A Gum Boil That Kept Coming Back on a Root-Canalled Tooth

Quick answer: A small pimple on the gum that keeps returning next to a tooth that has had a root canal — especially one without a crown — is often a vertical root fracture rather than a simple reinfection. Antibiotics settle it for a fortnight each time, then it comes back, because the crack is still there.

The call

Nechama, 55, from Migdal HaMayim, had been round this loop three times in eighteen months. A tender lump on the gum beside an upper right molar, a course of antibiotics, relief for two or three weeks, and then the lump again. The tooth itself barely hurt. She had begun to assume this was simply how that tooth was going to be.

She came to us wanting a fourth prescription. She left with a diagnosis.

What we found

The tooth had been root treated nine years earlier and restored with a large filling — never crowned. The root filling looked, on the x-ray, perfectly adequate. That is the trap: a good-looking root filling with a persistent infection points away from a failed root canal and towards something structural.

Three findings made the diagnosis:

• A narrow, deep pocket. Probing around the tooth gave 3mm everywhere except one spot on the palatal root, where the probe dropped straight to 11mm. A single isolated deep pocket beside a normal one is the hallmark of a fracture — infection tracking down the crack line.
• A sinus tract that traced, with a gutta-percha point, directly down the side of that root rather than to the root tip.
• A CBCT scan showing a thin J-shaped halo of bone loss wrapping the whole root, rather than a round area at the apex.

A vertical root fracture is not repairable. Nothing you can put inside the tooth seals a crack that runs the length of the root and communicates with the gum.

What we did

We removed the tooth. It came out in two pieces, and once it was out of the socket the fracture line was plainly visible running from the root tip to just under the old filling — confirmation you cannot get any other way.

We debrided the socket properly, since nine years of low-grade infection leaves granulation tissue behind, and placed a graft to hold the ridge. The bone on the cheek side had already thinned considerably.

The outcome

The gum boil never returned. Nechama had an implant six months later.

The preventable part is worth stating plainly. Root-filled back teeth without crowns fracture at a much higher rate than crowned ones. Her tooth was hollowed out by the access cavity, brittle from having no blood supply, and taking full chewing load with only a filling holding it together for nine years.

What to do if this happens to you

1. Take a recurring gum boil seriously, even when it does not hurt much.
2. Notice the pattern. Antibiotics helping and then the problem returning is diagnostic information, not treatment failure.
3. Ask for the tooth to be probed all the way round, not just x-rayed.
4. Ask about a CBCT scan if a standard x-ray does not explain a persistent problem.
5. Do not accept repeat antibiotic courses for the same site without a diagnosis. Three rounds is too many.
6. Get root-treated back teeth crowned. This is the single most effective thing you can do to prevent it.

Recurring gum boil or a root canal that never settled? Ramat Beit Shemesh Urgent Dental Care investigates properly before prescribing again. 055-985-8845 · WhatsApp https://wa.me/972559858845 · Harav Kook 28/1, Beit Shemesh.

Based on real cases treated at the clinic. Names have been changed.