solubility, flexural strength, and elastic modulus tests. The results indicated that BDO and PA were effective coinitiators in the photoinitiator system based on CQ. Comparisons between the benzodioxoles derivative coinitiators and EDAB showed similar performance in the kinetics of polymerization and flexural strength. For water sorption and solubility evaluation, BDO and PA demonstrated significantly more sorption of water and less solubility than the EDAB control group. The findings suggest that BDO and PA were feasible alternatives to conventional amine as coinitiator. Copyright © 2012 Wiley Periodicals, Inc. Source

Leal F.B.,Federal University of Pelotas | Madruga F.C.,Federal University of Pelotas | Prochnow E.P.,Federal University of Pelotas | Lima G.S.,University of Varzea Grande | And 3 more authors.
International Journal of Adhesion and Adhesives

This study evaluated the effect of the concentration of acidic functional monomer on the dentin bond stability of a model two-step, self-etch adhesive system. Six self-etch primers were formulated using hydroxyethyl methacrylate (HEMA), 1,3-glycerol dimethacrylate phosphate (GDMA-P), ethanol and water. Different mass concentrations of GDMA-P were tested: 0, 15, 30, 50, 70 or 100% (primers labeled P0100). The pH of the solutions was measured. The bonding resin was composed of (di)methacrylates. Bond strength to bovine dentin was assessed through a microtensile bond test. The beam specimens were stored in distilled water, at 37 °C, for 24 h, 6 months or 1 year. Data were statistically analyzed and failure modes classified under magnification. The increase in acidic monomer concentration was associated with an exponential decrease in pH (R2=0.999; P<0.001). All specimens debonded prematurely for the primers P0, P70 and P100. After 24 h, the bond strengths for P50>P30=P 15. After 6 months and 1 year, P50=P30> P15. The bond strength after 6 months was similar to 24 h for P 15 and P50, but significantly lower after 1 year. P 30 showed no differences in bond strength over the 1-year storage period. A predominance of mixed failures was detected for all primers at 24 h. After 6 months, P30 and P50 showed a predominance of adhesive failures. After 1 year, the predominant failure mode for all primers was cohesive within dentin. In conclusion, a mass fraction of 50% of phosphate monomer is a limit to be added to self-etch primers; a more stable longevity of the bonds was obtained with the primer with 30% of phosphate methacrylate. © 2011 Elsevier Ltd. All rights reserved. Source

Leal F.B.,Federal University of Pelotas | Lima G.S.,University of Varzea Grande | Collares F.M.,Federal University of Rio Grande do Sul | Samuel S.M.,Federal University of Rio Grande do Sul | And 3 more authors.
International Journal of Adhesion and Adhesives

The aim of this study was to evaluate the influence of an iodonium salt on the immediate and long-term microtensile bond strength to dentin of an experimental dental two-step, self-etching adhesive system. A model dental adhesive resin was formulated using bisphenol A glicidyl dimethacrylate (Bis-GMA), triethylene glicol dimethacrylate (TEGDMA), and hydroxyethyl methacrylate (HEMA), which was polymerized using four combinations of photo-initiators and coinitiators. A group using only camphorquinone (CQ), two binary systems (CQ and ethyl 4-dimethylamine benzoate (CQEDAB), CQ and diphenyliodonium hexafluorphosphate (CQDPIHFP)) and a ternary system (CQEDABDPIHFP) was investigated. Clearfil SE Bond (CSEB) was used as a commercial reference. Bond strength to bovine dentin was assessed through microtensile bond tests measured in MPa in a universal testing machine. The beam specimens were stored in distilled water at 37 °C for 24 h and 1 year. Two-way ANOVA and Student-Newman-Keuls' post-hoc tests were used to compare means of groups (α=5%) and failure modes classified under magnification. After 24 h, the ternary system showed a bond strength similar to that of the binary system CQEDAB and the commercial material. After 1 year of storage, the μTBS values of the group CQEDABDPIHFP showed a bond strength significantly higher (p<0.05) than those of the CQ, CQDPIHFP, and CQEDAB groups and no difference from that of the CSEB group. The ternary photo-initiator system with iodonium salt maintained increased bond strength to dentin of model self-etching adhesive systems after 1 year of aging. © 2012 Elsevier Ltd. Source

de Aguilar-Nascimento J.E.,Federal University of Mato Grosso | de Aguilar-Nascimento J.E.,University of Varzea Grande | Caporossi C.,Federal University of Mato Grosso | Metelo J.S.,Federal University of Mato Grosso | And 3 more authors.
Nutricion Hospitalaria

Objective: To investigate the gastric emptying of an oral supplement containing carbohydrate plus whey protein drunk before sedation for gastroscopy. Methods: This is a randomized double-blind trial including adult patients (ages 18-65) with a chief complaint of epigastric burning and who were candidates to elective gastroscopy. After overnight fast subjects were randomized to drink 200 mL of an oral nutritional supplement containing maltodextrine in addition to whey protein 150 to 210 min before the gastroscopy (intervention group, n = 12) or to undergo the endoscopic procedure with no supplement (control group, n = 12). The residual gastric volume (RGV) suctioned and measured during the exam was the main endpoint of the study. Results: There were no complications during all exams. The median (range) fasting time was greater (P < 0.001) in control group (770 min, ranging from 660-917 min) than in the study group (175min ranging from 150 to 210 min). The median (range) RGV was similar in between the two groups (control group: 25 (10-70) mL versus intervention group: 10 (0-100) mL; p = 0.32). Conclusion: Gastric emptying 150-210 min after the ingestion of an oral supplement containing carbohydrate plus whey protein is similar to an overnight fasting condition. Although limited by the number of cases, the sedation for endoscopic procedures is safe with this fasting protocol. Source

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