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. 2022 Aug 12;14(16):3296.
doi: 10.3390/polym14163296.

Polymerization Kinetics and Development of Polymerization Shrinkage Stress in Rapid High-Intensity Light-Curing

Matej Par  1 , Phoebe Burrer  2 , Katica Prskalo  1 , Saskia Schmid  2 , Anna-Lena Schubiger  2 , Danijela Marovic  1 , Zrinka Tarle  1 , Thomas Attin  2 , Tobias T Tauböck  2
Affiliations

Polymerization Kinetics and Development of Polymerization Shrinkage Stress in Rapid High-Intensity Light-Curing

Matej Par et al. Polymers (Basel). .

Abstract

This study investigated polymerization kinetics, linear shrinkage, and shrinkage stress development for six contemporary composite materials of different viscosities cured using radiant exitances of 1100-2850 mW/cm2. Real-time measurements of degree of conversion, linear shrinkage, and shrinkage stress were performed over 5 min using Fourier-transform infrared spectrometry, a custom-made linometer, and a custom-made stress analyzer, respectively. For most tested variables, the factor "material" had a higher effect size than the factor "curing protocol". Maximum polymerization rate and maximum shrinkage stress rate were the most affected by changes in curing conditions. In contrast, no significant effects of curing conditions were identified within each material for shrinkage stress values measured at the end of the 5 min observation period. Linear shrinkage and shrinkage stress values measured after 5 min were closely correlated (R = 0.905-0.982). The analysis of polymerization kinetics suggested that the two composites specifically designed for rapid light-curing responded to higher radiant exitances differently than other composites. Polymerization kinetics and shrinkage stress behavior of contemporary restorative composite materials of different viscosities were overall more affected by material type than differences in curing conditions. Subtle differences in polymerization kinetics behavior shown by the two composites specifically designed for rapid high-intensity light-curing did not translate into significant differences in the development of polymerization shrinkage stress.

Keywords: bulk-fill composites; light-curing; rapid light-curing; resin composites.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Degree of conversion, linear shrinkage, and shrinkage stress measured at the end of the 5 min observation period (mean values ± 1 SD). Statistically similar values among curing protocols are connected with square brackets. Statistically similar values among materials are denoted by same uppercase, lowercase, and Greek letters for the 3, 5, and 10 s curing protocols, respectively.
Figure 2
Figure 2
Maximum polymerization rate and maximum shrinkage stress rate (mean values ± 1 SD). Statistically similar values among curing protocols are connected with square brackets. Statistically similar values among materials are denoted by same uppercase, lowercase, and Greek letters for the 3, 5, and 10 s curing protocols, respectively.
Figure 3
Figure 3
Time of maximum polymerization rate and time of maximum shrinkage stress rate (mean values ± 1 SD). Statistically similar values among curing protocols are connected with square brackets. Statistically similar values among materials are denoted by same uppercase, lowercase, and Greek letters for the 3, 5, and 10 s curing protocols, respectively.
Figure 4
Figure 4
The component loading plot in rotated space for representing the amount of covariance among degree of conversion, linear shrinkage after 5 min, shrinkage stress after 5 min, and filler load expressed in wt% and vol%.
Figure 5
Figure 5
Scatterplots of shrinkage stress as a function of linear shrinkage and results of Pearson correlation analysis. Error bars represent ± 1 standard deviation.
Figure 6
Figure 6
Fit parameters (a–d) of double exponential function used for describing polymerization kinetics. Error bars represent 95% confidence intervals.
See this image and copyright information in PMC

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