Effect of Different Adhesives and Aging Periods on the Shear Bond Strength of a Repaired Bulk Fill Resin Composite

Abstract

By increasing the use of composite restorations, some defects can be seen in these restorations, which can lead to clinical failure of the restorations (1). Repair of the preexisting restoration is more conservative than replacement as it can increase the restoration longevity, preserve the sound tooth structure and decrease operative trauma (2). There is still a debate about the best repair technique. Therefore, a combination of mechanical and chemical methods is often used to improve the bond between new and aged resin composite. Mechanical pretreatment of composite surface is performed to remove superficial layer to expose a clean composite surface with high energy and increasing irregularities to promote mechanical interlocking (3). diamond bur roughening and acid etching with phosphoric acid as surface treatment in repair procedure are the most common and easy repair approach that does not need additional tools(4). Applications of resin adhesives enhance surface wetting and chemical bonding between new and aged composite (3). A silane coupling agent has been added to universal adhesives as it is considered that it has beneficial effect in restoration repairs (5). Bulk-fill resin composites were introduced to overcome the need for resin composite layering and adapting procedures which cause time-consuming, air entrapment and contamination. They allow for the placement of materials in 4 mm increments without compromising cure and increasing shrinkage (6).