Influence of photoinitiator type on the rate of polymerization, degree of conversion, hardness and yellowing of dental resin composites

Schneider, Luis Felipe J.; Pfeifer, Carmem S.C.; Consani, Simonides; Prahl, Scott A.; Ferracane, Jack L.

doi:10.1016/j.dental.2008.01.007

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Volume 24, Issue 9 , Pages 1169-1177, September 2008

Influence of photoinitiator type on the rate of polymerization, degree of conversion, hardness and yellowing of dental resin composites

Luis Felipe J. Schneider
- Dental Materials Division, Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil
- Corresponding author at: FOP-UNICAMP, Área Materiais Dentários, Av. Limeira 901, Caixa Postal 52, CEP 13414-903 Piracicaba, SP, Brazil. Tel.: +55 19 2106 5345; fax: +55 19 21060144.
Carmem S.C. Pfeifer
- Biomaterials and Oral Biochemistry Department, University of São Paulo, São Paulo, SP, Brazil
Simonides Consani
- Dental Materials Division, Piracicaba Dental School, University of Campinas, Piracicaba, SP, Brazil
Scott A. Prahl
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, USA
Jack L. Ferracane
- Division of Biomaterials & Biomechanics, Oregon Health & Science University, Portland, OR, USA

Received 10 December 2007; received in revised form 6 January 2008; accepted 7 January 2008.

Abstract

Objectives

To evaluate the degree of conversion (DC), maximum rate of polymerization (), 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 and yellowing than CQ alone without affecting DC and KHN, and (ii) , DC, and KHN would be directly related to the absorbed power density (PD_abs).

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_abs and each of DC, and KHN.

Results

The PD_abs increased with photoinitiator concentration and PPD samples had the lowest values. In general, maximum DC was comparable at intermediate concentration, while and KHN required higher concentrations. DC was similar for all photoinitiators, but 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. PD_abs showed significant correlations with DC, and KHN.

Conclusion

PPD or CQ/PPD reduced in experimental composites without affecting the DC. The use of PPD did not reduce yellowing, but reduced KHN. DC, and KHN were dependent on PD_abs.