Abstract: PURPOSE: The purpose of this in vitro study was to measure the color difference(△E) on titanium alloy background and translucency parameter(TP) of four kinds of zirconia-based all-ceramic specimens, providing a clinical reference for restoring grayish abutment. METHODS: Four groups with a total of 24 ceramic specimens were fabricated to a final specimen dimension of 14 mm×14 mm×1.5 mm, two kinds of zirconia with different translucency（Beitefu high-translucency, Cercon low-translucency）and their corresponding body porcelain at the shade of A2 were used as followed:high-translucency zirconia sintered dentine porcelain(Group A),low-translucency zirconia sintered dentine porcelain(Group B),high-translucency zirconia sintered opaque and dentine porcelain(Group C),low-translucency zirconia sintered opaque and dentine porcelain(Group D).The color parameters of the specimens under two backgrounds (titanium alloy and shade A3 light-activated resin-based composite) were measured by Shade Eye NCC colorimeter, then the △E value was determined by the relevant equations. The color parameters under black and white background were measured, and TP value was calculated. The experimental data were analyzed with SPSS 17.0 software package. RESULTS: There was significant difference of the TP value and the △E value among four groups specimens(P<0.05), the TP value was arranged as follows: group D<group C<group B<group A. The specimen used with opaque porcelain showed significantly reduced translucency. The △E value was arranged as follows :group D < group C < group B < 1.5 < 2 <group A, the △E value of group A cannot be accepted in clinic. CONCLUSIONS: The restoration of low-translucency zirconia sintered translucency veneering ceramic has better translucency, with value of △E<1.5 when used on the grayish abutment, which has a good aesthetic performance.

Key words: Zirconia, All-ceramic, Translucency parameter, Color difference