Effect Of Percelain Thicknesses On The Color Parameters And Masking Ability Of IPS E.max All-ceramic Restoration

Objective:The purpose of this study is to evaluate the effects of different thicknesses of core and dentin porcelain on the color parameters and masking ability of IPS e.max all-ceramic restoration.Methods.1. Disk-shaped specimens with different core/dentin thickness(mm) were made from IPS e.max ceramics.The samples were divided to three groups:0.8mm,1.0mm,and 1.5mm,based on the core thickness.Color parameters of samples were measured with ShadeEye Ncc,and calculate the color difference(△E) of samples of each core thickness groups which built up different thicknesses dentin porcelain.The date were statistically analyzed.2.Disk-shaped IPS e.max Press specimens(0.8,1.2,1.6,or 2.0mm in thickness)were fabricated ,five disks per group.Contrast ratio of specimen were measured with a spectrophotometer aginst black and white backgrounds; Color parameters of samples were measured with ShadeEye Ncc,and calculate the color difference(△E) of samples of each thickness, The date were statistically analyzed.Results.1.Increasing the total disk thickness resulted in decrease of L* and an increase of a* and b*.The dentin thickness exhibited significant influence on the mean values of L*,a* and b*(P< 0.001);the core thickness exhibited significant influence on the mean values of L* and b*(P< 0.001);the interaction exhibited significant influence on the mean values of L*(P< 0.001).2.Mean color difference values(△E)of units in 0.8mm core thickness group are all greater than 2.0, 1.0mm group which were built up 0.2mm and 1.0mm dentin porcelain,is over 2.0,while the△E between other units are all less than 2.0.3.Increasing the disk thickness resulted in increase of contrast ratio and decrease of△E values of the specimens aginst black and white backgrounds.Contrast ratio and△E of specimens with different thickness has significant difference (P< 0.001).Concluson.The color parameters of IPS e.max all-ceramic restoration can be varied by core thickness,dentin thickness and their interaction; the core thickness is bigger,the mean color difference values is minor with different dentin thicknesses.The thickness of IPS e.max Press exhibits significant influence on the masking ability,however,in severe discoloration teeth and metal post surface should be used with caution.