[Field study on the accuracy of fit and the marginal seal of In-Ceram crowns and bridges].

It was the objective of this in-vitro field study to evaluate the marginal fit of the In-Ceram system (Vita). All the materials applied in this system were compared with each other under the aspect of their dimensional behavior to determine the influence of this factor on die adaptation. The mean value of the marginal fit of the In-Ceram restorations on the master models was 12 (+/- 10) microns. The PFM bridges showed marginal openings of 9 (+/- 10) microns. The values on the patient models were 38 (+/- 12) microns for In-Ceram, and 44 (+/- 19) microns for PFM. This increase had been anticipated because of the grain size of the Harvard Cement. The dimensional changes of the materials involved were in great harmony. At least one coat of die spacer is necessary to compensate for the contraction of the ceramic and the expansion of the special plaster. Two paints are recommended for crowns and three for bridges. Careful shoulder or chamber preparation is required to create smooth surfaces.