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Thirty-five implant torque wrenches were tested for torque delivery accuracy. Seven of these drivers had a 10-Ncm value, 12 had a 20-Ncm value, 10 had a 30-Ncm value, and six had a 35-Ncm value. All of the wrenches had been in clinical service for a minimum of 1 month or a maximum of 3 years and were assumed by the clinicians to be fully effective in delivering the required torque values. Torque delivery accuracy was determined using a Tohnichi torque wrench calibrated to +/- 1% of the scale value. All torque wrenches had been subjected to steam sterilization following clinical use. Data collected on all wrenches included (1) age since purchase, (2) number of sterilization cycles to which each wrench had been subjected during the use period, and (3) 10 sequential torque readings using the Tohnichi wrench as the torque reading device. The results of this study showed that there was no significant correlation of delivered torque with (1) age or (2) number of sterilization cycles. Furthermore, in each torque category there were torques both above and below the control values. For the 10-Ncm torque wrenches, the largest value was 455.0% greater than the control, the largest values were 41.6% greater for 20-Ncm wrenches, 17.0% greater for the 30-Ncm torque wrenches, and 58.6% greater for the 35-Ncm wrenches. Corrosion of the spring in the handle of the torque wrench was found to be the reason for the 455.0% value.

Fifteen laser-welded Olympia alloy samples were divided into three groups of five samples each, with different gap distances between the welded halves. The first group was welded with a 0.0-mm gap distance. The second and third groups had Olympia shims placed in 0.3- and 1.0-mm gaps, respectively, prior to laser welding. Each of the samples was tested to failure in load fatigue at 30 Hz in a fatigue testing device using an applied stress of 35,000 psi (241.4 MPa). The means and standard deviations for the number of cycles required to produce fatigue failure for each group was 494,618 +/- 118,311 cycles for the group welded with 0.0-mm gap distance, and 242,741 +/- 44,623 and 232,021 +/- 55,877 cycles for the 0.3- and 1.0-mm specimens, respectively. A one-way analysis of variance showed that the 0.0-mm gap specimens had the greatest number of cycles to failure (P < or = 0.05). There was no significant difference between the other two groups. With the exception of two specimens that failed at the weld center, all failures occurred at the edge of the weld.

This research investigated the fatigue life (ie, the number of cycles of a given stress that can be sustained by a sample prior to catastrophic failure) of metal ceramic soldering. One metal ceramic alloy was joined using four postceramic solders and one preceramic solder. All specimens received appropriate heat treatment simulating ceramic application although no porcelain was applied. Five specimens were fabricated for each solder type, and a 35,000 psi (241.4 MPa) fatigue stress was applied to each solder joint during specimen testing. The test variable was the number of stress cycles required to fail each specimen. The postceramic solders exhibited significantly higher fatigue lives than did the preceramic solder. Scanning electron microscope analysis showed that the preceramic solder not only exhibited a larger grain size, but also showed micropores between these grains.