J Adv Prosthodont.  2018 Jun;10(3):236-244. 10.4047/jap.2018.10.3.236.

Comparison of the marginal fit of milled yttrium stabilized zirconium dioxide crowns obtained by scanning silicone impressions and by scanning stone replicas

• Aranda Yus E
• Cantarell
• Miñarro Alonso A

• KMID: 2413493
• DOI: http://doi.org/10.4047/jap.2018.10.3.236

Abstract

PURPOSE
To determine the discrepancy in monolithic zirconium dioxide crowns made with computer-aided design and computer-aided manufacturing (CAD/CAM) systems by comparing scans of silicone impressions and of master casts.
MATERIALS AND METHODS
From a Cr-Co master die of a first upper left molar, 30 silicone impressions were taken. The 30 silicone impressions were scanned with the laboratory scanner, thus obtaining 30 milled monolithic yttrium stabilized zirconium dioxide (YSZD) crowns (the silicone group). They were poured and the working models were scanned, obtaining 30 milled monolithic yttrium stabilized zirconium dioxide (YSZD) crowns (the plaster group). Three predetermined points were analyzed in each side of the crown (Mesial, Distal ,Vestibular and Palatal), and the marginal fit was evaluated with SEM (×600). The response variable is the discrepancy from the master model. A repeated measures ANOVA with two within subject factors was performed to study significance of main factors and interaction.
RESULTS
Mean marginal discrepancy was 22.42±35.65 µm in the silicone group and 8.94±14.69 µm in the plaster group. The statistical analysis showed significant differences between the two groups and also among the four aspects. Interaction was also significant (P=.02).
CONCLUSION
The mean marginal fit values of the two groups were within the clinically acceptable values. Significant differences were found between the groups according to the aspects studied. Various factors influenced the accuracy of digitizing, such as the design, the geometry, and the preparation guidance, as well as the texture, roughness and the color of the scanned material.

Keyword

Computer-aided design and computer-aided manufacturing (CAD/CAM); Marginal discrepancy; Marginal fit; Scanning silicone impressions; Scanning stone replicas

MeSH Terms

Computer-Aided Design
Crowns*
Molar
Silicon*
Silicones*
Yttrium*
Zirconium*
Silicon
Silicones
Yttrium
Zirconium

Figure

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  Fig. 1 Work flow of study.

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  Fig. 2 Cr-Co master die in zirconium support.

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  Fig. 3 Specimen fixation of the master cast.

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  Fig. 4 Scanning electron microscope image (×600) of distal aspect of crown Y4 (crown 4 plaster group).

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  Fig. 5 Graph of the logarithm of the Marginal Discrepancy (in µm) variable of the Silicone group and the Plaster group. Significant differences (P < .05) between faces (M, D, V, and P) within each group, as well as between the groups (Silicone and Plaster), and the interaction between the two groups, specifically the mesial face, are presented.

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