Unusual Case of Labial and Lingual Talon Cusps

Military Medicine, Feb 2004 by Dunn, William Jackson

Talon cusp is an uncommon developmental anomaly affecting the anterior teeth, characterized by cusp-like projections, usually presenting on the lingual surface of the affected tooth. The occurrence ranges from 0.73% to 8% of the population. Talon cusp has been associated with other dental anomalies such as dens invaginatus, odontomas, and impacted teeth; associations with somatic anomalies such as Mohr's, Rubenstein-Taybi, and Sturge-Weber syndromes have also been reported. Only a few cases of labial talon cusp have been reported and only one previously published report exists documenting talons appearing both labially and lingually on the same tooth. This study reports the unusual case of a 10-year-old girl with bilateral talon cusps and one tooth possessing both lingual and labial talons. The lingual talon on the right maxillary lateral incisor was interfering with normal occlusion and was responsible for labioversion of the tooth. Treatment options were presented.

Introduction

Talon cusp is an uncommon dental developmental anomaly characterized by accessory cusp-like projections of the teeth. The projections may be subtle but may also be significant enough to complicate occlusion, or if located on the facial aspect of anterior teeth, a significant dental cosmetic situation may result. This anomaly has been named talon cusp because the projections often resemble an eagle's talon.1 Most reported cases of talon cusp are located in the permanent dentition.2-4 The permanent maxillary lateral incisor is the most commonly affected tooth with 55% of reports published in the literature. Maxillary central incisors have been identified in 33% of all reported cases.5 Less frequently, mandibular incisors (6%) are involved.4 In the vast majority of cases, the talon cusp is observed on the lingual surface of the tooth characterized as a projection emerging from the cingulum extending to the incisai edge.6 Because the term talon cusp has been used to loosely describe many different cusp-like aberrations in anterior teeth, attempts have been made to categorize the degree of severity of the condition.2 Some reports suggested that the tenu talon cusp be reserved to those cusps with a projection of at least 1 mm7 or in cases in which the cusp extends at least one-half the distance from the cementoenamel junction to the incisai edge.8

Mitchell9 first described the talon cusp in 1892, but most reports have been published in the last 30 years. Hattab et al.2 reported a male-female ratio of 47:26 among 73 cases reported in the literature. Davis and Brook10 reported a male:female incidence ratio of 32:18. Extensive prevalence studies have not been performed, but it is estimated that the frequency of talon cusp may range from 1% to 8% of the population.4,5 However, observations of the occurrence of talon cusps among Chinese11 and Arab12 populations suggest that the condition may be more common in certain ethnic groups. Talon cusp is a term usually confined to anterior teeth. Dens evaginitus is preferred when describing posterior teeth with additional cusp-like projections. Dens evaginitus is reported to be higher in Asians, American Indians, and Eskimos.6 The lack of precise criteria to accurately define talon cusp has made documentation of the actual prevalence difficult.

Talon cusp has been reported as an individual dental abnormality6 but also in association with other dental anomalies2,13-15 (e.g., supernumerary teeth, odontomas, impacted teeth, pegshaped lateral incisors, dens invaginitus, posterior dens evaginitus). Although talon cusp is not documented as an important part of any specific syndrome, there appears to be an increased incidence of the condition in patients with Mohr,16 RubinsteinTaybi,17 and Sturge-Weber syndromes.11 In isolated cases, identical talon cusps have been documented in twins, suggesting a genetic influence.4

The etiology of talon cusp is poorly understood. It has been suggested that the condition may have a multifactorial etiology to include both genetic and environmental factors.18 Hyperactivity of the dental lamina early in odontogenesis has been suggested as a factor. Hattab et al.2 suggested that the aberrant cusp might be formed as a result of an outward folding of the inner enamel epithelial cells and a transient focal hyperplasia of the mesenchymal dental papilla. Gungor et al.19 reported a composition of normal enamel and dentin with varying extensions of pulpal tissue into the talon projection.

Talon cusps have been defined as cusp-like projections occurring exclusively on the palatal or lingual surface of teeth.20 Although very rare, two cases have been reported documenting talon cusps on the labial surface of maxillary permanent central incisors,21,22 and only one case has been reported where a facial and lingual talon cusp have occurred on the same tooth.3 The following case describes the second reported case of a facial and lingual talon cusp on the same tooth and the bilateral occurrence of a lingual talon cusp on the antimeric permanent maxillary lateral incisor.