Carnoy\'s solution, composed of 3 ml of chloroform, 6 ml of absolute ethanol, 1 ml of glacial acetic acid, and 1 g of ferric chloride, is often used as a complementary treatment of lesions with high recurrence rates, such as the keratocystic odontogenic tumor (KOT).\[[@ref1][@ref2]\] Occasionally, soft tissues might be adjacent to the lesion; for example, in cases in the posterior region of the mandible, the inferior alveolar vascular--nervous plexus might be exposed after removal of the lesion.  Complementary treatment involves treatment of the remnant surgical bed.  In this example, Carnoy\'s solution can be applied to the vascular--nervous plexus of the mandibular canal when a fenestration exposes it to the surgical bed (although some paresthesia may be a side effect).  Studies have already reported on the safety of the application of Carnoy\'s solution over a nerve, but to date, no clinical report has been made.\[[@ref3][@ref4]\]

The aim of this paper is to report a case of mandibular KOT and was treated with Carnoy\'s solution over the inferior alveolar plexus without any definitive damage to lip sensitivity. 

Case Report {#sec1-1}
===========

A 33-year-old woman was referred for an evaluation of an osteolytic lesion in the right mandibular body.  A panoramic radiographic image showed a radiolucent, multilocular \[[Figure 1](#F1){ref-type="fig"}\], well-defined lesion extending from the roots of the right mandibular third molar to the left mandibular second premolar \[[Figure 2](#F2){ref-type="fig"}\].  KOT was histologically confirmed after incisional biopsy.  Enucleation of the lesion by intra approach and removal of the involved teeth were accomplished under general anesthesia.  Soft tissues adhering to the capsule of the lesion in the lingual fenestration were also removed.  In the proximity of the mandibular canal, the capsule of the lesion was dissected from the inferior alveolar plexus.  Then, peripheral ostectomy of the whole surgical bed was completed, followed by a single application of Carnoy\'s solution, including over the inferior alveolar plexus \[[Figure 3](#F3){ref-type="fig"}\]. 

![ Preoperative panaromic view](JPBS-4-183-g001){#F1}

![ Intraoral view of the lesion](JPBS-4-183-g002){#F2}

![ Peripheral ostectomy followed](JPBS-4-183-g003){#F3}

In the immediate postoperative period, the patient presented with paresis of the lower lip, which had a total regression after 9 months.  After 9 weeks, the surgical bed was well granulated \[[Figure 4](#F4){ref-type="fig"}\].  After a period of 36 months, no sign of recurrence was observed. 

![ Postoperative view after 9 weeks of application of Carnoy\'s solution](JPBS-4-183-g004){#F4}

Discussion {#sec1-2}
==========

Carnoy\'s solution was first used as a fixative in the 19^th^ century.  Late in the last century, it started to be applied after the removal of the odontogenic keratocyst in the remaining cavity.  It promotes chemical necrosis of up to 1.5 mm and elimination of epithelial remnants and possible microcysts.\[[@ref3]\] The use of this solution is intended to diminish the recurrence rates such that they are similar to those for resection, and to cause lower morbidity.\[[@ref2]\]

The effects in the inferior alveolar nerve were first reported by Frerich *et al*.  in 1994.\[[@ref4]\] The authors applied the substance in the inferior alveolar nerve of rabbits and did not observe axonal damage during the first 3 min of direct application.\[[@ref5]\] In contrast, in another important study, Wolgen *et al*.\[[@ref6]\] noted that the alterations in neural conductivity developed after 2 min of direct application, with few signs of recovery after 2 weeks of follow-up.  However, there was no mention on how long the solution was left in contact with the nerve, an important point that has been questioned.\[[@ref6]\]

Previous studies have not correlated the lab findings during the application of Carnoy\'s solution over neural tissue with the clinical results; however, in this case report, we showed that when a proper protocol is followed, the chemical treatment of the nerve can be accomplished without permanent functional damage.  In both cases, the sensitive alteration was transitory and compatible with the lab findings described earlier.\[[@ref3][@ref4]\] Forssell\[[@ref7]\] and Forssell *et al*.\[[@ref8]\] demonstrated increased recurrence rates in the first 3 years with much lower recurrences after that period, suggesting that the first few years are critical for the follow-up.  The cases presented here were followed up around this time period.  Even though they will still need lifelong follow-up, good prognoses can be expected, and data from continuous case series are encouraging. 

We prefer to apply Carnoy\'s solution after a slight peripheral ostectomy over the remaining bone surgical bed.  This promotes mechanical regularization of the bone cavity as well as the mechanical removal of any soft tissue left behind, decreasing the likelihood of a recurrence.  The solution is applied for 3 min in the cavity using imbibed gauze, while taking care to protect the adjacent soft tissues.  When the nerve is exposed in the cavity, the application is performed only once.\[[@ref2][@ref4][@ref9]\]

**Source of Support:** Nil

**Conflict of Interest:** None declared.