Dental Fistula (Gum Boil): What It Means, Why It’s Never “Nothing,” and What Treatment Actually Looks Like

The Bump Patients Almost Always Downplay

In our Denver office, this is one of the most common things a patient points to and says, “It’s probably nothing — it comes and goes.” It’s a small, round bump on the gum, often near the base of a tooth. Sometimes it’s tender. Often it isn’t. Patients describe it as a “pimple” or a “blister,” and because it doesn’t hurt much, it gets ignored for weeks or months.

In our experience, that lack of pain is the most misleading part. A dental fistula is not a surface irritation — it’s the visible end of an infection that’s already established itself inside the tooth or the bone underneath it. By the time we see the bump, the infection has typically been active for some time.

If you’re noticing a bump like this on your own gums, don’t wait for it to become painful before getting it checked. Call Lowry Advanced Dentistry at (303) 333-5148 to schedule an exam with Dr. Hoagburg, Dr. Torrance, or Dr. Moore— early treatment is almost always simpler and less costly than waiting.

Below, we’ll walk through what a fistula actually is, what causes it, how we diagnose and treat it, and — just as importantly — how to tell the difference between something that can wait for a routine visit and something that needs same-day attention.

What Is a Dental Fistula, Exactly?

A dental fistula (clinicians also call it a parulis, sinus tract, or, informally, a gum boil) is a small tunnel that the body forms through the gum tissue and bone to release pus from an infection at the root of a tooth or in the jawbone. It’s a pressure-relief valve, not the infection itself.

Clinically, we look for:

• A raised bump on the gum, usually white, yellow, or reddish, sometimes with a visible pinpoint opening
• Intermittent drainage — the bump may flatten out for a few days after it drains, then refill
• A salty, bitter, or metallic taste that shows up when it’s actively draining
• Little to no pain, because the drainage relieves the pressure that would otherwise cause an abscess to hurt

That last point is worth repeating: a fistula usually means the infection has found a way to relieve its own pressure. Pain easing up is not the same as the infection resolving.

What Causes It

In our clinical experience, the underlying cause is almost always one of the following:

1. A dying or dead tooth nerve (pulp necrosis) — bacteria reach the pulp through a deep cavity, crack, or old filling, and the infection spreads to the root tip.
2. A root canal that didn’t fully seal off the infection — this can happen years after the original treatment.
3. Advanced gum disease (periodontitis) that has tracked down along the root surface into the supporting bone.
4. A fractured or cracked tooth that lets bacteria into the inner tooth structure.
5. Untreated trauma — a tooth that took a hit years ago and quietly died without ever causing noticeable pain at the time.

Signs and Symptoms to Take Seriously

Because a fistula muffles pain, patients often notice these secondary signs first:

• A recurring bump or blister on the gum, near one specific tooth
• Persistent bad breath or an ongoing bad taste that doesn’t improve with brushing
• Mild sensitivity to hot, cold, or biting pressure on one tooth
• Localized gum or facial swelling
• A bump that appears to heal, then reappears in the same spot

If any of these are present for more than a few days, that’s a reason to schedule an exam — not to wait and watch.

Why We Don’t Recommend Waiting It Out

A fistula does not heal on its own, even when it temporarily flattens or disappears. The tract may close over, but the infection driving it is still active underneath. Left untreated, we typically see one of these outcomes:

• Progressive bone loss around the root, which can undermine the tooth’s support structure over months
• Loss of the tooth, if the infection or bone damage becomes too extensive to restore
• Spread to neighboring teeth and tissue
• Systemic spread, in rare but documented cases, where oral bacteria enter the bloodstream and reach other parts of the body — this is uncommon, but it’s the reason dentists treat oral infections as a medical issue, not a cosmetic one

How We Diagnose a Dental Fistula

Diagnosis isn’t just “look and treat” — tracing the fistula back to its actual source matters, because treatment depends entirely on which tooth (and which condition) is behind it. In our office, that typically involves:

1. Visual and manual exam of the bump and surrounding gum tissue
2. Percussion and palpation testing on nearby teeth to identify which one is symptomatic
3. Dental X-rays, which usually show a dark area (radiolucency) at the root tip or along the bone where the infection has eaten away structure
4. Gutta-percha tracing, in less obvious cases — a thin, rubber-like point is threaded gently into the tract opening and an X-ray is taken, which shows exactly which tooth the tract leads back to

Skipping this step and treating the “closest” tooth without confirming the source is a common reason fistulas come back after treatment.

Treatment Options

Treatment is chosen based on whether the tooth can be saved and how far the infection has progressed.

Root Canal Therapy

A root canal is the most common and most conservative option when the tooth structure is salvageable. The infected nerve tissue is removed, the canals are cleaned and sealed, and the tooth is typically restored with a crown. Once the infection source is eliminated, the fistula generally closes on its own within a few weeks — we don’t need to do anything additional to the gum tissue itself.

Antibiotics

Antibiotics are sometimes prescribed alongside dental treatment to help control spread, but they cannot cure a fistula on their own. The infected tissue inside a dead tooth has no blood supply, so antibiotics carried through the bloodstream can’t reach it in effective concentrations. Relying on antibiotics alone typically just delays the bump’s return.

Extraction

If the tooth is too compromised — from bone loss, a fracture, or extensive decay — a tooth extraction eliminates the infection source directly. We’ll discuss replacement options, such as an implant or bridge, as part of that conversation.

Surgical Treatment

For infections that have spread more extensively into the surrounding bone, procedures like surgical debridement or bone grafting may be needed to restore the area before or alongside restorative treatment.

Can It Be Prevented?

Most of the time, yes — because the underlying causes are largely preventable:

• Brushing twice daily and flossing daily to limit decay and gum disease
• Keeping up with routine cleanings and checkups, so small problems are caught with X-rays before they progress
• Treating cavities and gum disease promptly rather than waiting for symptoms
• Wearing a properly fitted mouthguard during contact sports
• Getting any tooth trauma checked, even if it doesn’t hurt at the time — dead nerves are often silent for years before a fistula shows up

When to Call a Dentist

Any recurring bump, blister, or sore on the gum — with or without pain — is worth having examined, ideally within a few days of noticing it. If you also have facial swelling, fever, or difficulty swallowing, that combination can indicate a spreading infection and warrants same-day care.

In our experience, treating a fistula early (before significant bone loss occurs) is almost always simpler, less invasive, and less costly than treating one that’s been left for months.

Don’t Wait on That Gum Bump — We Can Help

If you’ve noticed a bump, blister, or recurring sore on your gum, the sooner it’s evaluated, the simpler treatment usually is. Our team at Lowry Advanced Dentistry can trace the issue back to its source and walk you through the right treatment option for your tooth.

Call (303) 333-5148 to schedule an appointment with our dentist in Denver, or reach out through our website. We welcome patients throughout Denver, CO and the surrounding areas.