Missing the Merk Manual

"Halitosis most often results from fermentation of food particles by anaerobic gram-negative bacteria in the mouth, producing such volatile sulfur compounds as hydrogen sulfide and methyl mercaptan. Causative bacteria may be present in areas of gingival or periodontal disease, particularly when ulceration or necrosis is present. In patients with healthy periodontal tissue, these bacteria deposit on the dorsal posterior tongue. Factors contributing to the overgrowth of causative bacteria include decreased salivary flow (eg, due to parotid disease or Sjögren's syndrome), salivary stagnation, and increased salivary pH."


Necrosis..