title: Evaluation of different bonded investments for dental titanium casting.
abstract: The properties of several different investments were investigated including phosphate bonded, magnesia bonded, and alumina cement investments. Measurements included the setting expansion, thermal expansion, and compressive strength of investments, as well as the tensile strength, elongation, Vickers hardness (VHN) and surface roughness of titanium castings. For phosphate bonded investment, the setting expansion after being mixed with its own mixing solution was 2.10%, which was larger than the other investments; the thermal expansion was -0.25% at 200 degrees C, the compressive strength 14 and 5 MPa after heating. For titanium cast in phosphate bonded investment, the hardness on its top surface was 655 Hv, the tensile strength was 379 MPa, the elongation was 19.4%, and the surface roughness was 2.29 microm. Although the thermal expansion of phosphate bonded investment is small, the setting expansion is large enough to compensate for the shrinkage of titanium castings. As its thermal expansion at T > or = 600 degrees C was constant and its heating-cooling cycle was almost reversible, these two properties can reduce the thermal shock and thus avoid cracking of the investment.
authors.affiliation: Department of Dental Technology, Chung Tai Institute of Health Sciences and Technology, Taichung, Taiwan. hchsu@chtai.ctc.edu.tw
authors.forename: H C
authors.initials: HC
authors.lastname: Hsu
authors.forename: H
authors.initials: H
authors.lastname: Kikuchi
authors.forename: S K
authors.initials: SK
authors.lastname: Yen
authors.forename: M
authors.initials: M
authors.lastname: Nishiyama
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D019245:Compressive Strength; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique; D005069:Evaluation Studies as Topic; D006244:Hardness; D006358:Hot Temperature; D008277:Magnesium Oxide / Q000737:chemistry; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry; D013499:Surface Properties; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry*
chemical_list: D003734:Dental Casting Investment; D010710:Phosphates; D008277:Magnesium Oxide; D014025:Titanium; D000537:Aluminum Oxide