Abstract
Objectives. To determine temperature dependence of shrinkage stress kinetics for a set of resin composites formulated with dimethacrylate monomer matrices.
Methods. Six representative resin composites with a range of resin matrices were selected. Two of them were considered as low shrinking resin composites: Kalore and Venus Diamond. The shrinkage stress kinetics at 23 degrees C and 37 degrees C were measured continuously using a Bioman instrument for 60 min. Stress levels between materials were compared at two intervals: 2 min and 60 min. Specimen temperatures were controlled by a newly designedheating device. Stress measurements were monitored for 1 h, after irradiation for 40s at 550mW/cm(2)(energy density = 22J/cm(2)). Three specimens (n = 3) were used at each temperature per material.
Results. Shrinkage stress at 23 degrees C ranged from 2.93MPa to 4.71MPa and from 3.57MPa to 5.42MPa for 2 min and 60 min after photo-activation, respectively. The lowest stress-rates were recorded for Kalore and Venus Diamond (0.34 MPa s(-1)), whereas the highest was recorded for Filtek Supreme XTE (0.63 MPa s(-1)). At 37 degrees C, shrinkage stress ranged from 3.27 MPa to 5.35MPa and from 3.36MPa to 5.49 MPa for 2 min and 60 min after photo-activation, respectively. Kalore had the lowest stress-rate (0.44 MPa s(-1)), whereas Filtek Supreme XTE had the highest (0.85 MPa s(-1)). Materials exhibited a higher stress at 37 degrees C than 23 degrees C except for Kalore and Venus Diamond. Positive correlations were found between shrinkage stress and stress-rate at 23 degrees C and 37 degrees C (r = 0.70 and 0.92, respectively).
Significance. Resin-composites polymerized at elevated temperature (37 degrees C) completed stress build up more rapidly than specimens held at 23 degrees C. Two composites exhibited atypical reduced stress magnitudes at the higher temperature. (C) 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.