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

•Poly-acrylic acid coated copper iodide (PAA-CuI) adhesives delayed degradation of resin- adhesive bonds.•Incorporation of PAA-CuI particles did not affect the tensile strength of any of the adhesives.•No changes in cell viability were observed for XTR with 0.1 mg/ml or Solo with 0.1 and 0.5 mg/ml.•Cell viability values decreased for XTR with 0.5 mg/ml and XP with 0.1 and 0.5 mg/ml.•XP demonstrated the highest copper release with a similar pattern of release shown for all adhesives.

ObjectiveTo investigate the effect of poly-acrylic acid (PAA) copper iodide (CuI) adhesives on bond degradation, tensile strength, and biocompatibility.MethodsPAA-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.ResultsXTR 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.SignificancePAA-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.