OBJECTIVETo compare the color differences of different metal bases and different opaque thickness, and evaluate the best thickness of opaque on different metal bases.

METHODSPrecious metal, gold sediment and Ni-Cr plates were prepared as bases, then opaque samples of 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5 mm thickness were fabricated on such plates. Minolta chromatics meter CR-321 was used to examine the color properties of these samples, and deltaE was calculated to evaluate the color difference of the specimens.

RESULTSFor the restoration based on Ni-Cr and precious alloys, the color of restorations was not affected by the color of metal bases as the thickness of opaque reached 0.3 mm, and the chromatic value deltaE < 1.5 NBS. For the restoration based on gold sediment, the color of restoration was not affected by the color of metal as the thickness of opaque reached 0.1 mm, and the chromatic value deltaE < 1.5 NBS.

CONCLUSIONDifferent opaque thickness was necessary to obtain ideal color appearance in clinic. As the opaque thickness increased, the color of restoration based on Ni-Cr and noble metal increased but the color of restoration based on gold sediment decreased.