Lidocaine Patch and Lower Third Molar

* Completed medical and dental history will take for all patients and the position of the impacted teeth will evaluate by panoramic films. Patients will fully inform about the treatment procedures, follow-up examinations and complications of surgical procedures. * Full thickness mucoperiosteal flap will be raised to expose sufficient bone on lateral and distal aspect of the impacted molar. Removal of bone will be done with stainless steel bur under Constant irrigation with normal saline while removing bone to prevent thermal necrosis. * When necessary, sectioning of crown and roots will be performed with a fissure bur. After tooth extraction, the alveolus will be inspected, curetted, and irrigated with 0.9% sterile saline solution. * Surgical removal of impacted mandibular third molar will be done,1% metformin gel or placebo gel in the socket following removal of the impacted third molar . * The mucoperiosteal flap will be repositioned and sutured with 3-0 black silk suture. * Control side : use transmucosal placebo patch * Study side: use transmucosal lidocaine patch Postoperative care * Postoperatively, the patients were instructed to apply ice bags 20 min/hour for the next 6 hours to the surgical side, eat soft cold diet by the aid of a straw and to avoid hot diet and fluid on the day of surgery. * Sutures were removed after 7 days postoperatively. * All the patients will be evaluated on the 1st, 3rd, and 7th postoperative days for pain, preoperative and postoperative mouth opening, and degree of postoperative swelling.