Thermo-hygrometric aging increases marginal gap of lithium disilicate and leucite-reinforced CAD/CAM veneers but not resin nano-ceramic: an in-vitro comparative study

Backgound: Marginal adaptation is a critical determinant of veneer longevity; thermo‑hygrometric artificial accelerated aging (AAA) may alter luting interfaces and material‑specific deformations. Methods: Using the same 30‑specimen dataset as Article 1, vertical marginal gap (µm) was measured by USB microscope and image analysis before and after 300 h AAA (UV‑B 280–320 nm; 4 h UV at 50 °C + 4 h condensation cycles). Results: Non‑aged vs aged mean gaps (µm) were Lava Ultimate 62.0±22.6→85.3±24.1 (ns), IPS e.max CAD 52.9±17.7→84.4±5.4 (p=0.009), and IPS Empress CAD 61.6±7.2→89.4±12.3 (p=0.009). Between‑materials differences were not significant at either timepoint. Conclusions: AAA significantly widened marginal gaps for glass‑ceramics but not for the resin nano‑ceramic, consistent with polymer‑matrix resilience. All gaps remained within common clinical acceptability ranges (≈40–120 µm) in this setup.