Hypersensitivity is most commonly caused by a lack of insulation from the triggers in the mouth due to gingival recession (receding gums) exposing the roots of the teeth, although it can occur after scaling and root planing or dental bleaching, or as a result of erosion. The pulp of the tooth remains normal and healthy in dentin hypersensitivity. Many topical treatments for dentin hypersensitivity are available, including desensitizing toothpastes and protective varnishes that coat the exposed dentin surface. Treatment of the root cause is critical, as topical measures are typically short lasting. Over time, the pulp usually adapts by producing new layers of dentin inside the pulp chamber called tertiary dentin, increasing the thickness between the pulp and the exposed dentin surface and lessening the hypersensitivity. Periodontal In general, chronic periodontal conditions do not cause any pain. Rather, it is acute inflammation which is responsible for the pain. Apical periodontitis Apical periodontitis is acute or chronic inflammation around the apex of a tooth caused by an immune response to bacteria within an infected pulp. It does not occur because of pulp necrosis, meaning that a tooth that tests as if it's alive (vital) may cause apical periodontitis, and a pulp which has become non-vital due to a sterile, non-infectious processes (such as trauma) may not cause any apical periodontitis. Bacterial cytotoxins reach the region around the roots of the tooth via the apical foramina and lateral canals, causing vasodilation, sensitization of nerves, osteolysis (bone resorption) and potentially abscess or cyst formation. The periodontal ligament becomes inflamed and there may be pain when biting or tapping on the tooth. On an X-ray, bone resorption appears as a radiolucent area around the end of the root, although this does not manifest immediately. Acute apical periodontitis is characterized by well-localized, spontaneous, persistent, moderate to severe pain. The alveolar process may be tender to palpation over the roots. The tooth may be raised in the socket and feel more prominent than the adjacent teeth. Food impaction Food impaction occurs when food debris, especially fibrous food such as meat, becomes trapped between two teeth and is pushed into the gums during chewing. The usual cause of food impaction is disruption of the normal interproximal contour or drifting of teeth so that a gap is created (an open contact). Decay can lead to collapse of part of the tooth, or a dental restoration may not accurately