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|Type:||Artigo de periódico|
|Title:||Influence of photoinitiator type on the rate of polymerization, degree of conversion, hardness and yellowing of dental resin composites|
|Abstract:||Objectives. To evaluate the degree of conversion (DC), maximum rate of polymerization (R-P(max)), Knoop hardness (KHN) and yellowing (b-value) of resin composites formulated with phenylpropanedione (PPD), camphorquinone (CQ), or CQ/PPD at different concentrations. The hypotheses tested were (i) PPD or CQ/PPD would produce less R-P(max) and yellowing than CQ alone without affecting DC and KHN, and (ii) R-P(max), DC, and KHN would be directly related to the absorbed power density (PDabs). Methods CQ/amine, PPD/amine and CQ/PPD/amine were used at low, intermediate and high concentrations in experimental composites. Photoinitiator absorption and halogen-light emission were measured using a spectrophotometer, R-P with differential scanning calorimetry (DSC), DC with DSC and FTIR, KHN with Knoop indentation; and color with a chromameter. The results were analyzed with two-way analysis of variance (ANOVA)/Student-Newman-Keul's test (p < 0.05). Correlation tests were carried out between PDabs and each of DC, R-P(max) and KHN. Results. The PDabs increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while R-P(max) and KHN required higher concentrations. DC was similar for all photoinitiators, but R-P(max) was lower with PPD and CQ/PPD. PPD produced the lowest KHN. Yellowing increased with photoinitiator concentration. PPD did not reduce yellowing at intermediate and/or high concentrations, compared to CQ-formulations. PDabs showed significant correlations with DC, R-P(max) and KHN. Conclusion. PPD or CQ/PPD reduced R-P(max) in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, R-P(max) and KHN were dependent on PDabs. (c) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.|
molar extinction coefficient
|Editor:||Elsevier Sci Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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