J Adv Prosthodont.  2017 Dec;9(6):463-469. 10.4047/jap.2017.9.6.463.

Evaluation of marginal and internal gap of three-unit metal framework according to subtractive manufacturing and additive manufacturing of CAD/CAM systems

• Kim DY
• Kim EB
• Kim HY
• Kim JH
• Kim WC

• KMID: 2398051
• DOI: http://doi.org/10.4047/jap.2017.9.6.463

Abstract

PURPOSE
To evaluate the fit of a three-unit metal framework of fixed dental prostheses made by subtractive and additive manufacturing.
MATERIALS AND METHODS
One master model of metal was fabricated. Twenty silicone impressions were made on the master die, working die of 10 poured with Type 4 stone, and working die of 10 made of scannable stone. Ten three-unit wax frameworks were fabricated by wax-up from Type IV working die. Stereolithography files of 10 three-unit frameworks were obtained using a model scanner and three-dimensional design software on a scannable working die. The three-unit wax framework was fabricated using subtractive manufacturing (SM) by applying the prepared stereolithography file, and the resin framework was fabricated by additive manufacturing (AM); both used metal alloy castings for metal frameworks. Marginal and internal gap were measured using silicone replica technique and digital microscope. Measurement data were analyzed by Kruskal-Wallis H test and Mann-Whitney U-test (α=.05).
RESULTS
The lowest and highest gaps between premolar and molar margins were in the SM group and the AM group, respectively. There was a statistically significant difference in the marginal gap among the 3 groups (P < .001). In the marginal area where pontic was present, the largest gap was 149.39 ± 42.30 µm in the AM group, and the lowest gap was 24.40 ± 11.92 µm in the SM group.
CONCLUSION
Three-unit metal frameworks made by subtractive manufacturing are clinically applicable. However, additive manufacturing requires more research to be applied clinically.

Keyword

CAD/CAM; Micro-stereolithography; Metal framework; Marginal gap; Internal gap

MeSH Terms

Alloys
Bicuspid
Dental Prosthesis
Denture, Partial, Fixed
Molar
Replica Techniques
Silicon
Silicones
Alloys
Silicon
Silicones

Figure

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  Fig. 1 Experimental design to evaluate marginal and internal gap by fabricating a three-unit metal framework.

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  Fig. 2 Prepared three-unit working dies. (A) Prepared Type IV three-unit working die, and (B) prepared scannable three-unit working die.

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  Fig. 3 Manufacturing process of subtractive manufacturing.

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  Fig. 4 Manufacturing process of the µ-SLA system of additive manufacturing.

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  Fig. 5 Production of three-unit metal copings. (A) Production of three-unit metal copings in the LW group, (B) the SM group, and (C) the µ-SLA group.

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  Fig. 6 Marginal and internal fit using silicone replica technique.

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  Fig. 7 Marginal and internal gap measurement location.

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