@article{schneider08a,
  author = {Luis F. J. Schneider and Carmem S. C. Pfeifer and Simonides Consani and Scott A. Prahl and Jack L. Ferracane},
  title = {Influence of photoinitiator type on the rate of polymerization, degree of conversion, hardness and yellowing of dental resin composites},
  journal = {Dental Materials},
  pages = {1169--1177},
  volume = {24},
  year = {2008},
  abstract = {OBJECTIVES: To evaluate the degree of conversion ({DC}), maximum rate of polymerization ($R_p^{\mathit{max}}$), 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 $R_p^{\mathit{max}}$ and yellowing than {CQ} alone without affecting {DC} and {KHN}, and (ii) $R_p^{\mathit{max}}$, DC, and KHN would be directly related to the absorbed power density (PD$_{\mathit{abs}}$). \\[3mm] 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 PD$_{\mathit{abs}}$ and each of DC, $R_p^{\mathit{max}}$ and KHN. \\[3mm] RESULTS: The PD$_{\mathit{abs}}$ increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while $R_p^{\mathit{max}}$ and KHN required higher concentrations. DC was similar for all photoinitiators, but $R_p^{\mathit{max}}$ was lower with PPD and CQ/PPD. PPD produced the lowest KHN. Yellowing increased with photoinitiator concentration.scmc PPD did not reduce yellowing at intermediate and/or high concentrations, compared to CQ-formulations. PD$_{\mathit{abs}}$ showed significant correlations with DC, $R_p^{\mathit{max}}$ and KHN. \\[3mm] CONCLUSION: PPD or CQ/PPD reduced $R_p^{\mathit{max}}$ in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, $R_p^{\mathit{max}}$ and KHN were dependent on PD$_{\mathit{abs}}$.},
}