A 7-year-old child complains of pain and swelling in the left submandibular region. The swelling in this region showed up 2 days ago. Objectively: the child is in satisfactory condition, body temperature is of 37,3°C. Face is asymmetrical due to the soft tissue swelling in the left submandibular region. Palpation reveals a round formation sized 2x2 cm. The formation is mobile, painful, not attached to skin. The 74 tooth is changed in colour, percussion is painful. What is the provisional diagnosis?