Evaluation of resin composite polymerization by three dimensional micro-CT imaging and nanoindentation

Micro-computed tomography evaluation of volumetric polymerization shrinkage and degree of conversion of composites cured by various light power outputs

“…µCT analysis has been an important tool to quantify and evaluate not only volumetric polymerization shrinkage 20,22,41) , but also to characterize the restorative material volumetric distribution such as fillers or presence of voids 18,22,42,43) . This method has been shown to depict locations of composite shrinkage when the substrate adherent was uniform, revealing gap formation regions and regions of potential interfacial failure 24) .…”

“…µCT analysis Each sample was scanned twice using µCT as previously described, before and after light-activation 18) . The µCT was calibrated with a phantom standard at 70 kVp/ BH 200 mgHA/cm.…”

“…Besides these items, the composition of the monomer and the photoinitiation system play an important role on the polymerization and subsequently the amount of residual monomer 17) . Since measurement of the shrinkage in a cavity has proven to be technically difficult, several indirect methods to evaluate the effect of polymerization shrinkage have been described in the literature 7,18,19) . The most used method to evaluate gap formation was dye penetration, which involved the sectioning of sample, being a destructive method that allows limited further material characterization 20) .…”

“…Other methods include optical instruments, fiber-optic sensing method, mercury dilatometer, electromagnetic balance and video imaging 12) . Contemporary 2D and 3D imaging methods have been used to analyze in a non-invasive and non-destructive way the behavior of materials inside a standardized cavity, such as finite element analysis 18,21,22) , optical coherence tomography 7,23) , and micro-computed tomography (µCT) 19,22) . These methods have been widely described in literature, due to reliable and significant results 7,18,24,25) .…”

“…Contemporary 2D and 3D imaging methods have been used to analyze in a non-invasive and non-destructive way the behavior of materials inside a standardized cavity, such as finite element analysis 18,21,22) , optical coherence tomography 7,23) , and micro-computed tomography (µCT) 19,22) . These methods have been widely described in literature, due to reliable and significant results 7,18,24,25) . The aim of this study was to evaluate and quantify the volumetric polymerization shrinkage of a composite resin at three locations of a class I cavity and its degree of conversion when composite resin restorations were light activated with different irradiance modes of a light curing unit.…”