Evaluation of The Effect of 980nm Diode Laser Intracanal Irradiation on Levels of Interleukin-8 Expression

* Thorough medical and dental history for the eligible patients * Thorough intraoral and extraoral diagnosis * Local anesthesia * Isolation and removal of any previous filling or restoration * Removal of old gutta percha and establish patency to the full working length. * 1st sample: will be collected using 3 sterile paper points * Chemo-mechanical preparation. * 2nd sample collection • Laser group: The canals will be irradiated with a high-power diode laser, with wavelength of 980 nm, maximum output of 3 watts and coupled with a fiber optic tip of 200 µm diameter. • Mock laser application (Placebo group): The fiberoptic tip will be inserted inside the root canal, mimicking the laser irradiation, but not activated. * 3rd sample collection * A piece of dry cotton will be placed in the access cavity, and then will be sealed with glass ionomer filling material * 2nd visit: 1 week later, 4th sample collection then Obturation * Number of visits \& follow up period: Two visits