Effect of fatigue loading on the fracture strength and failure mode of lithium disilicate and zirconia implant abutments

Objective: The aim of this study was to test five types of implant restorations using titanium, zirconia and lithium disilicate abutments after being subjected to long-term fatigue loading. Materials and methods: Forty single-tooth implant restorations were assembled on titanium implants (FairTwo; FairImplant). The restorations differed only in the type of abutment used and were divided into five groups [Ti: titanium; Zr: zirconia with no metal base; ZrT: zirconia with titanium base; LaT: lithium disilicate abutment with titanium base; and LcT: lithium disilicate hybrid-abutment-crown with titanium base]. Specimens were subjected to dynamic load of 49 N up to 1,200,000 cycles using a dual-axis chewing simulator (Kausimulator; Willytech). The surviving specimens were subjected to quasi-static loading using a universal testing machine (Z010; Zwick) until the implant-abutment connection failed. The values of force (N) at which fracture or plastic deformation of the restoration occurred were calculated and the rate of deformation was analyzed. The data was then analyzed using Mann-Whitney tests. Results: Groups Ti, ZrT, LaT and LcT withstood 1,200,000 fatigue load cycles and higher forces than physiological occlusal forces without fracture or debonding of the ceramic suprastructure. In group Zr, some specimen did not survive the chewing simulation and this group showed the lowest resistance to failure with a median of 198 N. Conclusions: Within the limitations of this study, it could be concluded that lithium disilicate abutments and hybrid-abutment-crowns show promising durability and strength after long-term dynamic loading. The use of titanium base enhances the strength of the zirconia abutments.