Artículo Clínico

Therapeutic approach to impacted third molar follicles

Actitud terapéutica ante sacos foliculares de terceros molares incluídos

R. González García¹, V. Escorial Hernández¹, A. Capote Moreno¹,P.L. Martos Díaz¹, J. Sastre Pérez²,
F.J. Rodríguez Campo²

Recibido: 07-07-2004

Aceptado: 20-10-2004

1 Médico Residente.
2 Médico Adjunto.
Servicio de Cirugía Oral y Maxilofacial
Hospital Universitario de La Princesa, Madrid, España.

Correspondencia:
Raúl González García
C/ Los Yébenes nº 35, 8º C
28047 Madrid, España
E-mail: raugg@mixmail.com

Introduction

The dentigerous or follicular cyst is a developmental odontogenic cyst. It is the second most common following the radicular cyst, and it is covered by epithelium of the dental follicle.¹ It is frequently related to an impacted permanent tooth, usually the inferior third molar.² It is normally asymptomatic, in the center or surrounding the crown.

The indications regarding the extraction of impacted third molars are in most cases controversial.³ There is no general consensus as to the extraction of asymptomatic third molars. On considering the need for surgery, the possibility of extraction complications should be taken into account.

The presence of a cystic lesion associated with an inferior third molar is indicative of the extraction and a cystectomy. However, when there is no evidence of cystic formation, and if in its place there is a radiolucent image compatible with the follicle of the impacted tooth, the indications for prophylactic extraction become more problematic, especially taking into account the not uncommon spontaneous evolution of a follicle into a dentigerous cyst.

Case report

Male patient, 28 years old attended our Service presenting hemimandibular pain on the left side and a high temperature. He had no pathologic background of interest. The physical examination did not reveal any specific signs, but there was pain on palpating the pericoronal tissue of the left lower third molar. Emergency tests were requested as a slight increase in the number of leukocytes was observed with no other obvious alterations. In the orthopantomography (OPG) both impacted third molars were visible, in a mesioangular position together with both the follicles, the right one being larger (Fig. 1). As a possible infection of odontogenic origin (pericoronitis) was suspected, antibiotic treatment was initiated, and the various symptoms were completely resolved. Extraction of both inferior third molars was recommended. The histological study confirmed the presence of a follicle associated with the third molar, formed by a polystratified non-keratinized epithelium. Following the extraction of the lower left third molar the patient did not return to complete the treatment. Twenty months later he attended again as he was experiencing pain in the lower right third molar. In the OPG a large radiolucent image could be appreciated around the crown of the lower right third molar (Fig. 2). With the suspected diagnosis of a dentigerous cyst associated with a third molar, surgical treatment was carried out, the tooth was extracted and a cystectomy performed. The anatomopathologic study confirmed the suspected diagnosis of a lesion with a wall of conjunctive tissue lined on the inside by a stratified epithelium of ciliated keratinized cells and with an abundance of mucous cells. During the follow-up at three months, an active ossification process was observed (with formation of bone trabeculae) in the residual cavity generated by the cyst (Fig. 3), which was considered adequate.

Discussion

The dentigerous cyst is a common lesion. It is the second most common odontogenic cyst following the radicular cyst. It mainly affects patients between the ages of 10 and 30, and it is slightly more predominant in the male sex.¹ The radiological image is characterized by a well-circumscribed, unilocular and normally symmetric radiolucent image around the crown of an impacted tooth. Some, however, are multilocular and irregular.⁴ It originates from the enamel epithelium when the crown of the tooth is starting to be formed. It is usually found in the region of the third molar, and they are more commonly an isolated finding.² They occur with a descending frequency: maxillary canine, third maxillary molar and second mandibular premolar.

The indications for the extraction of impacted third molars are controversial. Not all require surgical treatment. For some authors, the presence of pathological changes in impacted asymptomatic third molars having no previous radiological changes is infrequent and, as a result, prophylactic surgical removal is not recommended if there are no clinical or changes in the imaging tests.^3,5 Other authors, on the contrary, affirm that there is a risk of pathological change in the pericoronal tissue of impacted third molars, and that this risk increases with age. They recommend prophylactic surgical removal before the onset of pathological changes.^6,7 Age is important with regard to the indication for surgical treatment. Morbidity is lower if the extraction is carried out in younger patients. Probably, in asymptomatic patients aged 30 to 40, periodical examination is preferable, and extraction should be carried out if there are pathological changes.⁸

The extraction of impacted third molars is necessary if there is evidence of irreversible pathological changes, and likewise erupted healthy teeth should be kept for possible orthodontic needs in the future. There is little evidence that third molars should be extracted in order to minimize overcrowding either at the time or in the future, and neither is there consensus as to the extraction of asymptomatic impacted third molars having no associated pathology.⁹

With regard to dentigerous cysts, the fact that they can expand through the bone leading to pathological fractures is well known. The risk of infection increases also with size and pain, inflammation and erythema can appear. Radicular resorption can occur if there is contact with neighboring teeth.¹ Diagnosis is based on radiological and histological findings.

The usual treatment for a dentigerous cyst associated with an impacted third molar is its enucleation together with the extraction of the tooth. Large cysts can also be treated with marsupialization, and they can be completely resected at a later date, or drainage can be placed in order to reduce the pressure and size of the cyst, and it can later be enucleated. If complete resorption is achieved, the prognosis is excellent and recurrence is rare. Exceptionally, a dentigerous cyst that is not treated can evolve into an ameloblastoma, squamous cell carcinoma or mucoepidermoid carcinoma.¹

The present case shows the spontaneous evolution of a follicle of an impacted third molar into a dentigerous cyst. The presumed diagnosis was made on the basis of a radiolucent lesion that measured more than 2 mm in the orthopantomography (OPG). The posterior histological study confirmed the diagnosis. In the same patient, a radiological lesion similar to this one, but on the contralateral side, had a different evolution on being removed with the impacted tooth as a prophylactic measure.

In our clinical experience, and in concordance with previous works,^10-12 we consider that radiolucent images of more than 2-3 mm obtained in the OPG around an impacted third molar, mean that there is a high probability of it evolving from a follicle into a dentigerous cyst. In these cases we recommend the prophylactic extraction of the impacted tooth together with the follicle. In those cases in which the radiolucent image is less than 2 mm and prophylactic extraction takes place, routine anatomopathologic studies are not carried out, so the real rate of dentigerous cysts associated with follicles measuring less than 2 mm is not known. The criteria used to differentiate between a follicle and a follicular cyst is based on empirical measurements. A follicle measuring 2-3 mm is considered typically normal.¹² In spite of all this, some authors claim that the incidence of dentigerous cysts associated with impacted third molars is greater than has been assumed from radiological studies alone.^11,13

It would be desirable for detailed studies to be carried out with the aim of establishing reference values regarding the size of radiolucent pericoronal images of impacted third molars, and the relationship with an increase in the probability of the cysts being, or becoming, a histologically diagnosed dentigerous cyst. This would allow an aggressive therapeutic approach to be adopted in cases with a high probability of cystic formation, and the resulting deleterious effects could be avoided or diminished.

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