Sir, a 49-year-old male patient with no systemic medical history other than controlled diabetes came to the Department of Dentistry, Jeju National University Hospital. The patient underwent intraoral incision and drainage for swelling on the right side of his face that began to develop a year previously. Due to a relapse, the patient was prescribed with antibiotics from a local clinic. But as his condition did not heal, the patient was referred to the department of dermatology, then to plastic surgery and dentistry.

A protruding lesion was observed around the retracted skin on the right cheek of the patient (Fig. 1). In the intraoral radiographic imaging, a dilated root lesion of dental origin in the maxillary first molar tooth was seen and the patient was diagnosed with buccal fistula of dental origin, and was given endodontic treatment. A water-soluble agent made of calcium hydroxide was applied to control the root canal infection. In a cone beam CT image conducted to check for the presence of maxillary sinus infection, the pushed-out agent showed a sinus tract from the tooth root to the buccal fistula (Figs 2-3).

Figure 1
figure 1

Fistula formed through the skin

Figure 2
figure 2

Accidental tracing with calcium hydroxide agent in CBCT image

Figure 3
figure 3

Accidental tracing with calcium hydroxide agent in 3D image

There were no side effects due to the pushed out agent and all symptoms disappeared within four months of the conservative endodontic treatment. The fistula was obliterated and a scar formed (Fig. 4).

Figure 4
figure 4

Healing of fistula with scar