Effect of digital impressions and production protocols on the adaptation of zirconia copings

Statement of problem

Proper marginal, axial, and occlusal adaptation of dental restorations is essential for their long-term success. Production protocols including digital impression systems have been developed, but little information is available on the adaptation of zirconia restorations produced via them.

Purpose

The purpose of this in vitro study was to compare the effects of digital impression protocols on the marginal, axial, and occlusal adaptation of zirconia copings.

Material and methods

Thirty extracted human maxillary premolar teeth without caries or defects were used. The teeth were prepared for zirconia crowns and randomly divided into 3 groups. Zirconia copings were designed at a thickness of 0.5 mm with 30 μm of simulated die spacer starting 1 mm from the margin of preparations. They were produced using computer-aided design-computer-aided manufacture (CAD-CAM) protocol with a conventional impression (group Cn) and 2 different production protocols with digital impressions (group C) and group Tr. The marginal, axial, and occlusal discrepancies of these copings were measured using the silicone replica technique with stereomicroscopy at ×50 magnification, and the data were analyzed with 1-way ANOVAs (α=.05).

Results

The mean marginal discrepancy values were 85.6 μm for group Cn, 58.7 μm for group C, and 47.7 μm for the Tr group. Significant differences were found among the production protocols in marginal, axial, and occlusal discrepancies (P<.05). Copings fabricated with the aid of digital impressions had significantly fewer marginal discrepancies than those of group Cn (P<.05). Group Tr exhibited the lowest marginal discrepancy, whereas groups Cn and C demonstrated similar axial adaptations (P>.05), and group Tr revealed the lowest axial discrepancy (P<.05). With regard to the occlusal discrepancy evaluation, group Tr had the lowest discrepancy. However, no significant differences was found between groups C and Cn (P>.05).

Conclusions

The copings produced with the aid of digital impression systems exhibited better marginal and occlusal adaptation than those of the copings produced with the aid of conventional impression.