Tabriz University of Medical Sciences Journal of Dental Research, Dental Clinics, Dental Prospects 2008-210X 20 2 2026 06 30 Fracture Resistance and Failure Modes of Ultrathin Occlusal Veneers Made of Different Ceramic Materials: An In Vitro Study 80 87 10.34172/joddd.44718 EN Mohamed Ezzat Elbanna https://orcid.org/0009-0004-2642-4618 Hesham Ibrahim Othman Ahmed Mohammed Leithy Alameldin Journal Article 10.34172/joddd.44718 2026 03 15 2026 06 01 Introduction: The current in vitro study was designed to assess the failure mode and fracture resistance of ultrathin occlusal veneers made from different ceramic materials. Methods: Twenty-four ultrathin occlusal veneers were fabricated on maxillary extracted first premolar teeth. Three ceramic materials were used: lithium disilicate (LDS), zirconia-reinforced lithium disilicate (ZLS), and zirconium dioxide (ZIR). An adhesive luting agent was used to adhesively bond occlusal veneers. Each sample was subjected to thermocycling, ranging from 5 to 55°C. Fracture resistance was tested using a universal testing machine, and fractured surfaces were examined with a stereomicroscope and a scanning electron microscope (SEM) to assess failure modes. Results: A statistically significant difference was observed; the highest mean fracture resistance was observed in LDS (1741±308.3 N), followed by ZLS (1192±89.44 N), and then ZIR (866.9±60.23 N), which had the lowest mean fracture resistance. The failure mode of the ZIR group differed significantly from those of the other groups. Conclusion: All the tested ceramic materials used as ultrathin occlusal veneers exhibited fracture loads significantly higher than the average physiological masticatory forces. Compared with the other two groups, LDS had the highest fracture resistance value. ZIR occlusal veneers exhibited more repairable fractures than LDS and ZLS.