Comparison of fracture strength and failure mode of different ceramic implant abutments.

STATEMENT OF PROBLEM: The whitish color of zirconia (ZrO(2)) abutments offers favorable esthetics compared with the grayish color of titanium (Ti) abutments. Nonetheless, ZrO(2) has greater opacity, making it difficult to achieve natural tooth color. Therefore, lithium disilicate (LaT) abutments have been suggested to replace metal abutments. PURPOSE: The purpose of this in vitro study was to evaluate the fracture strength and failure mode of single-tooth implant restorations using ZrO(2) and LaT abutments, and to compare them with titanium (Ti) abutments. MATERIAL AND METHODS: Five different types of abutments, Ti; ZrO(2) with no metal base; ZrO(2) with a metal base (ZrT); LaT; and LaT combination abutment and crown (LcT) were assembled on 40 Ti implants and restored with LaT crowns. Specimens were subjected to quasistatic loading using a universal testing machine, until the implant-abutment connection failed. As bending of the metal would be considered a clinical failure, the values of force (N) at which the plastic deformation of the metal occurred were calculated, and the rate of deformation was analyzed. Statistical analysis was done using the Mann-Whitney U test (alpha=.05). RESULTS: Group ZrO(2) revealed the lowest resistance to failure with a mean of 202 +/-33 N. Groups ZrT, LaT, and LaC withstood higher forces without fracture or debonding of the ceramic suprastructure, and failure was due to deformation of metal bases, with no statistically significant differences between these groups regarding the bending behavior. CONCLUSIONS: Within the limitations of this in vitro study, it was concluded that LaT abutments have the potential to withstand the physiological occlusal forces that occur in the anterior region and that ZrO(2) abutments combined with Ti inserts have much higher fracture strength than pure ZrO(2) abutments.