Evaluation of density and microgeometrical characteristics of glass-ionomer cement and composite resin fillings: a biomechanical ex vivo study

Modern photopolymer filling (restorative) materials are important tools for practicing dental clinicians when treatment cannot be limited to non-invasive or minimally invasive dentistry methods. In this work, using X-ray computed microtomography (micro-CT), an ex vivo non-destructive study of the density of fillings from glass ionomer cement and composite resin on human teeth was carried out. Using the technique of segmenting regions of interest on tooth microtomograms before and after dental intervention, the advantages of a composite material over glass ionomer cement were revealed, and the microstructure features of each material were studied. The density of the composite filling turned out to be closer to natural enamel compared to the density of the glass ionomer cement filling, it also contains a smaller number of artifacts, and the artifacts themselves are smaller in size. A separation of a filling from a composite resin into an outer and an inner layer was found during dental intervention. On the surface of a filling made of glass ionomer cement, several regions of integrity violations in the form of large cavities were found. After the preparation of longitudinal sections of tooth samples, a study of the microgeometrical characteristics of fillings was carried out using atomic force microscopy (AFM). Analysis of the results showed the closeness of both the average roughness values and the maximum roughness height for a composite filling to those for natural sound enamel.