Odontogenic keratocyst (OKC) and ameloblastoma (AM) are commonly developed in the posterior mandibular region and have a high recurrence rate [11]. OKC is one of the dental cysts, and it is known to have an aggressive tendency and high recurrence rate because a patient does not feel pain before it is discovered by chance. There is a two-third chance that it is more frequent in the mandible and occurs about three times more frequently in the posterior molar than in the premolar, mostly in the bone, and 50% of OKCs occur concerning the impacted teeth. Residues in the epithelial lining of keratocyst have been reported to have intrinsic growth potential [12].
Next, AM is a benign but locally aggressive odontogenic tumor that develops in the enamel organs of the dental tissue, the ameloblast. This lesion is the second most frequent oral tumor after OKC. AM is most commonly developed in the mandible (85%) and is rare in the maxilla and elsewhere (15%) [13]. Seventy percent of them occur in the posterior and ramus area in the mandible. Most AMs are derived from epithelial rests in the bone tissue but sometimes occur directly from the surface or epithelial rests of the dental lamina located on the outer surface of the bone. The recurrence rate of AM after relatively conservative treatments is high, ranging from 50 to 90%, except for the case of extensive resection of the tumor [2].
Unicystic ameloblastoma (UAM) is one of the three clinical variants of AM. UAM has become established as a distinct clinicopathological entity on the general basis of its unicystic radiographic appearance, histologic findings, association with an unerupted tooth, and occurrence in the mandible of younger patients. UAM represents the clinical and radiological characteristics of the common cyst that occurs in the jaw, but histologically represents the typical ameloblastoma epithelium that surrounds the cyst. UAMs are considered to be less deformed and less aggressive than OKC, with or without lumen or wall tumor proliferation. UAM’s recurrence rate after conservative surgical treatment is lower than that of its conventional counterpart [14]. In this study, only UAM was studied among different variants of AM.
Because UAM is quite similar to a dentigerous cyst, the clinical, radiological, and biological behavior of these two types of cyst groups have been researched. In addition, the recurrence of OKC and UAMs can occur over a long period, so long-term postoperative follow-up is essential for proper management [15, 16]. OKC and UAM proliferate slowly but have a similar tendency to be locally invasive and prone to recurrence [1, 17, 18]. Therefore, the surgical procedure of these lesions requires a complete removal or degeneration of the daughter’s sac or remaining cells around the lesion to reduce the recurrence rate. Among the surgical methods to reduce the recurrence rate of lesions, resections that sacrifice extensive bones around the lesions have the lowest recurrence rates but have the disadvantage that the surgery itself leads to large morbidity. Therefore, enucleation with Carnoy’s solution (CS) has been suggested as an alternative surgical method that contributes to a low recurrence rate [3, 12].
In spite of such a possible advantage of using CS, there has been concern that CS can degenerate normal tissue and cause nerve damage. To evaluate the impact of CS on nerve damage, we evaluated sensory function by dividing patients into the control group with cyst enucleation only and the experimental group with CS treatment as well as the enucleation. Even if chemical cauterization is applied to the exposed IAN for 19 patients in this study, the majority of patients did not experience sensory dysfunction. In addition, the recovery of sensory function was achieved in a relatively short period so that they feel comfortable in daily life.
Overall, the cyst enucleation did not cause a serious sensory dysfunction right after the surgery for groups, both with and without CS treatment. On average, the NRS for all 77 patients right after the surgery was 7.94 and only a little improvement of 0.67 at the end of the follow-up period (8.61) was observed. Additionally, it appeared that a large invasion size of the legion is related to an increased odd of sensory dysfunction for the non-CS use group, but the invasion size is not associated with sensory dysfunction for the CS use group. However, a substantial variation existed for individual patients. For example, NRS right after the enucleation for two patients who were treated with CS was two and the NRS for them was still two at the end of the follow-up period. Therefore, a further in-depth research is required to examine why some patients sustain severe sensory damage right after the enucleation with CS treatment and their sensory functions did not recover at the end of the follow-up period.
A few limitations of the present research deserve a brief discussion. First, the sample size was small and the number of experimental (19) and control groups (58) was not balanced. Second, the patients in the experimental and control groups had different types of lesions and the lesions may be larger and more invasive to IAC among the OKC and UAM patients with CS treatment than among those with DC and RC. Therefore, future researchers need to randomly divide the patients with OKC and UAM into the experimental and control groups to test the effect of the use of CS on the sensory dysfunction. Third, the sensory evaluation may not be accurate, depending on the subjective feeling of a patient. Finally, the follow-up period is somewhat short and not consistent across patients.
