Temperature-dependent polymerization shrinkage stress kinetics of resin-composites.
OBJECTIVE
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°C and 37°C were measured continuously using a Bioman instrument for 60min. Stress levels between materials were compared at two intervals: 2min and 60min. Specimen temperatures were controlled by a newly designed heating device. Stress measurements were monitored for 1h, 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°C ranged from 2.93MPa to 4.71MPa and from 3.57MPa to 5.42MPa for 2min and 60min after photo-activation, respectively. The lowest stress-rates were recorded for Kalore and Venus Diamond (0.34MPas(-1)), whereas the highest was recorded for Filtek Supreme XTE (0.63MPas(-1)). At 37°C, shrinkage stress ranged from 3.27MPa to 5.35MPa and from 3.36MPa to 5.49MPa for 2min and 60min after photo-activation, respectively. Kalore had the lowest stress-rate (0.44MPas(-1)), whereas Filtek Supreme XTE had the highest (0.85MPas(-1)). Materials exhibited a higher stress at 37°C than 23°C except for Kalore and Venus Diamond. Positive correlations were found between shrinkage stress and stress-rate at 23°C and 37°C (r=0.70 and 0.92, respectively).


CONCLUSIONS
Resin-composites polymerized at elevated temperature (37°C) completed stress build up more rapidly than specimens held at 23°C. Two composites exhibited atypical reduced stress magnitudes at the higher temperature.
School of Dentistry and Photon Science Institute, University of Manchester, UK; Institute of Materials Science and Technology, Friedrich-Schiller-University, Jena, Germany. Electronic address: David.Watts@manchester.ac.uk.
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Watts
School of Dentistry and Photon Science Institute, University of Manchester, UK; School of Dentistry, Taibah University, Medina, Saudi Arabia.
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Alnazzawi
D003188:Composite Resins; D007700:Kinetics; D058105:Polymerization; D013314:Stress, Mechanical; D013696:Temperature
D003188:Composite Resins
Polymerization; Resin composite; Shrinkage; Stress; Temperature