Measuring abutment/implant joint integrity with the Periotest instrument.

Maintenance of the integrity of the abutment/implant interface is essential and is dependent on the abutment screw retaining a preload. Evaluation of this joint is usually done by manual assessment. The purpose of the current study was to determine whether the Periotest instrument could be used to evaluate abutment screw loosening. A custom-designed apparatus was constructed to measure abutment screw loosening. Abutment screws were torqued to 10, 20, 32, and 45 Ncm and then loosened. Objective assessment of screw loosening was carried out with the Periotest device. Subjective evaluation was done by 3 experienced clinicians. The Periotest was found to be more sensitive than manual detection of abutment screw loosening. With a change of 2 in the Periotest value, it was found that the tensile preload in the joint was lost. While the Periotest was more sensitive than manual evaluation, the instrument was not sensitive enough to indicate deterioration of abutment screw loosening prior to loss of tensile preload.