Diagnosis and management of odontogenic cutaneous sinus tract: a case series

Abstract

Introduction

Odontogenic cutaneous sinus tract (OCST) is an uncommon sequela of chronic endodontic infection and is frequently misdiagnosed as a dermatological lesion because dental symptoms are often minimal.

Case presentation

This case series reports four patients who presented with extraoral cutaneous sinus tracts of endodontic origin. Diagnosis was based on clinical examination, pulp sensibility testing, conventional radiography, sinus tract tracing when feasible, and cone-beam computed tomography (CBCT). CBCT is particularly useful for identifying periapical lesions, buccal cortical perforations, and tooth-related complexities when sinus tract tracing is inconclusive. Management includes nonsurgical root canal treatment/retreatment, endodontic microsurgery, and root amputation, depending on the underlying pathology. Elimination of the odontogenic source resulted in the resolution of all sinus tracts, with progressive cutaneous healing and radiographic evidence of periapical repair during follow-up, including long-term stability.

Conclusions

OCST should be considered in patients with persistent facial skin lesions. Accurate identification of the causative tooth and selection of the appropriate treatment based on the underlying pathology are essential for favorable outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-026-08264-z.

Background

Odontogenic cutaneous sinus tract (OCST) refers to a condition in which a chronic periapical lesion, resulting from a pulpal infection such as pulp necrosis, drains to the skin surface and forms a sinus tract [1–4]. Periapical inflammation spreads through the bone and soft tissue along the path of least resistance, perforates the cortical plate, and drains onto the facial skin, resulting in a cutaneous lesion [1, 2, 5]. The cutaneous manifestation of OCST typically appears as an erythematous nodule, and dimpling of the skin along the sinus tract pathway can also be observed [2, 3, 6, 7].

Because OCST commonly develops as a consequence of chronic low-grade infection, pain is often mild or absent. The causative tooth is most frequently located in the mandible (approximately 80% of cases), and cutaneous lesions typically appears in the mandibular angle, lower border of the mandible, or chin region [6, 8, 9].

Since dental symptoms, including toothache, are often absent or minimal, patients frequently misinterpret OCST as a primary dermatological condition. Consequently, they often seek treatment in dermatology or plastic surgery clinics, where prolonged management may be required before referral to a dental clinic [3, 4, 6, 7, 9]. When the cutaneous lesion is distant from the causative tooth, identification of the dental origin becomes even more challenging, and patients may undergo antibiotic therapy, biopsy, or surgical excision before an odontogenic cause is recognized [3, 4, 9, 10].

Accurate diagnosis of OCST requires a thorough consideration of the clinical history, careful intraoral examination, and periapical radiographic evaluation to identify the causative tooth [1–3, 7]. Tracing of the extraoral sinus tract using a gutta-percha (GP) cone is commonly performed to confirm its origin [1–3]. In addition, cone-beam computed tomography (CBCT) allows three-dimensional assessment of the extent of periapical lesions and cortical bone perforation, thereby facilitating identification of the causative tooth and treatment planning [1, 5, 11].

This case series presents the clinical outcomes of non-surgical and surgical endodontic treatment in four cases of OCST and discusses important considerations in the diagnosis and management of this condition.

Case presentation

This study was approved by the Institutional Review Board (IRB) of the Chosun University Dental Hospital (CUDHIRB 2601 003). All patients provided written informed consent for the use and publication of their clinical information and accompanying images. The Preferred Reporting Items for Case reports in Endodontics (PRICE 2020) standards were followed in the preparation of this report [12]. The PRICE 2020 flowchart (Supplementary Fig. 1) provides the key features of the cases.

Case 1

A 43-year-old female patient presented with a chief complaint of swelling of the lower chin. The patient was initially evaluated at the department of oral and maxillofacial surgery and subsequently referred to the department of conservative dentistry. She reported no remarkable medical or dental history, and denied any tooth-related symptoms, including pain.

Extraoral examination revealed a crust-covered cutaneous lesion in the submandibular region with evidence of drainage and surrounding erythema (Fig. 1A). Intraoral examination showed no obvious caries or tooth fracture (Fig. 1B). On clinical examination, mandibular left canine (#33) showed tenderness to percussion and no response to the electric pulp test (EPT), whereas tooth #32 was not tender to percussion and showed a positive response to EPT. Panoramic radiography revealed radiolucent periapical lesions associated with the mandibular left lateral incisor (#32) and canine (#33) (Fig. 1D, E). To trace the course of the sinus tract, tracing radiograph was performed using an ISO size #25 GP cone (Fig. 1C); however, the cone was directed toward the mandibular symphysis region (Fig. 1F).

Fig. 1.

Preoperative clinical photographs and radiographs of Case 1. A Extraoral clinical photograph showing a crusted skin lesion on the chin. B Intraoral clinical photograph. C Extraoral clinical photograph showing the GP cone inserted into the sinus tract for tracing. D Panoramic radiograph showing periapical radiolucency on the mandibular left lateral incisor (#32) and canine (#33). E Periapical radiograph. F Tracing radiograph with an ISO size #25 GP cone. Note that the GP cone points toward the mandibular symphysis rather than the expected root apex

CBCT (CS 9300; Carestream, Rochester, NY, USA) was performed to accurately determine the location and extent of the periapical lesion. CBCT revealed a non-corticated radiolucent lesion in the periapical region of teeth #32 and #33. Buccal cortical plate thinning was observed at tooth #32, while perforation of the buccal cortical plate was noted at tooth #33 (Fig. 2). Based on these findings, tooth #33 was diagnosed with pulpal necrosis and chronic apical abscess, and nonsurgical root canal treatment was planned. Tooth #32 showed a positive vitality response; therefore, its treatment was deferred, and the clinical signs and radiographic findings were scheduled to be re-evaluated after completion of the treatment on tooth #33. Regarding cutaneous lesion, the patient was planned to be referred to the dermatology or plastic surgery clinic for further management if additional intervention was required after endodontic treatment.

Fig. 2.

CBCT images showing periapical radiolucency and buccal cortical bone perforation of the mandibular left lateral incisor and canine. A Axial view. B Sagittal view of tooth #32. C Sagittal view of tooth #33. D Coronal view

Root canal treatment was initiated during the second visit. After local anesthesia with 2% lidocaine containing 1:100,000 epinephrine, tooth (#33) was isolated with a rubber dam. An access cavity was prepared and necrotic pulp tissue was confirmed during access preparation. Apical patency was verified using a #10 K-file (Dentsply, Milford, DE, USA), and the working length was determined using an electronic apex locator (DentaPort II; Morita, Tokyo, Japan). Root canal was prepared using stainless steel K-files with copious irrigation using 2.5% sodium hypochlorite (NaOCl) throughout the procedure. After completion of canal preparation, the root canal was dried with sterile paper points, and calcium hydroxide paste (Calcipex II; Nishika, Shimonoseki, Japan) was placed as an intracanal medicament. A cotton pellet was positioned and the access cavity was temporarily sealed with IRM (Dentsply, Milford, DE, USA) (Fig. 3A, B).

Fig. 3.

Endodontic treatment procedure. A Initial apical file (IAF) radiograph. B After intracanal dressing with calcium hydroxide and temporary restoration with IRM. C Extraoral clinical photograph at 3 weeks, showing resolution of the crust. D Master cone fit radiograph. E Post-obturation radiograph. F Extraoral clinical photograph after obturation showing complete healing of the sinus tract

At the 3-week follow-up visit, the crust over the cutaneous lesion had resolved, with no drainage observed and only slight dimpling of the skin remaining (Fig. 3C). This clinical improvement confirmed that the lesion was an OCST originating from tooth #33. Additional irrigation and replacement of the intracanal medication were performed at that visit, and the patient was placed under further observation.

Subsequently, the cutaneous dimpling gradually improved over the following 3 weeks (Fig. 3F). After significant resolution of the cutaneous lesion and complete relief of clinical symptoms, root canal obturation was performed. Following confirmation of the master cone fit (Fig. 3D), the canal was obturated using the lateral compaction technique. Core build-up was completed with a dual-core composite resin (LuxaCore Z Dual; DMG, Hamburg, Germany) (Fig. 3E).

At the 3-month follow-up, the cutaneous lesion further improved, and no remarkable clinical symptoms were observed in either tooth #32 or #33. Tooth #32 showed a positive response to the EPT, and radiographic examination demonstrated healing of the periapical lesion; therefore, no additional treatment was performed for tooth #32 (Fig. 4A, B). At the 6-month follow-up, the cutaneous lesion had healed to a level comparable to that of the surrounding skin. Clinical examination revealed no abnormal findings, and radiographic evaluation revealed continued healing of the periapical lesion (Fig. 4C, D).

Fig. 4.

Follow-up examinations. A Three-month follow-up periapical radiograph showing initial bone healing. B Three-month follow-up extraoral photograph. C Six-month follow-up periapical radiograph showing progressive bone healing. D Six-month follow-up extraoral photograph showing a resolved skin lesion with minimal scarring

Case 2

A 47-year-old male patient presented with a chief complaint of a hard, palpable lump on the gingiva. The patient reported that the symptoms had begun approximately 1 year earlier and that he had recently visited a private dental clinic, which referred him to our hospital for further evaluation. The patient had no remarkable medical history. Extraoral examination revealed a cutaneous lesion with crusting superior to the right oral commissure. Panoramic radiography revealed previous root canal treatment of the maxillary right canine (#13) and a fixed prosthesis extending from the maxillary right canine (#13) to the left maxillary canine (#23) (Fig. 5). Clinical examination revealed that tooth #13 was tender to percussion, and periapical radiography revealed a radiolucent lesion at its apex. Periapical radiolucency was also observed around the right maxillary first premolar (#14); however, the tooth responded positively to the EPT.

Fig. 5.

Preoperative radiographs and clinical photographs of Case 2. A Panoramic radiograph. B Periapical radiograph showing periapical lesion of the maxillary right canine. C Extraoral clinical photograph showing a crusted skin lesion

Sinus tract tracing with a GP cone was attempted to evaluate the odontogenic origin of the cutaneous lesion. However, the procedure could not be performed because the crust was firm and the opening was narrow. Therefore, we decided to assess the relationship between the tooth and the cutaneous lesion by observing changes in the skin lesion after the retreatment of tooth #13. Based on these findings, tooth #13 was diagnosed with a chronic apical abscess, and the possibility of an OCST was considered. After the removal of the fixed prosthesis, nonsurgical endodontic retreatment of tooth #13 was planned, and the teeth with severe caries (#11, #21, and #23) were extracted. Tooth #14 was planned to be re-evaluated after treatment of tooth #13, depending on the clinical course and symptoms.

At the subsequent visit, nonsurgical endodontic retreatment of tooth #13 was initiated. All the procedures were performed under rubber dam isolation. After access cavity preparation, the existing root canal filling material was removed, the working length was established, and canal cleaning and shaping were performed (Fig. 6A). Calcium hydroxide paste (Calcipex II) was then administered intracanally, and the tooth was temporarily restored. Periapical radiography revealed that the calcium hydroxide paste extended from the apical region toward the cutaneous lesion following the sinus tract pathway (Fig. 6B).

Fig. 6.

Periapical radiographs and extraoral clinical photographs during endodontic retreatment and follow-up. A IAF radiograph. B After intracanal dressing with calcium hydroxide, showing extrusion of the medicament along the sinus tract toward the skin lesion. C Master cone fit radiograph at 8 weeks. D Post-obturation radiograph. E Three-month follow-up periapical radiograph showing periapical bone healing. F Two weeks after treatment initiation. G Four weeks after treatment initiation. H Eight weeks after treatment initiation showing the healing process of the sinus tract

At the 2-week follow-up visit, improvement in the cutaneous lesion was observed (Fig. 6F), and additional canal irrigation and replacement of calcium hydroxide paste were performed. Two weeks later, at the third visit, further improvement in the skin lesion was noted (Fig. 6G). At the subsequent visit 4 weeks later, root canal obturation was performed, and resin core build-up was completed (Fig. 6C, D, H). Progressive resolution of the cutaneous lesion during treatment confirmed that tooth #13 was the causative tooth of OCST. At the 3-month follow-up, periapical radiography revealed bone healing in the periapical region (Fig. 6E).

Case 3

A 34-year-old female patient presented with the chief complaint of a pimple-like lesion on the right jaw. The patient reported that she had undergone root canal treatment of the mandibular right first molar (#46) at a private dental clinic 1 year earlier, followed by nonsurgical endodontic retreatment and prosthetic restoration 6 months prior to presentation. Approximately 4 months before referral, a cutaneous lesion developed in the right mandibular region for which she received dermatologic treatment. She was subsequently referred to dental clinic because of suspected odontogenic origin of the lesion. The patient had no remarkable medical history.

An extraoral examination revealed a cutaneous lesion with dimpling and discoloration of the right mandibular ramus (Fig. 7A). An intraoral examination revealed no remarkable findings (Fig. 7B). Periapical radiograph revealed a previously obturated and prosthetically restored mandibular right first molar (#46), with a radiolucent periapical lesion around the mesial root. Additionally, a radiopaque object suggestive of a separated instrument was observed in the mesial canal (Fig. 7C).

Fig. 7.

Preoperative clinical photographs and radiographs of Case 3. A Extraoral clinical photograph showing skin dimpling and pigmentation on the right mandible. B Intraoral clinical photograph. C Periapical radiograph showing a periapical lesion and a separated instrument in the mesial root of the mandibular right first molar (#46). D CBCT axial view showing buccal cortical bone perforation. E CBCT sagittal view showing the extent of the periapical lesion. F CBCT coronal view showing buccal cortical bone perforation

CBCT was performed to evaluate the precise location and extent of the lesion (Fig. 7D–F). The images revealed a non-corticated ovoid radiolucent lesion in the periapical region of the mesial root of tooth #46 with perforation of the buccal cortical plate. The lesion measured 4.30 × 3.88 × 4.48 mm in the buccolingual, mesiodistal, and vertical dimensions. An anatomical configuration was also observed in which the mesiobuccal and mesiolingual canals merged in the apical region. To confirm the relationship between the cutaneous lesion and tooth #46, sinus tract tracing with a GP cone was attempted. However, the sinus tract opening appeared to be closed, making insertion of the GP cone difficult, and GP tracing could not be performed.

Based on these findings, tooth #46 was diagnosed with a chronic apical abscess, and the possibility of an associated OCST was evaluated throughout the clinical course. Considering the history of retreatment, presence of a separated instrument, and complex root canal anatomy, endodontic microsurgery targeting the mesial root was planned.

During a subsequent visit, endodontic microsurgery was performed on the mesial root of tooth 46. All procedures were performed under a dental operating microscope (OPMI Pico; Zeiss, Oberkochen, Germany). After local anesthesia with 2% lidocaine containing 1:100,000 epinephrine, a full-thickness mucoperiosteal flap was elevated to expose the lesion (Fig. 8A). Granulation tissue was observed around the periapical area of the mesial root of tooth #46 and was curetted (Fig. 8B). An apical root-end resection of 3 mm was performed on the mesial root (Fig. 8C). Inspection of the resected root surface following methylene blue staining revealed no cracks, and the presence of an isthmus was confirmed (Fig. 8D). A retrograde cavity of 3-mm in depth was prepared along the long axis of the canal using ultrasonic tips (JETip; B&L, Ansan, Korea) (Fig. 8E) Root-end filling was performed using EndoCem MTA (Maruchi, Wonju, Korea), followed by flap repositioning and suturing (Fig. 8F-H).

Fig. 8.

Clinical photographs of the endodontic microsurgery procedure. A Flap elevation. B Exposure of the root apex after curettage of granulation tissue. C Resected mesial root end. D Magnified view (20x) of the resected root-end surface. E Retro-cavity was prepared using ultrasonic tip. F After retro-filling with EndoCem MTA. G Before suturing. H After suturing

At the 1-week postoperative visit, the surgical site exhibited favorable healing, and the sutures were removed. Although the cutaneous lesion persisted, skin dimpling reduced (Fig. 9A, D). At the 2- and 5-month follow-up visits, the dimpling and discoloration of the skin lesion showed gradual improvement, and radiographic examination demonstrated progressive healing of the periapical radiolucency (Fig. 9B, C, E, F).

Fig. 9.

Follow-up examinations. A-C Periapical radiographs at 1 week, 2 months, and 5 months postoperatively, showing progressive bone healing. D-F Extraoral clinical photographs at 1 week, 2 months, and 5 months postoperatively, showing the resolution of the skin lesion

Case 4

A 62-year-old male patient presented with the chief complaint of purulent discharge from the right cheek. Patient reported that a cutaneous lesion had developed approximately 3 months earlier and that he had undergone incision and drainage, laser treatment, and antibiotic therapy at a plastic surgery clinic without symptomatic improvement. He was subsequently advised by an acquaintance with a similar experience to seek a dental evaluation and visited a nearby private dental clinic, which referred him to university hospital for further examination. The patient had no remarkable medical history.

Extraoral examination revealed a cutaneous lesion with deep dimpling and discoloration, located superior to the right oral commissure. Intraoral examination revealed that the maxillary right first molar (#16) was prosthetically restored, and periodontal probing revealed a localized 10-mm deep periodontal pocket at the mesiobuccal root. Radiographic examination confirmed previous root canal treatment of tooth #16 and revealed a radiolucent periapical lesion surrounding the mesiobuccal root (Fig. 10A–D).

Fig. 10.

Preoperative clinical photographs and radiographs of Case 4. A Extraoral clinical photograph showing deep skin dimpling and pigmentation. B Panoramic radiograph. C Periapical radiograph. D Magnified view of the extraoral sinus tract. E An ISO size #30 GP cone inserted into the sinus tract. F Tracing radiograph showing the GP cone pointing to the mesiobuccal root apex of the maxillary right first molar (#16)

A tracing radiograph using an ISO size #30 GP cone demonstrated that the tip of the cone was toward the apex of the mesiobuccal root of tooth #16, suggesting the odontogenic origin of the cutaneous lesion (Fig. 10E, F). Based on these findings, an OCST associated with tooth #16 was suspected, and nonsurgical endodontic retreatment of tooth #16 was planned. The cutaneous lesion was scheduled to be re-evaluated after the completion of endodontic retreatment, and additional dermatological or surgical intervention was considered only if necessary.

At the subsequent visit, the crown restoration of tooth #16 was removed, and nonsurgical endodontic retreatment was initiated. The existing root canal filling materials were removed from all four canals, working lengths were established, and canal shaping and irrigation were performed. Calcium hydroxide paste (Calcipex II) was then administered intracanally, and the tooth was temporarily restored (Fig. 11A, B).

Fig. 11.

Non-surgical endodontic retreatment process. A IAF radiograph. B After intracanal dressing with calcium hydroxide. C Master cone fit radiograph. D Post-obturation radiograph showed sealer extrusion along the suspected root fracture

At the 2- and 5-week follow-up visits, the cutaneous lesion did not resolve, and persistent drainage from the lesion was observed. Considering the continued presence of the cutaneous lesion, the localized deep periodontal pocket around the mesiobuccal root, and persistent periapical radiolucency, the possibility of a root crack or vertical root fracture was suspected. Therefore, after the completion of nonsurgical endodontic retreatment, root resection was planned (Fig. 11C, D).

After completion of nonsurgical root canal retreatment, CBCT evaluation was performed for preoperative lesion assessment. CBCT revealed extensive bone destruction centered around the mesiobuccal root of tooth #16. A vertically extending low-density lesion was observed along the mesiobuccal root, accompanied by perforation of the buccal cortical plate (Fig. 12). In addition, extrusion of the root canal sealer was observed after obturation (Fig. 11D). Based on the combined clinical and radiographic findings, amputation of the mesiobuccal root was planned.

Fig. 12.

Preoperative CBCT images. A Axial view showing extensive buccal bone destruction. B Sagittal view. C Coronal view showing buccal cortical bone perforation

At a subsequent visit, mesiobuccal root amputation of tooth #16 was performed. After local anesthesia, the mucoperiosteal flap was elevated, the granulation tissue was curetted, and the mesiobuccal root was resected. Examination of the resected root revealed vertical root fracture and internal contamination. The exposed GP was removed and a retrograde cavity was prepared using ultrasonic tips (JETip), followed by root-end filling with resin-modified glass ionomer cement (Fuji II LC; GC, Tokyo, Japan). A collagen plug (Ateloplug; Bio-land, Cheongju, Korea) was placed in the osseous defect created after the root amputation, and the flap was repositioned and sutured (Fig. 13).

Fig. 13.

Clinical photographs of the root amputation procedure. A Preoperative intraoral view. B After flap elevation and mesiobuccal root resection. C Resected mesiobuccal root. D Confirmation of the vertical root fracture and contamination. E After retro-filling and placement of a collagen plug (Ateloplug). F After suturing

At the 1-week postoperative visit, the surgical site was disinfected and the sutures were removed. At the 1-month follow-up, the cutaneous lesion persisted; however, the dimpling and discoloration decreased (Fig. 14A, H). At the 2-month follow-up, the patient was asymptomatic, and a definitive prosthetic restoration of tooth #16 was performed (Fig. 14B, I).

Fig. 14.

Long-term follow-up examinations (A-G: Periapical radiographs, H-N: Extraoral clinical photographs). A, H One-month postoperatively. B, I Two months. C, J Seven months. D, K One year. E, L Two years. F, M Four years. G, N Eight years postoperatively, showing stable periapical bone healing and complete resolution of the skin lesion

At 1-year follow-up, radiographic examination revealed bone healing at the mesiobuccal root amputation site (Fig. 14D, K). At 2-year follow-up, cutaneous dimpling was barely noticeable (Fig. 14E, L). At the subsequent 4- and 8-year follow-ups, no remarkable clinical symptoms were observed, and radiographic evaluation of tooth #16 showed stable periapical bone regeneration (Fig. 14F, G, N, M).

To facilitate comparison among the four cases, the key clinical characteristics, diagnostic findings, treatment approaches, and follow-up outcomes are summarized in Table 1.

Table 1.

Summary of clinical features and management of the four OCST cases

Case number	1	2	3	4
Age/Sex	43/F	47/M	34/F	62/M
Chief Complaint	Swelling of the lower chin with cutaneous drainage	Hard, palpable gingival lump and facial cutaneous lesion	Pimple-like lesion on the right jaw	Purulent discharge from right cheek
Duration before diagnosis	Not specified	1 year	4 months	3 months
Location of cutaneous sinus tract	Submandibular region (chin)	Superior to right oral commissure	Right mandibular ramus region	Superior to right oral commissure
Affected tooth	#33 (mandibular left canine)	#13 (maxillary right canine)	#46 (mandibular right first molar)	#16 (maxillary right first molar)
Previous treatment	None	Previous root canal treatment	Previous root canal treatment and retreatment	Previous root canal treatment
Sinus tract tracing	Performed with GP (traced toward mandibular symphysis)	Not performed (narrow opening)	Not performed (closed sinus tract)	Performed with GP (traced to MB root apex)
CBCT findings	Periapical radiolucency with buccal cortical bone perforation	Not performed	Periapical radiolucency with buccal cortical bone perforation	Extensive bone destruction and buccal bone perforation
Diagnostic findings	Percussion tenderness, negative EPT, periapical radiolucency	Percussion tenderness, periapical radiolucency	Separated instrument and periapical radiolucency	Deep periodontal pocket suspected vertical root fracture
Final diagnosis	Pulp necrosis with chronic apical abscess	Previously treated and chronic apical abscess	Previously treated and chronic apical abscess	Vertical root fracture on mesiobuccal root
Treatment	Nonsurgical root canal treatment	Nonsurgical endodontic retreatment	Endodontic microsurgery on the mesial root	Nonsurgical retreatment followed by mesiobuccal root amputation
Outcome	Complete resolution of cutaneous lesion and progressive bone healing at 6 months	Resolution of sinus tract and periapical bone healing at 3 months	Gradual resolution of skin lesion and bone healing at 5 months	Stable bone healing and complete resolution of skin lesion at 8-year follow-up

Discussion

OCST develops when inflammation originating from pulpal necrosis or periapical infection progresses along the path of least resistance within the bone, perforates the cortical plate, and subsequently spreads through soft tissues to drain onto the skin surface [1, 2]. The direction of sinus tract formation and the location of cutaneous drainage are influenced not only by the position of the causative tooth but also by anatomical factors, such as cortical bone thickness and muscle attachments [13].

Delayed diagnosis of OCST is common. Guevara-Gutiérrez et al. reported that the average interval from onset to correct diagnosis was approximately 8 months, with nearly half of patients initially misdiagnosed [9]. Furthermore, unnecessary procedures such as biopsy, dermatologic surgery, and prolonged antibiotic therapy are frequently performed before an odontogenic origin is identified [2, 3, 7, 9]. This diagnostic delay can be attributed to the fact that dental symptoms are often mild or absent, and that cutaneous lesions are usually the primary complaint [2, 3, 6, 7]. In the present case series, 4 and 3 months were required to establish a definitive diagnosis in Cases 3 and 4, respectively; in Case 2, the correct diagnosis was made 12 months after the initial appearance of the cutaneous lesion. These findings further highlight the diagnostic challenges associated with OCST.

The cutaneous manifestations of OCST vary in appearance and most commonly present as erythematous nodules measuring 1–2 cm in diameter or granuloma-like lesions. Drainage may or may not be present and crusting, ulceration, or dimpling can be observed at the center of the lesion [3, 6–9]. Lesions most frequently occur near the mandibular angle, chin, and perioral region. However, in cases involving the maxillary teeth, the cheek or other adjacent facial areas may be affected [2, 6, 8, 9]. As pain is often minimal or absent, patients may delay seeking dental care for weeks or months. Therefore, OCST should be included in the differential diagnosis when persistent facial cutaneous lesions are observed in patients with a history of caries, trauma, tooth fracture, or endodontic treatment [2, 3, 7].

Tracing of the sinus tract using GP cone has long been used to identify the origin of OCST [1–3, 14]. However, the insertion of a GP cone may be difficult when the sinus opening is narrow, fibrotic, or partially closed, and tracing may be incomplete when the tract is tortuous within soft tissues [13, 14]. In the present series, GP tracing could not be performed in Cases 2 and 3 due to closure of the sinus opening. Although tracing was possible in Case 1, the direction of the cone did not correspond to the location of the periapical lesion, necessitating further imaging. In contrast, GP tracing in Case 4 clearly demonstrated a tract extending toward the apex of the causative tooth.

To overcome these limitations, CBCT has been increasingly advocated as a valuable adjunctive tool for the diagnosis of OCST [5, 11]. CBCT enables three-dimensional assessment of periapical lesions, cortical plate perforation, and their spatial relationship with adjacent anatomical structures, thereby facilitating identification of the causative tooth and treatment planning [5, 11]. It is also useful in detecting complex root canal anatomy, root fractures, and extensive bone destruction. In the present case series, CBCT was used to localize intraosseous lesions and cortical perforations in Case 1, assess the perforation sites and root canal anatomy in Case 3, and identify extensive periapical bone destruction and cortical plate involvement in Case 4.

Recently, the use of high-resolution ultrasound has been reported as a noninvasive method for visualizing sinus tract pathways and assisting in differential diagnosis [13, 15]. As ultrasound devices have become more accessible in dental settings, further studies are warranted to explore their potential role in the diagnosis of OCST.

OCST is a secondary lesion caused by an odontogenic infection; therefore, management should focus on eliminating the source of the infection rather than the cutaneous lesion itself [1, 2, 14]. Previous studies have emphasized that surgical excision or biopsy of skin lesions is generally unnecessary and may result in irreversible scarring, highlighting the need for a cautious diagnostic approach [2, 3, 16]. Antibiotic therapy should be reserved for patients with systemic involvement, such as fever, malaise, cellulitis, or for immunocompromised patients [17, 18]. Extraoral sinus tracts typically undergo epithelialization and close within 7–14 days once appropriate treatment of the causative tooth is completed. If residual dimpling or pigmentation persists after the resolution of infection, esthetic management may be considered after scar tissue stabilization [19, 20].

Depending on the condition of the causative tooth and lesion characteristics, various treatment modalities have been reported, including nonsurgical root canal treatment or retreatment, endodontic microsurgery, root amputation, and extraction [1, 10, 14, 19, 21–23]. In the present case series, Cases 1 and 2 were successfully managed with nonsurgical endodontic treatment and retreatment, respectively. In Cases 3 and 4, a surgical intervention was required. Endodontic microsurgery was performed in Case 3 because of a separated instrument and complex canal anatomy, whereas root amputation was performed in Case 4 after confirmation of a vertical root fracture, with stable healing observed over an 8-year follow-up period. In all cases, the cutaneous lesions resolved after appropriate dental treatment. These outcomes underscore the importance of accurately identifying the causative tooth and selecting an appropriate treatment strategy for successful management of OCST.

Accurate diagnosis of OCST requires integrated assessment of pulp status, periapical osseous lesions with cortical perforation, and the soft tissue tract extending to the cutaneous lesion. In this case series, GP cone tracing helped identify the sinus tract direction, while CBCT provided information on periapical lesions and cortical perforation. However, these modalities alone could not fully integrate all diagnostic components. GP tracing was not feasible in Cases 2 and 3 because the sinus opening was closed, and in Case 1 the traced pathway did not correspond to the causative tooth. Although CBCT was useful for detecting osseous destruction and periapical pathology, its ability to directly visualize the soft tissue tract was limited. In addition, the small sample size and retrospective design may limit the generalizability and completeness of the findings.

Despite these limitations, the present cases suggest that CBCT has important adjunctive value when GP tracing is not feasible or inconclusive. In three of the four cases, GP tracing was either not possible or insufficient to localize the causative tooth. In such situations, CBCT allowed three-dimensional assessment of periapical lesions and cortical perforation, supporting identification of the causative tooth and treatment planning. Although CBCT cannot replace sinus tract tracing or therapeutic confirmation, it may be particularly useful in chronic lesions with a closed sinus opening or when conventional tracing is inconclusive. Clinicians in dermatology, plastic surgery, and related fields should consider dental referral when persistent cutaneous draining lesions occur near the jaw and adjacent periapical radiolucency is observed on conventional radiographs.

Further research is needed to improve diagnostic evaluation of OCST, particularly for visualization of the soft tissue tract. High-resolution ultrasound may serve as a useful adjunct because it allows noninvasive visualization of sinus tract pathways. Prospective multicenter studies are warranted to establish standardized diagnostic pathways integrating pulp sensibility testing, conventional radiography, GP tracing, CBCT, and soft tissue imaging.

Conclusions

OCST is frequently misdiagnosed as a primary dermatologic condition because dental symptoms are often mild or absent, which may result in delayed diagnosis and unnecessary treatment. Accurate identification of the causative tooth and elimination of the odontogenic infection are essential for successful management. Although GP cone tracing can assist in identifying the origin of the sinus tract, its application may be limited; in such cases, CBCT provides valuable three-dimensional information that can support diagnosis and treatment planning. The present case series demonstrates that appropriate tooth-specific management, ranging from nonsurgical root canal therapy to surgical endodontic procedures, can lead to resolution of cutaneous lesions and healing of periapical pathology.

Abbreviations

OCST

odontogenic cutaneous sinus tract

GP

gutta-percha

CBCT

cone-beam computed tomography

EPT

electric pulp test

IAF

initial apical file

Authors' contributions

Conceptualization, Resources, Supervision: Sung KH, Jo HH. Clinical treatment, Data collection, Visualization: Chung HW, Moon JY, Jo HH. Writing - original draft: Sung KH, Chung HW, Moon JY. Writing - review & editing: Sung KH, Jo HH. All authors read and approved the final manuscript.

Funding

This case series was supported by Wonkwang University in 2025.

Data availability

All data generated or analyzed are included in this article.

Declarations

Ethics approval and consent to participate

This study was approved by the Institutional Review Board (IRB) of the Chosun University Dental Hospital (CUDHIRB 2601 003).

Consent for publication

All patients provided written informed consent for the use and publication of their clinical information and accompanying images.

Competing interests

The authors declare no competing interests.