Interfacial gaps of resin cemented ceramic inlays

A method was developed for measuring presence, location and extent of interfacial contraction gaps of resin-cemented ceramic inlays in dentin cavities. Cylindrical ceramic inlays were cemented using one of 12 commercially available resin composite cements to make a film thickness of 200-microns. Cross-sections revealed absence of marginal gaps but contraction gaps occurred at all dentin-cement interfaces at the cavity floors and ranged from 1.6 to 7.1 microns. This was equivalent to 0.8-3.5% of the cement film thickness and was 3-10 times greater than the wall-to-wall contraction in percent observed when resin composites are used as filling materials in 3-5 mm butt-joint dentin cavities. The results support the theory that contraction gaps developing adjacent to thin films of resin cements reach a size equivalent to the cement film thickness multiplied by the volumetric polymerization shrinkage of the cement.