Influence of irradiant energy on degree of conversion, polymerization rate and shrinkage stress in an experimental resin composite system

Calheiros, Fernanda C.; Daronch, Márcia; Rueggeberg, Frederick A.; Braga, Roberto R.

doi:10.1016/j.dental.2008.01.006

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Volume 24, Issue 9 , Pages 1164-1168, September 2008

Influence of irradiant energy on degree of conversion, polymerization rate and shrinkage stress in an experimental resin composite system

Fernanda C. Calheiros
- Department of Dental Materials, School of Dentistry, University of São Paulo, FOUSP, Av. Prof. Lineu Prestes, 2227, São Paulo, SP 05508-900, Brazil
Márcia Daronch
- Department of Dental Materials, School of Dentistry, University of São Paulo, FOUSP, Av. Prof. Lineu Prestes, 2227, São Paulo, SP 05508-900, Brazil
- Dental Materials Section, Department of Oral Rehabilitation, Medical College of Georgia, Augusta, GA, USA
Frederick A. Rueggeberg
- Dental Materials Section, Department of Oral Rehabilitation, Medical College of Georgia, Augusta, GA, USA
Roberto R. Braga
- Department of Dental Materials, School of Dentistry, University of São Paulo, FOUSP, Av. Prof. Lineu Prestes, 2227, São Paulo, SP 05508-900, Brazil
- Corresponding author. Tel.: +1 55 11 3091 7840x224; fax: +1 55 11 3091 7840x201.

Received 4 October 2007; received in revised form 5 December 2007; accepted 7 January 2008.

Abstract

Objective

This study evaluated the degree of conversion (DC), maximum rate of cure (), and polymerization stress (PS) developed by an experimental dental composite subjected to different irradiant energies (3, 6, 12, 24, or 48J/cm²) under constant irradiance (500mW/cm²).

Methods

DC and were monitored for 10min on the bottom surface of 2-mm thick disks and on 150-μm thick films (representing the top of the specimen) using ATR-FTIR. PS was monitored for 10min in 2-mm thick disks bonded to two glass rods (Ø=5mm) attached to a universal testing machine. One-way ANOVA/Tukey tests were used and differences in DC and between top and bottom surfaces were examined using Student's t-test. Statistical testing was performed at a pre-set alpha of 0.05.

Results

For a given surface, DC showed differences among all groups, except at the top between 24 and 48J/cm². was similar among all groups at the same surface and statistically higher at the top surface. PS also showed significant differences among all groups. Data for 48J/cm² were not obtained due to specimen failure at the glass/composite interface.