Two year effects of Chlorhexidine containing adhesives on the in vitro durability of resin dentin interfaces and modeling of drug release

Objectives: To evaluate the effects of addition of diacetate chlorhexidine (CHX) at different concentrations into two etch-and-rinse adhesive systems on CHX release, as well as the immediate (IM) and two-year (2-Y) resin-dentin microtensile bond strength (mu TBS) and nano-leakage (NL). Methods: CHX was added to XP Bond (XP) and Ambar (AM) at concentrations of 0.0 wt% (control); 0.01 wt%; 0.05 wt%; and 0.1 to 0.2 wt%. To assess the cumulative CHX release, adhesive disks were made in a metallic matrix and after light-curing were stored in water. Ultraviolet spectrophotometric measurements of the storage solution were performed to examine the release kinetics of CHX. For mu TBS and NL, the occlusal enamel of molars was removed and the adhesives were applied to the dentin surface after acid etching. After composite resin build-up, specimens were sectioned to obtain mu TBS sticks. The specimens were subjected to mu TBS and NL at IM and after 2-Y. In addition, specimens underwent examination for CHX using micro-Raman spectroscopy. All data were submitted to statistical analysis (alpha=0.05). Results: With regard to CHX release, AM showed a slower and gradual release of CHX while XP released CHX more quickly (p<0.05), and CHX was still present in the hybrid layers after 2-Y. Both adhesives showed CHX release at 2-Y water storage. Both CHX-containing adhesives showed higher mu TBS values than did the control group (p