Influence of cementation on in vitro performance, marginal adaptation and fracture resistance of CAD/CAM-fabricated ZLS molar crowns.

Objectives: This study investigated the influence of conventional cementation, self-adhesive cementation, and adhesive bonding on the in vitro performance, fracture resistance, and marginal adaptation of zirconia-reinforced lithium silicate (ZLS) crowns.

Methods: Human molar teeth (n=40) were prepared and full-contour crowns of a ZLS ceramic (Celtra Duo, DeguDent, G, n=32) and a lithium disilicate ceramic (LDS; IPS e.max CAD, Ivoclar-Vivadent, FL, n=8) were fabricated and glazed. Four groups of ZLS crowns were defined (n=8/group) and cemented with different glass-ionomer cements, resin, and resin-modified self-adhesive luting materials. The LDS crowns served as reference group with adhesive bonding. A combined thermal cycling and mechanical loading (TCML: 3000×5°C/3000×55°C; 1.2×10(6) cycles à 50N) with human antagonists was performed in a chewing simulator. Fracture force of surviving crowns was determined. Marginal adaptation at the cement/tooth and cement/crown interface was investigated by scanning electron microscopy before and after TCML, and the share of perfect margins was determined. Data were statistically analyzed (one-way ANOVA; post hoc Bonferroni, α=0.05).

Results: One crown of the adhesive group failed during TCML (879,000 cycles=3.7 years). No statistically significant (p=0.078) differences in fracture resistance were found between different cementations, although highest data in tendency were found for adhesive bonding. Shares of perfect margins at the cement/tooth (93.8±5.6-99.6±0.8%) and cement/crown (84.7±6.6-100.0±0.0%) interfaces did not differ significantly (p>0.05) between the different cementation groups.

Significance: Marginal adaptation and fracture forces of all tested groups are in a range, where no restrictions should be expected for clinical application.