Comparative study of all-ceramic crowns obtained from conventional and digital impressions: clinical findings

Objective

To compare clinical aspects of all-ceramic crowns fabricated from conventional and digital impressions.

Methods

Thirty patients with 30 posterior teeth with the need of a crown restoration were selected. Zirconia-based ceramic crowns were made using an intraoral digital impression system (TRIOS®, 3shape) and two-step silicone impression technique. Two external blinded operators evaluated the all-ceramic crowns. Five selection items were assessed of which four were clinical: “marginal fit,” “occlusal contacts,” “interproximal contact points,” and “primary retention.” Then, the last selection item “final selection” was assessed when the operators considering all the variables had to select which of the digital or conventional crown had the best clinical conditions. Data was analyzed using Kappa index test and the Pearson’s chi-square test (α = 0.05).

Results

For the items marginal fit and interproximal contact points, moderate agreement between the two operators was described and significant differences were found between the two study groups. Conversely, for the variables primary retention and occlusal contacts, the agreement between the operators was fair and no significant differences were found. For the final selection, a substantial agreement was reached between the two operators and significant differences were found between the two groups (p < 0.05).

Conclusion

In most cases and in a significant way, the digital crowns had better clinical conditions according to both evaluators. The digital crowns were statistically superior for the interproximal contact points and marginal fit. For the variables occlusal contacts and primary retention, no difference between the two groups was observed.

Clinical significance

Digital intraoral impressions can be used for manufacturing ceramic crowns, with the same or better clinical results as conventional impressions.

     

Clinical evaluation comparing the fit of all-ceramic crowns obtained from silicone and digital intraoral impressions

Objectives

The aim of this study is to compare the fit of all-ceramic crowns fabricated from conventional silicone impressions with the fit of all-ceramic crowns fabricated from intraoral digital impressions.

Methods

Twenty patients with 26 posterior teeth with a prosthetic demand were selected for the study. Two crowns (Straumann-Zerion) were made for each preparation. One crown was fabricated from an intraoral digital impression system (IDI group; Cadent-iTero), and the other crown was fabricated from a conventional one-step silicone impression (CI group; Express Penta Putty and Body Light). To replicate the interface between the crown and the preparation, each crown was cemented on its corresponding clinical preparation with ultra-flow silicone (Express Ultra Light Body). Each crown was embedded in resin to stabilize the registered interface, cut in 2-mm-thick slices in a buco-lingual orientation. Internal misfit was measured in microns using stereomicroscopy with a magnification of ×40. Measurements were taken at different landmarks: margin, chamfer angle, axial, crest, and occlusal fosse. After checking for normality, data was analyzed using paired Student’s t test (α?=?0.05).

Results

Fit values were significantly affected by the impression technique (p?=?0.000). Mean internal misfit and mean marginal misfit were 111.40 μm (SD?=?54.04)/80.29 μm (SD?=?26.24) for the crowns of the IDI group and 173.00 μm (SD?=?92.65)/133.51 μm (SD?=?48.78) for the CI group.

Conclusion

All-ceramic crowns fabricated from intraoral digital impressions with parallel confocal technology demonstrated a clinically acceptable internal and marginal fit as conventional impression.

Clinical significance

Intraoral digital impressions as initial step to the digital workflow could further improve the marginal adaptation of all ceramic single crowns.

Trial registration

http://www.isrctn.com/ISRCTN16111844