The Effects of Light Intensity, Temperature, and Comonomer Composition on the Polymerization Behavior of Dimethacrylate Dental Resins

Abstract

One of the most common combinations for the organic phase of dental restorative materials is BisGMA (2,2bis[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl]propane) and TEGDMA (triethylene glycol dimethacrylate). However, this copolymer has some drawbacks, such as volume shrinkage during cure and lack of complete double-bond conversion. If the properties of this system are to be improved, an attempt must be made to understand the underlying kinetics of the reaction. This work examines the effects of light intensity, temperature, and composition on the polymerization behavior of BisGMA/TEGDMA copolymerizations. Using differential scanning calorimetry, we monitored the rates of photopolymerization for various experimental conditions. The BisGMA/TEGDMA copolymerization behaved similarly to other dimethacrylate systems and exhibited diffusion-controlled kinetics. It was found that the maximum rate of polymerization was significantly affected by the intensity of the light, and the temperature of the polymerization affected the conversion at which the maximum rate occurred. When the composition of the mixture was varied, it was discovered that the viscosity of the system played a significant role in the polymerization rate and the onset of reaction-diffusion-controlled termination. Mixtures which contained from 50 wt% to 75 wt% BisGMA displayed the highest maximum rate. This feature suggests that TEGDMA is an excellent diluent, since it increases the mobility of the reacting medium; however, the high reactivity is due to the presence of BisGMA. Therefore, based on compositional dependence, we conclude that the BisGMA portion of the mixture largely controls the polymerization mechanisms and kinetics.

Photocuring and thermal post-curing of a cycloaliphatic epoxide resin with a trithiol and a vinyl epoxy compound

“…Table 2 shows the maximum degrees of conversion of the photocuring by DSC of the epoxy resin at different temperatures with different proportions of the trithiol and the vinyl compound. This degree of conversion increases with temperature, as commonly observed for other photocuring systems [6,[20][21][22][23] due to vitrification occurring at higher degrees of conversion when the photocuring temperature increases [24]. However, it is shown that the effect is very small when the proportion of thiol-ene modifiers is 5 % or greater, showing that, even if the temperature increases, the stability of the alkylsulfonium salts formed in the photocuring stage is sufficiently high to prevent epoxy homopolymerization from taking place at these temperatures, as reported previously [17].…”

Influence of different shades and LED irradiance on the degree of conversion of composite resins

“…According to some studies, the DC is influenced by the organic content, because characteristics such as reactivity and monomer mobility are related to the formation of polymeric chains. 16,17 The higher amount of filler present in the nanofilled resin could influence the results by promoting a lower DC.…”

Influence of a heating device and adhesive temperature on bond strength of a simplified ethanol-based adhesive system

“…Bonding effectiveness of adhesive systems may be associated with their temperature of application. Increased adhesive temperature promotes superior solvent evaporation and reduces the adhesive viscosity, hypothetically ensuring a stable and lasting bond [6][7][8][9][10][11][12] . Enhanced solvent evaporation limits the residual solvent 13 , enhances wettability 11,14,15 -which influence the hybrid layer formation positively 16 -and yields a highly reticulated polymer, with reduced water sorption and lower hybrid layer solubility 17 .…”

“…It is widely accepted that the polymerization rate of adhesive systems is also improved by a temperature rise up to 60°C, which promotes a more stable and less degraded resin-dentin interface over time, whereas low temperatures have a negative impact on both aspects [7][8][9]11 .…”

“…Use of warm air to raise adhesive temperature promotes solvent evaporation; consequently, the chemical content of the adhesive solution is altered 9 .…”