Effect of denture cleansers on hardness of denture-base resins

Objectives: To determine the effect of denture cleansers on the hardness of some denture-base resins. Methods: The denture base materials tested were Eclipse (Dentsply) a visible light curing resin, Valplast (Valplast International) a nylon-based material and Minacryl Universal (Minerva Dental) conventional PMMA. The denture cleansers were Steradent - 3 Minutes (Reckitt Benckiser), Dentural (Martindale Pharmaceuticals), Corega Bio (Corega), and Val-clean (Valplast International). Water 55°C was used as comparison. Ten specimens of each material 22mm diameter x 2mm thickness were produced in stone moulds and were cured according to manufacturers' instructions. Specimens were suspended in the respective denture cleaners and cleaned according to manufacturers instructions for up to one hundred cycles. Hardness was measured using aWallace Micro-indentation tester, model H6B.H.W. Wallace & Co. Ltd., Croydon, UK. Ten measurements were recorded for each specimen after 7, 14, 21, 50 and 100 cleaning cycles. Data were tested for normality using Statgraphics Plus for Windows v5. This shows that the data were non-parametric and the data were tested using a Kruskal-Wallace test followed by Box Whisker plots to establish statistical differences at 95% confidence level. Results: No changes or small changes were detected for Minacryl and Eclipse with all cleansers. Cleaning Eclipse in Steradent, Dentural or water over 100 cycles resulted in distortion of specimens that prevented hardness evaluation. Significant softening of specimens was noted when Valplast was cleaned by Steradent, Dentural. Significant hardening occurred when Valplast was cleaned in Corega-Bio. Conclusion: The denture cleansers had little effect on the hardness of Minacryl or Eclipse. The effect of cleansers on the hardness of Valplast was dependent on the cleanser used.