Evaluating Translucency and Color Changes in Lithium Disilicate Ceramics After Sintering Modification and Artificial Aging

Recent developments in all-ceramic restorative materials have enhanced the clinical applicability of lithium disilicate for aesthetic dental restorations. The current study explores the influence of sintering parameter modulation over the translucency and color change of Amber Mill and IPS e.max CAD ceramics at baseline and following simulated aging through thermocycling and simulated toothbrushing. Sixty discs of lithium disilicate were assigned to two groups according to material type (Amber Mill; E-max), then according to translucency level (HT: high translucency; LT: low translucency). All specimens were sintered, polished, and ultrasonically cleaned in accordance with manufacturer guidelines. Optical properties—including translucency parameter (TP), color difference (ΔE), and color coordinates (L*, a*, b*)—were measured using a spectrophotometer at baseline and after a five-year clinical simulation. Scanning electron microscope (SEM) analysis was performed. Amber Mill-HT demonstrated the highest initial translucency (15.48 ± 0.89), followed by Amber Mill-LT (12.52 ± 0.61). Aging increased TP values in Amber Mill groups, while a slight reduction was observed in E-max groups. Amber Mill-LT exhibited the lowest color change (ΔE = 0.80 ± 0.10), reflecting superior color stability, whereas E-max-LT showed the highest ΔE (1.43 ± 0.21). SEM analysis demonstrated distinct microstructural differences between materials and translucency levels. High-translucency ceramics exhibited finer, more uniform lithium disilicate crystals and continuous glassy matrices, whereas low-translucency groups showed larger crystals, increased heterogeneity, and greater surface irregularities after aging. Overall, Amber Mill-LT displayed the greatest color stability, whereas E-max groupsretained translucency more consistently. All evaluated ceramics showed optical alterations within clinically acceptable limits, confirming their suitability for aesthetic restorative applications.