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Abstract
Objective: This study was carried out to investigate the effect of different surface treatment protocols on bond strength of nano-composite as a repair material to two types of resin composite either direct composite or indirect resin composite blocks for CEREC system. Materials and methods: Total of 80 composite discs were prepared and were divided into two main groups (40 each) according to the type of composite used (C), nano composite (C₁) and composite blocks for CEREC system (C₂). All specimens were aged for one month in a distilled water solution at 37{u00BA}C. Each group was sub-divided into four subgroups (10 each) according to the surface treatment protocol (T) that was done on the discs, either no treatment (T₀) (control), application of Ortho phosphoric acid (T₁), Hydrofluoric acid (T₂) and Sandblasting(T₃) . Each sub group was subdivided into two classes (5 each) according to silane application (S₁) or without (S₀).Silane{u2011}containing bonding agent (Single BondUniversal adhesive, 3M ESPE) was applied to the pre{u2011}treated discs. Prior to light curing, irises were cut from tygon tubes (internal diameter = 0.8 mm and height = 0.5 mm) and mounted on each treated surface. Nanofilled resin composite (Filtek Z350 XT, 3M ESPE) was packed into the cylinder lumen and light{u2011}cured. The specimens were subjected to microshear bond strength testing (o{u2011}SBS) using universal testing machine