Reliability and Failure Modes of a Hybrid Ceramic Abutment Prototype

Objectives: Accelerated life testing was used to assess the probability of survival of a new abutment prototype, comprised of a metal sleeve with ceramic transcutaneous abutment. The research hypothesis was that a hybrid lithium disilicate ceramic abutment prototype would lead to survival limited by the abutment/fixture connection
Methods: Lithium disilicate CAD-milled abutments (n=24) were cemented to titanium sleeve inserts and restored with anatomically correct central incisor machined e.max. lithium disilicate crowns (n=24) attached to titanium fixtures and then embedded at 30 degree angulation. Fatigue testing was employed using the step-stress method with lingual mouth motion loading. Reliability calculations were performed using Reliasoft (Alta PRO, AZ) and probability Weibull (Weibull ++7) curves plotted with 90% CB intervals. Fracture modes were classified with a stereomicroscope and representative samples imaged with scanning electron microscopy.
Results: Fatigue results indicated that the limiting factor in the current design is the fatigue strength of the abutment screw, where its fracture often leads to failure of the abutment metal sleeve and/or cracking in the implant fixture. Reliability at 200 N and 100K cycles was only 0.16 (0.31-0.00 90% CI).
Conclusions: No ceramic crown or ceramic abutment initiated fractures occurred supporting the research hypothesis.