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Repairability of Cross-linked Biopolymers

Repair of biopolymers is a critical issue, especially with aged restorations. Obtaining a chemical bond to the repair surface might solve this problem. We hypothesized that certain repair liquids are suitable to establish a strong bond to an artificially aged dimethacrylate-based biopolymer for temporary restorations. Specimens made of a self-curing temporary crown-and-bridge material were prepared and thermocycled for 7 days (5000x, 5–55°C). Cylinders made of light-curing composites (n = 10) were bonded onto the specimen surface, either after grinding or after the application of 4 different experimental repair liquids (Bis-GMA:TEGDMA mixture = bonding, methylmethacrylate = MMA, bonding & acetone, bonding & MMA). A shear bond strength test was performed 24 hrs after repair. The highest bond strength was obtained with the bonding & acetone liquid (20.1 ± 2.2 MPa). The use of MMA significantly affected the bond strength (6.8 ± 1.9 MPa). MMA is inadequate as a repair liquid on aged composite-based biopolymers.