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The treatment of odontogenic keratocysts is reviewed in light of the aetiology and pathogenesis of these lesions. The role of the dental lamina and submucosal hamartias, as frequently seen in nevoid basal cell carcinoma syndrome, is discussed, and the implications for treatment are emphasized.
, a large number of publications have been devoted to this subject. The aetiology, pathogenesis, presentation, and the various modes of treatment, as suggested by several authors, have resulted in hundreds of articles in various journals. It is particularly the tendency of keratocysts to recur after surgical treatment that has prompted many follow-up studies, all but one of which have been retrospective in nature
. In the 1960s and 1970s, the reported recurrence rates were in the order of 40% to 60%, which probably reflected the fact that surgeons were not familiar with the potential aggressiveness of this newly discovered entity
. In all of these reports, the cyst was just enucleated or removed by curettage.
Current follow-up studies are still reporting fairly high recurrence rates despite attempts to remove possible epithelial cell nests from the cyst membrane by peripheral ostectomies, the use of Carnoy’s solution, or marsupialization and secondary enucleation of the lesion. Blanas et al.
performed a systematic review to summarize the results of these interventions up until the year 2000, and found only 14 studies that met their inclusion criteria. The reported recurrence rates varied from 17% to 56% when just an enucleation was performed. If any adjunctive treatment was applied, such as the use of Carnoy’s solution or decompression before enucleation, the recurrence rates went down to 1% to 8.7%. The follow-up periods, however, varied from 6 months to 21 years. They did not specify how many of them recurred within the first 5 years. It is generally assumed that most recurrences occur in the first 5 years, but this is difficult to prove since most studies have only included a few cases with follow-up of more than 10 years. There is, however, a fair amount of evidence that late recurrences may occur after 10–25 years
showed lower recurrence rates in patients who underwent primary enucleation with or without adjuvant therapy versus a group who underwent decompression ± secondary enucleation. A total of 997 odontogenic keratocysts (OKCs) were included in the review, of which 843 underwent primary enucleation and 154 underwent decompression ± secondary enucleation. The recurrence rates were 18.2% and 27.1%, respectively. Follow-up in both groups, however, varied from 1 to 29 years, and this was reported as either an average follow-up time or by mentioning the shortest and longest follow-up time. The fairly moderate recurrence rates are probably due to a substantial number of cases that were not followed up for longer than 5 years.
It is only fair to say that little progress has been made over the last 40 years with regard to the recurrence rates of OKCs. One may easily become confused by the variety of opinions and treatment protocols that have been presented. It is the aim of this review to put all aspects of this intriguing lesion into perspective, including the aetiology, pathogenesis, and treatment. Both the solitary OKC and OKCs occurring in the context of nevoid basal cell carcinoma syndrome (NBCCS) will be addressed.
Despite the fact that solitary OKCs and syndrome OKCs appear alike when studied histologically, they probably have a different origin in many instances. There was and still is a general belief that all OKCs derive from remnants of the dental lamina. This hypothesis was first suggested by Hjörting-Hansen et al.
. These hamartias are almost certainly derived from offshoots of the basal layer of the epithelium covering the mucosa, since in many cases they were connected to this basal layer. This theory was endorsed by Gorlin et al.
. The aetiology and pathogenesis of the syndrome OKCs make the adjective ‘odontogenic’ questionable.
The name ‘solitary OKC’ is somewhat misleading, because they may occur as multiple cysts in persons without the symptoms of NBCCS. Yet, this name is understood to be a keratocyst not related to NBCCS. Solitary OKCs may occur anywhere in the jaws, but the frequency is higher for the posterior mandible and somewhat less so for the posterior maxilla
. In short, the dental lamina disintegrates after it has laid down the tooth buds of the permanent teeth. The possible remnants are expected to be located in the gingiva or periodontium and certainly not in the bone
. The remote possibility exists that after the formation of the third molars, an offshoot of the distally growing dental lamina persists. It is fully understandable that remnants of the dental lamina, including a distal offshoot, would be responsible for the development of OKCs, and that is certainly true for the tooth-bearing area. The fact that many lateral periodontal cysts and lateral follicular cysts turn out to be OKCs fits with this picture
. There is, however, no actual proof of this hypothesis.
An alternative theory might be that, like in the syndrome cysts, submucosal hamartias play a role. In a prospective study in which the overlying, attached mucosa was excised in 23 of the 44 cases, these hamartias were seen
. These islands were probably displaced when the cyst expanded and penetrated into the bone.
The fact that the OKCs originate from an epithelial residue of the dental lamina located in the gingiva, or a hamartia in the submucosa, does not disprove the fact that they are located in the bone. This penetration into the bone has to be based on an induction phenomenon very similar to what happens when the permanent molars are developing. The dental lamina is growing distally in the submucosa to lay down the molar tooth buds. The epithelial–mesenchymal interaction apparently induces bone resorption, creating crypts in which the developing tooth buds will be positioned
. An example of the potential of the growing dental lamina to resorb even a bone graft and to lay down a tooth bud in the graft is shown in Fig. 3.
Implications for treatment
Considering the aspects of the aetiology and pathogenesis of OKCs described, it is unlikely that the recurrence rate of these lesions can be brought down to zero. True recurrences might be due to remnants of the fragile cyst membrane that are left behind. The same is true for microcysts or epithelial islands, as sometimes seen in the connective tissue wall of the cyst. The use of Carnoy’s solution or, in certain cases, electrocauterization when the cyst has reached the soft tissues, be it mostly lingual in the mandible or buccal in the maxilla, may prevent this from happening. It is important to mention in this context that in many countries chloroform is no longer a permitted constituent of Carnoy’s solution. It follows that there is a need for a study on the efficacy of Carnoy’s solution without chloroform. A suitable substitute that has the same working mechanism as the original Carnoy’s solution would also be very welcome.
Recurrences as a result of new cyst formation due to the presence of hamartias in the overlying mucosa, whether it concerns epithelial islands or microcysts, are more difficult to avoid. Even when the attached mucosa has been excised it cannot be ruled out that new offshoots of the mucosa will occur or that the excision has not included all epithelial islands or microcysts present. This obviously was the reason for some of the recurrences in a previous study
. In short, the usually small cysts in the dentate area that are just enucleated and turn out to be an OKC, could be treated in a second intervention with Carnoy’s solution. This would help to eliminate possible epithelial cell nests that were left behind. All unicystic lesions in the posterior mandible, including the third molar area and ascending ramus, are best treated as a possible OKC or unicystic ameloblastoma. This would require excision of the overlying attached mucosa after which the cyst is enucleated in conjunction with the excised mucosa and the defect wiped out with (a modified) Carnoy’s solution. The area where the mucosa is attached to the cyst wall can easily be located using modern imaging techniques, which will clearly show the anterior fenestration in the ascending ramus, when present. The defect is left to heal by secondary intention, which implies the use a ribbon soaked in Whiteheads varnish or iodoform Vaseline that is packed in the bony defect. This needs to be changed every 7–10 days until the defect can be kept clean by rinsing. Cysts in the maxilla that include the tuberosity area may be treated the same way. The use of Carnoy’s solution, however, should be limited to the tuberosity area. Many of these cysts have expanded into the maxillary sinus, which prevents the use of Carnoy’s solution in that area for obvious reasons. In those cases, the wound needs to be closed primarily. The fenestration is usually located on top of the tuberosity. When hamartias are seen in the attached mucosa, long-term follow-up is warranted since it will not be certain that all of the epithelial islands have been removed or that new ones will develop.
The protocol described does not include multicystic lesions. They would require a preoperative biopsy to rule out another pathology.