Most of the removable partial denture castings examined showed radiographic evidence of internal porosity. In general the porosity occurred in characteristic regions associated with abrupt changes in cross-sectional thickness. These were located either within the partial denture framework or at the casting-sprue junctions. The porosity is due to metal shrinkage caused by a premature solidification at some point, which in turn interferes with a controlled unidirectional solidification of the casting. © 1978 C. V. Mosby Company.
