An impacted tooth is one that fails to erupt into the dental arch within the expected developmental window. Because impacted teeth do not erupt, they are retained throughout the individual's lifetime unless extracted or exposed surgically. Teeth may become impacted because of adjacent teeth, dense overlying bone, excessive

soft tissue Soft tissue is all the tissue in the body that is not hardened by the processes of ossification or calcification such as bones and teeth. Soft tissue connects, surrounds or supports internal organs and bones, and includes muscle, tendons, ...

or a genetic abnormality. Most often, the cause of impaction is inadequate arch length and space in which to erupt. That is the total length of the alveolar arch is smaller than the tooth arch (the combined mesiodistal width of each tooth). The

wisdom teeth A third molar, commonly called wisdom tooth, is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. The age at which wisdom teeth come through ( erupt) is variable, but this generally occurs betw ...

(third molars) are frequently impacted because they are the last teeth to erupt in the oral cavity.

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 ...

third molars are more commonly impacted than their maxillary counterparts. Some dentists believe that impacted teeth should be removed except, in certain cases, canine teeth: canines may just remain buried and give no further problems, thus not requiring surgical intervention. However, removal of asymptomatic, pathology-free, impacted teeth isn't a medical consensus: watchful monitoring may be a more prudent and cost-effective strategy and make the future placement of a dental implant through such impacted tooth a feasible approach.

Classification

Classifications enable the oral surgeon to determine the difficulty in removal of the impacted tooth. The primary factor determining the difficulty is accessibility, which is determined by adjacent teeth or other structures that impair access or delivery pathway. The majority of classification schemes are based on analysis on a

radiograph Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...

. The most frequently considered factors are discussed below.

Angulation of tooth

Most commonly used classification system with respect to treatment planning. Depending on the angulation the tooth might be classified as: * Mesioangular * Horizontal * Vertical * Distoangular * Palatal * Buccal * Lingual

Relationship of tooth to anterior border of ramus

This type of classification is based on the amount of impacted tooth that is covered with the mandibular ramus. It is known as the Pell and Gregory classification, classes 1, 2, and 3.

Relationship of tooth to occlusal plane

The depth of the impacted tooth compared with the adjacent second molar gives the basis for this type of classification. This was also given by Pell and Gregory and is called as Pell and Gregory A, B and C classification. Relationship to occlusal plane Class A-C

Complications

Erupted teeth that are adjacent to impacted teeth are predisposed to

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 caus ...

. Since the most difficult tooth surface to be cleaned is the distal surface of the last tooth, in the presence of an impacted tooth there is always

gingival inflammation Gingivitis is a non-destructive disease that causes inflammation of the gums. The most common form of gingivitis, and the most common form of periodontal disease overall, is in response to bacterial biofilms (also called plaque) that is attache ...

around the second molar that is invariably present. Even this minor amount of inflammation can provide

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...

access to a larger portion of the root surface that results in early formation of

periodontitis 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 cau ...

compromising the tooth. Even in situations in which no obvious communication exists between the mouth and the impacted third molar there may be enough communication to initiate

dental caries Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicat ...

(tooth decay).

Pericoronitis

Pericoronitis is an infection of the soft tissue that covers the crown of an impacted tooth and is usually caused by the normal

oral The word oral may refer to: Relating to the mouth * Relating to the mouth, the first portion of the alimentary canal that primarily receives food and liquid **Oral administration of medicines ** Oral examination (also known as an oral exam or or ...

microbiota. For most people there exists a balance between the host defenses and the oral micriobiota but if the host defenses are compromised like during minor illness such as influenza or an

upper respiratory tract infection An upper respiratory tract infection (URTI) is an illness caused by an acute infection, which involves the upper respiratory tract, including the nose, sinuses, pharynx, larynx or trachea. This commonly includes nasal obstruction, sore thro ...

, pericoronitis results. Another common cause is entrapment of food beneath the gum flap (also called an operculum). Pericoronitis can present as a mild infection or severe infection. In its mildest form it is just a localized tissue swelling and soreness whereas in severe forms the swelling is slightly larger even sometimes creating

trismus Trismus, commonly called ''lockjaw'' as associated with tetanus, is a condition of limited jaw mobility. It may be caused by spasm of the muscles of mastication or a variety of other causes. Temporary trismus occurs much more frequently than perma ...

(difficulty opening the mouth). Occasionally, an impacted tooth causes sufficient pressure on the roots of adjacent teeth causing it to resorb. An impacted tooth occupies space that is usually filled with bone. This weakens that area of bone and renders the jaw more susceptible to fracture. When impacted teeth are retained completely within the alveolar process, the associated follicular sac is also retained along with it. Though in most persons the

dental follicle The dental follicle, also known as dental sac, is made up of mesenchymal cells and fibres surrounding the enamel organ and dental papilla of a developing tooth. It is a vascular fibrous sac containing the developing tooth and its odontogenic organ ...

maintains its original size sometimes it may undergo

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...

ic degeneration and become a

dentigerous cyst Dentigerous cyst, also known as follicular cyst is an epithelial-lined developmental cyst formed by accumulation of fluid between the reduced enamel epithelium and crown of an unerupted tooth. It is formed when there is an alteration in the redu ...

or a

keratocyst A keratocyst is a type of cutaneous cyst. They appear similar to epidermoid cysts; however, are not limited to a specified location on the body. Keratocyst are most often reported in persons with nevoid basal cell carcinoma syndrome Nevoid basal-ce ...

Symptoms

Most commonly the individual complains of food getting lodged beneath the gums and a soreness that is usually confused with throat infections. In slightly milder forms a swelling is visible and mouth opening becomes difficult in severe cases. Pain is invariably present.

Management

Impacted teeth might be extracted or left alone, depending on the dentist (and the health authority's guidelines in that country) and the situation. Extraction might be contraindicated and might be simple or surgical, often depending on the location of the teeth. In some cases, for aesthetic purposes, a surgeon may wish to expose the canine. This may be achieved through open or closed exposure. Studies show no advantage of one method over another. Laser can be used to uncover superficially impacted teeth with no bleeding and quick recovery

References

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