8: Gypsum materials

8

Gypsum materials

Figure 8.1 Effect of drying time on compressive strength of dental plaster.

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Figure 8.2 Effect of the W/P ratio (shown above the columns) on the strength of gypsum materials.

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Figure 8.3 Wet and dry compressive strengths of gypsum materials.

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Table 8.1 Dental gypsum products

ANSI/ADA specification nomenclature Traditional nomenclature
Type I—Plaster, impression Impression plaster
Type II—Plaster, model Model or laboratory plaster
Type III—Dental stone Class I stone; model stone
Type IV—Dental stone, high strength Class II stone; die stone
   Low expansion (ISO Type 4)
   High expansion (ISO Type 5)

Table 8.2 Water-to-powder (W/P) ratios for gypsum materials

Product W/P ratio
(g water/100 g powder)
Plaster 40–50
Dental stone 25–30
Die stone 19–24

Table 8.3 Effect of W/P ratio on characteristics of mixed gypsum materials

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Table 8.4 Comparative properties of dental gypsum products

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8.1 Dental gypsum materials

Widely used in dentistry, gypsum materials are obtained from natural deposits of gypsum, CaSO4·2H2O, which when heated loses 1.5 g mol of water and converts to the hemihydra/>

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Jan 1, 2015 | Posted by in Dental Materials | Comments Off on 8: Gypsum materials
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