ANDREW MCCLENAGHAN / SCIENCE PHOTO LIBRARY. ANDREW MCCLENAGHAN / SCIENCE PHOTO LIBRARY.
Young woman using dental floss (a cotton thread which may be waxed or unwaxed) to clean particles of food from around her teeth and gingival crevices (the spaces between the gums and the surface of the teeth). Bacterial action on any food particles deposited in these areas leads to the formation of plaque, which eventually forms a hard deposit - tartar, which enlarges the gingival crevices and precipitates periodontal disease. Early symptoms include swollen and bleeding gums; ulceration may follow. If untreated the plaque spreads to and destroys the underlying periodontal membrane and alveolar bone: in this chronic stage the teeth become loosened and eventually fall out.
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