An in vitro study to compare shear bond strength of aged composite to two single-shade composites

(a) To evaluate and compare the repair bond strength of aged composite to two single-shade composites. (b) To determine the prominent mode of failure.

Thirty composite discs of Filtek 250 (micro hybrid, 3M ESPE, USA) were aged in artificial saliva for 4 weeks and thermocycled for 5000 cycles. The samples were roughened with diamond points (TF12, Mani, Japan) and etched with 37% phosphoric acid. The composite discs were then divided into 3 groups of ten each and the surface was treated with silane coupling agent, followed by bonding agent application. The three groups were restored with one layer of 2-mm thickness of Filtek 250 (Group 1), Omnichroma (Group 2), and Topaz ONE (Group 3) composites, respectively. The samples were subjected to universal testing machine to evaluate the shear bond stress. The detached samples were assessed under 20X stereomicroscope to determine the mode of failure.

Multiple comparisons between the three groups demonstrated significantly higher mean repair bond strength when the same composite was used for repair and between the two single-shade composites, Omnichroma demonstrated significantly higher repair bond strength (P = 0.002). Within the limitation of this study, it was concluded that repair with the same composite resulted highest repair bond strength, while the single-shade composites provided acceptable repair bond strengths.