Periodontology Anatomy - Periodontium

The periodontium is the specialized tissues that provide two functions, surrounding and supporting the teeth. In addition to maintaining them within the maxillary and mandibular bones. The word is derived from the Greek terms peri-, which means "around" and -odont, which means "tooth". In a literary sense, periodontium translates to "around the tooth". Periodontics is the dental specialty that specifically docuses on the care and maintenance of these specific tissues. The specialty provides the support that is necessary to maintain functioning teeth. The practice consists of four main components which include the following:

1. Gingiva
2. Periodontal ligament (PDL)
3. Cementum
4. Alveolar bone proper

The tissues found in the periodontium combine together to form an active group of tissues. The alveolar bone is almost completely surrounded by the subepithelial connective tissue of the gingiva. The connective tissue of the gingiva is covered by the various characteristic gingival epithelia. The cementum, which overlays the tooth’s root, is attached to the adjacent cortical surface of the alveolar bone. It is attached by the alveolar crest, horizontal and oblique fibers of the periodontal ligament.

Each of these components is distinct by the location, architecture and biochemical properties. Properties which adapt during the lifetime of the structure. As an example, as teeth respond to forces, bite or migrate medially, the bone structure resorbs on the pressure side and is added as reinforcement on the tension side. In a similar fashion, cementum adapts to wear on the occlusal surfaces of the teeth by apical deposition. The periodontal ligament is located in an area of high turnover. This allows the tooth not only to be suspended in the alveolar bone, but to also respond to the applicable forces. While it is seemingly static and have independent functions, all of these components function as a single unit.

External forces and the periodontium

The periodontium exists in order to support teeth while they are in use. It depends on the stimulation it receives from this daily function in order to preserve its structure. As a result of this relationship, there is a constant state of balance that exists between the periodontal structures and their external forces.

The alveolar bone undergoes constant physiologic remodeling as it responds to external forces. Specifically, in its response to occlusal forces. Bone is removed or resorbs from areas where it is no longer needed and it is then added to areas where the additional support is needed. The socket wall reflects the responsiveness of the alveolar bone to external forces. Osteoblasts and newly formed osteoid support the areas of increased tension. In contrast, lines of compression are lined by osteoclasts. The forces also influence the amount, density and overall alignment of trabeculae located inside the bone. The bony trabeculae are aligned in the path of tensile and compressive stresses. This enables them to provide maximum resistance to occlusal forces with the least amount of bone structure. When forces increase, the bony trabeculae also increase in both number and thickness. Bone is also added to the applicable external surfaces.

The periodontal ligament (PDL) relies on stimulation received through regular function in order to preserve its structure. Within physiologic limits, the PDL is able to accommodate the increased function by increasing its width. Forces which exceed the adaptive capacity of the periodontium result in injury or trauma from occlusion. When occlusal forces are reduced, the PDL atrophies and is ultimately thinned. This phenomenon is referred to as disuse atrophy.