The child is 13 years old. The disease began suddenly with a body temperature rise up to 39°C, swelling of the upper jaw on the left. Objectively: the face is asymmetric due to the left cheek edema. The skin over the swollen area is hyperemic and tense. The 26 tooth exhibits a large carious cavity, percussion of the tooth causes pain reaction. The 25, 26, teeth are mobile. Mucogingival junction in the region of the 24, 25, 26, 27 tooth is indistinct, alveolar mucosa is hyperemic and bilaterally swollen in the region of the 25, 26. 27 teeth. What is the most likely diagnosis?