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Anomalies of Tooth Structure

Course Number: 651

Accessory Cusps

Accessory Cusps

Teeth with accessory cuspal anatomy can impact the overall size of the teeth.5 When accessory cusps are present, it is not uncommon for the other teeth in the dentition to be slightly larger.5 Examples of accessory include the cusp of Carabelli, the talon cusp and dens evaginatus.

Cusp of Carabelli

The cusp of Carabelli is located on the mesiolingual cusp of maxillary molar teeth and can occur in both primary and permanent dentitions.5 The cusp tend to be the most prominent on the first molars and lesser so or absent on the second and third molars.7 When present, particularly in the permanent dentition, the other teeth frequently appear wider mesiodistally.5 The cusp of Carabelli is the most prevalent in white populations.5

Talon Cusp

The talon cusp, another supernumerary or accessory cusp, affects maxillary or mandibular incisor teeth.10 This extra cusp occurs on the cingulum of maxillary lateral incisor teeth (Figure 37), most commonly, followed respectively by maxillary central incisors, mandibular incisors, and maxillary canine teeth.5 More common in the permanent dentition, the cusp extends from the lingual aspect of the tooth with a formation that resembles an eagle’s talon.10 Facial talon cusps have been reported but are rare.10 The cusp is well-formed and extends at least half the distance from the cementoenamel junction to the incisal edge, often containing a pulpal extension.5,10 A deep developmental groove may exist between the talon cusp and the underlying tooth structure.5,10 Radiographically, the cusp anatomy will appear superimposed over the other tooth structure components.5,10 The pulpal extension, if present, may not be demonstrated radiographically.10

Talon cusps tend to occur more frequently in Native American, Asian, Inuit and Arab populations with prevalence ranging from 1-8%.5,10 This cuspal anomaly can occur in either gender and may present unilaterally or bilaterally.5,9 The talon cusp is often associated with other dental anomalies such as supernumerary teeth, impacted teeth and dens invaginatus.(Figure 38)9,10

ce651 - Images - Figure 37

Figure 37.

Periapical radiograph of a talon cusp on maxillary left lateral incisor tooth, #10.

ce651 - Images - Figure 38

Figure 38.

Periapical radiograph of talon cusp anatomy on a peridens impacted between mandibular left premolar teeth #21 and #20.

Dens Evaginatus

Dens evaginatus is an external outcropping of tooth structure in the form of a cusp-like projection of enamel on the tooth crown.5,9 Dens evaginatus is usually found in the central groove or on the lingual ridge of the buccal cusp of a molar or premolar tooth (Figure 39).5,9 Most often, the mandibular premolar teeth are involved bilaterally.5,9 This extra cusp or tubercle is composed of enamel and dentin, and in many instances pulp tissue as well. This particular anomaly occurs in less than 5% of the population, most commonly in Native American, Asian, and aboriginal racial groups.5,9 Exposure and necrosis of the pulp can result from cuspal wear or fracture.9

Often teeth with dens evaginatus occur in association with incisor teeth with shovel-shaped anatomy.5 This variation in coronal anatomy is seen predominantly in Native American and Inuit populations and most commonly affects the maxillary central and lateral incisor teeth.5 The hallmarks of the affected incisor teeth include heavy lateral marginal ridges and dished out lingual surfaces that resemble the shape of a shovel (Figure 40).5 The ridges coalesce at the cingulum often forming a deep pit or a dens invaginatus defect. The later condition will be discussed next.

ce651 - Images - Figure 39

Figure 39.

Periapical radiograph showing dens envaginatus mandibular left premolar teeth #20 and #21.

ce651 - Images - Figure 40

Figure 40.

Panoramic radiograph demonstrating shovel-shaped anatomy of the maxillary incisors.