Chlorhexidine binding to mineralized versus demineralized dentin powder

Objectives: The purposes of this work were to quantitate the affinity and binding capacity of chlorhexidine (CHX) digluconate to mineralized versus demineralized dentin powder and to determine how much debinding would result from rinsing with water, ethanol, hydroxyethylmethacrylate (HEMA) or 0.5 M NaCl in water. Methods: Dentin powder was made from coronal dentin of extracted human third molars. Standard amounts of dentin powder were tumbled with increasing concentrations of CHX (0-30 mM) for 30 min at 37 °C. After centrifuging the tubes, the supernatant was removed and the decrease in CHX concentration quantitated by UV-spectroscopy. CHX-treated dentin powder was resuspended in one of the four debinding solutions for 3 min. The amount of debound CHX in the solvents was also quantitated by UV-spectroscopy. Results: As the CHX concentration in the medium increased, the CHX binding to mineralized dentin powder also increased up to 6.8 μmol/g of dry dentin powder. Demineralized dentin powder took up significantly (p < 0.01) more CHX, reaching 30.1 μmol CHX/g of dry dentin powder. Debinding of CHX was in the order: HEMA < ethanol < 0.05 M NaCl < water. The highest CHX binding to demineralized dentin occurred at 30 mM (1.5 wt.%). Significance: As CHX is not debound by HEMA, it may remain bound to demineralized dentin during resin-dentin bonding. This may be responsible for the long-term efficacy of CHX as an MMP inhibitor in resin-dentin bonds.