The alveolar bone, also called the alveolar process, is the ridge of jawbone that is at the surface, just under the gums, and in which the tooth sockets are located. The alveolar bone is a dense bone that lines the tooth sockets, which are known as the alveoli, and is attached to the teeth by the periodontal ligament. Although the bone itself is dense and compact, it contains multiple small holes that allow blood and nerves to connect to the periodontal ligament and that house the fibers, called Sharpey fibers, that make up this ligament. In a healthy, functionally developed mouth, the alveolar crest, or the apex of the alveolar bone, is uniform in height along each jaw and is also uniformly proximal to the area where the cementum and the enamel of the teeth join. In simpler terms, this means that the alveolar bone snugly encompasses the roots and cementum of the teeth where they are not protected by enamel on their exposed surfaces.
Alveolar bone is made of inorganic mineral material, including calcium and phosphate, and organic material, including collagen and cells that affect bone growth. These cells are called osteoblasts, osteoclasts, and osteocytes. Osteoblasts form bone; osteoclasts absorb tissue while bone is growing or healing; and osteocytes are formed when osteoblasts are trapped in the bone as it is forming. These organic materials are an important part of alveolar bone, which can be resorbed by the body, especially in cases of advanced periodontal disease, leading to a net loss of alveolar bone and resultant weakening of the entire periodontium. Periodontal disease is, in its most simple terms, the inflammation of the gingival tissue, or gums. Periodontal disease can prevent new bone from forming after resorption, and it can also slow or limit the formation of new bone; both of these problems lead to overall loss of alveolar bone. Alveolar bone may also be adversely affected by developmental disturbances, such as the absence of germinal teeth in utero and infancy. Because the alveolar bone develops in response to the development of teeth, the bone itself may not develop if there are no teeth for it to support.
In addition to congenital disturbance and the risks related to periodontal disease, alveolar bone may also be affected by various pathologies. For example, when a tooth is extracted, the clot that remains in the tooth socket gradually develops into alveolar bone. If, however, this clot is disturbed, the socket may require professional treatment to stave off infection and encourage the eventual redevelopment of bone to fill the socket through medical intervention.
While periodontal disease and the resultant loss of the natural teeth can lead to the resorption of alveolar bone, the underlying bones of the jaw are less likely to be affected, as they do not require the presence of teeth to be viable. The combined loss of teeth and alveolar bone, however, can ultimately lead to a visibly sunken appearance in the lower jaw and loss of height in the overall jaw. As the alveolar bone lessens in density, this may also affect the formation of dental abscesses and the efficacy of local anesthesia.