Shrinkage assessment of low shrinkage composites using micro-computed tomography

Abstract

Both low shrinkage composites showed less volumetric polymerization contraction than the regular composite. The use of dental adhesive decreased the total volumetric shrinkage for all evaluated composites.

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

“…Studies reported that shrinkage may occur at deeper areas of restorations 21) , while other investigation found that changes in the bottom of the cavity were delayed when compared to the surfaces closer to the light source 33) . Clinically the bottom and lateral shrinkage generated (gap formation), represented by 3D deformation of the uncured composite, are relevant once it may result in post-operative sensitivity, internal and marginal gaps 24) . In this study, volumetric shrinkage was primarily detected at the occlusal surface, little at bottom and almost inexistent at sides.…”

“…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) . Reducing the light intensity and modifying the polymerization technique with Soft-start mode did not significantly change the volumetric polymerization shrinkage and neither affect the degree of conversion achieved.…”

“…By doing this, we avoid the scattering and possible noise between both structures, due to its similar radio density. The "superimposition" tool has been previously used in other studies 24) and is trustable, once it is done automatically by the software and allows correlating one scan to another, which ends up making sure all the cavities are at the same position and allows measuring volumetric shrinkage at different locations.…”

“…The "Material Statistics" command computed the volume changes. From these measurements, the volumetric loss following polymerization shrinkage was calculated as percentages 24) . Data was analyzed by one-way analysis of variance (ANOVA) at the 5% level of significance using IBM SPSS software (IBM, Armonk, NY, USA).…”

“…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.…”