In group @ , teeth were prepared and irrigated with @ % sodium hypochlorite and calcium hydroxide inter-appointment dressing was applied ; in group @ teeth were prepared with saline solution and irradiated with Er , Cr : YSGG laser using RFT@ ( @ s , @ mJ , @ Hz ) and RFT@ ( @ s , @ mJ , @ Hz ) at the first and second appointments , respectively , four times each , moving at @ mm/sec ( -@ ) from apical to coronal .