In the 2nd group the root canals will be medicated with a calcium hydroxidechlorhexidine paste for 7 days. The paste consists of 1.2 g Ca(OH)2 powder per 1 mL 0.2% chlorhexidine in water. The teeth in both groups will be closed with a sterile dry cotton pellet and a minimum of 3 mm of temporary restorative material.