Interface dimensions of CEREC-2 MOD inlays

Objectives: To quantify the width of the cement interface between ceramic inlays generated by the CEREC-2 CAD–CAM system and the tooth, and to determine the effect of cement viscosity on the interface width. Methods: Standardised MOD cavities were cut in 15 human premolar teeth using a custom paralleling device. A ceramic inlay was made with a CEREC-2 CAD–CAM machine for each tooth. The inlays were cemented using one of three resin-based composite systems of varying viscosity; a hybrid microfilled posterior composite, a compomer restorative and a dual-cure luting composite. The teeth were subsequently sectioned and measurements were taken at 21 key points with the aid of an image-analysis light microscopy system. Results: Statistical significance tests were applied to examine for difference in interface dimensions at specific points within each of the cement-groups and amongst groups. The interface space at the occlusal walls has a distinct wedge shape, being narrower at the external interface (50 μm, SD 15) than internally (211 μm, SD 38). There is no statistically significant difference in the interface dimensions of the gingival floor between the boxes that lie above and below the CEJ. There is no statistically significant difference in the width of the interface at any given point between the three cement groups. Significance: There is a significant improvement in the fit of CEREC-2 restorations when compared with the original CEREC system. Cements of varying viscosity (within the measured range) may be used for cementation of these inlays, without adversely affecting the width of the interface. Caution must be exercised with light-activated composite cements to ensure adequate transmission of light through the ceramic and the underlying composite cement.