Effect of denture cleansers on the hardness of heat- or auto-cured acrylic- or silicone-based soft denture liners

Purpose: To investigate the effect of short (24 hours) and long term (6 months) exposure to a variety of commercially available denture cleanser solutions on the hardness of a variety of acrylic- and silicone-based resilient liners that were either heat- or auto-cured. Methods: The denture liners investigated were an acrylic-based heat-cured (Vertex Soft), acrylic-based auto-cured (Coe-Soft), a silicon-based heat-cured (Molloplast-B) and silicon-based auto-cured (Mollosil Plus) resilient liners. Cylindirical specimens (20 mm diameter, 12 mm high) were made of each material, using 10 replications for each test condition. Immersion solutions consisted of distilled water (control), and those based on alcohol, chlorhexidine, or an alkaline peroxide (Dermacol, aqueous chlorhexidine, Steradent) as a major active component. Specimens were fabricated according to manufacturer directions. Shore-A durameter hardness readings were taken on all specimens at each time interval and then compared statistically using four-way ANOVA and Tukey HSD (alpha= 0.05). Results: The results of this study indicated that, compared with distilled water, significant effect on the hardness of the specimens were found after immersion in all of the denture cleanser solutions at 24 hours and at 6 months. Specimens immersed in chlorhexidine showed higher and significant hardness changes than those immersed in other cleanser solutions. Also, it was determined that hardness of resilient liner materials increased with time and significantly higher hardness was recorded at 6 months for the auto-cured specimens compared with their heat-cured counterparts.