Introduction
Dentigerous cyst is a type of odontogenic cyst and accounts for 20-24% of all jaw cysts (1). There are two types of dentigerous cysts: one of developmental origin, associated with impacted teeth (2) and the other one, of inflammatory origin, associated with non-vital primary teeth (3,4). Inflammatory dentigerous cysts are only found in the mixed dentition and they generally involve mandibular premolars (3,5).
A dentigerous cyst encloses the crown of an unerupted tooth by expansion of its follicle and is attached to the tooth along the cervical region (6). Dentigerous cysts are often asymptomatic and they are usually detected during routine radiographic examination, X-rays taken for orthodontic reasons or in order to find the reason for delayed eruption (2,7,8). In the radiographic examination, dentigerous cyst lesion shows a well-demarcated unilocular radiolucency with a sclerotic border, surrounding the crown of an unerupted tooth (3,9).
The cyst may cause swelling, tooth displacement, tooth mobility and sensitivity if it reaches a size larger than 2 cm in diameter (7).
Odontogenic keratocyst, unicystic ameloblastoma, central giant cell granuloma and a large radicular cyst must be considered in the differential diagnosis of a dentigerous cyst. Radiograph alone cannot differentiate the above-mentioned lesions, thus a histopathological examination can help accurate diagnosis (1,3).
Histologically, dentigerous cysts consist of a fibrous wall containing variable amounts of myxoid tissue and odontogenic remnants. The cyst is lined with nonkeratinized stratified squamous epithelium consisting of muco-sebaceous, ciliated and, rarely, sebaceous cells. The epithelial-connective tissue interface is typically flattened, but becomes highly irregular when associated with inflammation (10). Pseudoepitheliomatous hyperplasia with thicker epithelium and acute and chronic inflammatory infiltrate are frequently found (8).
Extraction of non-vital primary teeth and marsupialization represent the best strategy to conserve teeth affected by a dentigerous cyst and to permit their eruption, especially in young patients (1,3,5). When unerupted third molars are involved, coronectomy (intentional partial odontectomy) can be a solution (11,12). There are currently more published reports on odontogenic cysts found in adults than in pediatric patients (4).
This report presents two clinical cases of children with dentigerous cysts of inflammatory origin. The two cases were managed differently due to the associated medical condition of one of the patients who had autism, which limited patient cooperation under common dental office circumstances.
Discussion
Inflammatory follicular cysts occur most frequently in the premolar region, after primary molars affected by deep caries become non-vital. Inflammatory follicular cysts occur more frequently in boys than girls and are 10 times more likely to occur in the lower jaw than in the upper (3).
The pathogenesis of dentigerous cysts is still controversial. Benn and Altini (13) proposed three possible mechanisms for cyst histogenesis. The first hypothesis suggests that the developmental dentigerous cyst might form from a dental follicle, secondarily inflamed from a non-vital tooth as a source of inflammation. The second proposed explanation would be the formation of a radicular cyst at the apex of a non-vital deciduous tooth, followed by eruption of its permanent successor into the radicular cyst, thus resulting in a dentigerous cyst of extrafollicular origin. They also suggested that the follicle of a permanent successor might get secondarily infected from other sources than the non-vital deciduous predecessor, leading to a dentigerous cyst formation. Available evidence in both our cases indicated that infection of the predecessors (second primary molars) could have been the source of inflammation of the dentigerous cysts.
Pulp treatment cannot prevent the development of these cysts as they have been noted to occur both after pulp treatment and in the absence of it (3). In our cases, inflammatory dentigerous cysts occurred in primary molars with endodontic treatment.
Modern imaging [such as cone-beam computed tomography (CBCT)] can provide useful information for the diagnostic and clinical management of dentigerous cysts, especially for large ones, with displacement of adjacent teeth (7). In our first clinical case, the CT investigation recommended by the referring colleague was very helpful for quick diagnostic and efficient decision-taking. However, careful evaluation of the benefits and need for such investigations compared with the potential risks of exposure to ionizing radiation is extremely important in pediatric patients. The European Academy of Paediatric Dentistry's guidelines for prescribing radiographs in children and adolescents clearly point out that CBCT examination can be justified only when it results in a substantial net gain of information which directly influences the decision-making (14). Besides the age of the patient and the expected diagnostic benefits, the child's capacity to cooperate for complex imaging (needing a longer acquisition time) is also to be taken into account when indicating such investigations, especially when general conditions (e.g., intellectual challenge) are present (14).
Both of our clinical cases provide information on the growth rate of inflammatory dentigerous cysts: In the first case, the cyst reached a diameter of 1.4 cm in 14 months, while in the second case cysts with diameters >1 cm developed over a period of ~3 years. Shear (6) reported radiological findings showing that dentigerous cysts of 4-5 cm in diameter may develop in 3-4 years. Early recognition of dentigerous cysts, often as incidental findings, and prompt treatment limit the extent of jaw bone destruction (4). Uneventful healing with spontaneous gradual filling of the residual cavities, without any graft material, can be obtained even in large cysts after marsupialization if the cavity is sufficiently surrounded by bony walls (15).
Although rarely, untreated dentigerous cysts may sometimes develop into an odontogenic tumor or a malignancy such as squamous cell carcinoma (1). Therefore, early diagnosis and treatment of a dentigerous cyst lesion is important for the prevention of development into more destructive lesions.
It is generally accepted that extraction of a non-vital primary tooth and marsupialization will allow rapid healing of the lesion and eruption of the permanent tooth, provided that these procedures are performed at the normal time of eruption (3). However, opinions that the treatment plan for dentigerous cysts should consider extraction of the involved permanent tooth are not completely ruled out. In this respect, removal of the associated permanent tooth along with cyst enucleation may be necessary if it shows arrested development, is severely displaced or if the lesion is extensive (3,5).
By extracting the infected primary teeth, marsupialization of the cyst and ensuring continuous drainage, it is possible to achieve spontaneous eruption of the involved permanent teeth even if they are badly dislocated. Healing and ossification of the bony defect can take place simultaneously with the eruption of the permanent teeth. The reparatory process is completed in one to two years, depending on the dimensions of the bone defect (15).
In our first case, drainage was maintained with a custom-made removable appliance (modified Howley plate), which also played the role of a space maintainer, prevented food impaction and allowed access for regular cleansing. The same method has been successfully used in previous reports (16).
No evidence of recurrence was noted on follow-up radiography after marsupialization. These results are consistent with previous studies, which have shown that recurrence is rare after total lesion removal or when the involved tooth erupts after marsupialization (1,15-17).
In conclusion, conservative treatment of large inflammatory dentigerous cysts in young patients provides good results with minimal invasion, ensures preservation and physiologic development of teeth and proper bone healing. Modern imaging can substantially help diagnostic and clinical decisions, but indications for high radiation investigations must be carefully evaluated. Patients must be followed-up until full eruption of the displaced permanent teeth and bony consolidation of the cyst.