Aim: to investigate sign and symptoms ,bactericidal effect for using diode laser 810nm ,and calcium hydroxide ,povidone iodine on endodontically treated tooth with periapical abscess

Material And Method: patient with tooth no.9 failed endodontic treatment with periapical abcess,x ray ,diode laser 810nm,water irrigation,calcium hydroxide ,povidone iodine ,removing gutta percha from infected tooth ,reaming and filling ,laser fiber passed over the apical foramen 2mm ,4mm according to the size of lesion ,,lasing 2sc then stop for 4 sc with water irrigation to avoid over heat ,, till 20 sc of lasing

completed ,apply calcium hydroxide dressing with povidone iodine ,examine patient sign and symptom during 8 days ,x ray after 6 months.

Result: the patient show no swelling,sevirity of pain became less ,however antibiotic and analgesic are recommended .

conclusion: using diode laser in PERIAPICAL ABCESS IF WE REACH THIS AREA had less traumatic effect than using a flap ,, less healing time ,with cooling technique consideration, and calcium hydroxide and povidone iodine with bactericidal effect on the lateral canal, we will get fine result.