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Introduction
Cystic lesions are characterized by the presence of a cavity lined by epithelial cells and filled with a liquid secreted by these and/or surrounding tissue cells 1. Internal pressure generated by fluid is responsible for the growth of the lesion, which is radiographically represented as a well-defined radiolucent area. Cysts of the jaws can be classified as odontogenic and non-odontogenic. Odontogenic cysts may originate from both epithelium of tooth formation and mesenchymal tissue, with periapical and dentigerous cysts being the most common ones 2.
Dentigerous cysts arise from a follicle of an impacted or a developing tooth through the accumulation of fluid between the reduced enamel epithelium and the crown of the affected tooth 3. These cystic lesions are often associated with third molars, upper canines and lower second premolars 4. They commonly occur in Caucasian males, with an estimated rate of 1.44 per 100 impacted teeth 3,4. The highest incidence rates occur during the second to the fourth decade of life 5. Dentigerous cyst represents 14-20% of all cysts of the jaws and 15.2-33.7% of all odontogenic cysts 4. In addition, it is known to be the most common cyst in childhood 6.
Clinically, dentigerous cysts are asymptomatic and discovered occasionally during routine radiographic evaluation. The presence of an unilocular radiolucent area circumscribed around the impacted tooth or developing crown is considered to be the classic finding for differential diagnosis 5. Regarding cystic lesion size, in some cases, dentigerous cysts may become large, changing the original position of the involved tooth and leading to bone and root resorption. Consequently, it is essential to be aware of treatment modalities, especially for children, in which more conservative surgery should be considered to avoid injuries to centres of facial growth.
Taking into consideration the importance of correct diagnosis using images for a safer therapeutic approach, this article reports a clinical case to characterize the main features of impacted teeth with dentigerous cyst and the treatment guided by cone-beam computed tomography (CBCT) imaging. Therefore, it presents a review of the literature relating to this condition.
Literature Review
Diagnosis
Dentigerous cyst diagnosis occurs through imaging and histopathology, as these lesions are often asymptomatic and may exist for years without being discovered. Patients usually do not report pain or discomfort associated with these kinds of lesions. However, an important sign is the absence of a tooth during clinical examination, which makes this a low-sensitivity exam for dentigerous cyst diagnosis. In some cases, dentigerous cysts become large, leading to local inflammation and bone expansion, which may result in facial asymmetry and even mandibular fracture 6.
Regarding dentigerous cyst radiographic findings, it is typical to observe a well-defined unilocular radiolucent area associated with the crown of a developing or impacted tooth, which is often detected in a routine evaluation. However, this exam alone is insufficient to reach a final diagnosis due to similarities with other odontogenic lesions, such as keratocyst, central giant cell granuloma and unicystic ameloblastoma. Three-dimensional CBCT provides additional diagnostic information, such as the accurate and reliable measurements of cystic diameter and volume, proximity to important anatomical structures and precise location of the involved tooth 7. It is important to highlight that these pieces of information are essential to determining the surgical technique and planning treatment.
The final diagnosis of dentigerous cyst must be established by an association of clinical examination and imaging, followed by histopathologic confirmation. The presence of a pericoronal radiolucent area larger than 4 mm in diameter, histological findings of a non-keratinized stratified squamous epithelium and a cystic space between the enamel and the surrounding tissue during surgery are the recommended criteria for an accurate dentigerous cyst diagnosis 3.
Treatment Modalities
Treatment of dentigerous cysts consists of complete surgical enucleation and associated impacted tooth removal 5. However, when a developing permanent tooth is involved, more conservative treatment approaches must be considered, such as decompression or marsupialization 8. Both techniques aim to relieve intracystic pressure to promote potential bone regeneration and, consequently, reduce lesion size. This is a crucial point regarding large cyst treatment, as there is a risk of injuring anatomical structures, such as the inferior alveolar nerve, and the potential of causing mandibular fracture when enucleation is the first treatment choice. Furthermore, it was reported that when using decompression techniques, spontaneous eruption of impacted teeth can be expected in association with cystic lesion reduction 9.
Marsupialization involves the creation of a wide surgical bone window followed by the connection of the inner cystic wall with the oral mucosa to promote cystic content drainage 10. On the other hand, during decompression, limited access is created in the cystic capsule, and a tube is positioned to encourage drainage and allow for the irrigation of the cavity 11. This approach is especially interesting for paediatric patients, as it enables dentition development, minimizes injury to surrounding tissues and does not interfere with craniofacial growth 8, making the capsule lesion's removal safer and less invasive.
The eruption of the impacted tooth affected by the dentigerous cyst may occur up to 3 months after decompression/marsupialization, and orthodontic traction should be considered after this period 9. The prognosis associated with dentigerous cyst is considered to be good, and recurrence is rare after definitive treatment.
Case Report
An 11-year-old female patient came to the Pediatric Clinic of Sao Paulo State University (Unesp) - School of Dentistry, Araraquara for evaluation and orthodontic treatment. At clinical examination, there were neither changes in the texture and integrity of the skin and mucosa nor signs of swelling or regional lymphadenopathy. In panoramic radiograph, the presence of an extensive radiolucent image was noted on the right side of the jaw surrounding the tooth 85 and closely related to the crown of the tooth 45 without reports of painful symptoms and with a hypothesized diagnosis of dentigerous cyst. Due to the lesion extension and possible involvement of the noble structures, CBCT was requested for better assessment and planning of the case. Analysis of these images revealed a unilocular hypodense lesion surrounded by a hyperdense halo. Figure 1 provides details about the lesion location, such as the proximity to the mandibular canal.
Figure 1 (A) Panoramic radiograph; (B) Initial clinical aspect; (C) Cross section showing the proximity of the lesion to the mandibular canal; (D) Panoramic image; (E) Coronal view and extension of the lesion.
The treatment plan consisted of two surgical times, the first being cystic cavity decompression and the second being the enucleation of the cist. Before surgery, complementary haematological exams were conducted primarily to evaluate blood coagulation. Then, the right deciduous mandibular second molar 8 was extracted. After the cystic cavity was accessed directly, a sterile rubber cannula was positioned and was held via suture. Next, the cavity was irrigated with saline solution. The right mandibular second premolar was preserved in position. The patient was medicated with analgesic and antibiotic, and the parents were instructed to perform clean-up and daily irrigation with saline solution. The patient was evaluated monthly until the appropriate time came to complete the second surgical step (Figure 2).
Figure 2 (A) Aspiration of the cystic liquid; (B) Access to the cystic cavity after tooth extraction (right deciduous mandibular second molar); (C) Sterile rubber cannula positioned and irrigation of the cystic cavity with saline solution; (D) Final appearance immediately after the first surgery.
After 4 months of clinical and radiographic follow-up (Figure 3A), decreased cystic cavity and bone neoformation were noted. Cystic enucleation was performed by curettage of the cavity (Figure 3B), and removed fragments were sent for histopathological analysis, which confirmed the diagnosis of dentigerous cyst. Again, the patient was medicated with analgesic for three days. Weekly observation occurred for a month (Figure 3C).
Figure 3 (A) Panoramic radiograph at 4-month follow-up; (B) Curettage of the cystic cavity; (C) Postoperative at 1 week.
After 2 years of follow-up, the eruption of the lower right second premolar was observed without the need for orthodontic traction (Figure 4A). After one more year, the tooth was aligned in the dental arch with orthodontic appliance (Figures 4B-D).
Discussion
The treatment of cystic odontogenic lesions involves a series of abnormalities that the clinician must consider before determining what would be the most adequate technique for each type of lesion. It is interesting to note that the patient's age, size of the cystic cavity, presence of anatomic structures associated with the lesion, and clinical importance of the tooth involved may have a direct influence on the success of the selected treatment. In the case of dentigerous cysts, two surgical techniques may be indicated: 1 complete surgical enucleation of the lesion with or without osteotomy and 2 decompression/marsupialization, which aims to reduce the internal hydrostatic pressure of the cyst, allowing centripetal bone growth from the periphery to the interior of the cavity 8.
Generally, the standard treatment for dentigerous cysts is complete surgical enucleation of the lesion and extraction of the teeth involved 12, representing the therapy of choice in cases in which cysts are of smaller size and there is no relationship of proximity to important anatomic structures. This represents a definitive treatment with the possibility of histological study of the lesion. However, for cysts with large dimensions and accentuated bone loss, as described in the case reported in this article, any invasive surgical procedure could cause damage to the adjacent anatomic structures, such as the inferior alveolar canal, maxillary sinus and nasal cavity. In addition, there is a risk of complications, such as mandibular fracture, sinusitis and deficit in the inferior alveolar and infra orbital nerves 8, which contraindícate the use of this technique.
Decompression of odontogenic cystic lesions has been widely used as a more conservative alternative treatment that requires a smaller surgical window, creating an opening to the cystic cavity by suturing a device (tube or tent) at its periphery 13. This procedure relieves internal pressure, favouring the formation of bone tissue, reducing the risks of complications in comparison to enucleation, curettage and resection; however, this requires more frequent follow-up 13. According to Koca et al. (2009) 14, this technique must be the first treatment option in children, especially when the permanent tooth associated with the lesion prevents it from erupting. Nevertheless, the main disadvantage of cystic decompression is that the pathological tissue is left "in situ" without meticulous histological exam. Although the tissue collected from the surgical window may be submitted for histological exam, there may be a more aggressive lesion in the residual tissue 15.
In this reported case, apart from the risk of mandibular fracture, it was impossible for the permanent tooth associated with the lesion to erupt, and an attempt to enucleate the cyst could injure this tooth. CBCT was essential for planning a safe surgery because it showed clear evidence of the relationship between the lesion and the adjacent structures, especially the noble structures. Therefore, performing decompression was critical to reducing the cystic cavity and bone defect. After four months of follow-up, cystic reduction and bone neoformation were observed, making it feasible to perform complete enucleation of the remaining lesion. According to Zhao et al. (2011) 16, the time to perform enucleation after decompression/marsupialization is generally determined by the morphological changes within the cystic cavity. Therefore, it may be safely performed only when there is sufficient bone tissue formation. However, studies that have evaluated bone repair after decompression/ marsupialization are scarce.
The decision to use the decompression technique at the first surgery followed by complete enucleation allowed for lesion repair without transoperative and postoperative complications. In addition, it allowed for the maintenance of the tooth associated with the cyst in the case reported. The benefits of this approach may be especially important for children and include the preservation of tooth germs, minimal harm to skeletal growth, and lower risk of damage to anatomic structures adjacent to the lesion, such as the maxillary sinus, mandibular nerve, and nasal and orbital cavities. Furthermore, children and their parents may show greater cooperation in the face of a less invasive approach 8.
Moreover, the use of treatment modalities with the purpose of alleviating internal cystic pressure are suggested to promote spontaneous eruption of the teeth that are enveloped by the cyst 17. Miyawaki et al. (1999) 18 observed that impacted teeth are capable of erupting more quickly if marsupialization is performed while the tooth has the capacity to erupt, as there is a close relationship between this potential and the level of tooth root formation 19. Therefore, teeth that have not yet concluded their root formation have greater potential for spontaneous eruption. Other factors may also contribute to the spontaneous eruption of the impacted tooth, such as the presence of a rate of interdental space greater than or equal to 1.0 mm 20 and the angulation of the tooth associated with the cyst so that the smaller the inclination, the greater its chance of erupting spontaneously 9.
According to the literature, children aged 10 and 11 years have a higher percentage of spontaneous eruption after marsupialization in comparison to older individuals9,14,19,20. In the present case, the patient had favourable conditions for spontaneous eruption of tooth 45 (age, open apex, and little inclination). For this reason, the decision was made to follow-up on the case, and the beginning of its eruption in the oral cavity was observed at 6-month radiographic follow-up. However, in unfavourable cases and/or older individuals, spontaneous eruption generally does not occur, and orthodontic traction would be indicated with the purpose of guiding the occlusion or facilitating the surgical removal of the entire cyst with the impacted tooth 20. Therefore, additional operative time would be necessary for bracket bonding.
In conclusion, treatment of dentigerous cysts with large dimensions in children demands the use of less invasive techniques, with to the goal of preserving the tooth that is associated with the cyst. This approach stimulates bone repair and favours the spontaneous eruption of the related tooth. Therefore, decompression has been shown to be effective in reducing the cystic cavity and increasing bone density, allowing for subsequent enucleation of the lesion without surgical complications.
