Effect of wet and dry cellulose ring liners on setting expansion and compressive strength of a gypsum-bonded investment.

Effective setting expansion of gypsum-bonded investments is influenced by many variables. The purpose of this study was to determine the effect of using either water-saturated or dry cellulose ring lining material on (1) the fit of castings on a steel die and (2) the compressive strengths of investment cores using either type of liner. The mean gingival space in the water-saturated liner group was 0.241 +/- 0.048 mm and was 0.071 +/- 0.029 mm in the dry liner group (p < 0.001). The compressive strengths of investment cores from the dry liner group were 36.5% greater than those of cores from the water-saturated liner group. The results demonstrated that the use of dry liners may improve the fit of castings to dies.