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The effect of investment type on the fit of cast titanium crowns
Author(s) -
Mori Toshiko,
JeanLouis Michael,
Yabugami Masahiko,
Togaya Toshihiro
Publication year - 1994
Publication title -
australian dental journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.701
H-Index - 71
eISSN - 1834-7819
pISSN - 0045-0421
DOI - 10.1111/j.1834-7819.1994.tb03104.x
Subject(s) - type (biology) , titanium , investment (military) , orthodontics , materials science , dentistry , metallurgy , medicine , geology , political science , paleontology , politics , law
In order to determine the best laboratory procedure for titanium crown casting, a set of thermal expansion measurements and casting experiments were carried out using a casting machine (argon arc, pressure difference type) and three different investments, two conventional SiO 2 based investments and a new Al 2 O 3 /MgO based investment. The thermal expansion measurements involved a cycle of heating and cooling. The relatively low mould temperatures recommended (200°C) or chosen (350°C) for the conventional investments provided zero or negative mould expansion for the compensation of metal shrinkage. Crowns made from these investments exhibited heavy reaction with the mould, and the common cleaning method of sand blasting appeared to be essential. This cleaning process, however, was not adequate for the assessment of casting accuracy as the short sand blasting time (15 s) rapidly altered the fit of the crowns. The metal reacted little with the new investment and the best compensation (0.15 mm discrepancy) for the metal shrinkage, as assessed ‘as cast’, was achieved when the investment was heated to 950°C and then cooled to the recommended mould temperature (600°C).