RGD uses the Human Disease Ontology (DO, https://disease-ontology.org/) for disease curation across species. RGD automatically downloads each new release of the ontology on a monthly basis. Some additional terms which are required for RGD's curation purposes but are not currently covered in the official version of DO have been added. As corresponding terms are added to DO, these custom terms are retired and the DO terms substituted in existing annotations and subsequently used for curation.
Exposure of the root surface when the edge of the gum (GINGIVA) moves apically away from the crown of the tooth. This is common with advancing age, vigorous tooth brushing, diseases, or tissue loss of the gingiva, the PERIODONTAL LIGAMENT and the supporting bone (ALVEOLAR PROCESS).