Clinical results of lithium-disilicate crowns after up to 9 years of service

The purpose of this prospective study was to evaluate the clinical outcome of anterior and posterior crowns made of a lithium-disilicate glass-ceramic framework material (IPS e.max Press, Ivoclar Vivadent). A total of 104 single crowns were placed in 41 patients (mean age, 34 +/- 9.6 years; 15 male, 26 female). Eighty-two anterior and 22 posterior crowns were inserted. All teeth received a 1-mm-wide chamfer or rounded shoulder preparation with an occlusal/incisal reduction of 1.5-2.0 mm. The minimum framework thickness was 0.8 mm. Frameworks were laminated by a prototype of a veneering material combined with an experimental glaze. Considering the individual abutment preconditions, the examined crowns were either adhesively luted (69.2 %) or inserted with glass-ionomer cement (30.8 %). Follow-up appointments were performed 6 months after insertion, then annually. Replacement of a restoration was defined as failure. Four patients (10 crowns) were defined as dropouts. For the remaining 94 crowns, the mean observation time was 79.5 months (range, 34-109.7 months). The cumulative survival rate according to Kaplan-Meier was 97.4 % after 5 years and 94.8 % after 8 years. Applying log rank test, it was shown that the location of the crown did not significantly have an impact on the survival rate (p = 0.74) and that the cementation mode did not significantly influence the occurrence of complications (p = 0.17). The application of lithium-disilicate framework material for single crowns seems to be a reliable treatment option.