J Adv Prosthodont.  2013 May;5(2):179-186. 10.4047/jap.2013.5.2.179.

Evaluation of the marginal and internal gap of metal-ceramic crown fabricated with a selective laser sintering technology: two- and three-dimensional replica techniques

• Kim KB
• Kim JH
• Kim WC
• Kim HY
• Kim JH

• KMID: 2284759
• DOI: http://doi.org/10.4047/jap.2013.5.2.179

Abstract

PURPOSE
One of the most important factors in evaluating the quality of fixed dental prostheses (FDPs) is their gap. The purpose of this study was to compare the marginal and internal gap of two different metal-ceramic crowns, casting and selective laser sintering (SLS), before and after porcelain firing. Furthermore, this study evaluated whether metal-ceramic crowns made using the SLS have the same clinical acceptability as crowns made by the traditional casting.
MATERIALS AND METHODS
The 10 study models were produced using stone. The 20 specimens were produced using the casting and the SLS methods; 10 samples were made in each group. After the core gap measurements, 10 metal-ceramic crowns in each group were finished using the conventional technique of firing porcelain. The gap of the metal-ceramic crowns was measured. The marginal and internal gaps were measured by two-dimensional and three-dimensional replica techniques, respectively. The Wilcoxon signed-rank test, the Wilcoxon rank-sum test and nonparametric ANCOVA were used for statistical analysis (alpha=.05).
RESULTS
In both groups, the gap increased after completion of the metal-ceramic crown compared to the core. In all measured areas, the gap of the metal cores and metal-ceramic crowns produced by the SLS was greater than that of the metal cores and metal-ceramic crowns produced using the casting. Statistically significant differences were found between cast and SLS (metal cores and metal-ceramic crown).
CONCLUSION
Although the gap of the FDPs produced by the SLS was greater than that of the FDPs produced by the conventional casting in all measured areas, none exceeded the clinically acceptable range.

Keyword

CAD-CAM; Marginal adaptation; Metal ceramics restorations; Replica techniques

MeSH Terms

Computer-Aided Design
Crowns
Dental Porcelain
Dental Prosthesis
Fires
Replica Techniques
Dental Porcelain

Figure

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  Fig. 1 Titanium master model (1.2 mm and 360° chamfer form preparation was made on a maxillary right first molar).

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  Fig. 2 Two-dimensional replica technique. A: The inside of the core was first filled with the light body silicone and pressure (50 N for 10 min), B: Stabilization of the light body silicone using medium body silicone, C: The silicone replica sectioned four times (red line) and sixteen marginal points (P1-P16) were measured on each specimen.

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  Fig. 3 Measurement of marginal gap by digital microscope at ×160 magnification (Orange color: light body silicone; purple color: medium body silicone).

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  Fig. 4 Three-dimensional replica technique. A: The 3D surface model from the digitization of the study model used as the control model (CAD reference model; CRM), B: The point cloud model is the digitization of the light body silicone, C: The point cloud model is projected onto the surface of the CRM. The distribution of the internal gaps was measured and depicted on the color different map.

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  Fig. 5 Total mean and standard deviations (average of marginal and internal gap) for metal cores and metal-ceramic crowns of two groups (cast: conventional casting method; SLS: selective laser sintering method). Statistically significant differences between cast core and SLS core (P=.045), and between cast metal ceramic crown and SLS metal ceramic crown (P=.023).

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