The periodontium is the specialized tissues that both surround and support the

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

, maintaining them in the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

ry and

mandibular In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

bones. The word comes from the Greek terms περί ''peri''-, meaning "around" and -''odont'', meaning "tooth". Literally taken, it means that which is "around the tooth".

Periodontics Periodontology or periodontics (from Ancient Greek , – 'around'; and , – 'tooth', genitive , ) is the specialty of dentistry that studies supporting structures of teeth, as well as diseases and conditions that affect them. The supporting ...

is the dental specialty that relates specifically to the care and maintenance of these tissues. It provides the support necessary to maintain teeth in function. It consists of four principal components, namely: *

Gingiva The gums or gingiva (plural: ''gingivae'') consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health. Structure The gums are part of the soft tissue lini ...

Periodontal ligament The periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits. It inserts into root cementum one side and onto alveolar b ...

(PDL) *

Cementum Cementum is a specialized calcified substance covering the root of a tooth. The cementum is the part of the periodontium that attaches the teeth to the alveolar bone by anchoring the periodontal ligament.Illustrated Dental Embryology, Histology, a ...

* Alveolar bone proper Each of these components is distinct in location, architecture, and biochemical properties, which adapt during the life of the structure. For example, as teeth respond to forces or migrate medially, bone resorbs on the pressure side and is added on the tension side. Cementum similarly adapts to wear on the occlusal surfaces of the teeth by apical deposition. The periodontal ligament in itself is an area of high turnover that allows the tooth not only to be suspended in the alveolar bone but also to respond to the forces. Thus, although seemingly static and having functions of their own, all of these components function as a single unit. The

Wnt signaling The Wnt signaling pathways are a group of signal transduction pathways which begin with proteins that pass signals into a cell through cell surface receptors. The name Wnt is a portmanteau created from the names Wingless and Int-1. Wnt signaling ...

antagonist Sfrp3/

Frzb Frzb (pronounced like the toy ''frisbee'') is a Wnt-binding protein especially important in embryonic development. It is a competitor for the cell-surface G-protein receptor Frizzled. Frizzled is a tissue polarity gene in ''Drosophila melanogas ...

has been recently discovered as an early developmental marker of the periodontium.

External forces and the periodontium

The periodontium exists for the purpose of supporting teeth during their function and it depends on the stimulation it receives from the function for preservation of its structure. Therefore, a constant state of balance always exists between the periodontal structures and the external forces. Alveolar bone undergoes constant physiologic remodeling in response to external forces, particularly occlusal forces. Bone is removed from areas where it is no longer needed and added to areas where it is needed. The socket wall reflects the responsiveness to the external forces.

Osteoblast Osteoblasts (from the Greek language, Greek combining forms for "bone", ὀστέο-, ''osteo-'' and βλαστάνω, ''blastanō'' "germinate") are cell (biology), cells with a single Cell nucleus, nucleus that synthesize bone. However, in the p ...

s and newly formed osteoid line the areas of tension, whereas lines of compression are lined by

osteoclasts An osteoclast () is a type of bone cell that breaks down bone tissue. This function is critical in the maintenance, repair, and remodeling of bones of the vertebral skeleton. The osteoclast disassembles and digests the composite of hydrated prote ...

. The forces also influence the number, density, and alignment of

trabecula A trabecula (plural trabeculae, from Latin for "small beam") is a small, often microscopic, tissue element in the form of a small beam, strut or rod that supports or anchors a framework of parts within a body or organ. A trabecula generally ha ...

e inside the bone. The bony trabeculae are aligned in the path of tensile and compressive stresses to provide maximum resistance to occlusal forces with a minimum of bone substance. When forces are increased, the bony trabeculae also increase in number and thickness and bone is added to the external surfaces. The periodontal ligament depends on stimulation provided by function to preserve its structure. Within physiologic limits the PDL can accommodate increased function by increasing its width. Forces that exceed the adaptive capacity of the periodontium produce injury called ''trauma from occlusion''. When occlusal forces are reduced the PDL atrophies, appearing thinned. This phenomenon is called '' disuse atrophy''.

References

{{Authority control Periodontology Human mouth anatomy Dental anatomy