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Comparison the Marginal and Internal Fit of Metal Copings Cast from Wax Patterns Fabricated by CAD/CAM and Conventional Wax up Techniques.

Vojdani M, Torabi K, Farjood E, Khaledi A - J Dent (Shiraz) (2013)

Bottom Line: The Student's t-test revealed significant differences between 2 groups.Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001).All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore, only the conventional group results in copings with clinically acceptable margins of less than 120um.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.

ABSTRACT

Statement of problem: Metal-ceramic crowns are most commonly used as the complete coverage restorations in clinical daily use. Disadvantages of conventional hand-made wax-patterns introduce some alternative ways by means of CAD/CAM technologies.

Purpose: This study compares the marginal and internal fit of copings cast from CAD/CAM and conventional fabricated wax-patterns.

Materials and method: Twenty-four standardized brass dies were prepared and randomly divided into 2 groups according to the wax-patterns fabrication method (CAD/CAM technique and conventional method) (n=12). All the wax-patterns were fabricated in a standard fashion by means of contour, thickness and internal relief (M1-M12: representative of CAD/CAM group, C1-C12: representative of conventional group). CAD/CAM milling machine (Cori TEC 340i; imes-icore GmbH, Eiterfeld, Germany) was used to fabricate the CAD/CAM group wax-patterns. The copings cast from 24 wax-patterns were cemented to the corresponding dies. For all the coping-die assemblies cross-sectional technique was used to evaluate the marginal and internal fit at 15 points. The Student's t- test was used for statistical analysis (α=0.05).

Results: The overall mean (SD) for absolute marginal discrepancy (AMD) was 254.46 (25.10) um for CAD/CAM group and 88.08(10.67) um for conventional group (control). The overall mean of internal gap total (IGT) was 110.77(5.92) um for CAD/CAM group and 76.90 (10.17) um for conventional group. The Student's t-test revealed significant differences between 2 groups. Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001).

Conclusion: Within limitations of this study, conventional method of wax-pattern fabrication produced copings with significantly better marginal and internal fit than CAD/CAM (machine-milled) technique. All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore, only the conventional group results in copings with clinically acceptable margins of less than 120um.

No MeSH data available.


Virtual designed die
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Figure 1: Virtual designed die

Mentions: Twenty-four machined brass dies models were designed and prepared in a lathe (CNC350; Arix Co. Tainan Hesin, Taiwan) to simulate full coverage PFM crown preparation with a chamfer margin around the entire circumference. Preparation were standardized with a height of 5.5 mm, width of 6 mm at the margin, the convergence angle of 6 degrees, 0.7 mm chamfer width, chamfer radius of 2mm (R=2), and an anti rotational surface (Figure 1). To avoid any possible variations during the impression and casting stages, the brass dies were used as definitive dies to fabricate the restorations [11, 24-25, 28-29, 32, 35]. According to the method of wax pattern fabrication, they were randomly divided into one experimental group (CAD/CAM group) and one control group (conventional group) (n=12) and then numbered as M1 to M12 and C1 to C12 respectively.


Comparison the Marginal and Internal Fit of Metal Copings Cast from Wax Patterns Fabricated by CAD/CAM and Conventional Wax up Techniques.

Vojdani M, Torabi K, Farjood E, Khaledi A - J Dent (Shiraz) (2013)

Virtual designed die
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3927676&req=5

Figure 1: Virtual designed die
Mentions: Twenty-four machined brass dies models were designed and prepared in a lathe (CNC350; Arix Co. Tainan Hesin, Taiwan) to simulate full coverage PFM crown preparation with a chamfer margin around the entire circumference. Preparation were standardized with a height of 5.5 mm, width of 6 mm at the margin, the convergence angle of 6 degrees, 0.7 mm chamfer width, chamfer radius of 2mm (R=2), and an anti rotational surface (Figure 1). To avoid any possible variations during the impression and casting stages, the brass dies were used as definitive dies to fabricate the restorations [11, 24-25, 28-29, 32, 35]. According to the method of wax pattern fabrication, they were randomly divided into one experimental group (CAD/CAM group) and one control group (conventional group) (n=12) and then numbered as M1 to M12 and C1 to C12 respectively.

Bottom Line: The Student's t-test revealed significant differences between 2 groups.Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001).All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore, only the conventional group results in copings with clinically acceptable margins of less than 120um.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.

ABSTRACT

Statement of problem: Metal-ceramic crowns are most commonly used as the complete coverage restorations in clinical daily use. Disadvantages of conventional hand-made wax-patterns introduce some alternative ways by means of CAD/CAM technologies.

Purpose: This study compares the marginal and internal fit of copings cast from CAD/CAM and conventional fabricated wax-patterns.

Materials and method: Twenty-four standardized brass dies were prepared and randomly divided into 2 groups according to the wax-patterns fabrication method (CAD/CAM technique and conventional method) (n=12). All the wax-patterns were fabricated in a standard fashion by means of contour, thickness and internal relief (M1-M12: representative of CAD/CAM group, C1-C12: representative of conventional group). CAD/CAM milling machine (Cori TEC 340i; imes-icore GmbH, Eiterfeld, Germany) was used to fabricate the CAD/CAM group wax-patterns. The copings cast from 24 wax-patterns were cemented to the corresponding dies. For all the coping-die assemblies cross-sectional technique was used to evaluate the marginal and internal fit at 15 points. The Student's t- test was used for statistical analysis (α=0.05).

Results: The overall mean (SD) for absolute marginal discrepancy (AMD) was 254.46 (25.10) um for CAD/CAM group and 88.08(10.67) um for conventional group (control). The overall mean of internal gap total (IGT) was 110.77(5.92) um for CAD/CAM group and 76.90 (10.17) um for conventional group. The Student's t-test revealed significant differences between 2 groups. Marginal and internal gaps were found to be significantly higher at all measured areas in CAD/CAM group than conventional group (p< 0.001).

Conclusion: Within limitations of this study, conventional method of wax-pattern fabrication produced copings with significantly better marginal and internal fit than CAD/CAM (machine-milled) technique. All the factors for 2 groups were standardized except wax pattern fabrication technique, therefore, only the conventional group results in copings with clinically acceptable margins of less than 120um.

No MeSH data available.