J Dent Rehabil Appl Sci.  2022 Sep;38(3):127-137. 10.14368/jdras.2022.38.3.127.

Effect of milling and sintering process on integrity of zirconia prosthesis: a literature review

• Lee K
• Ko KH
• Huh YH
• Park CJ
• Cho LR

• KMID: 2535018
• DOI: http://doi.org/10.14368/jdras.2022.38.3.127

Abstract

Zirconia is fabricated through various processes. Each element in fabricating process can affect the physical properties of the definitive prosthesis. In particular, both the milling process and the sintering process can affect the final integrity of the zirconia prosthesis. Most of the milling machines adopt the ultra-precision 5-axis machining method, and the results vary depending on which milling method was used and how the milling equipment was managed. Milling blocks are selected according to cutting efficiency and aesthetic reproducibility. The sintering method can affect the grain growth and optical properties, and an accurate evaluation can be made only with additional research on the recent speed sintering procedure. Not only the sintering temperature but also the temperature holding time can affect the quality of definitive prosthesis.

Keyword

milling block; milling machine; milling methods; sintering; speed sintering

Figure

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  Fig. 1 Stage of manufacturing zirconia restoration. After making a block by pressing powdered zirconia, it is milled and then the definitive prosthesis is completed through a sintering process.

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  Fig. 2 Milling machine. (A) Schematic diagram, (B) Five-axis dental milling machine. a: Spindle and milling bur, b: Table and milling block.

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  Fig. 3 Orthogonal coordinate system (reference system). With a 3D axis, there are 3 axes rotating around each axis, so in theory there could be 6 axes. Most milling machines use 5 of them because of their fixation.

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  Fig. 4 Tool milling mode applied on a dental crown. Depending on the relationship between the milling tool or bur and the prosthesis surface, it can be called end milling when the tip is in contact, and flank milling when the body is in contact. Most of milling machine adopt a mixed milling method.

Reference

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