Passive Fit Evaluation of Implant Superstructures by Analyzing Accumulated Screw Tightening Torque: A Dental Technique

Achieving a stable passive fit is important in implant treatment, especially for restorations of screw-retained superstructures. A passive fit is often evaluated by tactile sensing of tightening a fixing screw; however, tactile sensing is a subjective procedure. Objective and quantitative assessment of passive fits can be performed by measuring the tightening torque on prosthetic screws. In this clinical case, accumulative screw tightening torques for passive fit and misfit superstructures were calculated to examine the usefulness of the proposed method. The results suggested that accumulative torques and time slopes of torques may be potentially useful parameters for quantitatively evaluating passive fits; further laboratory and/or clinical trials are necessary.