Periodontal Anatomy – Periodontium
The periodontium involves specialized tissues which support and surround the teeth. These tissues maintain the teeth within the mandibular and maxillary bones. The word periodontium comes from the Greek terms peri, which translates to "around" and odont, which translates to "tooth". In a literal sense, this means that which is "around the tooth". The dental specialty which specializes in the care and maintenance of these tissues is periodontics. The periodontium provides the teeth with the support needed to maintain their regular function. The four components included within the periodontium are:
- Periodontal ligament (PDL)
- Alveolar bone proper
Each of these components is unique in its location, architecture, and biochemical properties. Each of which adapts during the lifetime of the structure. As an example, when the teeth respond to forces which are sustained, the bone resorbs on the pressure side of the force and added on the tension side. In a similar way, the cementum adapts to wear on the occlusal surfaces of the teeth through apical deposition. The periodontal ligament (PDL) is an area with high turnover. This allows the tooth to be suspended in the alveolar bone and simultaneously respond to the forces it experiences. While it is seemingly static and each component has specific functions, each of the components functions as a cohesive unit.
The tissues which are present in the periodontium form together to create an active group of tissues. The alveolar bone is surrounded by the subepithelial connective tissue. Which is found in the gingiva. The gingival epithelia covers the connective tissue of the gingiva. The cementum, which covers the root of the tooth, is then connected to the adjacent cortical surface of the alveolar bone. This is connected through the alveolar crest, horizontal and oblique fibers of the periodontal ligament.
Periodontium and External Forces
The purpose of the periodontium is to support the teeth while they are being used. It relies on the stimulation received in order to preserve its own structure. As a result, there is a continuous state of balance which exists between the periodontal structures and their external forces.
The alveolar bone, in its response to external forces, is under a constant state of physiologic remodeling. This is specifically in response to the occlusal forces it received. Bone is eliminated or resorbed from areas where it is not needed, and is added to areas where there is a need for additional support. The socket wall, as an example, reflects the general responsiveness to these continual outside forces. The newly formed osteoid and osteoblasts line the areas that experience tension. This is in addition to the lines of compression, which are lined by the osteoclasts. These ongoing forces also influence the number, density, and overall alignment of trabeculae. The trabeculae is located within the bone. The bony trabeculae are aligned in the path of compressive and tensile stresses. Their purpose is to provide sufficient resistance to the occlusal forces with the least amount of bone structure. As these forces grow and increase, the bony trabeculae continue to increase in number and density. In addition, bone is added to the respective external surfaces.
The periodontal ligament (PDL) relies on stimulation which is provided through routine function to preserve its own structure. Within physiologic limits, the PDL is able to withstand increased function by way of increasing its own width. Forces which exceed this adaptive capacity of the periodontium ultimately produce an injury called trauma from occlusion. In cases where the occlusal forces are reduced, it causes the PDL to atrophy and appear thinner. This unique situation is called disuse atrophy.