After pulp chamber trepanation and localisation of the root canals (three filled and one unfilled), the rubber dam was placed on the tooth and the working field disinfected with chlorhexidine-ethanol solution. Old root fillings were removed by manual instrumentation without chloroform and a working length radiograph was taken to determine correct preparation length. K-files were placed in buccal canals and Hedstroem files in lingual canals. Mesial canals were prepared to size 45 and distal canals to size 50.

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