Aim:

To describe the failures in different implant systems when subjected to increasing torsional forces, determine the torque at which measurable damage occurs to the implant or one of its components, and determine the most frequent failure.

Materials and methods:

This was an experimental in vitro study. A total 88 implants were used, grouped according to design and trademark (Federa, Rosterdent, Biomet 3i, Tree-Oss, B&W, ML) into 11 groups of 8 implants each. The implants were immobilized in Duralay acrylic and fixed in a vice. Increasing torsional force was applied with a digital precision torque wrench until the occurrence of any failure in the implants or their components. The torque at which the failure occurred was recorded. Descriptive statistics were performed for data analysis.

Results:

100% of the implants or any of their components showed a detectable failure when subjected to increasing torsional forces (force range: 83.5 Ncm in an implant with 8-degree Morse taper connection to 384 Ncm in an implant with unmounted internal connection). The lowest average torque at which damage occurred was 103.75 (±8.08) Ncm for conical implants with Morse internal connection, while the highest was 279.87 (±89.73) Ncm for implant with unmounted internal connection. The most frequent failure (28.4%) was fracture of the implant retaining screw and distortion of the external hexagon simultaneously.

Conclusion:

Detectable failures at increasing torsional forces occurred between 83.5 Ncm and 384 Ncm. The repeated failure was the fracture of the implant retaining screw and simultaneous distortion of the hexagon.