| Abstract|| |
The author presents a case of submerged carious deciduous molar along with an inflammatory atypical follicular cyst associated with an impacted mandibular second premolar in the right mandible identified through clinical and routine radiological examination including cone beam computed tomography and histopathology. The involvement of submerged deciduous molar with dental caries by itself a rare occurrence and an impacted permanent premolar tooth associated with an infected follicular cyst is still more a rare event.
Keywords: Cone beam computed tomography, dental caries, follicular cyst, impacted molar, mental nerve, surgical planning
|How to cite this article:|
Balaji S M. Submerged mandibular carious deciduous second molar along with an impacted second premolar associated with an atypical inflammatory follicular cyst: A rare case report. Indian J Dent Res 2013;24:775-9
Primary failure of eruption is diagnosed when the unerupted tooth is covered by an intact mucosa and radiographs reveal the tooth to be deeply buried in the jaw bone. Posterior both deciduous and primary teeth are more commonly affected by primary failure of eruption and the involved tooth may have initiated its eruption into the plane of occlusion before submerging in the jaw bones. The involvement may be unilateral or bilateral and compromised primary or permanent teeth have been reported. 
|How to cite this URL:|
Balaji S M. Submerged mandibular carious deciduous second molar along with an impacted second premolar associated with an atypical inflammatory follicular cyst: A rare case report. Indian J Dent Res [serial online] 2013 [cited 2020 Jul 2];24:775-9. Available from: http://www.ijdr.in/text.asp?2013/24/6/775/127634
Developing cysts can occur in any phase of the tooth crown development, from enamel organ to formed tooth crown. Due to the fact that occurrence of developing jaw cysts in two or even three phases of the tooth crown development, they are called follicular cysts.  Benn and Altini have indicated that two types of dentigerous/follicular cysts occur. The first type is developmental in origin and occurs in mature teeth, usually as a result of impaction. The second type is inflammatory in origin and occurs in immature teeth as a result of inflammation from a non-vital deciduous tooth or other source spreading to involve the tooth follicle. 
Recent maxillofacial literature has numerous reports in support of use of cone beam computed tomography (CBCT) over traditional panoramic radiography (OPG) in a dental setting. ,,,, With much low radiation, effective, accurate three-dimensional (3D) multiplanar and cross-sectional views help to reveal the concealed anatomical truth, accurate relationship of structures and otherwise hidden pathologic entities and anatomical variants. 
We report a very rare case submerged carious deciduous molar along with an impacted premolar associated with an atypical inflammatory follicular cyst that was diagnosed based on the clinical, histological and radiological features including CBCT.
| Case Report|| |
The present case report is about a 22-year-old otherwise healthy male who sought surgical treatment for his prognathic mandible. On examination, he had a Class III malocclusion with a unilateral cross bite [Figure 1] erupting third molars and a missing mandibular right second premolar. His medical history was non-contributory to routine dental care. Extra oral examination revealed no swelling, asymmetries, in the head and neck areas. Radiological imaging (OPG and lateral cephalograms) were done to identify the extent of discrepancy and for diagnostic work-up.
|Figure 1: The clinical view of the patient. Note the absence of any evidence of an impacted tooth|
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Apart from the typical orthodontic Class III related abnormalities, OPG revealed an impacted mandibular right second premolar, underlying which was a submerged deciduous second molar. Both structures were overlying each other with the second premolar lying lingually. There was evidence of radiolucency around the crown of the impacted second premolar. The mental foramen was not clearly identifiable [Figure 2]a. The lateral cephalogram revealed a Class III malocclusion with a prominent genial tubercle. There was evidence of distinct radiolucency along the impacted teeth that appeared to overlay each other [Figure 2]b. A CBCT study was carried out to identify the exact orientation of the pathologies and to assess the proximity to the emergence of nerves and mental foramen.
|Figure 2: Conventional imaging studies. (a) Orthopantomogram. Note the submerged deciduous right mandibular second molar and the impacted permanent second premolar, the thickness of bone above the teeth as well as lack of radiolucency. (b) Lateral cephalogram. Note the radiolucency around the impacted teeth|
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In CBCT, a submerged deciduous second molar and permanent second premolar was observed. In sagittal section of the area of interest, radiolucency suggestive of a cyst was found to be in association with the impacted second premolar tooth [Figure 3]a-d and was 0.9 cm in maximum diameter and involved the entire crown and appeared to be attached along its cervical line. The submerged deciduous molar was also in the vicinity of the cyst [Figure 3e-g]. 3D reconstructions confirmed the association and position of the teeth as well as the mental foramen that was very close to the root of the second premolar [Figure 4]a and b.
|Figure 3: Cone beam computed tomography sections in sagittal view. (a and b) Note the extent of the follicular cyst and its extent. (c) Note the involvement of premolar and buccal cortex. (d) Note the lingual cortex. (e) Superio-inferior positioning of impacted teeth. (f) Labiolingual relation of impacted teeth. (g) In coronal section: Note the positioning of teeth|
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|Figure 4: (a) Three-dimensional reconstruction of the case. Note the impacted teeth and the absence of bone superiorly. (b) Cut section showing the cystic cavity|
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Surgery was done under local anesthesia after adequate preparation. On raising the flap, area of bony erosion was visualized on the buccal aspect. Through the window created along the bony erosion, access was gained to the impacted teeth. The window was sufficiently enlarged. It had been planned to bisect the premolar to prevent damage to the mental neurovascular bundles [Figure 5]. On visualizing the teeth, the deciduous molar appeared to be grossly carious [Figure 5], insert]. A pilot drill was done and the molar elevated carefully after sufficient luxation. The premolar was bisected and removed. The soft-tissues surrounding the tooth were curetted and submitted for histopathological examination. The histopathological study revealed an epithelial lining predominantly of 2-3 cell layers in thickness with an underlying inflamed connective tissue wall comprising of chronic inflammatory cells, cholesterol clefts, hemorrhage and extravasated red blood cells. Correlating with clinical, radiological and histopathology, the diagnosis of infected follicular cyst was given [Figure 6] and [Figure 7].
|Figure 5: Removal of the teeth through the buccal window. Note the dental caries in deciduous molar and resorbed root as well as the bisected premolar (insert)|
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|Figure 6: Histopathological section of the cyst. See the thin cystic lining with numerous cholesterol clefts, inflammatory cells along with extravasated red blood cells (H and E, ×10)|
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|Figure 7: Histopathological section of the cyst. See the thin cystic lining with cholesterol clefts, inflammatory cells along with extravasated red blood cells (H and E, ×40)|
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The CBCT sections were restudied for evidence of bony erosion as well as for the dental caries (DC). Evidence of cortical bone erosion at focal points had been identified at certain areas, both buccally [Figure 3]f and lingually [Figure 3]e. The relative radiolucency suggesting poor mineralization in teeth and the adjacent area identifies it as the potential route of spread. In the same sections, at the midpoint of the molar, radiolucency suggestive of DC in the impacted deciduous molar was observed [Figure 3]e and [Figure 8].
|Figure 8: Cone beam computed tomography section. Note the dental caries as well as the break in both cortex|
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The healing was uneventful. After 12 weeks of this minor surgery, patient underwent Bilateral Sagittal split Osteotomy with genial reduction and simultaneous orthodontic therapy. The patient is still under active orthodontic therapy and follow-up.
| Discussion|| |
The clinical diagnostic algorithm for this patient is very limited. A submerged tooth is a retained deciduous tooth which is frequently a molar with its occlusal surface at a lower level than the adjoining permanent teeth. However, in the adjoining areas, eruption and alveolar growth continue resulting in the submergence of the deciduous tooth. Documentation of severe infra-occlusion of deciduous molars is infrequent in children affecting only 2.5-8.3% of individuals.  Moreover, cases of impacted primary molars positioned inferior to the succeeding premolars has been as single cases only. This report herewith adds on to literature this rare occurrence. In the current case, the permanent second premolar may have developed in a superior and lateral position with respect to the crown of the impacted primary mandibular second molar as mentioned in the literature. ,,,
These teeth are prone to DC when they were in infra-occlusion as seen in our case. The impacted molar was noted to be in contact with the oral cavity through the superior weak bone and to the periodontal apparatus through the bicortical perforation which should have provided the route for the infection to spread to the impacted molar. Only one case of an impacted deciduous molar with DC has been described earlier in maxillary jaw without the involvement of the permanent dentition. Studies have reported that following factors need to be associated for DC to be initiated: (1) Presence of acidogenic bacteria (2) substrate for the bacteria (3) other factors such as saliva.  In the present case scenario, the small cortical perforation could be a cause of introduction of bacteria through periodontal system. As could be inferred from [Figure 2]a, there is strong evidence to indicate the presence of bone overlying the impacted teeth. However, 3D reformatted CBCT indicates that the bone in the region is not of sufficient quality or not continuous. Hence, the oral microflora would have reached the tooth through the periodontal system. The cystic fluid content is rich in protein  and would act as a perfect substrate to produce biofilm that is a prerequisite for caries initiation. Cariogenic bacteria Streptococcus mutans and Lactobacillus species thrive in this biofilm and leads to cavitations.
In view of the terminology and the possibility of other inflammatory pathways reaching the tooth follicle, like from the adjacent infected primary teeth, the follicular cyst in the current case might be more appropriately described as an atypical inflammatory follicular cyst rather than dentigerous cyst, occurring in a tooth with primary eruptive failure. This case shares etiological, radiological and histopathological features with inflammatory follicular cyst in an impacted permanent premolar with the source of origin of infection from the adjacent carious primary molar. The inflammatory exudate would have resulted in the separation of the reduced enamel epithelium from the enamel with resultant cyst formation. Thus, this case seems to represent an unusual inflammatory follicular cyst and indicate that the DC in the submerged tooth, as a result of eruption failure, has the potential to induce pathology due to infection in the neighboring tooth, which could subject the patient to compounding risk. 
The differential diagnosis included an enlarged infected dental follicle which was ruled out on the fact that the pericoronal radiolucency was more than 2.5 mm in greatest diameter. Other pathologies of inflammatory origin like radicular cyst of the submerged carious deciduous molar was negated as there was no periradicular involvement and grossly the cyst was attached at the cementoenamel junction of the impacted mandibular second premolar. ,
The clinical profile of the discussed case was that of a Class III malocclusion with a prognathic mandible and a cross bite. As mandibular second premolars are most often missing tooth  in the permanent dentition not much attention is given until radiological investigation is done. ,,, There was no previous element of suspicion with regard to the presence of the follicular cyst clinically and 2D radiological studies namely lateral cephalomteric radiographs revealed a thin radiolucency surrounding the teeth indicating a possible pathological event. CBCT has added important information and proved to be a valuable aid in diagnosis and treatment planning. To the best of my knowledge, there is no single study that concretely establishes that 3D reconstruction gives better information than conventional CBCT. Isolated case reports have identified that CBCT can be used to identify incipient dentigerous cyst betters that traditional OPG as also the DC in such a tooth.  Identical case, where in a CBCT was used to trace the path of spread of DC to impacted teeth has been reported in the literature.  Bicortical perforation would have weakened the area that would predispose to unfavorable fracture during the later osteotomy. This is a crucial factor that cannot be overlooked and hence much attention was given in this direction.
CBCT is the latest a radiographic imaging technique that allows for the production of 3D images with low radiation, much details and precision. CBCT imaging is increasingly used in dental settings, costing much less than medical computed tomography and produces a much lower radiation burden to the patient.  This renders this an extremely useful tool for head and neck imaging. Most important, by revealing actual position and measurement, it eliminates crude estimation and interpretation based on which precision surgery is performed. 
The advantages of head and neck CBCT have been well-documented. , Numerous studies highlight the advantages of CBCT over OPG in the elucidation of a patient's deviation in normal anatomy, specifically in cases of impacted teeth in close proximity to the vital nervous tissues. , In such cases, OPG has no sufficient use as shown in this present case. OPG failed to show the true anatomical relationships between the impacted teeth, its buccolingual or inferosuperior relationship of the impacted teeth and associated nervous tissue. ,,, The resorbed area of the roots of molars was not visualized. In such situations, CBCT scans have been proven useful in determining the true anatomical position and planning the treatment of impacted teeth. Hence, it was no surprise that the detailed 3D images derived from CBCT scans were of high diagnostic efficacy as seen in this case.
To conclude, we report a very rare case of submerged carious deciduous molar along with an impacted premolar associated with an inflammatory follicular cyst that was diagnosed based on the clinical, histological and radiological features including CBCT. Though the conventional radiological features were not conclusive, CTBT, the intra-operative features and histopathological pictures were directed to diagnosis of the follicular cyst. The case also underlines the importance of a careful study of CBCT images and pathological correlation for deciding the future treatment plan.
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S M Balaji
Director and Consultant, Balaji Dental and Craniofacial Hospital, Teynampet, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]