In vitro changes in hardness of sealed resilient lining materials on immersion in various fluids

During clinical use, resilient lining materials undergo changes in hardness that make them ineffective. The aims of this investigation were (1) to determine the effect of a resilient lining sealer on the hardness of four resilient denture liners; and (2) to determine the effect of the sealer on hardness after immersion in various solutions.

Two sets of specimens of four resilient liners, Coe-comfort (CC), PermaSoft (PS), Tokuyama soft reline (TK), and Total-Soft (TS), 6-mm diameter by 4-mm thickness, were fabricated. Two coats of Permaseal, a soft reline sealant, were applied to one set of specimens of each material according to manufacturers' instructions. Sealed and unsealed samples were divided into four groups (n = 10). Each group was immersed in one of the following solutions: artificial saliva at 37 degrees C, Efferdent, Efferdent with once daily scrubbing with a soft toothbrush, and 50% ethanol. Shore A hardness numbers were obtained at 0, 1, 3, 7, 30, and 90 days. A two-way ANOVA test was performed using materials (treated and untreated) and immersion solution as independent variables. The percentage change in hardness after the 90-day immersion period was the dependent variable.

The results show that the application of sealant significantly improved the durability of CC, PS, and TS in immersion solutions by maintaining hardness close to preimmersion values or delaying the softening effect of the solutions. The hardness of sealed and unsealed TK showed the significantly (p < 0.05) lowest change after immersion in the test solutions. Ethanol caused the most severe decrease in hardness of all solutions, followed by saliva. Immersion in Efferdent and daily brushing after immersion in Efferdent showed only a mild effect on the hardness of the soft reline agents.

The use of a sealer can play an important role in the preservation of the hardness of some resilient lining materials.