Dentigerous cyst: a rapidly expanding swelling in a young patient

Case report

A 4-year-old boy attended the paediatric dental emergency clinic with his father, who was concerned about a left-sided facial swelling that had been present for at least 1 month.

He reported a history of nocturnal pain. The patient had been prescribed oral antibiotics by his local dentist, which made no improvement in his symptoms. The patient's medical history was unremarkable.

Of note, 8 months prior to presentation, the patient had undergone dental treatment under general anaesthesia, which included multiple extractions of primary teeth and notably, extraction of the lower left first primary molar (LLD). There were no signs of intra- or extra-oral mandibular swelling at the time of extraction. Radiographs taken prior to the general anaesthetic revealed no peri-apical pathology or radiolucency in the region of the LLD (Figure 1).

Extra-oral examination revealed a palpable swelling in the left submandibular region. The patient was apyrexial. Intraorally, a firm buccal swelling was noted on the left mandible, extending from the lower left primary canine (LLC) to the lower left second primary molar (LLE) region (Figure 2). The mucosa was soft, fluctuant and normal in colour compared to the adjacent mucosa. The LLC displayed Grade 1 mobility.

A plain radiograph identified a large radiolucent area extending from LLC to LLE (Figure 3). The developing first permanent premolar (LL4) was present centrally within the radiolucent area. The lesion appeared uniformly radiolucent with well-defined margins.

The following differential diagnoses were considered at this stage:

Multidisciplinary input was sought from radiology and oral surgery departments. A decision was made to biopsy the lesion under general anaesthesia. An envelope flap was raised, and the cyst lining was visible with active suppuration. Curettage was carried out. The LL4 immature tooth was present in the middle of the cyst and was very mobile. This tooth was removed, and the cyst was enucleated. The LLC and LLE did not appear to be involved and were left in situ (Figures 4 and 5).

The sample was sent for histopathological assessment (Figure 6). A sample of the suppuration exudate was also sent for microbial culture and sensitivity testing. Post-operative antibiotics were provided. The patient was reviewed after 5 days.

Histopathological examination was suggestive of a diagnosis of an inflamed dentigerous cyst. The cyst lining featured non-keratinizing squamous epithelium. Extensive neutrophil and lymphoplasmacytic infiltrate in the epithelial lining was seen.

Discussion

There are a number of causes of intra-oral swellings in paediatric patients. These are commonly classified as inflammatory, developmental, odontogenic or non-odontogenic in origin. Most of these lesions are benign; however, aggressive local infiltration can occur resulting in functional impairment.⁴

The World Health Organization classifies jaw lesions based on diagnoses interpreted through histological findings. Therefore, biopsy of these lesions is warranted. The most recent 2017 World Health Organization classification denotes dentigerous cysts within the category ‘odontogenic and non-odontogenic developmental cysts’.⁵

Intra-osseous jaw cysts in children can be odontogenic and non-odontogenic in origin.³ These lesions vary in their clinical presentation. Some lesions have similar clinical features, therefore, having a working differential diagnosis in mind is essential. A careful history and thorough examination is required to identify possible diagnoses.⁶ History taking should include questions about dental history, specifically a history of dental trauma or previous dental treatment, including extractions. A thorough pain history should also be taken, and any symptoms of swelling, bad taste, displacement and mobility of teeth should be noted. A comprehensive clinical and radiographic examination is essential to determine the presence of swelling and bony expansion, tooth mobility, tooth displacement, loss of vitality and caries. In this case, a careful history reminded us of his previous dental treatment and radiographic findings aided our differential diagnosis.

Histological findings in this case confirmed the diagnosis of a dentigerous cyst. A dentigerous cyst arises from the dental follicle of an unerupted tooth.¹ The cyst lining is composed of non-keratinized, stratified squamous epithelium and surrounds the crown of an unerupted tooth.

Dentigerous cysts are common in both adults and children. In adults, dentigerous cysts are the second most common jaw cyst after radicular cysts.^7,8 Peak incidence is in the second and third decades.^8,9 In paediatric patients, dentigerous cysts are one of the most common jaw cysts.^1,2,3 A mean age of 11 years has been reported with male predilection.^8,10 Multiple retrospective reviews have demonstrated that dentigerous cysts and odontogenic keratocysts together account for the majority of paediatric jaw cysts.^2,3,4,11 In one 15-year retrospective review of paediatric patients who presented with jaw cysts, dentigerous cysts accounted for almost 30% of jaw cysts and odontogenic keratocysts were seen in 33% of cases.⁴ A similar study reported a higher prevalence of dentigerous cysts (76%) compared to odontogenic keratocysts (22%) among paediatric patients.² This patient was 4 years old, therefore, significantly younger than the reported mean age of presentation.

Below the age of 9 years, the mandibular second premolar is the most commonly affected tooth, followed by the maxillary canines.¹ This was confirmed in a recent retrospective histological analysis of paediatric dentigerous cysts.¹⁰ This peak age of incidence may correlate with the eruption of these teeth when widening of the follicle is observed as part of the tooth eruption process.¹⁰ In adulthood, unerupted third molars are the most frequently affected.

Developmental cysts are common in paediatric patients. This may be related to the fact that during the paediatric age period, the mandible and maxilla undergo a significant process of bony growth and tooth development.² Huang et al differentiated dentigerous cysts into inflammatory dentigerous cysts and developmental dentigerous cysts.¹⁰ These authors suggest that cysts in the inflammatory subtype are more prevalent in children. Inflammation of the follicle of the successor tooth may be triggered by a non-vital primary molar tooth.

Our case demonstrates a possible correlation of a previous extraction of a carious primary molar and development of a dentigerous cyst, and consideration of why the follicle of the LL4 became cystic is interesting. It could be considered in this case that the carious primary tooth (LLD) stimulated an inflammatory process of the dental follicle resulting in cystic changes.¹⁰ The rapid development of radiolucent changes in this case is also unique.

Most dentigerous cysts are asymptomatic and may be diagnosed as an incidental finding on routine radiographic examinations.⁴ Radiographic features include a well-defined, radiolucent, unilocular lesion that surrounds the crown of the unerupted tooth.² Dentigerous cysts in children are usually small in size; however, they can expand and lead to profound bony expansion.¹ Gradual facial asymmetry may be noted.¹⁰ Acute exacerbation with infection can also occur, which often prompts patients to seek professional advice.¹⁰ In this case, we demonstrate rapid development of radiolucent changes in the mandible, suggestive of a significant inflammatory process.

The differential diagnosis of dentigerous cysts can be seen in Table 1.

Malignant tumours

A jaw radiolucency in the mixed dentition may present clinicians with a diagnostic dilemma, because it may be difficult to distinguish between an enlarged follicle and a small dentigerous cyst.⁸ A pericoronal critical width of 4 mm has been reported, above which one should consider abnormal follicular tissue.⁸ In our case, the extent of the radiolucent area was suggestive of cystic and pathological change.

Early diagnosis and rapid management is essential to prevent facial asymmetry and bony destruction.¹ Dentigerous cysts can also lead to tooth displacement and in rare cases, malignant change.¹² Management of these cysts is dependent on patient and surgical factors including the size of the cyst, age of the child and proximity to adjacent structures.⁷ Spontaneous resolution of these cysts is unlikely, although there are some reported cases of complete resolution in adult patients.^13,14

Surgical intervention may involve cyst enucleation or cyst decompression. Cyst enucleation and removal of the affected teeth is a common treatment option for dentigerous cysts. Enucleation involves removal of the entire cyst lining.

The decompression technique is often considered in large-sized cysts. This conservative approach minimizes the risk of damage to unerupted tooth germs and neighbouring nerves and blood vessels. Multiple case reports demonstrate that this is a successful technique in paediatric patients.^1,15,16 Deciding whether to remove or retain the cyst-involved teeth depends on multiple factors. Several case reports demonstrate successful eruption of the cyst-involved tooth following decompression of the cyst.¹⁵ The average time for teeth to erupt has been reported as 109 days.¹⁶ Mandibular premolars are more likely to erupt compared to maxillary canines.¹⁷ Factors that favour successful eruption of mandibular premolars include shallow tooth angulation, shallow cusp depth and immature root development.¹⁷ Some authors have described successful orthodontic extrusion of affected teeth in dentigerous cysts.¹⁸ In our case, due to the extensive mobility of the LL4 and poor long-term prognosis, a decision was made to remove the tooth.

Management of this case involved loss of a permanent premolar tooth at a young age. Permanent tooth loss in early years may compromise later occlusion, function and aesthetics.¹⁸ In this case, careful explanations of consequences of early tooth loss were discussed with the parent and informed consent was gained. We also ensured to discuss the benefits as well as the significant, unavoidable and frequently occurring risks of the proposed treatment under general anaesthesia.

Conclusion

This case demonstrates rapid development of an inflamed dentigerous cyst in a young patient. Overall, paediatric jaw lesions are uncommon; however, dentigerous cysts are one of the most common intra-osseous lesions in children, and are often diagnosed on routine examination. Dental professionals should be aware of the varied clinical presentations and should consider inflamed dentigerous cysts as differential diagnoses in paediatric patients who present with dental swellings. This case highlights the importance of early multidisciplinary input in facilitating appropriate management.