[Deformation of crown margins by porcelain fusion]

This study attempted to measure marginal distortion of the porcelain-bonded-to-metal restoration due to porcelain fusion, 40 crowns were made of a PdAg-alloy on two dies with different extensions of the bevelled shoulder preparations. Only four crowns fit on the original dies after the firing procedure. Dimensional changes within oxide bake as well as dentine and glaze bakes could be achieved. Crowns with extended vestibular margins showed a higher amount of relative distortion. In a second simple experiment dimensional changes caused by the PFM-process could be found for other Au- and Pd-based alloys too.