Case Report
Efficacy of cone-beam computed tomography for the diagnosis of external dental fistula
Hideo Takenoshita and Toshiyuki Yamamoto*
Corresponding Author: Toshiyuki Yamamoto, MD, PhD, Department of Dermatology, Fukushima Medical University, Hikarigaoka 1, Fukushima 960-1295, Japan. Tel./Fax: +81.24.547.1307 E-mail:
Received: April 22, 2015; Revised: Aug 25, 2015; Accepted: May 21, 2015
Citation: Yamamoto T & Takenoshita H (2015) Efficacy of cone-beam computed tomography for the diagnosis of external dental fistula. Dermatol Clin Res, 1(2): 31-33
Copyrights: ©2015 Yamamoto T & Takenoshita H. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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External dental fistula often presents with facial sinus, and patients visit dermatology clinics.  Usually, diagnosis is not difficult by orthopantomography. We present a case of external dental fistula which was not detected by orthopantomography, but examination by cone-beam computed tomography (CT) revealed a small sequestrum.


A 62-year-old woman was referred to our hospital, complaining of a nodular lesion on her right cheek, with 2 months’ duration.  Previously, she visited otolaryngology department, and needle biopsy showed no malignancy.  Administration of antibiotics resulted in no effects.  On the initial visit to our department, a physical examination showed a reddish dimpled nodule located on the right cheek (Figure 1). Clinical diagnosis was external dental fistula, however, examination by pantomography did not detect any abnormalities.  Histological examination showed non-specific granulation with dense infiltration of inflammatory cells composed of lymphocytes, neutrophils, histiocytes and plasma cells in the whole dermis (Figure 2). Tissue cultures for bacteria, mycobacterium tuberculosis and non-tuberculous mycobacterium were all sterile. Also, polymerase chain reaction (RCR) analysis for mycobacterium tuberculosis and non-tuberculous mycobacterium were negative.  Laboratory examination showed no abnormalities including liver and kidney function, and tuberculin test revealed negative reaction.  Cone-beam computed tomography revealed the presence of a small sequestrum (Figure 3).  Surgical treatment with sequestrectomy resulted in improvement with scar within 3 months.


It is important to make a correct diagnosis of external dental fistulas, because they sometimes masquerade skin tumors [1]. Orthopantomography is frequently used for making a diagnosis of external dental fistula.  In this report, we show a case of external dental fistula, in which ordinal X-ray beam did not detect any abnormalities, such as apical infection, residual bone, radicular pulp, and fistula.  However, cone-beam CT demonstrated the presence of small sequestrum, which was the cause of the development of nodular lesions in this case.
Cone-beam CT scan is a cross-sectional, radiological imaging system for maxilla-facial skeleton. This technique has overcome many of the limitations of conventional radiography, and is now widely used in dental practice [2]. It should be reminded that orthopantomography is not always useful for the diagnosis of external dental fistula.  In particular, X-ray beam permeability is insufficient in case of the tiny lesions of the root apex. We dermatologists should also be aware of the useful imaging tool of cone- beam CT for the diagnosis of external dental fistula


1. Wilson SW, Ward DJ, Burns A (2001) Dental infections masquerading as skin lesions. Br J Plast Surg 54: 358-360. PMID: 11355994

2. Patel S, Kanagasingam S, Mannocci F (2010) Cone beam computed tomography (CBCT) in endodontics. Dent Update 37: 373-379. PMID: 20929151