Biocompatibility and bond degradation of poly-acrylic acid coated copper iodide-adhesives

Objective To investigate the effect of poly-acrylic acid (PAA) copper iodide (CuI) adhesives on bond degradation, tensile strength, and biocompatibility. Methods PAA-CuI particles were incorporated into Optibond XTR, Optibond Solo and XP Bond in 0.1 and 0.5 mg/ml. Clearfil SE Protect, an MDPB-containing adhesive, was used as control. The adhesives were applied to human dentin, polymerized and restored with composite in 2 mm-increments. Resin–dentin beams (0.9 ± 0.1 mm²) were evaluated for micro-tensile bond strength after 24 h, 6 months and 1 year. Hourglass specimens (10 × 2 × 1 mm) were evaluated for ultimate tensile strength (UTS). Cell metabolic function of human gingival fibroblast cells exposed to adhesive discs (8 × 1 mm) was assessed with MTT assay. Copper release from adhesive discs (5 × 1 mm) was evaluated with UV–vis spectrophotometer after immersion in 0.9% NaCl for 1, 3, 5, 7, 10, 14, 21 and 30 days. SEM, EDX and XRF were conducted for microstructure characterization. Results XTR and Solo did not show degradation when modified with PAA-CuI regardless of the concentration. The UTS for adhesives containing PAA-CuI remained unaltered relative to the controls. The percent viable cells were reduced for Solo 0.5 mg/ml and XP 0.1 or 0.5 mg/ml PAA-CuI. XP demonstrated the highest ion release. For all groups, the highest release was observed at days 1 and 14. Significance PAA-CuI particles prevented the bond degradation of XTR and Solo after 1 year without an effect on the UTS for any adhesive. Cell viability was affected for some adhesives. A similar pattern of copper release was demonstrated for all adhesives.