Consistency and softness of soft liners.

Consistency is evaluated by an initial flow test that allows the clinician to select the material of choice for relining procedures according to the size and shape of the ridge and the condition of the soft tissue. In this study, the consistency of four autopolymerized soft liners was compared and tested to determine whether they meet the new International Standards Organization (ISO) 10139-1 specifications. Softness, assessed with a Shore A durometer, was compared with that of two heat-cured silicone soft liners, because the latter are known for their steady softness over long periods of time. The consistencies of all four autopolymerized soft liners complied with ISO specifications and their disk diameter ranged from 41.3 to 72.2 mm. The softness of all four soft liners changed with time, unlike the silicones whose softness remained consistent. Softness readings varied significantly with sample thickness and indicated the need to develop criteria for measuring softness properties and determining the minimal thickness required for clinical performance.