Analysis of dimensional changes in the screw and the surface topography at the interface of a titanium screw and a zirconia abutment under cyclic loading: an in vitro study.

PURPOSE

The purpose of this experiment was to analyze the mechanics of the ceramic abutment-implant joint and the dimensional changes in the abutment screws from cyclic loading.

MATERIALS AND METHODS

Two groups of experimental assemblies were used, one with zirconia abutments and the other with titanium abutments (n = 10). Each specimen consisted of an implant, an abutment, and a metal crown affixed in an acrylic resin base. The specimens were subjected to cyclic loading of 200 N for 1 million cycles at 10 Hz. After loading, a torque-angle signature analysis was done, the dimensions of the screws were measured, and the implant-abutment interfaces were examined with scanning electron microscopy.

RESULTS

There was a statistically significant increase in the total length of the screws: 121 μm in the titanium group versus 88 μm in the zirconia group (P < .004). Microscopic analysis showed collected debris on the zirconia abutment undersurface and the screws. A statistically similar decrease in torque was observed: 18% for zirconia versus 13.5% for titanium. Radiographic microanalysis revealed that the debris collected in the zirconia assemblies was essentially a collection of titanium, vanadium, and aluminum, with traces of zirconium.

CONCLUSIONS

While there was a loss of torque in both types of abutments, the stability of the zirconia abutment-implant joint was not affected by the loading. The study provides a better understanding of zirconia abutments, screw designs, and the mechanism holding together the implant-abutment assembly.