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. 2022 Aug 25;15(17):5850.
doi: 10.3390/ma15175850.

A Study on the Photopolymerization Kinetics of Selected Dental Resins Using Fourier Infrared Spectroscopy (FTIR)

Mirosław Kwaśny  1 , Jakub Polkowski  2 , Aneta Bombalska  1
Affiliations

A Study on the Photopolymerization Kinetics of Selected Dental Resins Using Fourier Infrared Spectroscopy (FTIR)

Mirosław Kwaśny et al. Materials (Basel). .

Abstract

The aim of the presented study was a comparative analysis of the polymerization kinetics of dental resin-based composites currently used in dentistry in different environmental conditions (irradiance, activation time, layer thickness). The photopolymerization kinetics of eleven dental resins were investigated using a Woodpecker LED source. The DC was measured by FTIR in transmission mode and attenuated total reflection (ATR) from 5 s to 7 days. In the transmission mode, the spectra from parallel optical layers (about 0.2 mm thick) of samples placed between the KBr crystals were recorded. In the reflection mode, an ATR attachment with a diamond window was used. The DC calculation method was applied based on the application of a monomer absorption band at 1638 cm-1 (stretching vibration double bond C=C of the vinyl group) without using a reference band. The data were analyzed by performing an ANOVA test comparison between sample groups at the significance level α = 0.05. For all tested materials, the polymerization kinetics consist of three stages. The fastest stage occurs during the irradiation, and the achieved DC value is 70-75% of the maximum value 5 s after the irradiation. Another 15-20% DC increase at a moderate speed takes about 15-20 min. There is also a very slow further increase in DC of 5-10% within 5 days after irradiation. For 8 out of the 11 tested fillings, the optimal photopolymerization conditions are as follows: a power density of 400 or 1000 mW/cm2; an exposure time of 10 s; and a thickness of the irradiated resin layer of up to 2 mm. The influence of various conditions and factors on the reaction kinetics is dominant only in the early, rapid phase of the conversion. After longer times, the DC values gradually level out under different light conditions. The DC of the dental resins are dependent on the irradiance, light source, filler type, time after irradiance, and monomer thickness.

Keywords: FTIR; LED; degree of conversion; dental resin; photopolymerization.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
(a) Measurements with the ATR adapter, (b) Measurements in transmission mode.
Figure 2
Figure 2
(a) The method of determining the value of the absorbance of the bands by taking into account the baseline, (b) an example of the change of the absorption spectrum in the transmission mode, (c,d) examples of the changes of the absorption spectra in the reflectance mode (ATR).
Figure 3
Figure 3
Influence of the sample thickness on the DC value.
Figure 4
Figure 4
Effect of power density on DC values.
Figure 5
Figure 5
Effect of the exposure time on the DC values.
Figure 6
Figure 6
The polymerization kinetics of the materials with the average DC value.
Figure 7
Figure 7
Comparison of the maximum DC values for the tested materials. * DC for Estelite (400 mW/cm2) ** DC for Estelite (1000 mW/cm2).
Figure 8
Figure 8
Changes in the DC values with the aging time for irradiated dental resin samples.
See this image and copyright information in PMC

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