Unilateral Buccal Bifurcation Cyst: A Rare Cystic Lesion in Children and Adolescents

The World Health Organization (WHO) has included the BBC in its classification of odontogenic cysts and tumors since 1992 under the heading of "inflammatory collateral cyst," which is the same designation for paradental cysts despite the latter being exclusively related to a third molar. Comparatively, a BBC is associated with the mandibular first or second molar.^2-4 The commonality of these cysts is their origination from inflamed pericoronal tissue.^3,5

The name "buccal bifurcation cyst" has been widely accepted because of the lesion's site specificity, as the lesion has an intimate association with the bifurcation area of a mandibular first or second molar, and it occurs almost exclusively in the first two decades of life, predominantly in children aged between 4 and 14 years.⁶ The cyst is usually unilateral, but bilateral cases have been documented.^5,7-9 The exact etiology of such a cyst is largely undetermined because of the lack of conclusive evidence attributed to its rarity.^4,6,10 The most widely accepted etiology is that plaque induces a mild inflammation and infection during its eruption.^8,9 Another hypothesis proposes that buccal enamel projections on the molar extend to the root surface causing periodontal pocketing.⁷ The pathogenesis for both etiologies is that inflammation causes proliferation of the epithelial tissue, leading to cyst formation.^8-10

A BBC may be discovered as an incidental finding, or parents may be prompted to seek a consultation for their child due to symptomatic pain, swelling, and/or slow expansion of the mandible.⁶ Clinical examination of the dentition will reveal a deep periodontal pocket associated with the affected mandibular molar.^6,8,10 The crown may be buccally orientated due to the pressure of the cyst on the root apices pushing them in a lingual direction.

Imaging investigations for a BBC should include conventional radiographs, such as panoramic, periapical, and mandibular occlusal images. A well-circumscribed, unilocular ovoid radiolucency along with a periosteal reaction of the mandibular bone and a buccal orientation of the cyst can be clearly seen in these images.^7,8,11,12 A cone-beam computed tomography (CBCT) scan is indicated to confirm the presence of the BBC, evaluate its size, and provide information about its relationship to surrounding structures.

Management of the BBC has evolved since this cyst was first documented. Initial approaches involved enucleation of the cyst combined with extraction of the associated tooth.^2,3 Presently, the preferred management of choice for a BBC is surgical enucleation without tooth extraction.^3,10,12-14 A specimen should be sent for histological evaluation to rule out other potentially aggressive pathological entities. Other management options reported in the literature include daily irrigation of the socket or simple monitoring of the lesion with frequent follow-up to ensure that regression is occurring.^2,7

The purpose of this case re­port is to outline the presentation, clin­ical features, radiographic investigations, and surgical management of a BBC in a 13-year-old patient to demonstrate to general dentists and specialists the recognition and correct management of the lesion.

Case Presentation

A 13-year-old male patient presented to Midwestern University (MWU) College of Dental Medicine-Arizona with his parent, who was seeking a second opinion regarding an initial diagnosis by a previous endodontist of an infection or cyst. The patient was referred to the endodontist by his family dentist because of an incidental finding of localized, deep pocketing associated with tooth No. 18 at a 6-month recall visit. The parent wanted more information and requested a referral to the dental institute at MWU.

On presentation, the patient was asymptomatic and provided a history of his previous dental visits. His dental history was noted as regular attendance at a family general dentist, appliance therapy with a local orthodontist, and a previous endodontic consultation. The patient was reported to have no medical diagnosis, but a penicillin allergy was noted; immunizations were current. The patient was applying topical tretinoin 0.05% for acne.

A comprehensive clinical examination was completed. On extraoral examination, the left side of the mandible was observed for abnormalities such as tenderness, redness, swelling, and expansion of the lower border of the mandible, but nothing abnormal was detected. All other head and neck findings were also normal. On intraoral examination, the patient was found to have complete maxillary and mandibular fixed orthodontic appliances. Incipient carious lesions were noted on lingual pits of the permanent maxillary right and left lateral incisors and the occlusal surface of the mandibular right permanent first molar. Plaque accumulations were high with generalized gingivitis.

A focused examination of the mandibular left permanent second molar (tooth No. 18) revealed a periodontal pocket depth of 10 mm on the buccal aspect. Periodontal assessment of the remainder of the dentition showed no additional periodontal pocket depths exceeding 3 mm. There was no evidence of caries, swelling, or mobility associated with tooth No. 18, but a slight tenderness to palpation of the buccal gingiva was noted. The contralateral mandibular second molar was checked carefully for similar findings, but none were noted.

A panoramic radiograph and four bitewing intraoral radiographic projections were made (Figure 1 and Figure 2). The panoramic radiograph showed an open apex of tooth No. 18 and increased trabecular density in the interproximal area between teeth Nos. 18 and 19. Developing maxillary and mandibular third molars were also observed on the panoramic radiograph. Bitewing radiographs did not exhibit any significant periodontal bone loss. These 2-dimensional radiographic images provided non-significant radiographic findings that could not explain the patient's clinical findings.

The parent informed the providers that a 3-dimensional CBCT scan was acquired at a previous dental office. This CBCT scan was thus requested and reviewed by a board-certified oral and maxillofacial radiologist who was part of the authors' team at MWU. The limited field-of-view CBCT scan, acquired on a Veraview X800 (J. Morita, morita.com), was received and showed teeth Nos. 17, 18, and the distal half of No. 19. Well-defined, circular, corticated, homogeneous radiolucency, approximately 12 mm x 8 mm x 9 mm, with no internal contents was observed on the buccal aspect of tooth No. 18 (Figure 3). Vertically, the radiolucency extended from the alveolar crest to the level of root apices. The roots of tooth No. 18 appeared to be displaced lingually, with a slight buccal inclination of the tooth crown. No displacement of the left mandibular canal was observed (Figure 4).

An endodontic consultation was completed, and although the tooth did not respond to vitality testing, no strong indicators were present to suggest a lesion of endodontic origin. This aberrant result was considered to be due to a recently erupted tooth with an immature apex. Such teeth have been reported in the literature as having variable and inconsistent results with vitality tests.¹⁵

An oral surgeon reviewed the case and recommended an incisional biopsy, which was completed under local anesthesia. Using a small mucoperiosteal envelope flap for access, crestal bone was removed and sufficient lesional tissue was obtained for histological analysis. The lesion was histologically determined to be comprised of a fibrous connective tissue wall lined by a non-keratinized stratified squamous epithelium, containing acute and chronic inflammatory infiltrate (Figure 5). Based on the combined clinical, histological, and radiographic findings, and considering the anatomical site, a diagnosis of BBC was made with the recommendation for the complete surgical enucleation of the cyst. This was subsequently completed (Figure 6 through Figure 8), and an allogeneic bone graft was placed into the defect. Postoperative healing was evaluated at a 2-week interval with no complications.

Discussion

Overlooking or misdiagnosing a BBC can lead to the implementation of incorrect treatment modalities, including unnecessary endodontic treatment of a healthy vital molar or even extraction. Permanent first and second molars both have strategic importance for mastication and maintenance of occlusal relationships, so it is critical to investigate and manage this entity correctly. Dental professionals should have sufficient knowledge of the distinguishing features of a BBC and be able to easily differentiate it from other cystic entities.

A BBC can occur in unerupted, partially erupted, or completely erupted mandibular molars, and it will always manifest on the buccal surface, in the bifurcation area.⁶ According to published case reports, the mandibular permanent first molar tends to be affected more commonly than the second.^10,12 Signs and symptoms that would alert the dentist to possible pathology include localized pain, swelling, and deep periodontal pocketing.^2,6,8,10 Late signs may be a delay or cessation of eruption and bony expansion of the mandible.¹² Radiographic features can also be distinct illustrating an ovoid or u-shaped, well-circumscribed unilocular radiolucency. The radiolucency can encompass a portion of the root or whole root surface in a panoramic or periapical image. Coronal extension of the radiolucent area is rare and is a distinguishing feature from other cystic entities.¹⁶ Another characteristic feature viewable on the mandibular occlusal radiograph is a distinct localized periosteal reaction of the overlying buccal cortex of the mandibular bone, and this is due to a single or multiple layers of reactive bone formation.^7,8,11-13

The histology of a BBC can be summarized as a fluid-filled cavity lined by hyperplastic non-keratinized stratified squamous epithelium.^5,12 The cyst wall can be of variable thickness, composed of fibrous connective tissue containing a chronic inflammatory cell infiltrate of lymphocytes, plasma cells, and neutrophils.^4,17 The pathogenesis of the cyst lining has been postulated as arising from the proliferation of reduced enamel epithelium or the rests of Malassez of the periodontal ligament.^6,13 The stimulus for the proliferation of the epithelium is a local inflammation of the periodontiumcaused by plaque, or a blockage caused by food accumulation leading to increased pressure and inflammation within the periodontal pocket.^7-10

The most common differential diagnoses with features similar to a BBC are a dentigerous cyst, lateral radicular cyst, and odontogenic keratocyst. ^5,7,11,12,14

Dentigerous cyst-A dentigerous cyst is a developmental cyst attached at the cementoenamel junction and is thought to arise from the remains of the enamel organ.¹³ It most commonly affects mandibular third molars and maxillary canines.^13,16 Radiographic features of this cyst can be summarized as a unilocular radiolucency encompassing the crown or even the whole tooth causing displacement of the unerupted tooth. It can be differentiated from the BBC based on radiology and site of presentation.¹⁶

Lateral radicular cyst-A variant of the radicular cyst, the lateral radicular cyst histologically and radiographically presents similarly to the BBC.^4,17 This cyst, however, can be eliminated as a diagnosis because it is always associated with a necrotic tooth with an identifiable etiology such as caries or trauma.⁵ The radiological presentation of a lateral radicular cyst is similar to a BBC with a unilocular well-circumscribed radiolucency but with one fundamental difference: the radiolucency extends from the tooth with a disruption in the continuity of the periodontal ligament.¹⁶ This is in contrast to a BBC where there is always an intact, continual periodontal ligament space.^13,18 If the tooth has completed root formation it will exhibit a normal response to vitality testing.^4,11 In the case presented, the second molar did not respond to either the cold test or an electric pulp test. The reason for this anomaly can be explained by considering the stage of root formation and the immature apex of the tooth. Such teeth have been known to give variable and inconsistent or no responses to vitality testing.¹⁵

Odontogenic keratocyst-An odontogenic keratocyst is another developmental cyst that originates from the dental lamina. The WHO has recently reclassified it as an odontogenic tumor, and it is currently known as a keratocystic odontogenic tumor.¹⁶ Strong consideration should be given to this cyst as a differential because of its aggressive nature and tendency to reoccur. Features of this cyst include its site in the posterior of the mandible, either the ramus or the body, and it may present as a unilocular or occasionally a multi-locular radiolucency.¹⁶ It has characteristic histological features, namely the presence of keratin in the cyst lining and sometimes the lumen, so it can be readily diagnosed from its site of presentation, radiology, and histology, which all differ distinctly from the BBC.¹⁶

Managing a BBC has changed over the years with the dissemination of literature from several authors who have proposed different management options. Historically, treatment of a BBC was centered on enucleation and extraction of the affected tooth.² Pompura et al published a report in which 32 cases were treated with enucleation only, leaving the affected molar in situ.³ The results were consistent with successful healing and retention of the affected tooth without any symptoms, adverse effects, or recurrence of the cyst. Zadik et al then published an article in which the periodontal pocket of the associated tooth was irrigated with hydrogen peroxide. It was postulated that the cyst healed due to a type of marsupialization caused by the introduction and continued irrigation of the liquid agent.¹⁴

Most published case studies, especially recent ones, have utilized surgical enucleation of the cyst with excellent healing, bony in-fill, and continued health and vitality of the affected tooth.^13,18

Summary and Conclusion

Although rare, a BBC is a distinct entity that should be given strong consideration as a differential diagnosis for a cystic lesion that presents in a vital first or second mandibular molar in children and adolescents. The lesion should be thoroughly investigated with a comprehensive clinical examination, detailed periodontal probing depths, tooth vitality tests, and appropriate radiographic images, including a CBCT if surgical enucleation is considered. Appropriate follow-up is important to ensure healthy healing of the site and continued vitality of the tooth and to monitor the contralateral tooth for signs of cyst formation.

About the Authors

Sabita Rao, DMD
Assistant Professor, Clinical Faculty, Midwestern University, College of Dental Medicine-Arizona, Glendale, Arizona; Diplomate, American Board of Pediatric Dentistry

Vijay Parashar, BDS, MDSc, DDS
Professor, Oral and Maxillofacial Radiologist, Associate Dean, Midwestern University, College of Dental Medicine-Arizona, Glendale, Arizona

Douglas W. Beals, DDS, MS
Associate Professor, Oral and Maxillofacial Surgery, Midwestern University, College of Dental Medicine-Arizona, Glendale, Arizona

Olysia N. Takla, DMD
Assistant Professor, Clinical Faculty, Midwestern University, College of Dental Medicine-Arizona, Glendale, Arizona