Fracture Resistance, Marginal Gap and Internal Gap of Lithium Disilicate Occlusal Veneers with Two Preparation...

Objectives: Lithium disilicate is commonly used for restoring worn teeth. Various preparation designs have been introduced for occlusal overlay restorations, potentially impacting the properties of the restoration. This study evaluated the fracture resistance, marginal gap, and internal gap of lithium disilicate occlusal veneers prepared with two different preparation designs. Materials and Methods: In this in vitro study, 22 extracted mandibular molars were randomly assigned to two groups (n=11). In the non-retentive (NR) preparation group, the occlusal surface was reduced by 0.8mm in the fissures and 1mm at the cusp tips. In the retentive (R) group, in addition to occlusal reduction, the axial surfaces were reduced with a round-end shoulder finish line created around the axial wall, with both height and depth measuring 1mm. Occlusal veneers were fabricated using lithium disilicate (IPS e.max Press). The marginal and internal gaps were measured using the silicone replica technique before cementation. After cementation, the restorations underwent thermocycling and load cycling, followed by fracture resistance testing in a universal testing machine. Data were analyzed by independent t-test. Results: The fracture resistance of the R group was insignificantly higher than that of the NR group (P=0.310). The marginal gap (P=0.001) and internal gap (P=0.021) of the R veneers were significantly larger than those of the NR veneers. Conclusion: Both R and NR occlusal veneers exhibited sufficient strength for posterior tooth restorations. The marginal and internal gaps of R and NR occlusal veneers fabricated from lithium disilicate (IPS e.max Press) were found to be within the acceptable range.