Effect of surface treatment on the repairability of Short Fiber Reinforced Composite

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Objective: The aim of this study was to evaluate the effects of different surface treatments on the repair bond strength of short fiber reinforced composite (SFRC). Materials and Methods: EverX Flow (EXF, GC Group, Tokyo, Japan) SFRC blocks (10x10x7 mm) of 2 different shades (Dentin shade (D), Bulk shade (B)) were prepared using a custom-made TEFLON mold according to manufacturer’s instructions. The top surface of each composite block was polished with 500-grit silicon carbide discs which followed by a 24-hour storage at room temperature. The blocks were then assigned into 2 groups based on the different shades and the different surface treatments applied. The polished surface of the SFRC blocks were either treated with the Air abrasion (AA) + G2-Bond Universal (GBU) combination or Monobond Etch & Prime (MEP) before undergoing a repairing process with resin composite 3M Filtek Z250 Universal Composite. All repaired blocks were sliced with a hard tissue microtome (Leica 1600SP, Germany) into multiple 1x1x14mm specimens and microtensile bond strength (μTBS) test was performed using Instron 5544 (Massachusetts, USA) universal testing device. Finally, failure modes were evaluated under light microscope to assess cohesive or adhesive failure. The data were statistically analyzed at the significance level of 5% (α = 0.05). Results: The μTBS test shows no significant differences between the 2 different surface treatment groups in Dentin shade group (GBU D: 62,33 ± 4,02 MPa, MEP D: 61,92 ± 3,11 MPa) (p=0.76). The Bulk shade composite groups compare with Dentin shade composite groups in both surface treatment subgroups showed significantly lower microtensile bond strength results (GBU B: 52,16 ± 4,27 MPa, MEP B: 45,3 ± 3,12 MPa) (p0.05). Additionally, in the Bulk shade group GBU showed significantly higher μTBS result comparing to MEP (p0.05). Failure mode analysis revealed almost 100% cohesive fracture types in all composite groups. Conclusion: Under the tested condition, the EverX Flow Dentin shade performs better than the EverX Flow Bulk shade. Specimens treated with Air Abrasion + GBU show slightly higher repair bond strength compared to the group treated by MEP.

Short Fiber Reinforced Composite, microtensile bond strength, composite repair, surface treatments