Evaluating materials used for constructing soft earmoulds.

The use of penetrometry for the assessment of materials employed for soft earmoulds is investigated. Selected test conditions are used for the characterisation of 10 materials of five types (cold-cured methacrylate, heat-cured methacrylate, heat-cured silicone, polyvinyl chloride co-polymer and polyethylene copolymer) used in clinical practice. The results are compared with the outcome of subjective assessments surveyed for four representative materials. The effect of ageing is assessed for a heat-cured silicone (Molloplast B) and a heat-cured methacrylate (Coe Super-Soft).