What are Abnormalities of Tooth Form?

Double Teeth

Double teeth may be formed either by fusion of two developing tooth germs or by gemination (partial dichotomy) of one tooth germ. If fusion occurs between two teeth of the normal dentition, one of the teeth will appear to be missing from the dentition. If, on the other hand, one element is a supernumerary tooth, the normal number of teeth will be present (including the double tooth). This is also the case when the double tooth is formed by gemination of one tooth germ. Therefore, it is sometimes difficult to decide whether an abnormally large tooth is the result of fusion of a normal and a supernumerary tooth, or of gemination; use of the term 'double tooth' avoids this difficulty.
 
Abnormalities of Tooth Form

They occur most frequently in the maxillary incisor region, more commonly in the primary than in the permanent dentition, and may be unilateral or bilateral. A large tooth may be identified as a double tooth by notching in its incisal edge, or by a longitudinal groove in its crown, or by partial or complete separation of its roots.

Treatment

No treatment is necessary for primary double teeth, but in the permanent dentition treatment to improve their appearance is usually requested by the patient and parent.

Malformation of the Maxillary Permanent Lateral Incisor

The maxillary permanent lateral incisor is often abnormal in size or shape. The most common abnormalities are a 'peg-shaped' crovm and a deep palatal invagination. Peg-shaped lateral incisors have small, conical crowns and resemble conical supernumerary teeth. They may occur unilaterally (not uncommonly associated with a congenitally absent contralateral tooth) or bilaterally.
Palatal pits occur in many lateral incisors, but some times the pit is particularly deep and leads to a chamber formed by invagination of the developing tooth germ; this is known as dens in deme or dens i11vaginaws. Caries may begin in the depths of a pit or invagination and quickly involve the pulp.

Treatment

Peg-shaped laieral incisor

If the dental arch is crowded, peg-shaped lateral incisors may be extracted as pan of orthodontic treatment. However, this is rarely the treatment of choice because peg-shaped lateral incisors tend to occur in dentitions in which the other teeth are small or in which one or more teeth are congenitally absent. A normal crown shape can be produced with a porcelain 'thimble' crown. Usually no tooth preparation is required before taking an impression of the tooth. The entire enamel surface of the tooth is acidetched and the crown is bonded to it with composite resin.
It is possible but less satisfactory to improve the appearance of a peg-shaped incisor using composite resin in a cellulose acetate crown form or (if using a light-cured resin) by building up in increments. A problem arises in adapting a crown form to the narrow neck of the 'peg' tooth. This may be overcome by making a longitudinal cut in the palatal part of the crown form, overlapping the two sides and sticking with photographic film adhesive.

Deep palatal pits

Ideally, palatal pits should be sealed with composite resin or glass-ionomer cement as soon as the teeth erupt. If the teeth have erupted and the pits have not been sealed, careful clinical and radiological examination is required to assess whether they are carious.

Dens Evaginatus (Evaginated Odontome)

Dens evaginatus is a tooth in which an evagination of enamel and dentine appears as a tubercle on the occlusal surface. The tubercle is covered with enamel and a fine pulp horn usually extends into the dentine core. The anomaly is most common in .People of Mongoloid races but also occurs in Caucasians, and it is found most frequently in premolar teeth but occasionally also in other permanent teeth.
The condition is of clinical significance because the tubercles often become worn or fractured, exposing pulp and leading to pulp necrosis and periapical infection. Since this often occurs within a few years of the tooth's eruption it presents a problem for endodontic treatment.

Treatment

Treatment must be directed at preventing the complications associated with exposure and death of the pulp.
  1. If the tubercle causes no occlusal interference, seal the occlusal surface as described in Chapter 5. Use a filled composite resin and flow it around the tubercle and over the adjacent fissures.
  2. If the tubercle causes occlusal interference, administer local analgesic and isolate the tooth with rubber dam in readiness for pulp treatment. Reduce the height of the tubercle sufficiently to relieve the occlusal interference and examine it carefully.
    • If pulp is not exposed, proceed as for 1 above.
    • If pulp is exposed, perform a conservative partial pulpotomy by removing pulp to a depth of about 2 mm with a small diamond bur, following the technique described on page 2 13. This creates space to place a calcium hydroxide dressing over the pulp and to seal the cavity with glass-ionomer cement or composite resin. Seal the adjacent fissures with composite resin.

Talon Cusp

A talon cusp has been defined as 'an additional cusp that prominencly projects from the lingual surface of primary or permanent anterior teeth, is morphologically well delineated, and extends at least half the distance from the cemento-enamel junction to the incisal edge'. Talon cusps have been reported most frequently on maxillary permanent incisors, but also on maxillary primary incisors and on man-
Abnormalities of tooth form 151 dibular permanent incisors, and are often associated with other abnormalities (for example, evaginated premolars, peg-shaped maxillary lateral incisors, double teeth, complex odontomes).
A talon cusp may project at an angle from the tooth or lie close to its palatal surface. The junction between cusp and tooth may be smooth or, especially when the
cusp lies close to the tooth, it may be grooved or fissured. When the tooth is erupting, before the connection of the cusp and the tooth becomes vis ible, the cusp may appear to be a supernumerary tooth; it is important not to be hasty and attempt to extract it.

Treatment

Soon after the tooth erupts, carefully examine the junction between the cusp and the tooth. If it appears that it might be a site for plaque retention and therefore for caries, seal with composite resin or glass-ionomer cement.

Dilaceration

A dilacerated tooth is one that has a distorted crown or root. Dilaceration is most commonly associated with maxillary permanent central incisors. Severe trauma to primary incisors is a common cause of dilaceration, but some cases are not associated with trauma and simply reflect abnormal  development of the tooth.
Severe injury to a maxillary primary incisor may cause dilaceration of either the crown or the root of the permanent successor, depending on the stage of development of the permanent tooth and its relationship to the root of the primary incisor at the time of injury. Maxillary permanent incisors develop palatal to and very near the root apices of the primary incisors; as they erupt they move over the roots of the primary teeth. Therefore, intrusion or gross displacement of the primary incisor in infancy is most likely to displace the permanent tooth crown palatally. Since further development continues normally, the fully developed tooth has its crown bent palatally; it also has hypoplasia of the enamel in the area of the distortion, as evidence of the traumatic incident.

Treatment

Unerupted dilacerated teeth usually must be extracted, but sometimes it is possible to bring a tooth into the arch by a combination of surgery and orthodontics. Erupted teeth with root dilaceration are also usually extracted if they arc in an abnormal position because it is difficult to move them by orthodontic means. Following extraction, the space must either be maintained with a prosthesis (to restore aesthetics and to prevent tilting of adjacent teeth) or closed orthodontically.

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