The Effect of Different Water Temperatures on Retention Loss and Material Degradation of Locator Attachments.

PURPOSE: To examine the changes in Locator attachments after exposure to different water temperatures and cyclic loading. MATERIALS AND METHODS: Four groups of pink Locator attachments (3.0 lb. light retention replacement patrix attachments; 10 per group) were soaked for the equivalent of 5 years of use in distilled water at the following temperatures: 20 degrees C, 37 degrees C, 60 degrees C. One group was kept dry to test the effect of water. A universal testing machine was used to measure the retention force of each treated attachment during 5500 insertion and removal cycles, simulating approximately 5 years of use. The results were compared using Kruskal-Wallis one-way ANOVA by ranks. Surface changes of tested attachments were examined using scanning electron microscopy (SEM). RESULTS: The exposure to 60 degrees C water significantly increased the percentage of retention loss in Locator attachments (p < 0.05) compared to the 20 degrees C water group and significantly reduced the final retention force compared to the other groups (p < 0.05). SEM examinations revealed severe cracking and material degradation in Locator attachments after exposure to 60 degrees C water and cyclic loading, which were not evident in other groups. Cracking was observed after exposure to 60 C water before cyclic loading. CONCLUSIONS: Exposure to 60 degrees C water, potentially similar to denture cleansing procedures, could cause cracking in Locator attachments. Cracking is associated with hydrolytic degradation of nylon at 60 degrees C. The change in structure could result in a significant loss of retention.