IADR Abstract Archives
Mathematical Model for Polymerising BisGMA/TEGDMA Resins With Different Initiators
Objectives: To seek a mathematical model that can fit experimental data of degree of conversion (DC) bisGMA/TEGDMA resins with various photoinitiators and concentrations undergoing photopolymerisation.
Methods: Six bisGMA/TEGDMA resins at equal weight ratios were prepared with camphorquinone (CQ)/(dimethylamino)ethyl methacrylate (DMAEMA) photoinitiator system at a constant 1:4 weight ratio. CQ content was 0.1, 0.2, 0.4 and 0.8wt% in four of the groups; the fifth group contained 0.2wt% CQ and additionally 0.51wt% of diphenyliodonium hexafluorophosphate (DPI) as a co-initiator; the last group was a negative control (no photoinitiator). Samples were prepared (n=3) for each group in moulds (Ø6mm×3mm), irradiated for 20 seconds with an LED light source (Elipar S10, 3M ESPE) and analysed real time by Attenuated Total Reflectance-Fourier Transform near Infra-Red spectroscopy (ATR-FTIR). DC was calculated from spectral data. Data were fitted using two sigmoidal mathematical models (logistic function and Hill sigmoid equations) and goodness of fit was analysed by comparing R2 (Python 3.8; MATLAB R2021a, MathWorks, Inc., Natick, Massachusetts, United States). Results were displayed graphically.
Results: Resins with increasing photoinitiator content showed a gradual pattern in DC during the course of photopolymerisation. When DPI was incorporated, DC increased at nearly ten-folds the rate in the initial 3 seconds and reached a higher DC of over 80% compared with other resins. Regarding mathematical modelling, Hill sigmoid equation can fit DC data better at R2 > 0.995 regardless of photoinitiator type and content, whereas logistic function can only fit DC data containing CQ/DMAEMA only.
Conclusions: A narrow range of photoinitiator content optimises resin photopolymerisation in terms of polymerisation rate and DC. When a suitable co-initiator was present, the reaction follows a different trajectory with greatly accelerated conversion and higher DC within the duration of irradiation. Hill sigmoid model seems suitable in fitting various DC of bisGMA/TEGDMA with different initiator systems.
Methods: Six bisGMA/TEGDMA resins at equal weight ratios were prepared with camphorquinone (CQ)/(dimethylamino)ethyl methacrylate (DMAEMA) photoinitiator system at a constant 1:4 weight ratio. CQ content was 0.1, 0.2, 0.4 and 0.8wt% in four of the groups; the fifth group contained 0.2wt% CQ and additionally 0.51wt% of diphenyliodonium hexafluorophosphate (DPI) as a co-initiator; the last group was a negative control (no photoinitiator). Samples were prepared (n=3) for each group in moulds (Ø6mm×3mm), irradiated for 20 seconds with an LED light source (Elipar S10, 3M ESPE) and analysed real time by Attenuated Total Reflectance-Fourier Transform near Infra-Red spectroscopy (ATR-FTIR). DC was calculated from spectral data. Data were fitted using two sigmoidal mathematical models (logistic function and Hill sigmoid equations) and goodness of fit was analysed by comparing R2 (Python 3.8; MATLAB R2021a, MathWorks, Inc., Natick, Massachusetts, United States). Results were displayed graphically.
Results: Resins with increasing photoinitiator content showed a gradual pattern in DC during the course of photopolymerisation. When DPI was incorporated, DC increased at nearly ten-folds the rate in the initial 3 seconds and reached a higher DC of over 80% compared with other resins. Regarding mathematical modelling, Hill sigmoid equation can fit DC data better at R2 > 0.995 regardless of photoinitiator type and content, whereas logistic function can only fit DC data containing CQ/DMAEMA only.
Conclusions: A narrow range of photoinitiator content optimises resin photopolymerisation in terms of polymerisation rate and DC. When a suitable co-initiator was present, the reaction follows a different trajectory with greatly accelerated conversion and higher DC within the duration of irradiation. Hill sigmoid model seems suitable in fitting various DC of bisGMA/TEGDMA with different initiator systems.