As referred to in Part 5, some practitioners have concerns about the use of sodium hypochlorite and prefer to use a solution of chlorhexidine. Whilst this has a similar antibacterial spectrum, it does not have the ability to dissolve organic debris and may not clean the entire root canal system as effectively. However, chlorhexidine does exhibit substantivity (adherence to dentine) and there is some evidence to suggest that it may be a more appropriate irrigant for retreatment of failed orthograde cases where sodium hypochlorite was the original irrigant.