Comparison of three techniques for measuring wear of dental restorations.

Measurements of impression profiles, profilometer registrations, and scanning electron microscopy (SEM) photogrammetry of metal dies simulating worn restorations were compared as possible techniques for measuring and recording the wear rate of tooth restorations. The results showed that measurements of impression profiles and SEM photogrammetry gave the most accurate results adjacent to regions simulating steep cavity margins, whereas the profilometric technique gave erroneous results in these regions. These errors were related to interference between the conical stylus tip and the steep edges. Moreover, photogrammetry was time-consuming and complex and did not result in better overall precision than with the other evaluation techniques. These drawbacks with SEM photogrammetry were related to complex use of software and low precision of crucial hardware components such as SEM tilt stage and digitizer.