Periodontology Anatomy - Periodontium

The periodontium includes specialized tissues that serve two functions which include both surrounding and supporting the teeth in order to maintain them in the maxillary and mandibular bones. The word comes from the Greek terms peri-, meaning "around" and -odont, meaning "tooth". When taken literally, periodontium translates to "around the tooth". Periodontics is a dental specialty that focuses on the care and maintenance of these specific tissues. The specialty provides the support needed in order to maintain the function of the teeth. The practice consists of four principal areas which include the following:

1. Gingiva
2. Periodontal Ligament (PDL)
3. Cementum
4. Alveolar Bone Proper

Each of these components are distinct by their location, architecture and biochemical properties. Components that adapt throughout the structure’s lifetime. For example, as teeth respond to various forces, bite or migrate medially over time, the bone structure resorbs on the pressure side and is added on the tension side. Cementum also adapts to any wear applied to the occlusal surfaces of the teeth by apical deposition. The periodontal ligament itself is located in an area which has high turnover. This allows the tooth to not only be suspended in the alveolar bone, but to also respond any forces which are applied. While they are seemingly static and each has their own independent function, each of the components function together as a working unit.

The tissues located in the periodontium form together as an active group of tissues. The alveolar bone is surrounded by the subepithelial connective tissue of the gingiva. The connective tissue of the gingiva is then covered by the gingival epithelia. The cementum overlaying the tooth’s root, is attached to the adjacent cortical surface of the alveolar bone by the alveolar crest, horizontal and oblique fibers of the periodontal ligament.

External forces and the periodontium

The purpose of the periodontium is to support teeth while they are in use and relies on the stimulation it receives to preserve the overall structure. As a result, a constant state of balance must exist between the periodontal structures and external forces which are applied.

The alveolar bone is under constant physiologic remodeling in response to external forces. Particularly, in response to occlusal forces. Bone eliminated or resorbed from areas where it is no longer needed and added to areas where the additional support is necessary. The socket wall reflects the general responsiveness to these external forces. Osteoblasts and newly formed osteoid line these areas of tension and lines of compression are lined by osteoclasts. These regular forces also influence the number, density and overall alignment of trabeculae found inside the bone. The bony trabeculae are aligned in the path of tensile and compressive stresses to provide adequate resistance to occlusal forces with minimum bone structure. When the forces increase, the bony trabeculae also increase in number and thickness. In addition, bone is added to the respective external surfaces.

The periodontal ligament (PDL) relies on stimulation from routine function in order to preserve the structure. Within the physiologic limits, the PDL accommodates this increased function through an increases width. Forces that exceed this adaptive capacity, create injury or trauma from the occlusion. When the occlusal forces are reduced, the PDL can atrophy and is thinned. This condition is referred to as disuse atrophy.