Iranian Dental Association Journal of Iranian Dental Association 3060-8201 38 1-2 2026 01 01 Marginal Gap Comparison in CAD-CAM Endocrowns: Lithium Disilicate vs. Zirconia-Reinforced Lithium Silicate 15 22 10.34172/jida.2288 EN Ezzatollah Jalalian https://orcid.org/0009-0006-8339-1394 Mahyar Ezzati https://orcid.org/0009-0006-8339-1394 Amirahmad Pahlavan Hoseini https://orcid.org/0009-0006-8339-1394 Deniz Lesan https://orcid.org/0009-0006-8339-1394 Journal Article 10.34172/jida.2288 2025 10 05 2025 10 19 Aims: This study investigates the impact of ceramic material on the marginal gap of computer-aided design and computer-aided manufacturing (CAD/CAM) endocrowns using lithium disilicate (IPS e.max) and zirconia-reinforced lithium silicate (Suprinity).Materials and Methods: In this in vitro experimental study, 24 extracted mandibular first molars, free of cracks, fractures, abnormal morphology, previous endodontic treatment, or restorations, underwent standardized endocrown preparation. The teeth were randomly assigned to two groups (n = 12) for endocrown fabrication using either lithium disilicate (IPS e.max CAD) or zirconia-reinforced lithium silicate (Suprinity). Teeth were scanned with a CAD scanner, and endocrowns were designed using inLab Software version 15 (inLab SW 15) and milled with an imes-icore 350i milling machine. Marginal gap was measured using the replica technique. Data were analyzed using one-way analysis of variance (ANOVA), t-test, and covariance analysis, with a statistical significance threshold of P < 0.05. Results: Zirconia-reinforced lithium silicate (Suprinity) endocrowns exhibited a significantly higher mean marginal gap (82.95 ± 15.14 μm) compared to IPS e.max (76.22 ± 6.72 μm) across buccal, lingual, mesial, and distal surfaces (P < 0.05, Cohen’s d = 0.58). Specifically, mean marginal gaps were: buccal (82.33 ± 11.85 μm vs. 76.21 ± 5.80 μm), lingual (83.12 ± 14.61 μm vs. 77.17 ± 6.29 μm), mesial (84.08 ± 17.33 μm vs. 76.54 ± 6.30 μm), and distal (82.27 ± 16.76 μm vs. 75.00 ± 8.48 μm) for Suprinity and IPS e.max, respectively. Conclusion: IPS e.max endocrowns demonstrated significantly lower marginal gaps compared to zirconia-reinforced lithium silicate, suggesting that IPS e.max may enhance marginal integrity and reduce microleakage in endocrown restorations.