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Title: Investment strength as a function of time and temperature
Authors: Chew, C.L. 
Land, M.F.
Thomas, C.C.
Norman, R.D.
Keywords: Compressive strength
Issue Date: 1999
Citation: Chew, C.L., Land, M.F., Thomas, C.C., Norman, R.D. (1999). Investment strength as a function of time and temperature. Journal of Dentistry 27 (4) : 297-302. ScholarBank@NUS Repository.
Abstract: Objectives: The purpose of this investigation was to evaluate and compare the compressive strength characteristics of selected investments and to determine if these change as a function of time and temperature after mixing. Methods: Two phosphate-bonded investments and one gypsum-bonded investment were selected and 288 cylindrical specimens were fabricated (n = 9). Baseline compressive strength values were determined for each material at room temperature and compressive strength measurements were made for all materials at 700°C, and at 872°C only for phosphate-bonded investments. Each material was tested at 2, 6, 12, and 24 h after mixing. Specimens were heated at 15°C/min and heat soaked for 5 min in a burnout oven at the applicable testing temperature. They were transferred to a preheated chamber on an Instron testing machine and subjected to a compressive load at a crosshead speed of 2 mm/min until failure. The resulting strength data are presented in MN/m2. Results: The gypsum-bonded investment did not exhibit marked differences in strength as a function of either time or temperature. The phosphate-bonded investments, on the other hand, demonstrated considerable changes in compressive strength and differed in compressive strength characteristics at 700°C and 872°C respectively. Conclusions: At elevated temperatures, all materials approximated peak strength 2 h after initial mixing. At room temperature, the phosphate-bonded investments in this study were not significantly stronger than the gypsum-bonded investment material. However, they exhibited increased compressive strength as a function of time and temperature that was considerably higher than that exhibited by the gypsum-bonded investments. © 1999 Elsevier Science Ltd. All rights reserved.
Source Title: Journal of Dentistry
ISSN: 03005712
DOI: 10.1016/S0300-5712(98)00055-4
Appears in Collections:Staff Publications

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