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

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.

Investigation of the Degree of Monomer Conversion in Dental Composites through Various Methods: An In Vitro Study

“…Peaks corresponding to aliphatic (1638 cm −1 ) and aromatic double bonds (1608 cm −1 ) were identified for the calculation of the conversion degree. The change in the ratio of aliphatic carbon double bonds was used to calculate the conversion degree using the formula [18]…”

Photopolymerization Pattern of New Methacrylate Cellulose Acetate Derivatives

“…FTIR spectroscopy is a straightforward and adaptable technique for tracking the photopolymerization of (meth)acrylic bonds in response to UV or visible light. It evaluates the changes in photopolymerizable bonds over time and, via kinetic studies, enables the calculation of the rate of photopolymerization as well as the degree of conversion as a function of time [ 31 , 32 , 33 ].…”

Comparative Study of Transmission of 2940 nm Wavelength in Six Different Aesthetic Orthodontic Brackets

“…One of these spectroscopy technologies is Fourier transform infrared (FTIR) spectroscopy, which is considered a non-destructive and label-free vibrational spectroscopic technique and is widely used in research [ 44 ]. Dental material can be tested by FTIR in transmission mode [ 46 ].…”