The Influence of Water Storage on Durometer Hardness of 5 Soft Denture Liners Over Time

Purpose: This laboratory study investigated the influence of water storage on the durometer hardness of 2 RTV and 3 HTV soft denture liners over a 1‐year period. Materials and Methods: Five soft denture liners were used: 2 HTV silicone rubber (Luci‐Sof™ and Molloplast‐B®), 1 RTV silicone rubber (Tokuyama), 1 HTV polyphosphazene (Novus™), and an RTV plasticized acrylic (PermaSoft®) that uses a surface sealer. They were processed following manufacturers' instructions, cured, and stored in tap water at 37°C. The water was changed every 2 weeks. Five durometer A hardness measurements were made at logarithmically spaced intervals of 16.7 minutes, 27.8 hours, 11.6 days, 34.7 days, 115 days, and 347 days. Repeated measures analysis of variance (MANOVA), one‐way analysis of variance (ANOVA), Pillai trace statistic, the difference scores (last–first) among the groups, and the Tamhane T2 multiple comparison test were used to compare the groups over time, all on SPSS V. 7.5 and 9.0. Results: The order of highest initial indentation hardness was Luci‐Sof™, Molloplast‐B®, Novus™ (HD= 38 to 33). Tokuyama and PermaSoft® as a group were softer (HD= 18 to 22). Tokuyama Soft Relining changed the least over 347 days, followed by Luci‐Sof™, Novus™, Molloplast‐B®, and PermaSoft® in that order (p≤ 0.05). Within the PermaSoft® group, sealer applied only once changed the least over 347 days, followed by no sealer, and then sealer applied every month (p < 0.0005). Conclusions: After 347 days of water storage, Tokuyama had the lowest indentation hardness changes, followed by Luci‐Sof™, Novus™, PermaSoft® with sealer applied once; Molloplast‐B®, PermaSoft® without sealer; and PermaSoft® with sealer applied every month. All HTV soft denture liners had higher indentation hardness than RTV liners initially. After 347 days, PermaSoft® without sealer and with sealer every month became the hardest.