Effect of denture wax-pattern position on radial setting expansion.

Th dynamics of the setting expansion of gypsum-bonded investment is complicated by many variables and not well understood. The purposes of this study were to examine the fluid mechanics of the flow of investment during setting and to determine if the presence of wax patterns influences effective setting expansion. Mesial-occlusal-distal (MOD) inlay wax patterns were invested at six different radial positions and four different axial positions in plastics casting rings. Total expansion was determined by using xeroradiography. Combined results of radial expansion data at different axial and radial locations within casting rings suggest that expansion of gypsum-bonded investment may represent a variant of the laminar flow of a viscous fluid.