A 9-year-old child complains about pain and swelling of soft tissues beneath his mandible on the right. Objectively: general condition is satisfactory; there is face asymmetry due to the inflammatory infiltration and collateral tissue edema in the right submandibular area. Crown of the 85 tooth is decayed, mucous membrane of gums in the area of the 84, 85, 46 teeth is hyperemic, edematic; mucogingival fold is flattened. What treatment should be administered?