Fit of a new pressure-sintered zirconium dioxide coping

The aim of this study was to determine in vitro the internal and marginal fit of zirconium dioxide ceramic copings manufactured using a recently introduced CAD/CAM-based technique (Denzir).

Two master models were produced in metal, representing the maxillary right central incisor and first premolar. Two A-silicone impressions were used for each of the master models, and from each of the impressions five stone dies with the corresponding ceramic copings were produced, for a total of 20 copings. The A-silicone replica of the misfit of the ceramic coping to the corresponding stone die and master model was sectioned buccolingually and mesiodistally. The obtained sections were measured at occlusal, axial, and marginal locations under light microscopy. Twenty-four measurements for each replica were made. The Student's t test was used to detect significant differences between coping-stone die and coping-master model misfits.

For any combination, the marginal fit was superior to the axial and occlusal fit. In general, the misfit between the coping and the stone die did not differ significantly from the misfit detected between the coping and the master model. However, a better fit was recorded for the first premolar at the occlusal portion in the coping-stone die combination compared to the coping-master model combination. The mean marginal discrepancy between the copings and master models was clearly below 50 microm, with a range of 0 to 115 microm.

The accuracy achieved by the Denzir manufacturing process for the production of zirconium dioxide copings is well within the range of clinical acceptability.