A 19-year-old female visited our clinic complaining of malocclusion of mandibular dentition. There was no mandibular swelling or pain. However, panoramic radiography revealed a huge well-defined radiolucent lesion, and teeth displacement from #36 to #45 was observed. The labial cortical bony walls were moderately thinned and deviated, penetrating to the labial side of the mandible (Figs. 1 and 2).
The patient had no systemic problems, and because the cystic lesion had invaded to the inferior alveolar nerves, we chose enucleation after continuous drainage over cyst enucleation. A decompression device durable enough for long-term placement was required, because long-term drainage was expected, and there was concern about the possibility of continuous falling-outs, replacements, and infection if using a rubber tube. As a decompression device, 16G spinal needles were attached to a Ø2.0 mini plate with light-cured resin after forming two uneven holes using a round bur (Fig. 3).
It was possible to reduce the operation time by pre-surgical adjustment of the mini plate according to the patient’s dimensions after determining the position of the decompressor. The operation was performed under general anesthesia. The customized decompressor was attached below the mandibular anterior teeth. The attachment site had already been determined by confirmation of healthy bone on mandibular computerized tomogram (CT) images. For fixation, two mini plates were attached at the inferior border of the anterior mandible.
A tissue biopsy performed at the time of surgery indicated a keratocystic odontogenic tumor (Fig. 4). Self-cleaning of the holes in the mini plate was indicated by the 21G needle every day at the time of hospital discharge. Follow-up was performed at 1, 2, 3, and 6 months.
After 1 month, one of the needles had fallen out of its hole, but the other was well maintained (Fig. 5). Continuous bone formation in the lesion was confirmed by CT scanning of the mandible every 6 months (Fig. 6a, b). Final enucleation and removal of the mini plates were performed 15 months after surgery.
The dentition of the displaced teeth was restored somewhat to its original state by the completion of treatment (Fig. 7). Subsequently, following enucleation, continuous orthodontic treatment in our clinic was initiated.
Discussion
For cystic pressure reduction and preservation of teeth, Thomas [4], in 1947, recommended decompression, which proceeds by formation of a small hole in the cystic cavity and insertion of a drain. The cystic cavity is gradually closed, both by relieving the pressure within it and by regular washing through the drain. Due to the fact that decompression/drainage is a long-term treatment, it is necessary to establish an environment for continuous drain maintenance and easy oral hygiene control. When using a rubber drain, suture maintenance is difficult, and periodic replacement is required; in any case, leaving in the same sutures over long durations increases the risk of infection.
In the present study, continuous self-cleaning with a 21G needle was performed by means of a decompressor attached to the mandible. The device was found to have been well attached, except for the fact that a drain had fallen out. Over the course of the follow-up period, no infection or cell necrosis around the fistula was observed. The mini plate must be attached to healthy bones, whose sites are determined prior to surgery by radiographic analysis (e.g., CT). Even if it has to be located above the lesion, it is still desirable to find as solid an area as possible.
During our follow-up period, we continuously performed CT radiography, observing gradual bone formation and cyst reduction. Moreover, the displaced teeth were recovered to the previous status, and no damage to the adjacent anatomical structures was evident. On this basis, it is considered that extensive cysts can be successfully treated by decompression if an appropriate decompressor is designed according to the lesion location and size and is well maintained over a long period of time.
However, repeated deformation of the mini plate can cause fracture, and attachment to the 16G spinal needle can fail due to resin breakage. In the present case, whereas the preoperative plan was to attach one mini plate with two holes to the lesion (Fig. 8), two mini plates were attached, because fracture occurred in the process of fitting the first. Where sufficient sound bone is lacking, applying two mini plates can be much more difficult than one, and proceeding with two can incur decompressor instability. Also, although a slightly more accurate decompressor can be produced by CT and surgical replica model, the cost burden on patients thereby is increased. In the present case, it was considered that one drain had fallen out after surgery, due to the contact area with the 16G spinal needle having become weak in the process of mini-plate deformation during surgery. Fracture in the contact area can be effectively prevented, therefore, only if the 16G spinal needle is attached after full bending of the mini plate.
Furthermore, this device, as it is custom-designed for the individual patient, should be prepared prior to surgery. Certainly, adequate presurgical preparations are necessary, particularly given the difficulty of finding an alternative in the event of device failure.
