Mechanical cleaning, irrigation and dressing with antibacterial medicaments achieve a reduction of the number of living bacteria in infected root canals. Evaluation of the relative efficacy of these measures in eliminating the bacteria has shown that mechanical cleansing supported by irrigation significantly reduces the number of bacteria in the root canal, but that approximately 25 to 50 per cent of canals treated in this way still contain bacteria at the end of the appointment.

The clinical effectiveness of calcium hydroxide in infected canals has been tested in a number of in vivo studies and been shown to be an efficient antibacterial treatment eliminating microorganisms in previously untreated cases from 75 per centto more than 90 per cent of dressed canals.

Application of an interappointment calcium hydroxide dressing prior to obturation has been shown to yield improved healing responses over non-calcium hydroxide treated teeth in human and animal teeth.