dental anatomy Dental anatomy is a field of anatomy dedicated to the study of Tooth (human), human tooth structures. The development, appearance, and classification of teeth fall within its purview. (The function of teeth as they contact one another falls elsew ...

, the cementoenamel junction (CEJ) is the location where the enamel, which covers the anatomical

crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, parti ...

of a

tooth 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, tea ...

, and the

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. Structure The cells of cementum are ...

, which covers the anatomical root of a tooth, meet. Informally it is known as the neck of the tooth. The border created by these two dental tissues has much significance as it is usually the location where the

gingiva The gums or gingiva (: 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 lining of the ...

(gums) attaches to a healthy tooth by fibers called the

gingival fibers In dental anatomy, the gingival fibers are the connective tissue fibers that inhabit the gingiva, gingival tissue (gums) adjacent to Tooth, teeth and help hold the tissue firmly against the teeth. They are primarily composed of type I collagen, a ...

. Active recession of the gingiva reveals the cementoenamel junction in the mouth and is usually a sign of an unhealthy condition. The loss of attachment is considered a more reliable indicator of

periodontal disease Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main c ...

. The CEJ is the site of major

tooth resorption Resorption of the root of the tooth, or root resorption, is the progressive loss of dentine, dentin and cementum by the action of odontoclasts. Root resorption is a normal physiological process that occurs in the exfoliation of the Deciduous teet ...

. A significant proportion of tooth loss is caused by tooth resorption, which occurs in 5 to 10 percent of the population. The clinical location of CEJ which is a static landmark, serves as a crucial anatomical site for the measurement of probing pocket depth (PPD) and clinical attachment level (CAL). The CEJ varies between subjects, but also between teeth from the same person. There exists a normal variation in the relationship of the cementum and the enamel at the cementoenamel junction. In about 60–65% of teeth, the cementum overlaps the enamel at the CEJ, while in about 30% of teeth, the cementum and enamel abut each other with no overlap. In only 5–10% of teeth, there is a space between the enamel and the cementum at which the underlying

dentin Dentin ( ) (American English) or dentine ( or ) (British English) () is a calcified tissue (biology), tissue of the body and, along with tooth enamel, enamel, cementum, and pulp (tooth), pulp, is one of the four major components of teeth. It i ...

is exposed.

Formation

In the

bud, regions where enamel formation is completed, the enamel organ gives rise to Hertwig's epithelial root sheath, composed of two epithelial layers derived from the external and internal epithelia. The sheath is irregularly fragmented in time and space as it promotes cementum deposition on the newly formed dentin. After this fragmentation, Hertwig's epithelial root sheath also participates in cementogenesis and formation of the

periodontal ligament The periodontal ligament, commonly abbreviated as the PDL, are a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which they sit. It inserts into root cementum on one side and onto alveo ...

, giving rise to the epithelial rests of Malassez. This irregular fragmentation of Hertwig's epithelial root sheath yields an equally irregular limit of cervical enamel and an irregular onset of formation and deposition of cementum. Consequently, the relationship between cementum and enamel at the CEJ presents an irregular contour, as observed during scanning electron microscope (SEM) analysis of the primary teeth. Fragmentation of Hertwig's epithelial root sheath and exposure of dentin covered by a thin layer of intermediate cementum are fundamental for the onset of cementogenesis. If Hertwig's epithelial root sheath is not fragmented, there will be enamel deposition and it will be transformed into reduced epithelium, thus preventing cementum deposition on its surface.

Types

* Coronal cementum - where the enamel overlaps the cement. * Abutment - It is also known as vis a vis relation, where the cement and enamel meet at the butt joint, occurring in 30% of sections, and the least common, occurring in 10% of sections. * Gap between cementum and enamel exposing the dentin.

Curvature

The shape and location of the cementoenamel junction (CEJ) on each tooth surface should be considered. CEJs differ from tooth to tooth in terms of their anatomy. The curvature of the CEJ is greatest on anterior teeth due to the narrow profile of these teeth. On the anteriors, the distal aspect's curvature is usually one mm lower than the mesial aspect. Posterior teeth have flatter CEJ curvatures on the inter-proximal surfaces in comparison to the anteriors.

Teeth resorption

Root resorption often starts at cementoenamel junction (CEJ) in teeth. Types of tooth resorption include internal resorption and external resorption.

Internal

There are two types of internal resorption - root canal (internal) replacement resorption and internal inflammatory resorption. Types of Resorption

External

External resorption can be classified into four categories by its clinical and histologic manifestations: external surface resorption, external inflammatory root resorption, replacement resorption, and ankylosis. External inflammatory root resorption can be further categorized into cervical resorption with or without a vital pulp (invasive cervical root resorption) and external apical root resorption.

References

External links

Biology-Online
{{Authority control Dental enamel Parts of tooth Human mouth anatomy