Infected tooth pulp ranges in appearance from swollen, dark red tissue filled with blood to grayish, liquefied material with a foul smell, depending on whether the infection is in its early inflammatory stage or has progressed to full tissue death. Because the pulp sits deep inside the tooth, you won’t see it directly in your mouth. But there are visible signs on your gums, on X-rays, and sometimes even growing out of the tooth itself that reveal what’s happening inside.
What Healthy Pulp Looks Like
Healthy dental pulp is a soft, pinkish-red tissue that fills the hollow center of each tooth. It contains blood vessels, nerves, and connective tissue. When a dentist opens a healthy tooth, the pulp bleeds brightly and predictably, a sign that blood flow is intact. This is the baseline that makes the changes caused by infection so distinct.
Early Infection: Inflamed but Alive
In the earliest stage of pulp infection, called reversible pulpitis, the tissue becomes swollen and congested with blood. The pulp looks darker red than normal because the tiny blood vessels inside it are dilated. At this point, the inflammation is mild enough that removing the source of irritation (usually a cavity or a crack) can allow the pulp to heal and return to its normal state.
When inflammation intensifies and becomes irreversible, the pulp takes on a deep, angry red appearance. Blood pools in the tissue because the swelling inside the rigid tooth walls compresses veins and prevents normal drainage. A dentist can sometimes detect this congestion by shining a bright light through the tooth from behind, a technique called transillumination, which reveals a noticeably darker shadow compared to neighboring teeth. The internal pressure from this trapped blood is what causes the sharp, lingering, sometimes spontaneous pain that characterizes this stage.
Advanced Infection: Dying and Dead Pulp
If the blood supply gets fully strangled by swelling, the pulp begins to die. Necrotic pulp no longer looks like living tissue. Instead of bleeding red, it appears grayish-brown, yellowish, or even black. The texture changes from firm and fibrous to soft and liquefied. Opening a tooth with necrotic pulp often releases a distinctly foul odor from the bacterial breakdown of tissue. There may be no bleeding at all when the dentist accesses the chamber, which confirms the tissue is dead.
In some cases, the tooth itself changes color from the outside. A front tooth with a dead pulp can gradually darken to a gray or brownish hue as breakdown products from the blood seep into the surrounding tooth structure. This discoloration is sometimes the first thing that prompts someone to seek care, especially if the original infection caused little pain.
Pulp Polyps: When Infected Tissue Grows Out
One of the most dramatic visual signs of chronic pulp infection is a pulp polyp, technically called chronic hyperplastic pulpitis. This happens when a large cavity exposes the pulp, and instead of dying, the tissue responds by growing outward through the opening. The result is a fleshy, mushroom-like mass that can fill or even overflow the cavity.
Pulp polyps vary in color from cherry red (when the surface is raw granulation tissue) to pale pink or even opaque white (when the surface develops a tougher, skin-like covering). Published case reports describe polyps reaching 1.5 cm across, attached to the pulp by a narrow stalk just a couple of millimeters wide. They’re most common in molars of younger people, where the blood supply to the pulp is especially robust. Despite their alarming appearance, pulp polyps are often surprisingly painless because the overgrown tissue has few nerve endings at its surface.
What You Can See in Your Own Mouth
Since the pulp itself is hidden inside the tooth, the visible clues of infection show up on the gums and surrounding tissue rather than on the tooth surface. The most recognizable sign is a gum boil, a small, raised bump on the gum near the tip of the infected tooth’s root. These bumps range in color from yellow to red to pink. They feel soft and fluctuant, and pressing lightly on one may produce a small amount of pus. A gum boil is the exit point of a drainage tract that forms when infection breaks through the bone around the root tip and finds a path to the surface.
Other visible signs include localized gum swelling, redness around one specific tooth, and sometimes a bad taste in the mouth from pus slowly draining on its own. If swelling spreads to the cheek, jaw, or under the eye, the infection has moved beyond the tooth and surrounding bone into the soft tissues of the face.
What Infection Looks Like on X-Rays
Dental X-rays reveal the consequences of pulp infection in ways your eyes can’t detect. The hallmark finding is a dark shadow at the tip of the tooth’s root, called a periapical radiolucency. This dark area represents bone that has been destroyed by the infection spreading out from the dead pulp. Most of these dark shadows around root tips are caused by pulp necrosis.
X-rays can also show pulp stones, which are small calcified masses that form inside the pulp chamber. They appear as bright white spots or round opacities within the tooth. A single tooth can contain anywhere from one to a dozen or more of these stones, ranging from tiny specks to masses large enough to fill the entire pulp chamber. While pulp stones aren’t always tied to active infection, they often develop in teeth that have been irritated or inflamed over a long period.
What Happens After Diagnosis
The treatment path depends on whether the pulp is still alive or has died. Reversible pulpitis can resolve once the irritant is removed and the tooth is restored with a filling or crown. Irreversible pulpitis and necrotic pulp require root canal treatment, where the infected or dead tissue is cleaned out of the canals and replaced with a filling material.
Root canal therapy has a strong track record. A 10-year retrospective study found that treated teeth showed no signs of remaining infection on X-rays 93% of the time, and patients reported no pain or symptoms in about 96% of cases. Tooth retention after treatment was nearly 96%, meaning the vast majority of teeth saved through root canal therapy stayed functional for years afterward.