Evaluation of the fit of zirconia three-unit fixed partial dentures fabricated by different impression techniques

Aim

The aim of the present study was to evaluate the marginal and internal fit of zirconium fixed partial denture using different impression techniques.

Methods

A Nissin Typodont model, including maxillary central incisor and canine with missing lateral incisor, was selected for the present study. Thirty zirconium frameworks were fabricated following three impression techniques (N = 10), conventional silicone impression (group C), scanned dental impression (group S), and Trios 3 (3Shape) intraoral scanner (group T). An extra-fine milling strategy was applied.

Results

Group T had the smallest discrepancy compared to groups C (P = 0.006) and S (P = 0.052) at the marginal level, whereas it was larger at the incisal tip. Discrepancies in group T were smaller than group C (P = 0.004) when measured at the axial walls, and smaller than group S (P = 0.045) when measured at the chamfer area for the central teeth only. Samples in group T showed a greater percentage of equally extended restorations (52.5%), while other groups were mainly underextended (group C: 63.7%, group S: 68.8%).

Conclusion

Better adaptation was achieved with the intraoral scanner group, except at the incisal tip. Conventional and scanned impressions revealed a greater percentage of underextended restorations.