A 45-year-old man presents with facial asymmetry due to a dense isolated infiltration in his right buccal area; the skin over the infiltration is cyanotic, thinned out; in the center of the infiltration there is a fistula. In the oral cavity the crown of 46 is destroyed by 2/3, along the mucogingival fold the band connecting the tooth with the fistula can be palpated. Make the diagnosis: