In health, the gum and bone tissues that surround teeth are attached to the root surface by connective tissue fibers called the gingivo-dental fibers. This functional unit, called theperiodontium, is comprised of four types of tissue:
- cementum, which exists on the tooth root surface
- alveolar bone, which surrounds and supports the teeth in the jaw
- gingiva, or gum tissue, which is comprised of epithelium and a lamina propria of connective tissue
- periodontal ligament fibers, which run from the alveolar bone and insert into the cementum
In addition to the periodontal fibers that attach the tooth to the surrounding bone, there are also two types of connection between the tooth and the surrounding gum tissue. There is the more apical gingival fiber attachment and the more coronal junctional epithelium attachment. Together, these two are referred to as the gingival attachment apparatus and, in health, they keep the gingival tissue snug around the necks of the teeth.
In gingivitis, an inflammatory process in the gum tissue may cause a transient loss of this gingival attachment apparatus that is completely reversible if the inflammatory process is reversed. Gingivitis is therefor termed non-destructive periodontal disease because it does not entail loss of periodontal ligament fibers or alveolar bone. Once the inflammatory process initiates loss of periodontal fibers and/or bone, the gingivitis is deemed to have progressed to periodontitis.