Zirconia Crown Accuracy on 3D Printed and Conventional Stone Models

Objectives: To compare the marginal and internal adaptation of final restorations fabricated on 3D printed models and conventional stone models.

Methods: Tooth number three was prepared for an all-ceramic crown in a typodont Model (D95SDP-200, Kilgore, MI) and impressed using polyether impression material (Impregum Penta Soft Quick Step, 3M ESPE, Germany). Extra-hard dental epoxy resin material (EP85-215 dental epoxy, Eager Polymer, Chicago) was used to fabricate the reference model. Ten conventional polyether impressions of the reference model were taken and poured with dental stone type IV to fabricate the conventional stone casts (Group 1). The reference model was scanned with the Trios Intraoral scanner (3shape, Copenhagen, Denmark) and ten digital impressions (Group 2) were printed by Bego Varseo 3D printer (Bego, Bremen, Germany) using the SLA technique. All models were scanned and Zirconia crowns were designed with the Exocad software, milled using the Schutz Tizian cut 5® Milling Machine and evaluated for marginal and internal adaptation.
Descriptive statistics were calculated by group. The independent-samples t-test was utilized to compare the two groups in terms of internal and marginal discrepancy. The statistical software SPSS (Version 24) was utilized.

Results: The conventional gypsum model group had a lower mean value (± SD) of marginal and internal discrepancy (45.5 ± 4.4 μm) and (68.0 ± 6.8 μm) compared to the 3D printed model group (46.1 ± 5.2 μm) and (73.7 ± 7.1 μm) respectively.
The independent-samples t-test did not reveal any significant difference between the conventional and 3D printed models, (-p=0.679-) for marginal discrepancy and (-p=0.086-) for internal discrepancy.

Conclusions: Within the limitations of this study, 3D printed models and conventional stone models did not exhibit significant differences in terms of marginal and internal fit of final restorations fabricated on them.