Lump on the gum: a dental sinus tract, an abscess or a growth that needs checking?

What is a gum lump and why is it often a sinus tract?

A gum lump is any swelling of the gum lining, but beside a tooth affected by deep decay, injury or root canal treatment it is often the opening of a sinus tract. This narrow channel drains pus from infection around a root tip onto the gum surface, where a small pimple or blister appears.

The American Association of Endodontists (AAE) calls this a chronic apical abscess: it develops slowly, causes little or no pain and drains intermittently through a sinus tract. The source is infection in the root canal, so the pimple comes and goes until the tooth is treated.

Inflammatory lesions around root tips are common. A 2021 review by Tibúrcio-Machado et al., covering 114 studies and over 34 000 people, reports that 52% of participants had at least one affected tooth, with a lesion visible beside 39% of previously root-treated teeth.

Why does a gum sinus tract often not hurt?

A gum sinus tract often does not hurt because pus has an outlet and does not build up under pressure in the bone. Severe, constant abscess pain results from swelling and pressure; when infection finds an outward route, symptoms usually ease.

Absence of pain does not mean healing. The AAE identifies teeth with dead pulp as requiring root canal treatment, and a sinus tract shows that infection around the root continues. The pimple may disappear for a few days when its opening closes, then reappear in the same place.

What else can cause a lump on the gum?

A gum lump does not always come from an infected root: it may be a periodontal abscess, a root fracture, a benign tissue growth, a bony growth or sometimes a lesion needing urgent investigation. Examination, an X-ray and sometimes histopathology, examination of removed tissue under a microscope, establish the cause.

The MSD Manual advises dental assessment of a persistent lump or swelling on the gum. It states that a mucous cyst most often occurs on the lip; a separate article on lumps in the mouth covers lesions on the lips, cheeks and tongue.

Pus from the gum: could it be a periodontal abscess?

Pus from the gum beside a tooth with a deep pocket is typical of a periodontal abscess, a collection of pus in the pocket wall. The 2026 SDCEP guidance links it to a flare-up of untreated periodontitis or the period after pocket cleaning procedures.

Unlike a sinus tract, a periodontal abscess almost always hurts. A 2018 review by Herrera et al., prepared for the world classification of periodontal diseases, describes a deep pocket, bleeding on examination, pus discharge and pain; SDCEP adds tooth mobility and gum swelling.

Treatment involves draining pus through the pocket or an incision and cleaning the pocket, or extracting a tooth that is too badly damaged. SDCEP notes that recurrent periodontal abscesses may indicate undiagnosed type 2 diabetes, which is worth discussing with a GP.

What does a sinus tract after root canal treatment mean?

A sinus tract after root canal treatment means infection around the root persists or has returned despite the canals being filled. The European Society of Endodontology (ESE) considers absence of a sinus tract a condition of success, alongside no pain or swelling and a normal appearance of the bone on an X-ray.

Usually, bacteria have survived in the canals or entered through a leaking restoration. The tooth may be treated with repeat root canal treatment or root-end surgery, as described in the article on root canal retreatment.

A sinus tract near the gum margin, particularly several at once, beside a root-treated tooth can indicate a vertical root fracture. The 2025 ESE position statement lists a narrow, deep pocket at one site and multiple sinus tracts as typical of an advanced root fracture. Removing the old restoration helps assess whether a fracture is present.

How does a dentist identify which tooth a sinus tract comes from?

A dentist traces a sinus tract by inserting a gutta-percha point, a thin pin visible on X-rays, into its opening and taking an X-ray. The AAE describes gently advancing the point until resistance is felt; the image shows which root the channel leads to.

This is needed because the pimple often is not over the affected tooth. In a 2026 prospective study by Ahmed et al., only 20 of 100 sinus openings lay directly over the source tooth. In the remaining 80, the opening was displaced by half a tooth, one or two teeth; 82% opened towards the cheek.

• History: how long the pimple has been present, whether it drains and whether the tooth has been treated or injured.
• Cold or electrical pulp vitality tests and tapping the teeth around the lump.
• Gum pocket measurements to help distinguish a sinus tract from a periodontal abscess or root fracture.
• An intraoral X-ray with a gutta-percha point inserted into the sinus tract.
• A small-field CBCT scan if X-rays do not establish which root is the infection source.

How is a lump on the gum treated?

A gum lump is treated by removing its cause rather than cutting out the pimple itself. An infected root requires root canal treatment, retreatment, root-end surgery or extraction; once infection is eliminated, the sinus tract closes by itself.

In a 2025 randomised trial by Peker and Güneşer involving 60 people with a sinus tract beside single-rooted teeth, closure took around 7 days on average after root canal treatment, whether completed in one or two visits. Antibiotics do not replace this treatment and are usually unnecessary if infection is not spreading.

Lesions unrelated to a tooth need different treatment. A fibroma is removed surgically and examined microscopically. For pyogenic granuloma, DermNet stresses removing the irritant to prevent recurrence. The MSD Manual says a bony growth can remain unless it causes problems.

When does a gum lump need an urgent dental appointment?

A gum lump needs urgent assessment if accompanied by increasing swelling, fever or pain that does not settle with painkillers. Swelling that affects breathing, swallowing or opening the mouth requires a hospital emergency department (SOR) or 112, the emergency number, as explained in the dental abscess article.

Many gum lumps are inflammatory lesions or benign growths, but some need prompt investigation. MSD advises showing a dentist a lesion that does not disappear within 1 to 2 weeks; for lesions lasting more than a few weeks, most doctors recommend a biopsy, taking a tissue sample. However, do not wait two weeks with a lesion that discharges pus, grows, bleeds or looks otherwise suspicious; show it to a dentist without delay.

• Rapidly increasing gum or cheek swelling, fever or feeling unwell.
• A lump that discharges pus or grows, even if painless, and any other lump that does not disappear within 1 to 2 weeks.
• An ulcer or hard gum lesion that has not healed for several weeks.
• A lesion that bleeds for no clear reason, or numbness of the gum or lip.
• Loose teeth with no clear cause.

How it works at DentalBlue

At DentalBlue in Białystok, a gum lump can be assessed at a “Wizycie bez bólu” (visit without pain), including a panoramic X-ray, consultation, examination and written treatment plan, priced at 300 zł. The clinic’s own radiology unit takes intraoral X-rays and CBCT scans; root canal treatment and retreatment are performed under a microscope. For lesions unrelated to a tooth, “Usunięcie zmiany na błonie śluzowej” (removal of a mucosal lesion) costs 500 zł and “Badanie histopatologiczne” (histopathological examination) 100 zł. The dentist determines the final scope and cost after examination; prices may change.