Objectives: The purpose of this study was to investigate the effects of various investing conditions and patterning materials on the marginal discrepancy of conical outer crown with Co-Cr-Ti alloy(Dentitan, Krupp Medizintechnik GmbH, Germany). Methods: To investigate the effects of investing conditions, patterns for conical outer crown were invested using phosphate-bonded investment(Univest-nonprecious, Shofu, Japan) with three different liquid/powder ratios which were 1)standard-recommended by manufacturer, 2)10%-decreased and 3)10%-increased. At each condition, metal casting ring was lined with single or double layers of ceramic liner(Einlagen, Krupp Medizintechnik GmbH, Germany). To compare the effects of patterning materials, 1)plastic foil(Adapta, Bego Co., Germany), 2)casting wax(Inlay wax, Whip-mix, U.S.A.), and 3)pattern resin(Pattern resin, GC Co., Japan) were used and cast under 10%-decreased liquid/powder ratio with double layers of ceramic liner because this condition resulted in the best fit of outer crown. Six specimens of each group, a total of fifty-four specimens were cast using Dentin alloy. The marginal discrepancy was measured by compact measuring microscope(STM5, Olympus, Japan) under X100 magnification at four different sites of conical outer crown around cervical margin. Results: 1. 10%-decreased liquid/powder ratio with double layers of ceramic liner showed the best fit of conical outer crown(mean discrepancy of 38mm). 2. The thickness of ring liner had more influence on the marginal discrepancy than the liquid/powder ratio. 3. There was no difference on the marginal discrepancy among three patterning materials(P>0.05). Conclusion: An acceptable marginal fitness of conical outer crown for the double crown system could not be expected with the investing condition recommended by investment manufacturer for the conventional dental prosthesis.

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