30-08-2017, 03:17 PM
An alternative technique is presented to facilitate the calculation of the dissipation of frictional power in alternative dry sliding. The proposed technique can be used for predicting wear in circumstances where direct measurement of power dissipation is limited by practical limitations. Experimental tests are conducted to investigate the relationship between system wear rate, power dissipation, and thermal response. A convenient technique for estimating the average contact temperature in an alternate sliding contact is also proposed. The predicted temperatures coincide with the experimental measurements. It is also shown how the predicted temperatures for the wear estimation can be used under an alternative dry slip setting.
Alternative instruments made of M-wire alloy have been proposed to reduce the risk of fracture. There is no information available on surface alteration after single and multiple uses in root canals. Two alternative NiTi instruments were used on teeth extracted up to three times. An ESEM / EDS analysis was performed to determine defects, alterations and wear characteristics of the apical third of the instruments and a cross - sectional metallographic analysis of new and used instruments to compare alloy properties was performed. Topography of the apical portion was evaluated by AFM before and after the uses. The extracted single-root teeth were divided into two groups and were instrumented according to the manufacturer's recommendations with: (A) WaveOne Primary and (B) Reciproc R25. Each group was divided into three subgroups according to the number of instrumented channels: 1, 2 and 3, respectively. Chi squared was performed to verify the homogeneity of defect distribution and GLM to assess differences in RMS at baseline and after use for both groups (level α 0.05). No instrument was fractured and no spiral distortions were observed on the optical microscope, even when the number of uses increased. No significant differences were found for WaveOne and Reciproc. Blades presented a portion wrapped in the WaveOne group and a more symmetrical feature in the Reciproc group. The metallographic analysis revealed in both groups the presence of twin martensitic grains with isolated flat austenitic areas. Both instruments showed limited alteration, such as tip deformation and wear.
Alternative instruments made of M-wire alloy have been proposed to reduce the risk of fracture. There is no information available on surface alteration after single and multiple uses in root canals. Two alternative NiTi instruments were used on teeth extracted up to three times. An ESEM / EDS analysis was performed to determine defects, alterations and wear characteristics of the apical third of the instruments and a cross - sectional metallographic analysis of new and used instruments to compare alloy properties was performed. Topography of the apical portion was evaluated by AFM before and after the uses. The extracted single-root teeth were divided into two groups and were instrumented according to the manufacturer's recommendations with: (A) WaveOne Primary and (B) Reciproc R25. Each group was divided into three subgroups according to the number of instrumented channels: 1, 2 and 3, respectively. Chi squared was performed to verify the homogeneity of defect distribution and GLM to assess differences in RMS at baseline and after use for both groups (level α 0.05). No instrument was fractured and no spiral distortions were observed on the optical microscope, even when the number of uses increased. No significant differences were found for WaveOne and Reciproc. Blades presented a portion wrapped in the WaveOne group and a more symmetrical feature in the Reciproc group. The metallographic analysis revealed in both groups the presence of twin martensitic grains with isolated flat austenitic areas. Both instruments showed limited alteration, such as tip deformation and wear.