Statement of the problem: Treatment of posterior teeth with occlusal wear is complex. Treatment involving more tooth reduction in these cases may be inappropriate. Occlusal veneers are less invasive approach. However, there is insufficient information available regarding the impact of the design of preparation and the type of ceramic material on the marginal adaptation of such occlusal veneers.

Aim: This study aimed to examine marginal accuracy of occlusal veneers fabricated from two ceramic materials (Glass and Hybrid) with two designs of preparation (Planar and chamfer).

Materials and Methods: Two mandibular first molar typodont teeth were prepared to receive 24 occlusal veneers. They were split into 2 equal groups (n=12) based on the material (Group (I): Lithium disilicate (Rosetta SM) occlusal veneers and Group (II): Hybrid ceramics (VITA ENAMIC) occlusal veneers). According to the preparatory design, each group then split into 2 subgroups (n=6)) (planar and finish line). Preparations were scanned, occlusal veneers were designed, milled and checked for seating under magnification. The vertical gaps between the cervical margin of the occlusal veneers and the outermost part of the finish line were measured using an optical microscope and image analysis software (20 readings per specimen). The mean vertical gap for each occlusal veneer was then calculated.

Results: The Rosetta group showed a statistically non-significant higher gap mean value (26.32±3.61µm) than the Enamic group (23.15±5.15 µm) in the planar preparation design based on the results of student t-test (P=0. 2446 > 0.05). While for finish line preparation design, the Rosetta group recorded higher gap mean value (27.38±3.42 µm) than Enamic group (19.71±3.73 µm) and the difference was statistically significant confirmed by Student's t test (P = 0.004 < 0.05).

Conclusion: Lithium disilicate ceramic and hybrid ceramic materials can be used to fabricate occlusal veneers. Superior vertical marginal fit was demonstrated using hybrid ceramic. More important than the preparation design is the veneer's material in terms of marginal accuracy.