Effect Of The Porcelain Thickness And Illuminant On The Color Of IPS E.max All-ceramic Restoration

All ceramic materials are favoured by both patients and dentists, because they have the properties of aesthetics, low thermal conductivity, non-conducting, biocompatibility, wear resisting and no metal basement. The clinical shortcomings of these materials, however, such as brittleness, crack propagation, low tensile strength and marginal accuracy, continue to limit their clinical applications. In recent yeas, with the improvement of various mechanical properties of these ceramic materials, the anti-fracture strength of the high-strength all-ceramic dental materials have been substantially increased to meet the clinical requirements. Color is one of the important indicators to evaluate the all-ceramic restorations. Many factors influence the color of all-ceramic restorations, such as ceramic structural features, porcelain thickness, adhesive, post-core, abutment tooth, illuminant etc.IPS e.max Press is a new kind of lithium disilicate glass-ceramic ingot for the press technique. It is one of the most commonly used core ceramic materials, and its flexural strength reaches 400MPa. So investigations about the influence factors on the color of IPS e.max all-ceramic restoration are meaningful for clinical practice. This study adopted IPS e.max Press and IPS e.max Ceram A2 (Ivoclar Vivadent,Switzerland). CM-700d Spectrophotometer was used to measure the color parameters. The effects of the porcelain thickness and illuminant on the color and translucency of IPS e.max all-ceramic restoration were evaluated to provide a theoretical basis for the clinical practice.The study included three parts:Part one: Specimens of IPS e.max Press MO1 core ceramic with different thicknesses (0.30 mm, 0.60 mm, 0.90 mm and 1.20 mm) were made. The color parameters were measured with CM-700d Spectrophotometer. The translucency parameter (TP) and color difference (ΔE) were calculated and analyzed statistically. The influence of the porcelain thickness on the color and translucency of IPS e.max Press core ceramic was evaluated.Part two: Different thicknesses disk specimens with core and dentine ceramic were made. The color parameters were measured with CM-700d Spectrophotometer. The translucency parameter (TP) and color difference (ΔE) between adjacent groups were calculated, and statistically analyzed. The effects of the core and dentine porcelain thickness on the color and translucency of IPS e.max all-ceramic were discussed.Part three: Specimens of IPS e.max Press MO1 core ceramic with different thicknesses (0.30 mm, 0.60 mm, 0.90 mm and 1.20 mm) were made. IPS e.max Ceram A2 was sintered on the core ceramic. The final thickness was controlled to 1.50 mm. The color parameters were measured with CM-700d Spectrophotometer. The translucency parameter (TP), translucency difference (ΔTP) and color difference (ΔE) between adjacent groups were calculated. Statistical analysis was done. The influence of illuminant on the color and translucency of IPS e.max all-ceramic was evaluated.According the research, following conclusions could be obtained:1. Thickness of core porcelain had a significant effect on the color and translucency of IPS e.max Press. With the thickness of core ceramic increasing, the L* values decreased, resulting in redder, more yellow and more translucent specimens.2. Thickness of the core and dentine ceramic had a significant effect on the color and translucency of IPS e.max all-ceramic restoration. With the increase of the thickness of core and dentine ceramic, the L* values and translucency decreased, and a* values and b* values had no significant tendency. The better the translucency of materials, the higher the tanslucent parameter (TP) value.3. Illuminate had a significant effect on the color and translucency of IPS e.max all-ceramic restoration. Based on all the specimens, the following results were obtained: L* values for A illuminant > F2 illuminant > D65 illuminant; a* values for A illuminant > D65 illuminant > F2 illuminant; b* values for F2 illuminant > A illuminant > D65 illuminant. TP values relative to the illuminant D65 were lower than those to A and F2. Therefore, in daylight condition, translucency of all-ceramic materials was lower than those of incandescent or fluorescent lamp.