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The aim of this study was to evaluate the effect of different CAD/CAM materials (Lithium disilicate glass ceramic, Polymer infiltrated ceramic and Machinable resin composite) on the occlusal veneers' fracture resistance. Materials and Methods: A Mandibular first molar of a typodont model was prepared into flat occlusal veneer preparation, then it was duplicated using rubber base duplicating material to obtain 21 epoxy resin dies. Also, the prepared tooth was scanned, occlusal veneer design was done then milled to obtain 21 occlusal veneers. Occlusal veneers were divided into three groups based on the material of construction: Group (LD): IPS e.max® CAD, Group (VE): Vita Enamic® and Group (BC): BRILLIANT Crios®. The 21 occlusal veneers were bonded using DUO-LINK UNIVERSAL™ adhesive resin cement to their corresponding dies. Then a vertical compressive load was applied on the restorations using the universal testing machine. The maximum load and the failure mode were recorded. After testing for normality. Data were statistically analyzed at significance level (P ≤ 0.05). Results: Comparison between the three groups using One Way ANOVA test demonstrated that Group (VE) (1863.18 N) had the highest fracture resistance followed by Group (BC) (1697.17 N) then Group (LD) (1035.23N). Also, Group (LD) and (VE) had repairable mode of failure while Group (BC) had both repairable and irreparable mode of failure. Conclusions Groups (LD), (VE) and (BC) can withstand forces more than the physiologic masticatory forces. Also, Vita Enamic can provide satisfactory fracture resistance and a repairable failure mode for the posterior occlusal veneers.
Fouad et al. (Mon,) studied this question.