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 Table of Contents  
Year : 2017  |  Volume : 29  |  Issue : 1  |  Page : 78-81

Bilateral protostylids and parastyles associated with hypodontia of maxillary lateral incisor: Report of two rare clinical cases

1 Department of Oral Medicine and Radiology, Al-Ameen Dental College and Hospital, Bijapur, Karnataka, India
2 Department of Oral and Maxillofacial Surgery, Al-Ameen Dental College and Hospital, Bijapur, Karnataka, India

Date of Submission12-Jul-2016
Date of Acceptance28-May-2017
Date of Web Publication04-Aug-2017

Correspondence Address:
Sulabha A Narsapur
Department of Oral Medicine and Radiology, Al-Ameen Dental College and Hospital, Bijapur - 586 108, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jiaomr.JIAOMR_78_16

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Molars and premolars of maxilla and mandible infrequently exhibit a supernumerary inclusion or an anomalous cusp on their buccal surfaces which is known as a paramolar tubercle. When supernumerary cusps are associated with maxillary molars and premolars, they are termed as parastyle, and when associated with mandibular molars and premolars they are known as protostylid. This rare entity occurs singly in permanent dentition and is seen on the mesial half of the molars. The present paper reports two rare cases of bilateral paramolar tubercle in mandibular first molars and maxillary second molars associated with hypodontia of maxillary lateral incisor in both the cases. One paramolar tubercle in the mandibular molar was associated with accessory separate root on the distal aspect.

Keywords: Bilateral, parastyle, protostylid

How to cite this article:
Narsapur SA, Choudhari S. Bilateral protostylids and parastyles associated with hypodontia of maxillary lateral incisor: Report of two rare clinical cases. J Indian Acad Oral Med Radiol 2017;29:78-81

How to cite this URL:
Narsapur SA, Choudhari S. Bilateral protostylids and parastyles associated with hypodontia of maxillary lateral incisor: Report of two rare clinical cases. J Indian Acad Oral Med Radiol [serial online] 2017 [cited 2022 Aug 18];29:78-81. Available from: https://www.jiaomr.in/text.asp?2017/29/1/78/212093

   Introduction Top

Evolution and development has brought high degree of morphological changes and variations in human jaws and teeth of both dentations.[1],[2] These variations or changes may be in the form of supernumerary inclusions, anomalous cusp, or increase in the number of roots, etc., Paramolar tubercle is one such morphological variation. Paramolar tubercle is a term referred to any stylar anomalous cusp, supernumerary inclusion, or eminence occurring on the buccal surface of upper and lowers premolars and molars.[3] When this entity occurs in maxillary molars and premolars, they are referred as “parastyle” and when they occur in mandibular teeth they are termed as “protostylid.”[4]

Paramolar tubercle is relatively rare entity. Prevalence of parastyle is approximately 0.4–2.8% in the upper second molar, 0–0.1% in first molars, and 0–4.7% in the maxillary third molars among the given population.[1] When they occur in the mandible, they are often seen with the third molars.[5] Not much information is available on sex predilection. There is little information on its prevalence among the races as its occurrence is very low. Available studies show higher prevalence in southwestern Indian population.[1],[3],[6] Hence, this has become a frequent subject in anthropology and phylogenetic studies.[5],[7] These rare morphological variations provide a cognizance into dental evolution, genetics, and development research. These unique entities also play significant role in individual’s forensic identification.[1] The present article reports bilateral protostylids in mandibular first molar on the metacones in permanent dentition of a young Indian female with an additional separate root on the distal side of right protostylid and bilateral parastyles in maxillary second molars in an adult Indian male patient. Both the cases were associated with hypodontia of maxillary lateral incisor making the present article rarest of its kind.

   Case Reports Top

Case 1

A 28-year-old female reported with the chief complaint of decayed tooth in the right and left lower back region. Her family history and medical history were noncontributory. No abnormality was detected on extraoral examination. Intraoral examination revealed a total of 27 teeth with one retained right maxillary deciduous canine. Right maxillary lateral incisor was missing and its place was occupied by permanent canine. The left lateral incisor was peg shaped. All the third molars were absent.

Bilateral protostylids were noted on the right and left mandibular first molar [Figure 1]. Protostylid on the left molar was located on metacone (distobuccal cusp), and extended till the occlusal surface of the tooth. It was conical in shape with its base blending with the cervical portion of the buccal surface and a flat free cusp apex. This cusp was separated from the tooth by deep developmental grooves. Caries was noted on the occlusal surface of the tooth. The tooth was tender on percussion. The protostylid on the right side was also located on the metacone, extending till occlusal surface. It was also conical in shape with its base blending with the cervical portion of the buccal surface and a flat free cusp apex. It was also separated from the tooth by deep developmental grooves [Figure 2]. Caries was noted on the occlusal surface involving the developmental grooves of the protostylid.
Figure 1: Right and left prostylids on mandibular first molars

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Figure 2: Casts showing the right and left protostylids with deep developmental groves

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Supplementation by intraoral periapical radiograph and panoramic view revealed radio-opaque shadows in the crown portion extending from occlusal surface till middle third superimposing on normal tooth structures on both sides [Figure 3] and [Figure 4]. Caries was approaching the pulp in the left first molar associated with protostylid. Intraoral periapical radiograph (IOPA) of the right first molar associated with protostylid showed three matured roots, one on mesial side and two on distal sides. Because both the roots in the distal side were located in the same buccolingual plane, superimposition of both roots was noted. Right maxillary lateral incisor along with all the third molars were absent. Patient was advised endodontic therapy in the left first molar. Patient did not return for the treatment and was lost to recall.
Figure 3: IOPA of the right side showing radio-opaque shadow in crown and two roots in distal aspect

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Figure 4: Panoramic view showing dental anomalies

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Case 2

A 40-year-old male reported for routine oral check-up. His family, medical, and dental histories were not significant. No abnormality was detected on extraoral examination. Intraoral examination revealed a total of 28 teeth with absence of three third molars and the left lateral incisor. Bilateral parastyles were observed on the maxillary right and left second molars. Parastyle in the left second maxillary molar was placed on paracone. It was almost conical in shape with its base arising below gingival margin and the free cusp apex 1–2 mm short of the occlusal surface. Parastyle on the right side was located on the metacone. It was triangular in shape with its base arising below the gingival margin and a rounded free cusp apex, 1–2 mm short of the occlusal surface. There appeared another triangular elevation on the paracone with its base arising below the gingival margin extending only till the middle third of the buccal surface with caries affecting its apex. This was separated from the adjacent parastyle of metacone by a developmental groove. Both the parastyles were separated from the tooth by deep developmental grooves. This could be case of double paramolar tubercle which is rare [Figure 5] and [Figure 6]. Because the patient was not interested in any kind of the treatment or radiographs, we could not proceed with the case.
Figure 5: Bilateral parastyles in the maxillary second molars

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Figure 6: Casts showing the right and left parastyles

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   Discussion Top

Protostylids and parastyles are supernumerary inclusions or cusp occurring on the buccal surfaces of the lower molars and upper molars, respectively.[3] These are rare entities in the modern hominids.[2] These are the cingulum derivatives, and hence, should not be classified as anomalous structures, as they represent normal morphological variation in human dentition. Paramolar tubercle is expressed on the mesiobuccal cusp (paracone), and in rare instances it is seen on distobuccal cusp (metacone). Very rarely double cusp may be seen. These occur bilaterally in deciduous dentition but unilaterally in the permanent dentition.[2],[3] Case 1 documents bilateral protostylids in mandibular first molar on the metacone, which is a rare phenomenon. Case 2 documents parastyles in the maxillary second molars on both paracone and metacone. Right second molar in case 2 may be a case of double parastyles as it had two triangular elevations with their bases arising below the gingiva and apex of one tubercle lost due to caries leaving behind only the lower half.

Etiology of this extra cusp formation is unknown, however, it may be related to the over activity of dental lamina. However, at present it is believed that PAX and MSX gene are responsible for abnormal shape of the tooth.[8] The PAX family also plays key roles in several malignancies such as rhabdomyosarcoma and tumors of neural crest origin.[9] However, literature search has not shown any link of between these protostylids and carcinogenesis. Some studies reveal that paramolar tubercle arise during morphogenesis from the accessory enamel knot.[3] The paramolar tubercle has continuous variation in its size and pattern. Its expression is low and occurrences vary from a pit, groove delineation, furrow, prominence, cusp to surface irregularities, which is the most common form.[5] The varied clinical presentation was best described by Katich and Turner in 1974.[1],[3]

0- Buccal surface of cusp 2 and 3 are smooth*

1- A pit present in or near buccal groove between cusp 2 and 3

2- Small cusp present with attached apex, usually on cusp 2

3- Medium-sized cusp present with free apex anywhere on the buccal surface

4- Large cusp present with free apex anywhere on the buccal surface

5- Very large cusp present with free apex anywhere on the buccal surface

6- Free peg-shaped crown is present, attached to the third molar root.

*Cusp 2 – paracone/mesiobuccal and cusp 3 – metacone/distobuccal cusp. In the present cases, grade 3 was noted.

Because the occurrence of paramolar tubercle is rare, not much information is available in literature about its morphological characteristics, its relationship with root, and root canal of associated teeth.[3] Kustaloglu suggested that if paramolar cusp was large it might have separate root, however, it cannot be said with certainty that all well-developed lobulated cusp have root with their root canal while nonlobulated tubercles do not.[4] Bolk reported paramolar tubercles of maxillary molar tended to unite at the root whereas paramolar tubercle of the mandibular molars tended to possess their own roots.[3] This root is called “Radix Paramolaris” or mesiobuccal root. Radix Paramolaris is seen buccal to the mesial root. It has two forms as separate and nonseparate. It may be mature root with root canal to short conical extension.[10] Bolk also stated that paramolar root was often present without tubercle in lower molars.[3] In the present case, three paramolar tubercles were without any roots, however, in the right mandibular paramolar tubercle, mature separate root was seen. In very rare instances protostylids are located on distobuccal cusp, as in the present case, and hence accessory root was also seen in distal aspect.

Literature has scanty reports on this trait. Nirmala et al.[8] reported three cases of paramolar tubercle in primary dentition and one case of unilateral occurrence in permanent dentition. Lakshman[1] reported two rare unilateral cases of parastyle in permanent dentition. Nayak[3] reported canal configuration of a paramolar tubercle with the help of spiral computed tomography. Omal[11] reported a case of paramolar tubercle in maxillary first molar. Our search on bilateral paramolar tubercle in permanent dentition did not show any case reports. Unlike all other previous reports that had only unilateral presentation in permanent dentition, our both cases had bilateral presentation of paramolar tubercle, and both the cases were associated with hypodontia involving maxillary lateral incisor, which is a very rare presentation and makes this article unique. Association of these two entities has to be studied as both cases presented with the same clinical scenario. Occurrence of bilateral paramolar tubercle and hypodontia of lateral incisor in both the cases may be a coincidental finding because literature search did not show such traits. However, literature search has shown traits of shovel-shaped incisors, lingual tubercle, carabelli’s trait, and protostylid of molars in a Chinese population.[12]

Presence of these tubercles do not provide any functional adaption such as enlarging the occlusal surface because these are present on the buccal surface and do not occlude or enter any function.[1] They do not occlude against any cusp or groove of the antagonist tooth. Hence, these may not lead to occlusal disharmony. Radiographs such as intraoral periapical and panoramic views do not provide much information on these entities due to overlap with normal tooth anatomy.[3] Use of advanced modalities such as computed tomography, spiral computed tomography, or cone-beam computed tomography can give insight on this rare trait regarding its root, root canal morphology, and its relationship with the associated tooth. This helps in proper planning of the treatment of the tooth which is associated with protostylid.[3],[13],[14]

Apart from anthropological interest, these are clinically important as they influence the various treatment modalities in various disciplines of dentistry. These can lead to various clinical implications such as difficulty in the placement of crowns, interference with cementation of brackets, bandings, and alignment of wires during orthodontic treatment. These may be potential sites for plaque retention comprising the periodontal health of the tooth and increase the chances of localized gingivitis and periodontitis. Groves are likely sites for developing caries, as seen in the present report. These tubercles may pose special problem in endodontic therapy and cause root canal failures.[3],[10],[15]

   Conclusion Top

To conclude, these are relatively uncommon traits and its bilateral presentation in permanent dentition is still a more uncommon phenomenon. Its association with hypodontia needs further studies. As PAX and MSX genes are believed to be responsible for this, their link with carcinogenesis needs further studies. By reporting data on this rare trait about its frequency and expressivity, this rare dental trait would be more explored and would be of more value in near future in various researches.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Lakshman AR, Kannepady SK, Kalkur C. Parastyle: Report of two rare cases. Front Clin Med 2014;1:1-4.  Back to cited text no. 1
Nabeel S, Danish G, Hegde U, Mull Paras. Parastyle: Clinical significance and management of two cases. Int J Oral Maxillofac Pathol 2012;3:61-4.  Back to cited text no. 2
Nayak G, Shetty S, Singh I. Paramolar tubercle: A diversity in canal configuration identified with the aid of spiral computed tomography. Eur J Dent 2013;7:139-43.  Back to cited text no. 3
Kustaloghi OA. Paramolar structures of upper dentition. J Dent Res 1962;41:75-83.  Back to cited text no. 4
Gaspersic D. Morphology of most common form of protostylid on human lower molars. J Anat 1993:182:429-31.  Back to cited text no. 5
Carolina RF, Reddy M. Paramolar tubercle in the left maxillary second premolar: A Case report. Dent Antropol 2006;19:65-9.  Back to cited text no. 6
Gaspersic D. Identification of protostylid. Anthrop Anz 1997;55:43-53.  Back to cited text no. 7
Nirmala SVSG, Gaddam KR, Vimaladevi P, Nuvvula S. Protostylid: A case series. Contemp Clin Dent 2013;4:349-52.  Back to cited text no. 8
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Wang Q, Fang W, Kumar P, Kmar S, Selvin M, Krupinski J. PAX genes in embryogenesis and oncogenesis. J Cell Mol Med 2008;12:2281-94.  Back to cited text no. 9
Nagaveni NB, Umashankar KV. Radix entomolaris and paramolaris in children: A review of literature. J Indian Soc Pedod Prev Dent 2012;30:94-102.  Back to cited text no. 10
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Omal PM, Philipose L, Mathew AL, Nair S, Varghese AK, Babu SS, et al. Parastyle in permanent maxillary first molar tooth: A rare entity. J Indian Acad Oral Med Radiol 2013;25:137-40.  Back to cited text no. 11
Ohishi K, Oshishi M, Takahashi A, Kido J, Uemura S, Nagata T. Examination of roots of paramolar tuberoles with computed tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;88:479-83.  Back to cited text no. 12
Tsai. SJ, King NM. The catalogue of anomalies and traits of permanent dentition of southern Chinese. J Clin Pediatr Dent 1998;22:185-94.  Back to cited text no. 13
Jain P, Ananthnarayan K, Ballal S, Natanasabapathy V. Endodontic management of maxillary second molar fused with paramolar tubercles diagnosed by cone beam computed tomography- Two case reports. J Dent Teheran Univ Med Sci 2014;11:1-7.  Back to cited text no. 14
Desai VD, Sadnani H, Kumar SM, Pratik P. Protostylid: As never reported before- A unique case with variation. J Indian Acad Oral Med Radiol 2016;28:57-60.  Back to cited text no. 15
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]


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