Comparison of the torque transferred to the implant-bone interface when tightening abutment screws and when torque testing implants: An in vitro study

Abstract

Statement of problem: Before dental implants are restored, osseointegration is often verified by torque testing the implant. For this test, it might be appropriate to select the torque subsequently used to tighten the abutment screw during prosthetic delivery. However, whether the full torque applied to the abutment screw is transferred to the implant-bone interface remains unknown.

Purpose: The purpose of this in vitro study was to assess whether the same torque is transferred to the implant-bone interface when tightening abutment screws and when torque testing implants and to investigate whether the implant system used affects the torque transfer.

Material and methods: A digital torque gauge was used to register the torque directed to a simulated implant-bone interface. Twenty implants from 4 different manufacturers were successively secured to the digital torque gauge. An implant driver was used to torque test the implant. An implant abutment screw was then tightened to attach a universal base (TiBase) abutment to the implant. During both tests, a mechanical torque limiting device was used to apply the same manufacturer-specific torque. For both experiments, the peak torque transferred to the simulated implant-bone interface was recorded. To allow pooling data from different torque targets, the data were converted into absolute difference. A t test was used to evaluate whether the same magnitude of torque was transferred to the implant-bone interface when tightening abutment screws and when torque testing implants. An ANOVA was used to test whether the percentage of torque transferred to the implant-bone interface was impacted by the implant system used (α=.05).

Results: No significant difference was found between the torque transmitted when tightening an abutment screw and that transmitted when torque testing the implant (P=.600). Also, no difference was found in the percentage of torque transferred to the simulated implant-bone interface of different implant systems (P=.996).

Conclusions: Regardless of the implant system used, when tightening abutment screws and when torque testing implants, the same amount of torque is transferred to the implant-bone interface.