Objective: The aim of this study was evaluating the effect of immediate and delayed dentin sealing on tensile bond strength of hybrid ceramic restorations. Materials and methods: Sixty extracted human molars were used. The occlusal surfaces were ground flat to expose the dentin surface using a low speed diamond saw. The prepared teeth were randomly divided into two groups according to the dentin sealing protocol. For group (D): Delayed Dentin Sealing was used and for group (I): Immediate Dentin

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... Sealing was used. 60 vita enamic discs were machined into standard thickness of 2mm. For delayed dentine sealing treated teeth, it was covered by a layer of temporary filling material directly after cutting. The provisional restoration was then removed after 48 hours and dentin was cleaned using airborne-particle abrasion (CoJet, 3M ESPE). For immediate dentine sealing treated teeth, the single bond universal adhesive was applied and light cured immediately after cutting, and the provisionalization phase was done in the same manner of DDS group. The vita enamic discs were then cemented in its place for each group. The specimens in each group were then thermo-cycled, and tensile bond strength was measured using a Universal Testing Machine. One-way ANOVA was used to study the effect of different tested variables. Results: Samples with IDS protocol showed higher tensile bond strength with vita enamic discs than DDS protocol. Conclusions: Immediate dentin sealing treatment would be recommended in high tensile stresses as it positively affects the bond strength of indirect restorations