this study is the first to demonstrate the efficacy of minimally invasive root canal treatment combined with intracanal heating and activation of NaOCl using a prototype needle on the healing of asymptomatic apical periodontitis of necrotic single rooted teeth. 32 teeth will be randomaly assigned into 2 groups :conventional and conservative technique .In the conventional group : each canal will be prepared using Reciproc Blue 25/08, approximetly 27 ml of NaOCl will be used , the canal will be activated using 20.02 taper tip of a sonic decive . This cyclel will be repeated 3 times and the obturation will be done using a single cone technique with AH plus resin-based sealer . In the second group a size 10 k file will be introduced to confirm patency and to record working length after filling the canal with NaOCl. A glide path will be established using the size 10 FlexoFile to the WL, than Proglider 16.02 to the foramen. After the glide path, the canal will be irrigated with 3 ml of 5, 25 % of NaOCL .The prototype needle tip will be placed in the canal to the length that is a little shorter than the length at binding point , in order to heat and activate the irrigant solution for 30 seconds.Step one is repeated 4 more times and a fresh solution of NaOCl is replaced every time. Canals will be dried using sterile paper points size 15 and the obturation will be performed for all teeth using the same technique as group 1 but with a standardized gutta percha point 2% tapered