The purpose of this study was to determine how keratocystic odontogenic tumours (KCOTs) in the mandible are reduced during marsupialisation, and to predict the best time for secondary enucleation by analysing computed tomography (CT) images. 15 patients with KCOTs were treated with marsupialisation surgery, and 42 series of CT data taken during the marsupialisation process were analysed. CT data were reconstructed in three-dimensional (3D) images. The 3D images were used to measure the diameter and volume, and to analyse the changes that occurred after marsupialisation. Marsupialised KCOTs tended to be reduced equally towards the window in the tumour. The amount of volume reduction per day ( V r ) was reduced in proportion to the volume ( V ) with the formula V r = −0.0029 × V . The formula manipulation for V was V = V 0 × e −0.0029 t ( t = duration after marsupialisaton (day)). The volume of marsupialised KCOTs was reduced by half over a 239 day cycle. These results demonstrate that the future shape of marsupialised mandibular KCOTs, under good control, could be predicted with significant accuracy using CT data. This prediction could decrease the prolonged marsupialisation state in patients with KCOTs.
Odontogenic keratocyst (OKC) was designated by the World Health Organization (WHO) as a keratocystic odontogenic tumour (KCOT) in 2005. KCOT has been defined as ‘a benign uni- or multicystic, intraosseous tumour of odontogenic origin, with a characteristic lining of parakeratinized stratified squamous epithelium and potential for aggressive, infiltrative behaviour.’ These tumours are characterised by a high recurrence rate . Many attempts have been made to reduce the high recurrence rate with improved surgical techniques; the recurrence rate of OKCs ranges from 13% to 63% . Recommended techniques have included tanning the cystic cavity with Carnoy’s solution before enucleation , or using a combination of enucleation and liquid nitrogen cryotherapy . Other recommended techniques are marsupialisation or decompression of the cysts followed by secondary enucleation . B ramley recommended the use of radical surgery with resection and bone transplantation. E phros and L ee advocated removal of the lateral cortical plate and enucleation of the cyst. B ataineh and al Q udah advocated resection without continuity defects as a standard treatment for preoperatively diagnosed OKCs.
To reduce the high recurrence rate of KCOTs, it is essential to eradicate the epithelial components of the cyst . Radical treatment has been associated with numerous complications, including facial deformity, missing teeth, infection of transplanted bone, and/or permanent numbness of the region innervated by the mental nerve when the KCOTs involved the inferior alveolar nerve. Considering the benign characteristics of KCOTs, the priority of the treatment method should be discussed from the perspective of morbidity and the patient’s quality of life; the recurrence rate should not always be the primary factor.
Marsupialisation or decompression has been used as a conservative treatment for large OKC, minimising the tumour size and limiting the extent of surgery . N akamura et al. reported that marsupialisation did not affect the recurrence rate of OKC. M arker et al. reported long-term results after decompression for 23 OKCs, and they concluded that these cysts could be treated successfully by marsupialisation and secondary enucleation. One of the disadvantages of marsupialisation is that the time required is comparatively long .
The aim of this study is to clarify how KCOTs are reduced during the marsupialisation process and to predict the best time for secondary enucleation by analysing computed tomography (CT) images.
Materials and methods
This series consisted of 15 patients with histologically proven KCOTs of the mandible. All of the patients were treated by marsupialisation surgery from 2000 to 2010. Of the 15 patients, nine were male (60%) and six were female (40%). The mean age was 35.9 years (range 16–57 years). The tumours were located in the posterior molar to mandibular ramus in five lesions, in the angle to mandibular ramus in seven lesions, and in the anterior molar region in three lesions. Using X-ray images, the tumours were classified; 10 were unilocular lesions and five were multilocular lesions ( Table 1 ).
|The duration from day of marsupialisation to day of having taken CT before surgery|
|Location of the tumours|
|Molar region–mandibular ramus||5||3||2|
|Angular region–mandibular ramus||7||4||3|
|Anterior region–molar region||3||2||1|