@article{LIN2026, 
author = {Zhi LIN and Lei JIANG and Jia ZHENG and Zhifeng ZHENG and Hao YU},
title = {Effect of grain size and staining time on the color parameters of zirconia},
year = {2026},
journal = {Journal of Prevention and Treatment for Stomatological Diseases},
volume = {34},
number = {8},
pages = {771-779},
keywords = {zirconia, immersion staining, grain size, immersion time, porosity, mercury intrusion porosimetry, penetration depth, color difference},
url = {https://www.sciopen.com/article/10.12016/j.issn.2096-1456.202660065},
doi = {10.12016/j.issn.2096-1456.202660065},
abstract = {ObjectiveTo investigate the effects of grain size and immersion dyeing time on the dye penetration depth and color parameters of zirconia, and analyze the dyeing behavior in relation to the material's pore characteristics to provide experimental evidence for developing personalized immersion staining protocols for clinical applications targeting zirconia with different microstructures.MethodsA total of 135 pre-sintered zirconia specimens with three different grain sizes were fabricated using computer aided design/manufacturing technology and divided into three groups (S1, S2, S3; n = 45). Randomly select 6 specimens from each group, among which 3 zirconia pre sintered specimens are soaked in 10 mL A2 staining solution for 60 s, dried and sintered, and the other 3 are not treated. Observe the microstructure of the outer surface and bonding surface of the specimen under SEM, and use Image J software to count and measure the grain size. From each group, three randomly selected specimens were subjected to mercury intrusion porosimetry to analyze porosity and pore size distribution. For the remaining specimens, the bottom surface (10 × 10 mm) was designated as the staining surface and immersed in 10 mL of A2 staining liquid. The remaining specimens were stained at six time gradients (10, 20, 30, 60, 90, 120 s). After staining, half of the specimens were sectioned perpendicular to the stained surface and fully sintered to measure the staining penetration depth. The other half were directly fully sintered. A spectrophotometer was used to measure the color parameters (L*, a*, b*) of the stained surface, and the color difference (ΔE00) relative to a standard A2 shade tab was calculated.ResultsThe average grain sizes (G) for the three groups were GS1=(221.64±62.16) nm, GS2=(197.80±46.72) nm, and GS3=(150.21±42.11) nm; the average porosities (P) were PS1=37.82%, PS2=46.02%, and PS3=47.36%. Both grain size and staining time significantly affected the staining outcome of zirconia (P < 0.001), with a significant interaction effect (P < 0.001). Staining penetration depth increased with prolonged staining time and decreased grain size (P < 0.001). All fully sintered specimens exhibited a perceptible color difference (ΔE00>0.8) compared with the standard A2 shade tab (VITA, USA). Specifically, specimens from group S1 stained for 20 s, group S2 stained for 60 s, and group S3 stained for 10 s exhibited color differences below the clinically acceptable threshold (ΔE00<1.8), meeting clinical thickness requirements. Specimens stained for other time intervals exceeded the clinically acceptable color difference threshold (ΔE00>1.8).ConclusionThe porosity of pre-sintered zirconia with different grain sizes varied. Higher porosity correlated with deeper staining penetration. The staining time required to achieve the standard A2 shade differed among zirconia materials with different grain sizes. In clinical applications, the immersion dyeing protocol for zirconia should be optimized based on the grain size and pore characteristics of zirconia with different grain sizes, so as to avoid color deviations caused by improper dyeing time.}
}