J Adv Prosthodont.  2015 Apr;7(2):122-128. 10.4047/jap.2015.7.2.122.

Accuracy evaluation of metal copings fabricated by computer-aided milling and direct metal laser sintering systems

• Park JK
• Lee WS
• Kim HY
• Kim WC
• Kim JH

• KMID: 2118242
• DOI: http://doi.org/10.4047/jap.2015.7.2.122

Abstract

PURPOSE
To assess the marginal and internal gaps of the copings fabricated by computer-aided milling and direct metal laser sintering (DMLS) systems in comparison to casting method.
MATERIALS AND METHODS
Ten metal copings were fabricated by casting, computer-aided milling, and DMLS. Seven mesiodistal and labiolingual positions were then measured, and each of these were divided into the categories; marginal gap (MG), cervical gap (CG), axial wall at internal gap (AG), and incisal edge at internal gap (IG). Evaluation was performed by a silicone replica technique. A digital microscope was used for measurement of silicone layer. Statistical analyses included one-way and repeated measure ANOVA to test the difference between the fabrication methods and categories of measured points (alpha=.05), respectively.
RESULTS
The mean gap differed significantly with fabrication methods (P<.001). Casting produced the narrowest gap in each of the four measured positions, whereas CG, AG, and IG proved narrower in computer-aided milling than in DMLS. Thus, with the exception of MG, all positions exhibited a significant difference between computer-aided milling and DMLS (P<.05).
CONCLUSION
Although the gap was found to vary with fabrication methods, the marginal and internal gaps of the copings fabricated by computer-aided milling and DMLS fell within the range of clinical acceptance (<120 microm). However, the statistically significant difference to conventional casting indicates that the gaps in computer-aided milling and DMLS fabricated restorations still need to be further reduced.

Keyword

CAD/CAM system; Cobalt-chromium alloy; Computer-aided milling; Direct metal laser sintering; Marginal and internal fit

MeSH Terms

Replica Techniques
Silicones
Silicones

Figure

• 

  Fig. 1 Flowchart for the fabrication of metal copings.

• 

  Fig. 2 Schematic diagram of the measuring points (A) mesiodistal section: a,g = marginal gap (MG), b,f = cervical gap (CG) (400 µm above MG), c,e = axial wall at internal gap (AG), d = incisal edge at internal gap (IG). (B) labiolingual section: 1,7 = MG, 2,6 = CG (400 µm above MG), 3,5 = AG, 4 = IG.

• 

  Fig. 3 Measurement of the marginal area silicone thickness by digital microscopy (magnification 160×).

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