MARGINAL ACCURACY AND GEOMETRY OF CAST TITANIUM COPINGS

The biocompatibility of titanium with human tissue is well established ; its potential as an alternate metal for crown restorations has yet t o be fully investigated. This study measured the geometry and accuracy of coping margins cast in Ti, 99.5% chemically pure. Twenty castings with 45-degree facial and 90-degree palatal margins were made by indir ect technique with a commercial system using recommended procedures, T hey were then cemented with ZnPO4 cement. The coping and die assemblie s were embedded in resin, sectioned longitudinally, and measured with a microscope at x50 power. Casting shrinkage was characteristic, parti cularly along the horizontal axis in the plane of the shoulder. Althou gh horizontal linear shrinkage of 45-degree margins was greater than t hat for the 90-degree form, the surface of marginal discrepancy was gr eatest with the 90-degree configuration.