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Caries is a progressive destruction of any kind of bone structure, including the skull, ribs and other bones, or the teeth. Caries can be caused by osteomyelitis, which is a microorganism disease. A disease that involves caries is mastoiditis, an inflammation of the mastoid process, in which the bone gets eroded.
Dental caries is one of many types of caries. Dental caries affects different parts of the teeth, (enamel, dentin, or cementum) in the crown or the root of the tooth. Nearly all cases contain bacteria such as Streptococcus mutans and Lactobacillus, which produce lactic acid as the products responsible for the caries. Caries affecting bone is a chronic inflammation, with rarefaction or absorption of bone-tissue attended by suppuration; it is molecular death of bone, being a disintegration of the tissue. Both necrosis and caries of bone bear the same relation to the osseous tissue, that gangrene and ulceration do to the soft tissues. When percussion is made a different sound is distinguished between necrosis and caries of bone, owing to the difference in the degree of density. The probe reveals a sharp sound in the case of necrosed bone, owing to its hardness, while the use of this instrument reveals a dull sound in the case of caries of bone, and the probe also penetrates the diseased structure.
The causes of caries of bone depend upon a chronic inflammatory condition generally due to tubercular or syphilitic infection. Among the bones most frequently attacked are the bones of the face, and the lower jaw, especially the latter. The syphilitic form most commonly affects the bones of the nose and palate. When carious bone is exposed, it is found to be softened and disintegrated, and portions have been removed by liquefaction or absorption, leaving a greater or less cavity, the surface of which is covered with granulations and pus. Among the granulations may be found small spiculae of dead bone, surrounded by pus. In caries of bone resulting from syphilis, ulceration destroys the external surface of the bone, leaving a granulating surface, discharging the gummy pus.