|Year : 2014 | Volume
| Issue : 4 | Page : 280-282
Fourth molar tooth in the mandible: A rare case report
Arathi Karikal1, Arvind Karikal2
1 Department of Oral and Maxillofacial Pathology, A.J. Institute of Dental Sciences, RGUHS, Mangalore, Karnataka, India
2 Department of Oral and Maxillofacial Pathology, A.B. Shetty Memorial, Institute of Dental Sciences, Nitte University, Mangalore, Karnataka, India
|Date of Web Publication||20-Nov-2014|
Department of Oral and Maxillofacial Surgery, A. B. Shetty Memorial, Institute of Dental Sciences, Nitte University, Mangalore - 575 018, Karnataka
Source of Support: No funding or grants received., Conflict of Interest: The authors have written the article purely on academic interest.
Supernumerary teeth are located in the anterior maxilla, mandible and to a lesser frequency posterior region of the mandible. They are classified according to their location and form. Their presence may or may not give rise to a variety of clinical problems. Detection of supernumerary teeth is usually achieved by clinical and radiographic examination. Their management should form part of a comprehensive treatment plan. A fourth molar tooth is a very rare entity in modern humans although prevalent in early humans.
This article presents an overview of odontogenesis; aberrations associated with supernumerary teeth and includes a note on their incidence and prevalence.
Keywords: Distomolar, supernumerary, 4 th molar
|How to cite this article:|
Karikal A, Karikal A. Fourth molar tooth in the mandible: A rare case report. SRM J Res Dent Sci 2014;5:280-2
| Introduction|| |
Vertebrate teeth are specific organs that are mainly used for processing of food and defence; in humans they aid in phonation also. Human adult dentition has four groups of teeth which are sub-divided into incisors, canines, premolars and molars. Each quadrant of the jaw has two incisors, one canine, two premolars, and three molars. Tooth development takes place by mutual inductive interactions between two major cell types: Stomodeal ectoderm and cranial, neural crest-derived ectomesenchyme cells. 
Odontogenesis gets initiated between the 6th and 8th weeks via a series of interactions between odontogenic epithelium and neural crest-derived ectomesenchye in the developing jaws. The odontogenic epithelium and the underlying neural crest derived ectomesenchyme interact reciprocally and sequentially to undergo process of proliferation, histo-differentiation and morpho-differentiation of the tooth germ. ,,,
Permanent dentition, like deciduous dentition arises from dental lamina. The tooth germs that will give rise to the permanent incisors, canines and premolars form as a result of further proliferative activity within the dental lamina at a point where it joins the dental organ of the deciduous tooth germs. This increased proliferative activity leads to the formation of another epithelial cap and associated ectomesenchymal response on the lingual aspect of the deciduous tooth germ to develop completely into a formed tooth.
The molars of the permanent dentition do not have deciduous predecessors, so their tooth germs do not originate in the same way. Instead, when the jaws have grown long enough, the dental lamina burrows posterior, beneath the lining epithelium of the oral mucosa into the ectomesenchyme. This backward extension successively gives off epithelial ingrowths that together with the associated ectomesenchymal response, form the tooth germs of the 1 st , 2 nd and 3 rd molars. Because of this backward extension of the dental lamina into the flattened ramus of the forming mandible, on occasion teeth occur in the bony ramus of the adult mandible. The successional permanent teeth (molar) develop between 20 th week in-utero (1 st molar) & the 5 th year of life (3 rd molar). Aberrations in this pattern of development result in missing teeth or the formation of extra teeth. 
The developmental interactions are mediated by a relatively small number of signalling molecule families, with individual members often acting at numerous stages during the development of these organs.  Deviations in the number of teeth are seen sporadically leading to the formation of excess teeth, which are termed as Hyperdontia or supernumerary teeth. Hyperdontia or supernumary teeth as they are called are defined as teeth that exceed the normal dental formula, regardless of their location and morphology. ,,,
| Case Report|| |
A 21-year-old female was referred to the Department of Oral & Maxillofacial surgery due to the chief complaint of constant pain in relation to lower left side of the mandible. The patient had been managed symptomatically by the local doctor. Clinical examination was not contributory. The full component of adult dentition was visible except for maxillary first molar and pre-molar on the left side, as it had been extracted several years back.
Following a clinical examination, panoramic radiographs were taken. The radiographs revealed the presence of impacted unilateral fourth molar in the mandible. This tooth was a "Disto-molar" located just posterior to the lower third molar [Figure 1]. The teeth had normal morphology; crowns and roots were significantly developed and similar in size. The fourth molar was removed surgically under local anaesthesia. The subsequent follow-ups were uneventful and the patient was relieved of her chief compliant.
|Figure 1: Showing a 4th mandibular molar in the left side of the mandible|
Click here to view
| Discussion|| |
Important changes have taken place in the course of evolution of teeth from fish to reptiles to mammals. These changes can be highlighted as follows:
- Reduction in number of teeth from polydonty to oligodonty
- Reduction in generation of teeth from polyphyodonty to di & monophyodonty
- Increase in morphologic complexity of the teeth from homodonty to heterodonty. 
Supernumerary teeth are most frequently seen in the maxillary anterior and molar regions.  This type of supernumerary teeth can be differentiated based on their different locations in the jaw as follows. Those teeth that occur between or just lingual to the central incisors are referred to as "mesiodens". Those which are seen in the molar area are called "paramolar" teeth; and those that erupt distally to the third molar are "distomolar" teeth. The prevalence of such teeth ranges from 1.2 to 3%.  Supernumerary teeth seen with a normal morphology are referred to as "supplementary teeth", but usually are seen to be more often rudimentary in shape and smaller in size.  The maxilla is a more common site for supernumerary teeth than the mandible according to available literature. , Such supernumerary teeth may or may not erupt into the oral cavity; if they erupt they may cause mal-alignment of the dentition by crowding. In certain case such teeth may be found on routine radiographic evaluation and a decision must be taken on their management. The frequency of supernumerary teeth has been reported as being around 1-2% by various authors. ,, When we take the gender into consideration, such teeth are more frequent in males than females, with an average ratio of 9:2. ,,, The higher presences of supernumerary teeth in males have been seen in studies from other parts of the world also, as a Jordanian study among 152 teenagers show a marked higher incidence of supernumerary teeth in the male subjects with a male to female ratio of 2.2:1.  The prevalence of fourth molars as studied on a Japanese population is 2% and appeared to be more common in black patients with a higher incidence in the maxilla unilaterally. 
| Conclusion|| |
A huge amount of literature is devoted to origin, evolution & organogenesis of teeth, knowledge of which helps us to better understand the regulation of tooth development & their associated pathogenesis. The characteristic dental formula is Incisors 2/2, canines 1/1, premolars 2/2, and molars 3/3 on each side. However there can be number of variations from this formula as in our case where the patient had a fourth molar in the mandible which is a very rare entity in females,  as all available literature points out to a high prevalence of supernumerary teeth in males rather than females and in the anterior maxilla rather than the molar area of the mandible.
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