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Vollständiger Abstract

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<h4>Objective</h4>To evaluate the effect of ceramic translucency and resin cement shade on the translucency alteration after aging over different substrates.<h4>Methods</h4>Sixty specimens were divided into 12 groups (n = 5) composed of lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) in three translucencies (HT, MT, LT). The 0.5 mm thick specimens were cemented with Variolink Esthetic LC (Ivoclar Vivadent) Light+ (L+) and Neutral (N) over resin substrates A1 and A4. Samples were subjected to 20,000 aging thermocycles, alternating 55°C-5°C (30 s). Spectral reflectance was measured using a spectrophotometer (CM-3700d-Konica Minolta) at four intervals: before aging (t0) and after 10,000 (t10), 15,000 (t15), and 20,000 (t20) cycles. The Translucency Parameter (TP 00 ) and the ΔTP 00 were calculated. The thresholds for translucency perceptibility (TPT 00 ) and acceptability (TAT 00 ) were set at 0.62 and 2.62, respectively. Statistical analysis was performed using four-way repeated measures ANOVA and Tukey's post hoc test (α = 0.05).<h4>Results</h4>Aging time, ceramic translucency, resin cement color and substrate saturation had a significant effect (p < 0.001) on TP 00 . While TP 00 values declined across all groups, the lowest values for each measurement moment were consistently observed in the LTL+ groups [1.70 (t0) to 0.90 (t20)]. All ΔTP 00 values remained below the acceptability threshold (TAT = 2.62).<h4>Conclusion</h4>Aging resulted in a generalized decrease in translucency across all groups, particularly over lighter substrates and when using chromatic resin cement. However, no clinically unacceptable alterations were observed.<h4>Clinical significance</h4>Clinicians should select materials based on the balance between initial masking and long-term stability. For dark substrates, LT ceramics ensure consistent optical stability during aging, regardless of the resin cement shade. While combining translucent ceramics (HT/MT) with chromatic resin cements is an effective strategy for initial masking, clinicians must be aware that ceramic translucency is the primary factor controlling the final optical outcome over time.

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