|Year : 2013 | Volume
| Issue : 2 | Page : 92-97
Maxillary molar with dens evaginatus and multiple cusps: Report of a rare case and literature review
NB Nagaveni1, KV Umashankara2
1 Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka, India
2 Department of Oral and Maxillofacial Surgery, Bapuji Dental College and Hospital, Davangere, Karnataka, India
|Date of Web Publication||4-Jul-2014|
N B Nagaveni
Department of Pedodontics and Preventive Dentistry, College of Dental Sciences, Davangere, Karnataka
Source of Support: None, Conflict of Interest: None
Human teeth may show variations and changes in morphological structures. Such changes may be found on the crown either in the form of anomalous cusps or in an increased number of roots, which in some instances is associated with an anomalous cusp. Accessory or supernumerary cusps are common variations of tooth morphology that are occasionally encountered clinically. The most commonly reported accessory cusps are cusp of Carabelli of the molars, talons cusps of the incisors and Leong's tubercle of premolar. Herewith, we present a case of maxillary third molar associated with six supernumerary cusps along with a dens evaginatus that is a rarely reported dental variation in the literature. The article also discusses the need for continuous dental surveillance of this rare anomaly with a review of the literature.
Keywords: Accessory central cusp, dens evaginatus, maxillary third molar, supernumerary cusps
|How to cite this article:|
Nagaveni N B, Umashankara K V. Maxillary molar with dens evaginatus and multiple cusps: Report of a rare case and literature review. Int J Oral Health Sci 2013;3:92-7
|How to cite this URL:|
Nagaveni N B, Umashankara K V. Maxillary molar with dens evaginatus and multiple cusps: Report of a rare case and literature review. Int J Oral Health Sci [serial online] 2013 [cited 2017 Apr 29];3:92-7. Available from: http://www.ijohsjournal.org/text.asp?2013/3/2/92/135979
| Introduction|| |
"Central cusp," also known as "occlusal supernumerary cusp" or "Dens evaginatus," is defined as "the cusp situated between the buccal and lingual cusp tips on the occlusal surface of the premolars and molars, and on the lingual surface of the incisors and canines." Kocsis et al. defined central cusp as a "supernumerary macrostructure of the tooth surface, representing a cusp formation on the occlusal surface of premolars and molars, and on the lingual surface of canines and incisor teeth."  Leigh  in 1925 was the first person who described and reported an enamel tubercle on the maxillary right molar of an American Eskimo skull. Schulze  in 1987 concluded that central occlusal cusps are mainly characteristic of the East Asian populations and that they rarely occur in other populations. The macrostructure of a central cusp involves not only the strengthening of the original enamel layer of a cusp but also the presence of a circumscribed, well-defined elevation. The surrounding cusp enamel may sometimes be separated from the cusp by a mild groove.
Diagnosis of these cusps is important from the aspect of clinical dentistry because they may be associated with other anomalies and syndromes, or the elevation of the cusp sooner or later becomes damaged and produces a secondary pathology that manifests itself as pulpitis, periodontitis and periostitis and many other serious consequences.  As a result of the malocclusion of the teeth, complications can develop like irregular development of the root or the tooth becomes irregularly positioned and loosens. From an anthropological point of view, the significance of the study of these cusps is that their frequencies differ from population to population.
Most of the reported publications of dens evaginatus are on the first and second permanent molars.  There are no references of dens evaginatus occurring on the maxillary third molars. Therefore, the aim of this article is to present a development of dens evaginatus in a maxillary right third molar associated with anomalous multiple cusps, thereby being an unusual occurrence.
Normal anatomy of the maxillary third molar
All maxillary third molars show more variation in development than any of the other teeth in the mouth. It can vary considerably in size, contour and relative position to the other teeth. It is seldom well developed as the maxillary second molar, to which it often bears resemblance. The third molar supplements the second molar in function and its fundamental design is similar. The crown is smaller and the roots are shorter as a rule, with the inclination toward fusion with the resultant anchorage of one tapered root.
The occlusal aspect of a typical maxillary third molar presents a heart-shaped outline. The lingual cusp is large and well developed and little or no distolingual cusp is evident, which gives a semicircular outline to the tooth from one contact area to the other. Three functioning cusps of this tooth are two buccal and one lingual. The occlsual aspect of this tooth usually presents many supplemental grooves and many accidental grooves, unless the tooth is very much worn.
The third molar may sometimes show four cusps form. This type may have a strong oblique ridge, a central fossa and a distal fossa, with a lingual developmental groove similar to that of the rhomboidal type of second molar. In most instances, the crown converges more lingually from the buccal areas than the second molar does, losing its rhomboidal outline. 
| Case Report|| |
A 56-year-old male patient reported to a private dental practitioner complaining of root remnants in the lower arch. The family and medical history were non-contributory. On intraoral examination, no abnormalities of soft tissues were found. The patient had a moderate level of oral hygiene and mild gingivitis. On detailed dental examination, the maxillary right third molar exhibited different unusual morphology. It consists of anomalous supernumerary cusps (a total of six) along with a prominent central projection of the cusp on the occlusal surface [Figure 1]. Each cusp was separated by deep developmental grooves. An accessory central cusp was situated exactly in the center, surrounded by three buccal cusps and three lingual cusps resembling the shape of "flower" [Figure 2]. The projection of the central cusp was 3.5 mm × 4 mm in width, 5 mm in height with a rhomboid base. The tip of the central cusp lies 1 mm above the level of the remaining cusps of the third molar [Figure 3]. All cusps including the central cusp were found to be prominent with no evidence of attrition. Radiographic examination revealed a single, fused root with no pulpal extension into the central cusp [Figure 4]. The detailed description of this case is elaborated in [Table 1]. On the left side, the third molar was congenitally missing. Looking at the literature review and clinical presentation, it was diagnosed that the present case is a morphological variation of the maxillary third molar with accessory central cusp (dens evaginatus) in association with multiple supernumerary cusps. As the patient was not having any problems associated with this tooth, sealing of the deep developmental grooves using pit and fissure sealant was indicated.
|Figure 1: Maxillary right third molar with six cusps and dens evaginatus|
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|Figure 2: Picture of the third molar with cusp names (B - buccal, MB - mesiobuccal, MP - mesiopalatal, P - palatal, DP - distopalatal, DB - distobuccal) and dens evaginatus (yellow arrow)|
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|Figure 3: Cast model showing projection of the central cusp above the levels of other cusps (arrow)|
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| Discussion|| |
The central cusp seen on the occlusal surface of the posterior teeth has been suggested by several descriptions in the English literature, such as "supernumerary occlusal cusp," "dens evaginatus," "premolar odontome," "occlusal tubercle," "accessory central cusp," "tuberculated premolar" and "Leong's premolar." ,,,,,
The central cusp being an accessory cusp is a relatively rare anomaly, also referred to as dens evaginatus composed of enamel and dentin with or without pulp projections. The size, shape and location of this anomaly has wide variations. Dens evaginatus occurs primarily in the people of Asian descent, such as Japanese, Malay, American Indians, Chinese, Thai, Filipinos and Eskimos [Table 2].  The reported prevalence of dens evaginatus in the Asian population is 2-8%.  It has typically a bilateral symmetric distribution with a slight predilection for females. 
|Table 2: Survey of the available studies on prevalence of central cusps (dens evaginatus)|
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The exact etiology of extra cusp formation or abnormal shape is unknown. However, previously, it was said that, genetically, these features are probably due to overactivity of the dental lamina. But, now, it is believed that the PAX and MSX genes are responsible for the abnormal shape of the teeth.  It is stated to develop from an abnormal proliferation and folding of a portion of the inner enamel epithelium and subjacent ecto-mesenchymal cells of the dental papilla into the stellate reticulum of the enamel organ during the bell stage of tooth formation. ,, The resultant formation is defined as a tubercle or supplemental solid elevation on some portion of the crown surface. Current embryological evidence suggests that tooth morphogenesis is characterized by transient signaling centers in the epithelium, consisting of epithelial cell clusters that correspond to the initiation of individual cusps. ,
General features of central cusp
The "central cusp" is a group term as the types of central cusps differ, and there are large differences in the frequency, the symmetric occurrence and the infrequent simultaneous appearance of different cusp forms in one dentition or on one tooth. The traits are connected only through their localization, like they occur on the occlusal surface, inside the tip area of the buccal and lingual cusps on the posterior teeth. 
The dens evaginatus or tubercles of posterior teeth measure, on an average, 2 mm in width and up to 3.5 mm in length. In the anterior teeth, they measure about 3.5 mm in width and 6 mm in length.  In our case, it measured 3.5 mm × 4 mm in width and 5 mm in length. Other than the cusp like variable, the size and shape of tubercle of teeth with dens evaginatus, the remaining portion of the crown exhibits normal anatomy. This feature is an additional distinguishing characteristic from the accessory cusp of Carabelli, which when present shows that the associated teeth are often larger than the normal teeth, mesiodistally. Most of the forms of occlusal cusps can be observed on premolar teeth also. In 1955, Lau  distinguished two groups of these cusps. They are cusps grown out of buccal cusps and cusps grown out of the middle of the occlusal surface. They can be smooth, grooved, terraced or ridged.
Central cusp variations and classifications
Different authors have described the central cusps in different forms on the premolar, molar, incisor and canine teeth. Lau,  Merrill  and Oehlers et al. classified central cusp present on the occlusal surface of molar teeth as dens evaginatus. Pedersen  in 1949 described the central tubercle as "a peculiar enamel pearl-like cusp on the occlusal surface" on the right upper molar of an Eskimo from Greenland. Kirveskari et al., analyzed bulging of the lingual aspect of the buccal cusps on molars, similar to that on premolars.  The third molar was the least affected, and the maxillary first molar and the second premolar were the most commonly affected. Marcsik and Kocsis  in 1986 examined 106 upper and 86 lower molars of the 31 skulls, and found that bulging of the lingual aspect of the buccal cusps occurred on eight maxillary molars (4.16%). Occlusal enamel pearl was noticed on two lower molars. Recently, Nagarajan et al., reported the occurrence of an accessory central cusp in both maxillary deciduous second molars.  A similar occurrence of central cusp involving the maxillary deciduous left second molar was reported by Nirmala et al. in 2011. 
Kocsis et al. in 2002 studied the occlusal central cusps on the different tooth types and designed a classification system consisting of eight types [Table 3].  Schulge  categorized the dens evaginatus of posterior teeth into five types based on the location of the tubercle [Table 4]. Later, in 1955, Lau  modified the Shulge's classification and further classified each type of tubercle on the basis of the anatomical shape as four variations [Table 5]. Oehlers  identified the evagination according to the pulp contents within the tubercle by examining the histological appearance of the pulp using the decalcified serial sections of extracted teeth with dens evaginatus. These categories are listed in [Table 6] along with their percentage of occurrence.
|Table 4: Classification of dens evaginatus of the posterior teeth based on the location of the tubercle|
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Occurrence of supernumerary cusps indicates associated anomalies or syndromes. Development of central cusps on both premolars and molars has been reported in lobodontia, a syndromic disease characterized by an unusual triad such as microdontia, taurodontia and dens invaginatus. , Another case was described in a 5-year-old child from the 15 th century as a variant of the Ekman-Westborg-Julin syndrome, but dens evaginatus is not characteristic.  A case of lobodontia was also reported by Kocsis et al. in 1994.  In the permanent dentition of a 16-year-old boy, the anomaly affected practically all the teeth, including irregular tooth form, hypodontia, delayed tooth eruption and diminished tooth size. On the occlusal surface of the tooth, a large central cusp was diagnosed, surrounded by more than 10 smaller cusps. The large occlusal cusp was separated from the smaller cusps by a deep groove. The present case was similar to the case reported by Kocsis et al.,  with a difference in the number of cusps.  The central tubercle was surrounded by six smaller cusps, including three buccal and three lingual cusps.
The presence of this additional extension of the tooth structure may pose various dental problems to clinicians, such as development of caries in the pits or deep developmental grooves between the accessory cusp and the tooth, sensitivity or devitalization of the tooth due to fracture or attrition of the protruded portion of the cusp that has pulpal extension, premature tooth contact that leads to occlusal interference and habitual posturing of the jaw.
The occurrence of this trait can also be used in descriptions of recent and paleodontological forms of the human dentition. The central cusp forms may be referred to as "non-metric" traits and can be used in the examination of population history. 
Although occurrence of central cusp is rare, its presence may complicate the maintenance of daily routine oral health care. Pits and grooves surrounding the cusps are highly susceptible to caries. If premature contact and occlusal interferences are present, the premature contact should be removed to prevent habitual posturing of the jaws. Patients with additional tooth projections should be placed under routine and periodic dental surveillance, which includes monitoring of the degree of attrition and tooth vitality. The deep grooves and pits surrounding the cusps should be sealed with pit and fissure sealant to prevent the occurrence of caries.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]