PURPOSE

This laboratory study analyzed the influence of retention mode (screw- vs cement retained) and fatigue application on the failure load of monolithic lithium-disilicate (LDS) implant-supported single crowns (ISSC).

MATERIAL AND METHODS

A total of 72 samples of monolithic LDS (Ivoclar Vivadent) ISSC were divided into three groups (n = 24) according to their type of retention mode: Group Ti-CAD: Titanium base (SICvantage CAD/CAM Abutment red (SIC invent AG), screw-retained milled monolithic LDS (IPS e.max CAD); Group Ti-P: Titanium base (SICvantage CAD/CAM Abutment red), screw-retained pressed monolithic LDS (IPS e.max Press*) and Group Ti-Cust: Titanium base with cemented press LDS (IPS e.max Press*) crown on a LDS (IPS e.max Press*) custom abutment. A mandibular first molar implant-supported single crown model was investigated (Titanium implant: SICvantage-max, SIC invent AG, diameter: 4.2 mm, length: 11.5 mm). Half of each group (n = 12) w​ere exposed to fatigue with cyclic mechanical loading (F = 198 N, 1.2 million cycles) and simultaneous thermocycling (5-55°C). Single load to failure testing was performed, before (Subgroups Ti-CAD, Ti-P, and Ti-Cust) and after (Subgroups Ti-CAD-F, Ti-P-F, and Ti-Cust-F) fatigue. Weibull distribution was used to determine the characteristic strength and Weibull modulus differences between groups. Probability of survival at 900N load was calculated.

RESULTS

No samples failed during fatigue. Characteristic strength values were as follow: Ti-CAD: 3259.5N, Ti-CAD-F: 2926N, Ti-P: 2763N, Ti-P-F: 2841N, Ti-Cust: 2789N, Ti-Cust-F: 2194N. Whereas no difference was observed between pressed or milled monolithic crowns cemented to Ti-base, regardless of loading condition, fatigue decreased the characteristic strength of crowns cemented to custom abutments. Probability of survival at 900 N was not significantly different between groups.

CONCLUSIONS

Screw-retained pressed or milled monolithic LDS ISSC, cemented directly to Ti-base abutments or LDS crowns cemented to custom ceramic abutments resist physiological chewing forces after simulated 5-year aging in the artificial mouth and presented equally high probability of survival. However, a significant decrease in load to failure was observed in LDS crowns cemented to custom ceramic abutments after fatigue. Prospective clinical trials are needed to confirm the results of this laboratory investigation.