Objective        To determine the effects of different core ceramic and veneering porcelain thickness on the color of zirconia all-ceramic restoration.       Methods        The zirconia ceramic material was used to produce the zirconia ceramic core porcelain (0.4

0.6

0.8

1.0 and 1.2 mm)

which were then employed to construct different thickness of veneering porcelain (1.2

1.0

0.8

0.6

and 0.4 mm) to make the total thickness of 1.6 mm. Core porcelain of the thickness of 0.4 mm was constructed and veneering porcelain of 0.4

0.6

0.8

1.0 and 1.2 mm was prepared too. The paramet

er L*a*b* CM600d/700d spectrophotometry was used to measure color values of each group on a white background for the chromatic aberration.       Results        With the increase of zirconia core porcelain thickness

L* value and b* value were increased

the brightness was increased

color to yellow

between groups L* and b* values with significant differences (

P

0.05). With the increase of the thickness of veneering porcelain

L* was decreased

a* and b* were increased

L*

a* and b* values were significantly different (

P

0.05). With the zirconia core ceramic and veneering porcelain ratio increasing

the specimen had increased value of L*

and decreased a* and b*

and L* value had significant difference (

P

0.05). With the increase of the thickness of porcelain

color difference between the 2 groups △E was in a trend of decreasing.       Conclusion       Zirconia all-ceramic restorations core porcelain

porcelain veneer thickness

and the interaction between them can affect the color parameters of the core and veneering porcelain. With the porcelain layer thickness increasing

the color difference is small.