Bilateral gemination of permanent maxillary canine with labial and palatal talon's cusps: A rare entity.

Gemination is a morphologic anomaly of the tooth characterized by the formation of a macrodont. Bilateral presentation is rarely reported in permanent canines. Talon's cusp is an accessory cusp projecting lingually from the cingulum to the incisal edge and may be seen facially sometimes. Simultaneous occurrence of facial and lingual talons on the same tooth is rare. Concurrent occurrence of all the three entities has not been reported. These anomalies can cause unpleasant esthetic appearance due to irregular morphology. The presence of deep grooves on these teeth increases the susceptible to caries and periodontal disease requiring an endodontic intervention. Proper clinical and radiographic examination provides an accurate diagnosis and helps the clinician in the proper treatment planning and avoiding further complications. This article presents a unique case of simultaneous occurrence of bilateral gemination in the permanent maxillary canines with labial and palatal talon's cusps, which has not been reported in the literature till date. Copyright:

INTRODUCTION

Gemination and fusion are morphologic anomalies of the tooth characterized by the formation of a macrodont. Both these anomalies have been named as “double teeth” or “connoted teeth.” Gemination is an anomaly caused when a single tooth bud attempts to divide resulting in a structure with two completely separated teeth (twinning) or incompletely separated crowns with a single root and root canal. Fusion occurs when two separate tooth buds fuse together completely or incompletely during development, resulting in a large tooth. Tooth number is normal in gemination, while one tooth is missing in fusion. This rule does not apply if there are supernumerary teeth. Fusion can also be the union of a normal tooth bud with a supernumerary tooth germ. In such case, the tooth count is normal and the differentiation from gemination might be difficult, if not impossible. Gemination and fusion are more common in the primary dentition than the permanent dentition. Mandibular anterior region and incisors are more often affected. The unilateral occurrence is more commonly reported than bilateral presentation.[1] The frequency of gemination or fusion ranges from 0.01% to 0.04% in the primary dentition and 0.05% in the permanent dentition.[2]

Talon's cusp is an accessory cusp-like structure projecting from the cingulum area or labial surface of the tooth composed of normal enamel, dentin and varying degree of pulp tissue with or without pulp horn. It may be seen on palatal/lingual and facial/labial surface of incisors or canines and may connect with the incisal edge to produce a ‘T’ shaped, or if more cervical, a 'Y' shaped crown contour. The occurrence of talon's cusp is said to be 0.73% to 8% of the population.[3] The prevalence of talon's cusps in the Indian population ranges from 1% to 8%.[4]

Only one case of bilateral gemination in the permanent maxillary canines has been published so far by Gangadharan et al.[5] which makes this the second case. However, their case did not report talon's cusps. To the best of our knowledge, the present case is the first case reporting bilateral gemination with facial and palatal talon's cusps in permanent maxillary canines. Literature search showed no published case report involving all the three entities.

CASE REPORT

A female patient aged 23 years reported to the hospital with a chief complaint of discolored upper front teeth. On intraoral examination, the maxillary right and left canines appeared to have an abnormal morphology with an increased mesiodistal dimension and presence of facial and palatal talon's cusps [Figures 1-3]. The canine teeth bilaterally were unusually large with a groove showing blackish discoloration on the labial surface. The teeth count was found to be normal (28 teeth), and the third molars were clinically missing in all quadrants. Intraoral periapical radiograph of both canines revealed a single root and single root canal with a bifid crown [Figure 4]. The right canine (FDI 13) showed prominent coronal radio opacity which was separated by a radiolucent line in the crown while the left canine (FDI 23) revealed two distinct coronal radio opacity. Electric pulp testing, percussion and periodontal probing showed no abnormalities. Based on these findings, a diagnosis of bilateral gemination of permanent maxillary canines with labial and palatal talon's cusps was made. The patient was advised all the treatment options. The patient was not willing for reduction of the tooth surface and wanted only the removal of discoloration. Glass ionomer restoration was done to fill up the grooves in both the teeth.

Figure 1

Clinical photograph (a) and cast (b) showing bilateral gemination with facial and palatal talon's cusps on permanent maxillary canines

Figure 3

Gemination on the left permanent maxillary canine showing facial and palatal talon's cusps. (a) Clinical picture (b) on the cast

Figure 4

Intraoral periapical radiograph of the right (a) and left (b) permanent maxillary canines

Gemination on the right permanent maxillary canine showing facial and palatal talon's cusps. (a) Clinical picture (b) on the cast

DISCUSSION

Bilateral occurrence of gemination is a rare entity. Bilateral gemination with labial and palatal talon's cusps on permanent maxillary canine is an extremely rare occurrence. The etiology of gemination is uncertain. Evolution, trauma during development, heredity and environmental factors are thought to play a role in gemination. Hereditary tendency with autosomal recessive or dominant mode of inheritance affecting the dental lamina is suggested. Association of gemination with syndromes such as chondroectodermal dysplasia and achondrodysplasia is also observed. Nutritional deficiency, endocrine disturbances, infectious inflammatory processes, excessive ingestion of medicines and ionizing radiation are other suggested etiologies. A complex interplay between genetic and environmental factors seems to play a role causing this anomaly.[16] Aguiló et al.[7] classified gemination as shown in Table 1. Gemination is generally asymptomatic. However, the affected teeth may cause clinical problems in the form of poor esthetics, malocclusion, impaction of adjacent teeth, and caries or periodontal destruction.

Table 1

Classification of gemination according to Aguiló et al.[7]

Type	Diagram	Description
Type 1		Enlarged crown with notch on the incisal edge, pulp chamber can be bifid, normal radicular dimension, cervical widening of canal
Type 2		Straight/normal incisal edge, large pulp chamber and root canals with increased radicular dimension
Type 3		Two fused crowns, with complete or partial vertically running groove, which extends cervically. Coronal portion may or may not be symmetrical. Pulp chamber coronally can be fused or shared but end as two separate canals
Type 4		Two separate crowns with separate root and canals (Twinning

Talon's cusp was first recognized by Mitchell in 1892.[8] Mellor and Ripa later coined the term “talon” due to its resemblance to eagle's talon.[9] It is also called as dens evaginatus which is more commonly used for the posterior teeth. Multifactorial etiology with genetic and environmental involvement during the morphodifferentiation stage of tooth development is suggested. Talon's cusps may be associated with somatic abnormalities, such as Mohr's syndrome, Rubenstein–Taybi syndrome, Sturge–Weber syndrome, Ellis-van Creveld syndrome, Berardinelli–Seip syndrome and Alagille syndrome.[7] However, the present case was not associated with any anomalies.

Talon's cusps occur most commonly on the maxillary teeth than the mandibular teeth. Most commonly affected teeth include the maxillary permanent incisors (90% cases), especially the lateral incisors (67%) followed by the central incisors (24%), and less frequently the mandibular incisors (6%) and maxillary canine (9%).[10] Involvement of canine is very rare. Unilateral cases are more common. Talon's cusp usually occurs on the lingual surfaces of the teeth, while facial talons are rare. Talon's cusp is more often reported in males than females. The facial talon's cusp has a higher predilection for females. Simultaneous occurrence of facial and lingual talons on the same tooth is extremely rare. Some reported cases in the literature are shown in Table 2.[31112131415161718]

Table 2

Reported cases with labial and palatal talon’s cusps on the same tooth in permanent dentition[31112131415161718]

Authors	Year	Place	Sex	Affected tooth (FDI)
Abbott[11]	1998	Australia	Female	21
McKaig and Shaw[12]	2001	Birmingham	Female	11
Dunn WJ[3]	2004	America	Female	12
Shashikiran et al.[13]	2005	India	Female	21
Sumer and Zengin[14]	2005	Turkey	Female	11
Cubukcu et al.[15]	2006	Turkey	Female	11 Gemination with labial and palatal talon’s cusps
Ekambaram et al.[16]	2008	China	Female	41,42 Fusion with labial and lingual talon
Guven et al.[17]	2016	Turkey	-	Supernumerary tooth (mesiodens)
Goswami et al.[18]	2016	India	Male	31, 32 Fusion with facial and lingual talon’s cusps
Nandini et al. (present case)	2020	India	Female	13, 23 Bilateral gemination with facial and palatal talon’s cusp

The etiology of talon's cusp is poorly understood. It has been suggested that the condition may have a multifactorial etiology that may include both the environmental and genetic factors. Genetic inheritance in five siblings was reported by Elmubarak.[19] Hyperactivity of dental lamina early in the odontogenesis has been suggested. Hattab et al. suggested that the talon's cusp might be formed as a result of an outward folding of the inner enamel epithelial cells and a transient focal hyperplasia of mesenchymal dental papilla.[6]

Hattab et al.[6] have classified only lingual talons and Chin-Ying et al.[20] also included labial talons in their classification [Table 3]. In the present case, both geminated teeth had talon's cusps, and the mesiodistal width of the teeth was significantly increased. Facial talon's cusp has been categorized into three stages depending on its form starting from the slightest to most extreme forms by Mayes[21] [Table 4].

Table 3

Clinical classification of Talon’s cusp based on its length by Hattab et al.[6] and by Chin-Ying et al.[20]

Type	Description by Hattab et al.[6]	Description by Chin-Ying et al.[20]
Type 1	Talon: Well-delineated cuspal projections from the palatal surface of primary or permanent anterior teeth and extend at least half the distance from the cementoenamel junction to the incisal edge	Major talon: Talons with well-defined cusps projecting from an anterior tooth facial/labial or lingual/palatal surface and extend at least half the distance from the cementoenamel junction to the incisal edge
Type 2	Semi talon: Projection extends less than half the distance from the cementoenamel junction to the incisal edge	Minor talon: Talons occur on the same surfaces but extend more than one fourth and less than half from the cementoenamel junction to incisal edge
Type 3	Trace talon: Talon’s cusps are just prominent and well-developed cingula	Trace talon: Talons with enlarged talons and prominent cingula which occupy less than the one fourth the distance from the cementoenamel junction to the incisal edge

Table 4

Classification of Talon’s cusp according to Mayes[21]

Type	Description
Stage 1	The slightest form, consisting of slightly raised triangle on the labial surface of an incisor extending the length of the crown, but not reaching the cementoenamel junction or the incisal edge
Stage 2	The moderate form, consisting of a raised triangle on the labial surface of an incisor that extends the length of the crown, does not reach the cementoenamel junction, but does reach the incisal edge and can be observed clearly and palpated easily at this stage; and
Stage 3	The most extreme form, consisting of a freeform cusp, extending from the cementoenamel junction to the incisal edge on the labial surface of an incisor

The present case is similar to type 1 category of gemination with respect to incisal aspect and type II labial talon's cusp bilaterally and type II lingual talons on 23 and type III talons on 13, but radiographically both the maxillary canines have only enlarged pulp chamber without any bifid appearance [Figure 4].

The mere presence of talon's cusp does not warrant endodontic or restorative treatment unless other dental problems such as caries, loss of periodontal attachment, occlusal interference, irritation to the soft tissues or for esthetic reasons exist. Treatment modalities depend on the size and morphology of the talon's cusp and the extension of pulp tissue. As the patient wanted only restorative procedure for esthetic reasons, discoloration was selectively removed from the labial grooves and glass ionomer restoration was done.

CONCLUSION

The occurrence of bilateral gemination of permanent canines with labial and lingual talons is a very rare condition. A conservative approach was done to prevent caries and to maintain the vitality of the tooth.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initial s will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.