Laser-activated irrigation (LAI) has been introduced as a powerful method enhancing irrigant action; The laser radiation produces transient cavitation in the liquid through optical breakdown by strong absorption of the laser energy. The high-power diode laser has been tested in several areas of dentistry such as bleaching, depigmentation and gingivectomy, with promising results in dentinal disinfection. The diode laser has proved to be a resource worth testing, because of the it's properties and its low cost and availability in comparison to most lasers used in endodontics.

ultrasonics have been developed to improve the penetration and effectiveness of irrigation in peripheral areas of the root canal space. The efficiency of sonic and ultrasonic devices is based on the creation of hydrodynamic phenomenon in well-shaped canals filled with an irrigant.

Such active root canal irrigation has been shown to facilitate the disruption of biofilms and make the cell membrane of bacteria more permeable to NaOCl.

diode laser became the most common and affordable type of laser used in endodontics for many uses , its disinfection effect is an important issue which not discussed in clinical trial before , So this study is assigned to study that

intensity of post operative pain will be measured using a numerical rating (NRS)scale