Purpose: To investigate whether dental adhesives modified with polyacrylic acid copper iodide particles could inhibit esterase activity in vitro and the copper release rate from resin matrices, as well as the correlation between the two variables. Materials and Methods: Different concentrations of copper iodide (0.1, 0.5 and 1.0 mg/ml) were incorporated into three commercially available adhesives representative of each type. Disk specimens (n = 3) were fabricated and incubated in cholesterol esterase and pseudo-cholinesterase solutions for 16 days (37°C, pH 7.0). The enzymatic activity and rate of copper release from resin matrices were evaluated at different 4, 8, 12, and 16 days with a UV/visible-light spectrophotometer. Results: Increased copper release and reduced enzymatic activity were observed with higher concentrations of copper iodide (p 0.001). Greater copper release with reduced enzymatic activity was also demonstrated at the earlier time periods with this relationship reversing over time (p 0.001). A moderate negative correlation between the variables was evident (-0.441; p = 0.01). Conclusions: Adhesives containing copper iodide can inhibit esterase activity in a dose- and time-dependent manner. The correlation between the variables suggests that enzymatic activity may depend on the availability of copper. Keywords: adhesives, copper iodide, drug delivery, esterases, resins, saliva