The dentigerous or follicular cyst is the most common type of developmental odontogenic cyst and the second most common among all that occur in the jaws, repre- senting about 20 % of all cysts. By defnition, a dentiger- ous cyst is attached to the tooth cervix (cementoenamel junction) and encloses the crown of the unerupted tooth. It is a benign lesion associated with the odontogenic ep- ithelium of the crown of an unerupted tooth and origi- nates from the separation of the follicle around the crown of the tooth in question, forming a cavity bounded by the reduced enamel epithelium and the tooth enamel, which is flled with cystic fuid. As with other cysts, expansion of a dentigerous cyst is related to epithelial proliferation, release of bone-resorbing factors and an increase in cyst fuid osmolality.

Aetiology and pathogenesis

Although its aetiopathogenesis is not fully known, it is believed that epithelial proliferation around a fuid-flled cavity grows continuously by osmotic pressure over an extended period, as long as the tooth does not erupt. If this pressure is removed by the tooth erupting, the cyst will no longer be a pathological entity.

Initial dental panoramic tomogram

Histopathology

Histologically, the characteristics of dentigerous cyst are variable. If it is not infamed, it has a loose and thin con- nective tissue capsule, covered by non-keratinised epithe- lial cells, composed of two or three layers of fat or cuboi- dal cells. When there is a secondary infection present, the connective tissue is denser and there is variable infltration of chronic infammatory cells. The lining epithelium may show variable levels of hyperplasia, developing epithelial ridges with more striking scaly characteristics.

Differential diagnosis

Differential diagnosis of pericoronal radiolucency should include odontogenic keratocyst, ameloblastoma and other odontogenic tumours. Ameloblastic transforma- tion of a dentigerous cyst lining should also be part of the differential diagnosis. Adenomatoid odontogenic tu- mour would be a further consideration with anterior peri- coronal radiolucencies, and ameloblastic fbroma would be a possibility for lesions occurring in the posterior of the jaws of young patients.

Clinical features

Dentigerous cyst occurs predominantly in the frst three decades of life, has a predilection for the male sex and affects more Caucasian individuals. Although this pathol- ogy may occur in any unerupted tooth, the teeth most frequently affected are the mandibular third molars, max- illary canines and mandibular premolars. The occur- rence in primary dentition is extremely rare. Clinically, these lesions are, in most cases, of slow and asymp- tomatic growth; however, they can grow considerably and cause expansion of the cortical bone, facial defor- mation, impaction or displacement of teeth and adjacent structures, paraesthesia and discomfort. They may be associated with some syndromes, when they present in multiple or bilateral forms, such as Maroteaux–Lamy syn- drome and cleidocranial dysplasia. Radiographically, in most cases, dentigerous cyst appears as a radiolucent unilocular cavity with a well-defned sclerotic margin, in- volving the crown of an unerupted tooth, starting from the cementoenamel junction, although multilocular aspects can also occur in large lesions. While a normal dentalfollicle has 3–4 mm of space between the tooth and its margin, this cyst can be suspected when this space is larger than 5 mm. When located in the mandible, this cyst can cause the displacement of the mandibular ca- nal, the resorption of the wall of this canal, the root re- sorption of adjacent teeth or even pathological mandib- ular fracture.

Initial CT sagittal section

Initial CT sagittal section

Treatment options

Marsupialisation and enucleation are the classic tech- niques for the treatment of dentigerous cyst and may be associated. Decompression, using a decompression device, is an option, when followed by enucleation, for the treatment of large cysts. However, the criteria for choosing one of these modalities are not clearly defned, owing to the lack of exhaustive studies and adequate follow-ups.11 As accepted criteria for diagnosis and treatment, the size of the cyst, the age of the patient, the teeth involved and the involvement of anatomical structures must be taken into account. The treatment modality to be chosen will depend on the clinical and radiographic characteristics in question. Lesion aspiration should be performed in all cases, as radiographically similar lesions can be odonto- genic tumours or vascular lesions and not cysts as ex- pected, the detection of fuid inside the lesion being a major indication of cyst.

Incisional biopsy must then necessarily be performed to differentiate the type of cyst, as other lesions, such as odontogenic keratocysts and unicystic ameloblastoma, may have similar clinical and radiographic characteris- tics; however, they are more aggressive locally, requiring more extensive treatment and thus sacrifce of neurovas- cular tissue, bone and adjacent teeth. The progno- sis of dentigerous cyst is favourable and has a low recur- rence rate (3.7 %); even so, the follow-up must be strict.10 Enucleation of the cyst and extraction of the associated unerupted tooth are performed in about 85 % of cases and are the treatment of choice for small lesions with a safe distance from anatomical structures, such as the in- ferior alveolar nerve. In these patients, this is indicated if the unerupted tooth is considered useless for masti- catory or aesthetic function or there is a lack of clinical space for its eruption. In dentigerous cysts of third mandibular molars, the larger the cyst, the greater the risk of nerve injury and weakening of the mandibular an- gle caused by the surgery. Therefore, in these cases, the most appropriate therapeutic modality would be decom- pression followed by enucleation, after reducing the size of the lesion.

Bone reconstruction

The two-stage treatment is time-consuming, uncomfort- able for patients and requires frequent check-ups. One- stage cystectomy of large cysts with watertight closure of the postoperative bone cavity predisposes to compli- cations. Moreover, the weakened bone structure is prone to fractures in the postoperative period. This is why there is particular interest in flling the bone cavities with auto- grafts or bone substitutes.

Clinical case

A 43-year-old Caucasian female patient attended the oral and maxillofacial surgery consultation at Clitrofa medical centre in Trofa in Portugal to assess extraction of teeth #38 and 48. She was asymptomatic, without paraes- thesia, hypoaesthesia or other complaints. Anamnesis established that there were no allergies or use of med- ication. On extra-oral clinical examination, no abnormal- ity was observed. On intra-oral physical examination, a slight bulging of the cortical bone was noted in the region of the left external oblique line adjacent to tooth #37, but no chromatic alteration in the oral mucosa. The dental panoramic tomogram showed a unilocular, well-defned, homogeneous radiotransparent area surrounding the dental crown of the included tooth #38, extending to the tooth #35 region (Fig. 1a). In the coronal, sagittal and axial sections of the CT scan, it could be seen that the lesion was in close contact with the mandibular canal and there was cortical bulging (Figs. 1b & c).

Osteotomy with piezoelectric surgery

cystic capsule with impacted tooth 38

intraoperative image of the cystic cavity

Platelet-rich fbrin

CERASORB® Foam used to protect the inferior alveolar nerve

intraoperative image of inferior layer of bone reconstruction

 

Sticky bone for cystic cavity reconstruction

Osgide® resorbable membrane covering complete area of bone reconstruction

intraoperative image after suturing

As initial options for diagnosis, the possibilities of odon- togenic keratocysts, unicystic ameloblastoma, adeno- matoid odontogenic tumour and dentigerous cyst were considered. Aspiration puncture was performed under local anaesthesia, producing a small amount of light- yellow liquid and thus confrming the cystic nature of the lesion and working as decompression to reduce the lesion size. Endodontic treatment of tooth #36 was per- formed prior to surgical intervention. The patient was operated on under general anaesthesia, with nasal intu- bation. An intra-oral incision was made in the left retro- molar region that extended to the canine region, where a discharge incision was made. The osteotomy for access to the cystic cavity was performed by piezoelectric sur- gery. Based on 3D control of ultrasonic microvibrations, a micrometric and selective cut is allowed, under good visibility (cavitation effect) that results in minimal dam- age to soft tissue and nervous structures (Fig. 2a).19 The equipment used was the VarioSurg3 (NSK). The cystic capsule was excised together with the extraction of in- cluded tooth #38 and tooth #37 (Fig. 2b). The remaining cavity was cleaned with saline solution, keeping the lower border of the mandible intact (Fig. 2c).

Bone regeneration was performed with CERASORB® M (curasan) in granule and foam form combined with fbrin and Osgide® resorbable membrane (curasan). CERASORB® M is a resorbable and pure-phase beta- tricalcium phosphate ceramic for implantation flling, binding and reconstruction of bone defects, as well as bone fusion in the entire skeletal system. The granules have a polygonal shape, and owing to the open inter- communicating multi-porosity composed of micro-, meso- and macropores (about 65 %), the radiopacity is lower and absorption is effected faster. Over months in contact with the vital bone, the material is resorbed by the body and simultaneously replaced by autologous bone tissue. As a syn- thetic and bioactive ceramic material, CERASORB® M has no local or sys- temic toxicity and no risk of allergic re- action. CERASORB® M is radiopaque and can be used in granule, paste and foam form.20 The use of autologous platelet-rich fbrin (PRF) in the grafting process offers benefcial characteristics in the modulation of the infammatory response, immune response and tissue repair, tissue reorganisation and angio- genesis (Fig. 3a).21 The association of PRF with mineral biomaterials (I-PRF) facilitates handling and application and allows immediate adhesion to the re- ceiving bed (Figs. 3b & c).21

Final dental panoramic tomogram

fnal CT sagittal section

fnal CT cross section

The inferior layer of bone reconstruction was performed with CERASORB® Foam soaked with PRF in an attempt to protect the inferior alveolar nerve integrity and strengthen the lower border of the man- dible. The superior reconstruction layer was done with CERASORB® M gran- ules combined with PRF, creating what is described as sticky bone. Sticky bone provides stabilisation of the bone graft in the defect and is easy to manipulate and therefore accelerates tissue heal- ing and minimises bone loss during the healing period (Fig. 4a). An Osgide® re- sorbable membrane was used to cover the bone reconstruction. Osgide is a bio- resorbable barrier membrane for use in guided tissue regeneration and guided bone regeneration. The membrane cre- ates a protective environment for bone regeneration in the defect area and sup- ports osteoneogenesis by presenting a barrier to the infltration (migration) of soft tissue and promoting the growth of osteogenic cells in the bony defect (Fig. 4b). Suturing was performed with simple stitches using non-resorbable thread (silk, 4/0; Fig. 4c).

The patient underwent systemic antibiotic, analgesic and anti-infammatory therapy for eight days. In postoperative care, the patient was instructed to maintain strict oral hy- giene. The material obtained from the cystic cavity was sent for pathological examination, and the fndings were islands of odontogenic epithelium remains scattered in the fbrous connective tissue capsule, composed of three layers of fattened, non-keratinised cells. These fndings confrmed the diagnosis of dentigerous cyst. At the time of writing, the patient was in the postoperative period of 12 months and had shown no hypoaesthesia or any sign of recurrence of the lesion. In the postoperative dental panoramic tomogram (Fig. 5a) and CT scan, there was evidence of bone neo-formation in the area previously occupied by the lesion (Figs. 5b & c).

Discussion 

Among the possible treatment techniques for dentig-erous cyst, the most suitable for each clinical situation should be evaluated, considering all scenarios for each option.7 In the present clinical case, had the treatment been decided on considering only the size of the le-sion, enucleation would have been the most appropriate choice associated with the extraction of the impacted tooth #38. Owing to the proximity of the inferior alveo-lar nerve, decompression followed by cyst enucleation and extraction of the tooth in question was the most reasonable option. This allowed bone regeneration of the cystic cavity, as well as maintenance of nerve integ-rity. Enucleation is the technique of choice for cysts of smaller dimensions and when there is no involvement of important anatomical structures, since it provides the possibility of a histological study of the lesion. Mar-supialisation and decompression with the use of a de-vice should be reserved for clinical cases of extensive dimensions, involving important anatomical structures and increased risk of fracture, as they promote the re-duction of intracystic pressure, consequently reducing the size of the lesion. Taking into account this objective of decompression, it was decided in this clin-ical case to maintain the lesionoral cavity communi-cation created during the aspiration puncture, which, although reduced, was suffcient to regress the dimen-sions of the lesion.

Both marsupialisation and decompression are therapeu-tic modalities also indicated in the period when the bone repair capacity is high and the eruptive power of the teeth is present. Sticky bone is biologically solidifed bone grafting material which is entrapped in fbrin network. Sticky bone graft granules are strongly interconnected to each other by the fbrin network. Sticky bone has nu-merous advantages:

 

  1. It is mouldable, so it adapts well to various shapes of bony defects.
  2. Micro- and macro-movement of grafted bone is prevented, so the volume of augmentation is maintained during the healing period. Therefore, the need for block bone and titanium mesh is minimised.
  3. Fibrin network entraps platelets and leucocytes to re-lease growth factors, so bone regeneration and soft-tissue growth are accelerated.
  4. No biochemical additives are needed to make sticky bone.
  5. Fibrin interconnection minimises soft-tissue ingrowth into the sticky bone graft.
Conclusion

Dentigerous cyst is a frequent lesion which, despite be-ing a less aggressive pathology and without clinical symp-toms, has the potential to reach large proportions, caus-ing signifcant movement of teeth. The treatment decision must be based on objective criteria, such as age of the patient, size of the lesion, involvement of relevant anatom-ical structures, clinical importance of the tooth or teeth associated with the lesion, and risk of bone fracture. It is essential to perform a histopatho-logical examination for the differen-tial diagnosis, ruling out other types of lesions with similar clinical and radio-graphic characteristics, as well as to perform annual postoperative radio-graphic monitoring.

Drs Fernando Duarte & Carina Ramos, Portugal