Objectives: The objective of this study was to evaluate the marginal quality and resin-resin transition of milled CAD/CAM glass-ceramic inlays in deep proximal cavities with and without 3-mm proximal box elevation (PBE) using resin composites before and after thermomechanical loading.
Materials and methods: MOD cavities with one proximal box beneath the cementoenamel junction were prepared in 48 extracted human third molars. Proximal boxes ending in dentin were elevated for 3 mm with different resin composites (RelyX Unicem, G-Cem, and Maxcem Elite as self-adhesive resin cements and Clearfil Majesty Posterior as restorative resin composite in one or three layers bonded with AdheSE) or left untreated. IPS Empress CAD inlays were luted with Syntac and Variolink II (n = 8). Marginal quality as well as the PBE-ceramic interface were analyzed under an SEM using epoxy resin replicas before and after thermomechanical loading (100,000 × 50 N and 2,500 thermocycles between +5°C and +55°C).
Results: Bonding glass-ceramic directly to dentin showed the highest amounts of gap-free margins in dentin (92%, p < 0.05). Bonded resin composite applied in three layers achieved 84% gap-free margins in dentin; PBE with self-adhesive resin cements exhibited significantly more gaps in dentin (p < 0.05).
Conclusions: With a meticulous layering technique and bonded resin composite, PBE may be an alternative to ceramic bonding to dentin. Self-adhesive resin cements seem not suitable for this indication.
Clinical relevance: For deep proximal boxes ending in dentin, a PBE may be an alternative to conventional techniques.