Purpose: The aim of the present study was to clinically evaluate the effect of two different adhesive / resin composite combinations for luting IPS Empress inlays with a special focus on luting gap wear and marginal adaptation. Materials and Methods: In the course of a controlled prospective clinical split-mouth study, 94 IPS Empress restorations were placed in 31 patients. The inlays were luted with EBS Multi + Compolute (EC; 3M ESPE) or with Syntac + Variolink II low (SV; Ivoclar Vivadent). At baseline and after 0.5, 1, 2, 4, and 8 years, the ceramic restorations were examined according to modified USPHS codes and criteria. Thirty-five selected samples were investigated under an SEM regarding morphological changes; marginal quality analysis was carried out using a stereo light microscope, and luting composite wear was scanned with a profilometer. Results: Eight patients (including 25 restorations) missed the recalls; the recall rate at the last investigation was 72%. After 96 months of clinical service, seven restorations in five patients (six EC, one SV) had to be replaced due to hypersensitivities (n = 5) or inlay fractures (n = 2) resulting in a survival rate of 90%. Over the 8-year period, the restorations revealed no statistically significant differences in terms of surface roughness, color matching, proximal contact, sensitivity, or complaints (p > 0.05, Friedman test). Significant deteriorations were found for marginal integrity (p < 0.05). No significant differences were observed for the different luting systems (p = 0.096, Log rank test / Mantel Cox). Marginal analysis revealed no statistical difference among the materials (p > 0.05; Mann-Whitney U-test), however, the scans of the luting gap showed that Compolute was more prone to wear (p < 0.05). Conclusion: For luting of ceramic inlays, no difference between the two luting systems was detectable. The overall failure rate after 8 years was 10%.

Keywords: glass ceramics, dentin bonding agents, etch-and-rinse, self-etching, clinical trial