Introduction: Repair is indicated mainly in the event of localized shortcomings that are clinically unsatisfactory and no longer acceptable; it implies in any case the addition of a restorative material.
Objectives:Shear bond strength for immediate and delayed repair of composite with microhybrid and nanohybrid resins using different bonding agents.
Materials and methods: One hundred sixty nanohybrid composite discs were prepared. They were divided into 16 groups (10 each) according to 3 factors: Factor 1: Repair time, Factor 2: Repair protocol and Factor 3: Repair composite material. For immediate repair (I), discs (n=80) were divided into 4 subgroups 20 discs each. Each subgroup was divided into 2 groups as follows Group 1 (a): no conditioning with nanohybrid composite, Group 1 (b): no conditioning with microhybrid composite, Group 2 (a) Adhese Universal bond with nanohybrid composite, Group 2 (b) Adhese Universal bond with microhybrid composite, Group 3 (a) All-Bond Universal with Nano-hybrid composite ,Group 3 (b) All-Bond Universal with microhybrid composite, Group 4 (a) Scotchbond™ Universal with nanohybrid composite, and Group 4 (b) Scotchbond™ Universal with microhybrid composite. After 3 months of storage for delayed repair (II), the repair procedures were performed similar to the immediately repaired groups. After 1000 thermal cycles, all specimens were subjected to shear bond strength test.
Results:repair time and surface treatment revealed statistically significant effect on the shear bond strength values of all groups (p ≤ 0.05). Highest shear bond strength value was recorded in group I4b (21.97 ± 1.19) MPa and the lowest value was recorded in group II1a (4.42 ± 0.88 MPa)
Conclusions: Time of repair, bonding agent and repair material affected repair bond strength of composite.