Dicor crowns may present marginal defects, among other reasons because they require preparation of a circular ledge with rounded internal line angles. In studying this problem, 21 teeth that could no longer be saved were prepared in vivo and provided with Dicor crowns in our hospital. After remaining in place for 3 months these teeth were extracted. Subsequently their marginal areas were studied by SEM and histological preparations were made and measured. The marginal defects of Dicor crowns revealed slightly less favorable values than the Hi-Ceram crowns investigated one year ago, but these values are still within the range of clinical acceptability.