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Influence of curing modes on polymer network integrity of dual-cure resin cements
[Thesis]. Manchester, UK: The University of Manchester; 2022.
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Abstract
Dual-cure resin cements are the major resin-cement type used to bond indirect restorative materials to remaining tooth structure. Adequate polymer network properties of dual-cure cements are essential to their performance and durability. Therefore, aim of this research was to investigate the effect of each possible curing mode (light/self) on the polymer network integrity of dual-cure resin-cements. Eight dual-cure resin cements materials were investigated cured either by light (LC) or self-cure (SC) modes. Firstly, thermal stability, hardness development and cross-link density were investigated. Resin-cements with lower initial onset temperatures (IOT) of thermal decomposition showed a significant reduction in hardness after 168 h of water storage at 37 oC. However, the cement curing modes had a minor influence on the IOT. Secondly, the degree of conversion (DC) and polymerisation shrinkage (PS) of dual-cure cements were assessed. PS strongly correlated with the DC of dual-cure cements. Curing modes significantly influenced both DC and PS of resin-cements. SC specimens had lower DC but not necessarily lower PS compared to LC. Thirdly, monomer elution, water sorption and solubility of dual-cure cements were measured. The total monomer elution from the investigated cements strongly correlated with their water solubility. Furthermore, curing modes strongly influenced the magnitudes of both monomer elution and water solubility. SC specimens showed greater magnitudes of monomer elution and water sorption compared to LC specimens. This research concluded that, whenever possible, light-curing of dual-cure cements remains beneficial for improving their polymer network formation and reducing the risk of dimensional instability.