The onset, duration, rate, and magnitude of setting expansions of one gypsum product were compared under different conditions of restraint. Specimens were set normally or hygroscopically in a mercury bath or in tinfoil- or plastic-lined troughs. The final setting times were the same for all combinations. Both internal and external restraints altered the rates, and thus the magnitude, of expansion during all stages of setting. Conditions affecting the rate of restraint, in decreasing order, were tinfoil, plastic film, and mercury.
Get full access to this article
View all access options for this article.
References
1.
Wilson, G.H.: A Manual of Dental Prosthetics, ed 4, Philadelphia: Lea and Febiger, 1920, pp 72-81.
2.
Docking, A.R. ; Chong, M.P.; and Donni-Son , J.A.: The Hygroscopic Setting Expansion of Dental Casting Investments; Part 2, Aust J Dent52:160-166, 1948.
3.
Mahler, D.B. , and Ady, A.B.: An Explanation for the Hygroscopic Setting Expansion of Dental Gypsum Products, J Dent Res39:578-589, 1960.
4.
Jrgensen, K.D. : The Hygroscopic Setting Expansion of Gypsum , Acta Odont Scand18:461-477, 1960.
5.
Earnshaw, R. : The Effect of Restrictive Stress on the Setting Expansion of Gypsum Bonded Investments, Aust Dent J9:169-176, 1964.
6.
KusNER, W., and Michman , J. : Setting Expansion of Plaster of Paris: The Initial Contraction, J Dent Res46:661-666, 1967.
7.
Skinner, E.W.: The Role of Investment Setting Expansion in Gold Casting Techniques, Dent Cosmos75:1009-1018, 1933.
8.
Skinner, E.W., and Degni, F.: Hygroscopic Expansion of Dental Investments, 54 :603-608. 1957.
9.
Shell, J.S.: The Effect of Longitudinal Restrictive Force on Hygroscopic Expansion, J Dent Res40:287-293, 1961.
10.
Skinner, E.W.: The Science of Dental Materials, ed 4, Philadelphia: W. W. Saunders Co., 1954, p 34.
11.
Sweeney, W.T., and Taylor, D.F.: Dimensional Changes in Dental Stone and Plaster, J Dent Res29:749-755, 1950.
12.
Jrgensen, K.D.: "Setting Expansion of Gypsum," in de Boer, J.H., et al (eds.), Reactivity of Solids, Proc 4th International Symposium on the Reactivity of Solids, Amsterdam, 1960, Amsterdam: Elsevier Publishing Co., pp 638-642.
13.
Mahler, D.B. , and AscARzADEH , K.: The Volumetric Contraction of Dental Gypsum Materials on Setting, J Dent Res32 :354-361, 1953.
14.
Mahler, D.B. : Hardness and Flow Properties of Gypsum Materials , J Pros Dent, 1:188-195, 1951.
