Can a Tooth Infection Cause a Sinus Infection?

One of the more common scenarios I see in my practice is a patient who has been treated for a sinus infection multiple times, is not getting better, and eventually someone notices that the problem is not in the sinus at all. It is in the tooth sitting directly below it. The reverse also happens — patients come in convinced they need dental work, and what they actually have is a sinus infection pressing down on the roots of their upper teeth and generating dental pain that has nothing to do with the tooth itself.

These two structures — your upper teeth and your maxillary sinuses — share real estate in a way that causes genuine diagnostic confusion for patients and sometimes for physicians. Understanding the anatomy changes everything.

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How We Think About Facial Pain in the Exam Room

When a patient comes in with facial pain, one of the first things I am thinking about is which side it is on. Pain that is worse on one side — particularly one-sided maxillary pain, meaning pain in the cheek area — raises the possibility of a dental origin. Most sinus infections tend to produce bilateral pressure, even if one side is worse. Unilateral maxillary pain makes me look more carefully.

Patients will sometimes tell me directly that they have dental pain — what we call dentalgia. If that pain is in the lower jaw, that is off to the dentist, because the lower jaw has no anatomical relationship to the sinuses. But if the pain is in the upper teeth, we are already thinking about the maxillary sinus. The upper molar and premolar roots sit in very close proximity to the floor of the maxillary sinus, and in many patients they actually extend up into the sinus cavity itself.

Sometimes a dentist sends the patient to me. Sometimes I receive a patient with a CT scan showing one-sided maxillary sinus opacification — the sinus is filled or partially filled on one side while everything else looks normal — and when I look at the tooth roots on that CT, I will see swelling or opacification at the tip of the root. That finding, called apical periodontitis, points directly to a tooth as the source of the sinus problem. That is the classic picture of odontogenic sinusitis.

The Anatomy That Creates the Confusion

The root of an upper molar or premolar tooth often sits within the maxillary sinus proper. Not near it — inside it. The floor of the maxillary sinus is in intimate contact with the apex of these roots, and in a significant percentage of the population the roots actually penetrate the sinus floor and extend into the sinus cavity itself, separated from the sinus lining by only a thin membrane.

This creates a two-way street for inflammation. If the sinus becomes inflamed — from allergy, infection, or any other cause — that inflammation can transmit through the sinus floor to the root of the tooth and generate tooth pain. The tooth itself is perfectly healthy, but the patient feels dental pain because the inflamed sinus is pressing on the nerve supply at the root tip.

The reverse is equally true. If the tooth has an infection — a cavity that has progressed deeply enough, a cracked root, or an abscess at the root tip — that infection can transmit upward through the sinus floor into the maxillary sinus cavity and cause a sinus infection that originated from below. This is odontogenic sinusitis, and it behaves very differently from the sinusitis that comes from above.

What Odontogenic Sinusitis Looks Like

Odontogenic sinusitis is a sinusitis of tooth origin. Think of the infection coming from below and the inflammation creeping upward toward the sinus opening. The swelling comes from within — not from an external cause like allergy, pepsin from reflux, or air pollution — which is what distinguishes it clinically from the more common forms of sinus disease.

What makes odontogenic sinusitis recognizable is the pattern on imaging. It tends to be isolated to one maxillary sinus. On a CT scan you will typically see one maxillary sinus almost completely opacified while all the other sinuses look normal. That pattern — one sinus, one side, maxillary only — is a signal. Combined with the apical findings at the tooth root, the diagnosis becomes clear.

Patients with odontogenic sinusitis sometimes describe the drainage differently than patients with standard sinusitis. I have had patients tell me that the smell is putrid — distinctly foul in a way that goes beyond typical infected mucus. This is consistent with the polymicrobial anaerobic infection that tends to come from a dental source, which produces different organisms than the typical upper respiratory infection-driven sinusitis.

How We Treat It — and Who Goes First

When I find a maxillary sinus that is significantly opacified and the CT suggests a dental origin, I sometimes recommend balloon sinuplasty to open the sinus, drain it, irrigate it, and obtain a MicroGenDX culture to identify exactly what bacteria are present. Opening the sinus accomplishes something important beyond just drainage — it relieves the pressure that has built up inside the sinus cavity. When a sinus is completely filled and pressurized, it creates a more hostile environment for the dentist to work in. By opening and decompressing the sinus first, we make the dental work easier and less likely to cause complications.

That said, I do not feel that the sequence has to go one way every time. Sometimes the dentist addresses the tooth first and then sends the patient to me. Sometimes we treat the sinus first and then send to the dentist. Both approaches can work, and what matters most is that both of us know what the other is doing and that we are communicating. The message I give patients is that this is the dentist and the ENT working together — not competing, not sending you back and forth without a plan, but actually coordinating your care.

What to Do If You Have Been Bounced Between Your Dentist and Your ENT

This is unfortunately a common experience. The patient goes to the dentist, the dentist says the teeth look fine, send them to the ENT. The ENT treats the sinuses, the sinuses improve temporarily, the symptoms come back. Back to the dentist. Nothing found. Back to the ENT.

When a patient comes to me after this cycle, my job is to actually look at the imaging carefully and identify whether there is an upstream cause that has not been found yet. If the dentist has assessed the tooth and says everything is structurally normal, then we take over and try to identify what is driving the sinus problem from our side — whether that is allergy, reflux, posterior sinonasal inflammation, or something else entirely. We treat the upstream cause as thoroughly as we can, because the bouncing stops when someone actually finds the source.

The key is that a one-sided maxillary sinus problem that keeps coming back despite treatment deserves a careful look at the tooth roots. And a tooth that keeps hurting despite dental treatment deserves a careful look at the sinus sitting right above it. These structures are neighbors. When one of them is sick, the other one often knows about it.

Want to Understand More?

This post is part of the Why Sinus Treatments Fail — And What Starts Before Them series on the Airway & Sinus Wellness Review.

→ Why Antibiotics Keep Failing Your Sinus Infection

→ Does Balloon Sinuplasty Actually Work?

→ Will Balloon Sinuplasty Correct My Post-Nasal Drainage?

Airway & Sinus Wellness Review — Full Publication

Why Sinus Treatments Fail — And What Starts Before Them — Patient education from the Sinus & Allergy Wellness Center of North Scottsdale.

About the Author

Franklyn R. Gergits, DO, MBA, FAOCO is an otolaryngologist and rhinologist with over 30 years of clinical experience. He is the founder of the Sinus & Allergy Wellness Center of North Scottsdale, where he performs in-office balloon sinuplasty, turbinate reduction, NEUROMARK®, and swell body reduction procedures under local anesthesia. He performed the first balloon sinuplasty in Pennsylvania, holds dual Entellus Centers of Excellence certifications, and is the originator of the Posterior Sinonasal Syndrome (PSS) hypothesis, with a preprint available at Preprints.org (DOI: 10.20944/preprints202603.0858.v1). ORCID: 0009-0000-4893-6332.

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This content is for educational purposes only and does not constitute medical advice. If you are experiencing facial pain, tooth pain, or sinus symptoms, please consult a qualified physician for evaluation and diagnosis.