[Quality of the marginal seal of spark-eroded crowns using different modes of preparation].

: Six acrylic tooth stumps were prepared for an evaluation of the marginal quality of crowns produced by spark erosion. Four different methods were used for preparation of the crown margins. Each stump had two different margin preparations. The crowns were fabricated with the aid of spark erosion. Serrated sections were then made for an analysis of marginal defects. The results have shown that the mean size of marginal openings is highly dependent on the preparation method used.