The word “periodontium” comes from the Greek words for “around the tooth,” and this is a simple way of explaining what the periodontium is: the variety of tissues that are around the teeth. These specialized tissues support the teeth within the bones of the jaw, which are known as the maxillary and mandibular bones. The principle components of the periodontium are the alveolar bone, the periodontal ligament, the cementum, and the gingiva. Each of these tissues is distinct and specific to its location and function, and, while each component is distinct, they function inextricably as a single dynamic set of tissues. The alveolar bone, a ridge of bone that lies just on the surface of the jaw and is made primarily of calcium and collagen, is almost entirely contained by the gingiva, which is more commonly known as the gum tissue. The gingiva supports the teeth, which are primarily made of cementum, the mineral tissue that surrounds the root of the tooth the periodontium. This cementum is harnessed in place by the interconnected fibers of the periodontal ligament.

The primary purpose of the periodontium is to support the teeth as they perform their mechanical functions. The structure of the periodontium is reinforced and preserved by outside stimulation; for example, alveolar bone resorbs where it is not needed to support the force of chewing, and redistributes to areas where more support is needed, depending on the specific habits and needs of the person. The teeth themselves are also uniquely designed to support significant force while also being comparatively light in substance, and the area of bone that supports the teeth is strengthened as force, as in the forces of chewing, is added. The periodontal ligament also changes in size depending on forces applied by biting and chewing, known as occlusal force. If the periodontal ligament is exposed to an excess of occlusal force and has reached its maximum thickness, it may undergo trauma. Similarly, if the periodontal ligament is not exposed to enough occlusal force, it will shrink and become atrophied, ultimately affecting the correct functioning and structure of the periodontium as a whole.

Because the anatomy of the periodontium changes with the application of occlusal force, when people lose their natural teeth and can no longer bite or chew effectively, the tissue of the periodontium will eventually atrophy and resorb, causing the lower face of people who lack natural teeth to appear sunken and weak. Loss of natural teeth can result, in many people, from untreated disease of the gingival tissue, known as periodontitis, which loosens the gum tissue around the teeth. This is yet another demonstration of the interconnected mechanics of the different tissues of the periodontium. When teeth are replaced with implant-supported dentures or an implant-supported bridge, the dental implants support the bone, functioning similarly to a natural tooth root and encouraging the regeneration and proper redistribution of natural alveolar bone. Dental implants help restore the function of the teeth and stimulate the vitality of the periodontium, allowing it to continue to change and strengthen with use and force and gradually rebuilding the structure and mechanics of the mouth and jaw.