Title: 0882 - Accuracy Analysis of Crowns Fabricated Conventionally Versus Digitally


Karen Schulze (Presenter)
University of the Pacific

Bina Surti, University of the Pacific
Jordan Jew, University of the Pacific


Objectives: The purpose of this in-vitro study was to evaluate the internal fit of the zirconia and lithium-disilicate (ld) crowns fabricated on conventional stone models with the zirconia and lithium disilicatecrowns fabricated on a virtual model that was created with the Trios-Intraoral-Scanner(3Shape, Denmark).

Methods: A master model was created with a ceramic implant abutment (4.5mm regular emergence, Biohorizons, AL, USA) embedded in an acrylic round stand with 3cm in diameter. 12 stone models and abutments were fabricated with custom trays and a polysiloxane impression material, Imprint 4 Light and Heavy(3M ESPE). 6 models were used to fabricate zirconia-crowns using IPS e.max ZirCAD MT MultiA2 blocks in the Mastermill 5.0 Milling machine (Stone-Zir). The other six models models served for ld crowns using IPS e.max CAD HTA1/C14 blocks in the MastermillN4 (Stone emax CAD). Another 6 zirconia crowns were fabricated from a digital scan using the Trios scanner(Virtual-ZIR Trios) while additional 6 ld crowns were fabricated with the same STL file from the Trios scanner (Virtual-emaxCAD Trios). The internal fitting was examined by using the Rapid Plus 1276 CNC, 3D measuring machine (Thome Praezision,Germany). The crowns from the models were compared to the models as well as to the master model. All virtual designed crowns were compared to the master model only. The internal distance from the intaglio surface of the crown to the master-model/stone-model was measured. At a inner distance from the crown margin(1mm and 4mm)circles on the model as well as on the intaglio surface of the crowns were drawn, overlapped and subtracted. The room/gap for cement is calculated. Student t-tests compared the results at a 95% confidence interval if there is a significant difference.

Results: The table shows the results for a 1mm and a 4mm distance from the crown margin(n=6)in mm. The following statistical difference have been found: VirtualZIR Trios vs Stone emaxCAD Master (p=0.007),Virtual ZIR Trios vs Stone emax CAD (p=0.004), Virtual ZIR Trios vs Stone emax CAD Master (0.003) as well as Stone emaxCAD vs Virtualemax CAD Trios (p=0.03)

Conclusions: The virtually designed ZIR and emaxCAD crowns at the margins have a very good fit but at 4mm away the internal gap between model and restoration was the largest.


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This abstract is based on research that was funded entirely or partially by an outside source:

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: None