MSEO: The challenge of differential diagnosis and the conservative approach

Maxillary sinusitis of endodontic origin (MSEO) constitutes a major clinical challenge, representing up to 72% of unilateral maxillary sinusitis cases. Despite this prevalence, the failure of etiological diagnosis still frequently leads to unnecessary invasive surgical interventions. This case report documents the management of a 38-year-old female patient suffering from chronic headaches and intermittent rhinorrhea for one year, initially not associated with dental pathology.

The objective of this study is to demonstrate the relevance of a diagnostic protocol systematically integrating cone beam computed tomography (CBCT) to identify Schneiderian membrane pathologies related to the apices of the posterior maxillary teeth. In this specific case, imaging revealed a mucosal thickening of 6.6 mm in direct relation to the palatal root of tooth #27.

The study tests the hypothesis that rigorous non-surgical endodontic treatment, using Mineral Trioxide Aggregate (MTA) for palatal canal obturation, allows for complete resolution of sinus inflammation. The objective is to prove that conservative endodontic management, by eliminating the apical infectious source, restores sinus integrity and avoids the practitioner's recourse to more invasive surgical treatments.

Clinical methodology

This case report, written according to the CARE (Case Report Guidelines) recommendations, details the management of a 38-year-old female patient (ASA 1) presenting with chronic sinus symptoms (headaches and intermittent rhinorrhea) for one year. The study focuses on the diagnostic and therapeutic approach to the left maxillary second molar (#27).

• Diagnosis and imaging: The initial evaluation coupled an intra-oral clinical examination with cone beam computed tomography (CBCT) imaging. The CBCT allowed for the quantification of a 6.6 mm thickening of the Schneiderian membrane and confirmed the immediate proximity of the palatal apex to the sinus floor.
• Surgical protocol: The treatment was performed under magnification and rubber dam isolation. After removal of the temporary restoration, three canals (palatal, mesio-buccal, and disto-buccal) were identified. An intermediate medication phase with non-setting calcium hydroxide was established before the finalization of the treatment.
• Preparation and obturation: The biomechanical preparation was completed by an irrigation protocol using sodium hypochlorite and EDTA. The obturation was differentiated according to the roots: the palatal canal was sealed with Mineral Trioxide Aggregate (MTA) due to sinus involvement, while the buccal canals were obturated with gutta-percha.
• Clinical follow-up: Therapeutic success was evaluated through regular clinical follow-ups and radiographic reassessment (CBCT and periapical radiographs) at 12 months.

Results: Clinical and radiographic resolution at 12 months

The evaluation of this clinical case, documented by three-dimensional imaging (CBCT) and clinical examinations, demonstrates a complete resolution of maxillary sinusitis of endodontic origin (MSEO) following non-surgical root canal treatment.

Initial observations and CBCT diagnosis

The initial CBCT examination identified a localized sinus pathology, which was not visible on conventional periapical radiographs. Key measurements and observations included:

• Mucosal thickness: A significant hypertrophy of the Schneiderian membrane was measured, reaching a maximum thickness of 6.6 mm in the left maxillary sinus.
• Contralateral comparison: A marked asymmetry was visible compared to the right sinus, whose membrane showed a normal thickness.
• Anatomical relationships: The apex of the palatal root of tooth #27 showed immediate proximity to, or even penetration of, the sinus floor, accompanied by slight apical root resorption.
• Intraoperative clinical signs: During the first session, a clear exudate was persistently observed in the palatal canal, confirming the biological communication between the endodontium and the maxillary sinus.

Clinical evolution and follow-up imaging

The table below summarizes the evolution of clinical and radiographic parameters between the initial presentation and the one-year follow-up:

At 12 months, the patient reported high satisfaction, noting the total disappearance of extra-oral symptoms that she did not initially associate with her dental pathology. Periapical radiographs and follow-up CBCT confirm the stability of the MTA seal in the palatal root and complete periapical healing, with no recurrence of sinus mucosal thickening.

Clinical analysis and benefits of conservative treatment

The results of this clinical case confirm that non-surgical endodontic treatment allows for complete resolution of maxillary sinusitis of endodontic origin (MSEO), even in the presence of significant mucosal thickening (6.6 mm). The use of MTA in the palatal canal, due to its immediate proximity to the sinus floor and the presence of apical resorption, highlights the effectiveness of bioceramic materials in managing complex apices. The total disappearance of rhinorrhea and the reduction of headaches at 12 months demonstrate that removing the dental infectious focus is sufficient to restore the integrity of the Schneiderian membrane.

Limites and contribution of CBCT imaging

The main limitation of this study lies in its single case report format, which does not allow for statistical generalization. However, it highlights a major diagnostic flaw: the initial periapical radiograph revealed no pathology, whereas the CBCT identified clear unilateral sinus involvement. This difference illustrates why the diagnosis of MSEO is frequently missed in conventional practice, often leading to unnecessary treatment delays or ineffective systemic antibiotic prescriptions.

Implications for daily practice

This case is consistent with data reporting that up to 72% of unilateral maxillary sinusitis cases are of odontogenic origin. For the practitioner, the absence of classic respiratory symptoms (nasal obstruction, anosmia) associated with chronic headaches must systematically lead to an endodontic evaluation, even if the tooth appears asymptomatic upon percussion. The integration of CBCT becomes essential here to confirm the diagnosis of periapical mucositis (PAM) and to avoid invasive sinus surgical procedures, whereas a well-performed endodontic treatment ensures clinical and radiographic success.

Summary of results

This case report describes the management of a 38-year-old female patient suffering from headaches and unilateral rhinorrhea for one year. The CBCT examination revealed a 6.6 mm thickening of the Schneiderian membrane in contact with the palatal root of tooth #27; non-surgical endodontic treatment, including MTA obturation, resulted in complete clinical resolution and restoration of the sinus space at the 12-month follow-up.

In concrete terms, for the practitioner:

• Systematically consider an MSOD when faced with chronic unilateral maxillary sinusitis, even if the initial 2D radiographic assessment shows no obvious periapical lesion.
• Integrate CBCT from the outset to precisely locate reactive mucosal thickening and evaluate the close anatomical relationships between the apices and the sinus floor.
• Prioritize rigorous conventional endodontics (ultrasonic disinfection, hermetic sealing) as first-line treatment: it avoids invasive sinus or ENT surgeries by eliminating the primary bacterial source.

Technical lexicon of the study

MSEO (Maxillary Sinusitis of Endodontic Origin): Specific category of maxillary sinusitis resulting exclusively from an infection of endodontic origin, as opposed to odontogenic sinusitis (MSOO) which encompasses other dental etiologies (periodontal, iatrogenic, etc.).

Schneiderian membrane: Respiratory mucosa lining the inside of the maxillary sinus, composed of a ciliated pseudostratified columnar epithelium, whose thickening is a marker of sinus inflammation.

Periapical mucositis (PAM): Reactive proliferation of the antral mucosa stimulated by infectious agents of apical origin, which can lead to localized thickening visible on imaging.

Periapical osteoperiostitis (PAO): Periosteal reaction of the maxillary sinus manifesting radiographically as a distinctive "halo" lesion above the apex of an infected tooth.

CBCT (Cone Beam Computed Tomography): Three-dimensional imaging technology used in this case to quantify mucosal thickening (measured at 6.6 mm) and confirm the immediate proximity of the palatal apex to the sinus floor.

MTA (Mineral Trioxide Aggregate): Bioceramic material used for palatal canal obturation in this case report, chosen for its biocompatibility and sealing properties in the vicinity of the sinus area.

Rhinorrhea: Intermittent nasal discharge reported by the patient, constituting here a key extra-oral symptom of sinus pathology of endodontic origin.

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