|Year : 2014 | Volume
| Issue : 1 | Page : 30-34
Pericoronal radiolucency associated with an impacted premolar tooth
Ulkem Aydin1, Ufuk Ates2, Burcu Senguven3
1 Department of Dentomaxillofacial Radiology, Baskent University, Ankara, Turkey
2 Department of Oral and Maxillofacial Surgery, Baskent University, Ankara, Turkey
3 Department of Oral Pathology, Gazi University, Ankara, Turkey
|Date of Web Publication||2-Jun-2014|
11 Sokak No - 26, Bahcelievler, Ankara
Source of Support: None, Conflict of Interest: None
The mandibular second premolar is highly variable developmentally. Agenesis, abnormal tooth germ position, distal inclination of the developing tooth, and impaction are among the reported developmental anomalies. Detection of pathologic lesions associated with an impacted tooth usually requires removal of the tooth and the lesion. The purpose of the present report was to describe the radiographic and histopathologic features of a case of pericoronal radiolucency associated with an impacted mandibular premolar tooth.
Keywords: Dental anomaly patterns, hyperplastic follicle, impacted tooth
|How to cite this article:|
Aydin U, Ates U, Senguven B. Pericoronal radiolucency associated with an impacted premolar tooth. J Oral Maxillofac Radiol 2014;2:30-4
|How to cite this URL:|
Aydin U, Ates U, Senguven B. Pericoronal radiolucency associated with an impacted premolar tooth. J Oral Maxillofac Radiol [serial online] 2014 [cited 2019 Apr 25];2:30-4. Available from: http://www.joomr.org/text.asp?2014/2/1/30/133567
| Introduction|| |
The mandibular second premolar is highly variable developmentally. Agenesis, abnormal tooth germ position, and distal inclination of the developing tooth are among the reported developmental anomalies. ,,, In addition, the second most frequently impacted tooth was found to be the mandibular second premolar, excluding third molars, in some populations. 
Treatment options for impacted teeth include observation, intervention, relocation, and extraction.  Selection of the appropriate treatment option depends on the underlying etiological factors, degree of impaction, position and location of the impacted tooth, space requirements, need for primary molar extractions, and root formation of the impacted premolar. Factors such as the patient's medical history, dental status, oral hygiene, occlusal relationship, and attitude toward and compliance with treatment will also influence the choice of treatment option.  On the other hand, detection of pathologic lesions associated with an impacted tooth usually requires removal of the tooth and the lesion. 
The odontogenic tissue around the impacted teeth has the propensity to differentiate into a wide variety of pathological lesions and some of them present as pericoronal radiolucencies. Among the most frequently encountered of these is the dentigerous cyst.  Other pathologic entities such as dentigerous cyst, odontogenic keratocyst, unicystic ameloblastoma, and ameloblastic fibroma may also present as pericoronal radiolucencies.  A hamartomatous lesion associated with some impacted tooth is the hyperplastic dental follicle.  In some instances however, enlargement of the pericoronal space can be detected radiographically but histological examination does not reveal any pathology. Therefore, biopsy of the pericoronal follicular tissue is imperative in every case. 
The purpose of the present report was to describe the radiographic and histopathologic features of a case of pericoronal radiolucency associated with an impacted mandibular premolar tooth.
| Case Report|| |
A systemically healthy 16-year-old female patient was admitted to our clinic for a routine check-up. Patient history revealed that she had orthodontic treatment and at that time, her orthodontist told that she has an impacted tooth. As the tooth did not interfere with orthodontic treatment and as she did not have any complaints, extraction was not recommended at that time. Extraoral examination did not reveal any abnormality. On intraoral examination, absence of both mandibular second premolar teeth was evident.
A panoramic radiograph was made in order to evaluate the impacted tooth and a pericoronal radiolucency associated with the impacted right mandibular second premolar tooth was detected. The boundary of the pericoronal radiolucency was distinct but not corticated, and had a diameter of approximately 0.5 cm. The impacted tooth was located horizontally at the level of the roots of the right mandibular first molar, first premolar, and canine teeth, and distally directed orientation of the tooth crown was evident [Figure 1].
|Figure 1: Panoramic radiograph revealing the impacted right mandibular second premolar tooth and the associated pericoronal radiolucency|
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Review of the patient records revealed that a panoramic radiograph was made four years ago, just before the orthodontic treatment, and another one was made two years ago, during the treatment. The initial radiograph showed the right mandibular deciduous second molar tooth, and the incomplete crown of the right mandibular second premolar tooth that was pointing distally. The pericoronal space of the tooth was normal. On the left mandibular side, the second premolar tooth was missing and the mesial root of the deciduous second molar tooth was resorbed [Figure 2]. On the panoramic radiograph made two years ago, the crown formation of the right mandibular second premolar tooth was almost complete and a slight enlargement of the follicular space was seen [Figure 3].
|Figure 2: The initial radiograph showing the incomplete crown of the right mandibular second premolar tooth and the normal pericoronal space|
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|Figure 3: The panoramic radiograph showing the almost complete crown of the right mandibular second premolar tooth and a slight enlargement of the follicular space|
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A cone beam computed tomography scan was requested in order to determine the exact position of the impacted tooth. Examination of the axial, coronal, and cross-sectional images revealed that the right mandibular second molar tooth was obliquely impacted with its crown lingually and the root buccally at the level of the middle thirds of the right mandibular first molar and first premolar teeth. The crown of the impacted tooth was neighbouring the mesial root of the right mandibular first molar tooth and the apical portion of the impacted tooth was close to the root of the right mandibular first premolar tooth. In addition, the root of the impacted tooth was in contact with the superior border of the mandibular canal and the root apex of the tooth was located just above the mental foramen. A radiolucent, smooth contoured but uncorticated rounded lesion with 3.4 mm at its greatest diameter was detected surrounding the crown of the impacted tooth. The root formation of the impacted tooth was almost complete but the apex of the tooth was not closed yet [Figure 4]. The differential diagnosis was enlarged follicle and dentigerous cyst. The patient was then referred for surgical operation.
|Figure 4: CBCT images. Obliquely impacted tooth with its crown lingually and the root buccally at the level of the right mandibular first molar and first premolar roots (upper left). Three-dimensional reconstruction showing the impacted tooth (upper right). The open root apex of the tooth located just above the mental foramen (lower left). The radiolucent, smooth-contoured but uncorticated lesion surrounding the crown of the impacted tooth (lower right)|
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Full thickness mucoperiosteal flap reflection on the buccal and lingual sides and bone exposure was accomplished. Bone over both the crown and the root apex was removed. A straight elevator is placed in the groove that was prepared using a rounded bur and the tooth was removed lingually through the bone window. Mental nerve and mental foramen were preserved using a Farabeuf retractor; lingual flap and lingual nerve were preserved with the help of a periosteal elevator. Follow-up appointments held one day and 7 days after surgery showed that healing was uneventful without any neurosensory deficit.
On macroscopic examination, the specimen was a soft tissue material attached to a premolar tooth [Figure 5]. On hematoxylin and eosin staining, numerous odontogenic epithelial rests were seen on a mixoid connective tissue that has a minimal mononuclear inflammatory cell infiltration [Figure 6] and [Figure 7]. The definitive diagnosis was hyperplastic dental follicle.
|Figure 6: Fibro-myxoid follicle connective tissue containing hyperplastic dental epithelium remnants (arrow) (hematoxylene-eosine)|
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|Figure 7: Squamous odontogenic epithelium (large arrow) and abundant number of epithelial rests in the connective tissue (arrow) (hematoxyleneeosine, x100)|
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| Discussion|| |
Dental anomaly patterns (DAP) are described by Peck  as "associated dental abnormalities that are observed together much more frequently than can be explained by chance alone." Unilateral agenesis of mandibular second premolar, distal angulation, and delayed development of the unerupted contralateral second premolar is now considered as one of these dental anomaly patterns. ,, In the case presented, all the mentioned features were evident on the panoramic radiograph made when the patient was 12 years old. Hence, the case presented is an example of DAP. In addition, the mesiodistal diameters of the incomplete crowns of the third molars were shorter than the erupted molars.
One of the treatment options for the management of mandibular second premolar impaction is to uncover the tooth surgically and to move it into the arch by orthodontic treatment.  In the present case, the need for primary molar extractions due to the root resorption of the primary left second molar, agenesis of the left second premolar, and incomplete root formation of the impacted premolar were probably the factors that did not permit surgical exposure and orthodontic alignment of the tooth at the time of orthodontic treatment.
Observation is another option for the management of impacted teeth.  However, our literature research did not reveal any adopted protocol for the radiographic assessment of impacted teeth. In the case presented, the patient had an initial panoramic radiograph and another one made at the end of the orthodontic treatment, made with two-year interval. Two years later, she admitted to our clinic for a routine check-up and radiographic examination revealed the pericoronal radiolucency associated with the impacted tooth.
Extraction of impacted premolars may be challenging. Radiographic examination plays a major role in planning the surgical procedure. Knowing the position of the impacted tooth is very important in planning the incision.  In the case presented, cone beam computed tomography examination revealed the exact position of the tooth besides close proximity to the mental foramen and mandibular canal, and the lingual approach was taken.
When the diameter of a pericoronal space is greater than 2.5 mm on an intraoral radiograph and greater than 3 mm on a panoramic radiograph, pathosis is suggested, and if the radiopaque border, representing the surrounding cortical plate, is not well-defined, this is also a sign of pathologic change.  The differential diagnosis of pericoronal radiolucencies include enlarged follicular space, dentigerous cyst, odontogenic keratocyst, unicystic ameloblastoma, adenomatoid odontogenic tumor, calcifying cystic odontogenic tumor, and ameloblastic fibroma. Other rare lesions such as odontogenic fibroma, odontoma in premineralized stage, and odontogenic fibroma may also be encountered as pericoronal radiolucencies. , However, the most likely diagnoses include dentigerous cyst, keratocystic odontogenic tumor (odontogenic keratocyst), unicystic ameloblastoma, ameloblastic fibroma, and enlarged follicular space. 
Keratocystic odontogenic tumor occurs in a wide age range, but most of them develop during the second and third decades and has a slight male predominance; more than half of them are in the ramus region. Although the lesion may surround the tooth pericoronally, it is connected to the tooth at a point apical to the cementoenamel junction. , Therefore, the demographic and radiographic features of the case presented was not consistent with odontogenic keratocyst.
Unicystic ameloblastoma is a rare variant of ameloblastoma and it usually occurs in a young age group, with about half of the cases occurring in the second decade of life. Most of them are located in the mandible. Cases associated with tooth impaction can be encountered, the mandibular third molar being most often involved.  Due to the rarity of the lesion, inconsistency with the usual location, and relatively younger age of our patient, unicystic ameloblastoma was not ranked high in the differential diagnosis.
Ameloblastic fibroma mostly occurs during the period of tooth formation with an average age of 15 years. Radiographically, ameloblastic fibroma usually appears as unilocular or multilocular radiolucency with well-defined and corticated borders in the premolar-molar area of the mandible. The lesion may be located in a follicular relationship with an unerupted tooth. , Although the lesion lacks a well-defined and corticated border in the present case, ameloblastic fibroma may be included in the radiographic differential diagnosis.
The dentigerous cyst is the most common pericoronal radiolucency. The teeth most frequently affected are the mandibular third molars, the maxillary canines, and the mandibular premolars.  The cyst attaches to the crown of the impacted tooth at the cementoenamel junction. Dentigerous cysts typically have a well-defined cortex. In the case presented, the features of the lesion were in line with the reported characteristics of the dentigerous cyst, except a well-defined cortex. Regarding the high frequency of this pathosis associated with impacted teeth, dentigerous cyst was also considered in the differential diagnosis. White  states that one of the most difficult differential diagnoses to make is between a hyperplastic dental follicle and a small dentigerous cyst. The size of the pericoronal radiolucency can be helpful in distinguishing between the two and if the diameter of the radiolucency exceeds 5 mm, a dentigerous cyst is more likely. ,
Hyperplastic dental follicle is an unusual hamartomatous lesion. The mechanisms causing hyperplastic dental follicle are not definitively explained. The condition may involve just one tooth or may be associated with multiple teeth.  Downregulation of matrix metalloproteinases in hyperplastic dental follicles are suggested to result in abnormal tooth eruption.  In the present case, the distal angulation of the tooth seems to be responsible for impaction of the tooth. Nevertheless, further studies may be able to shed light on the association of this DAP with hyperplasia of the dental follicle.
Histopathologically, hyperplastic dental follicle differentiates from dentigerous cyst with the absence of significant lining epithelium. Although surface was partially lined by single-layered, reduced enamel epithelium in our case, this feature was not sufficient to diagnose the lesion as a dentigerous cyst. Odontogenic fibroma, both WHO type or simple type, is another lesion to be histopathologically differentiated from hyperplastic dental follicle. One third of the odontogenic fibromas are associated with an unerupted tooth. However, there were neither any stellate-shaped fibroblasts on connective tissue nor calcificated foci in the case presented. In addition, odontogenic epithelial rests were not in narrow cord shape as in WHO-type odontogenic fibroma in our case. 
In conclusion, awareness of dental anomaly patterns may change the radiographic interpretation process, diagnosis, and subsequent treatment planning significantly. The clinicians should investigate all teeth that fail to erupt at the expected time, and initiate appropriate assessment and management of suspected lesions.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]