An impacted molar is a tooth that fails to fully emerge through the gum line, remaining partially or completely trapped beneath the gum tissue or jawbone. This happens most often with wisdom teeth (third molars), which are the last to come in, typically between ages 17 and 25. Because they arrive after the rest of your adult teeth are already in place, there’s frequently not enough room for them to break through normally.
Why Molars Become Impacted
The root cause is a mismatch between the size of your teeth and the available space in your jaw. Your wisdom teeth need a clear path to erupt, and when the back of your jaw is too crowded, the tooth gets stuck. Genetics play a major role here. Research has found that the space-to-tooth-width ratio, the length of your dental arch, and even your overall body height are strongly influenced by hereditary factors rather than environmental ones. If your parents had impacted wisdom teeth, your odds go up considerably.
People with shorter statures, narrower retromolar spaces (the gap behind the last molar), or shorter dental arches are more likely to experience impaction. In some cases, a tooth may start growing in the wrong direction entirely, angling toward the front of the mouth, toward the back, or even sideways. Other teeth, cysts, or dense bone can also physically block the path.
The Four Types of Impaction
Impacted molars are classified by the angle at which the tooth is positioned beneath the gum:
- Mesial impaction: The tooth angles toward the front of the mouth, tilting into the molar next to it. This is the most common type.
- Vertical impaction: The tooth points in the right direction but can’t fully break through the gum tissue.
- Distal impaction: The tooth angles toward the back of the mouth, away from the neighboring molar.
- Horizontal impaction: The tooth lies completely on its side, parallel to the jawbone. This type is often fully buried under the gum and typically requires the most involved surgical removal.
A tooth can also be partially impacted, meaning part of the crown is visible above the gum line, or fully impacted, meaning it’s entirely enclosed in gum tissue or bone. Partially impacted teeth tend to cause more day-to-day problems because the opening in the gum creates a pocket where food and bacteria collect.
Symptoms to Watch For
Some impacted molars cause no symptoms at all and are only discovered on a dental X-ray. When problems do develop, they typically include red or swollen gums at the back of the mouth, tenderness or bleeding in that area, jaw pain, swelling around the jaw, bad breath, and an unpleasant taste that doesn’t go away with brushing. You may also have difficulty opening your mouth fully.
These symptoms often come and go. You might have a flare-up that lasts a few days, then feels fine for weeks before returning. That cycle usually means the area is repeatedly getting irritated or mildly infected without fully resolving.
Complications of Leaving It Untreated
Not every impacted molar needs to come out. But when one starts causing trouble, the problems can escalate. The most common complication is pericoronitis, an inflammation of the gum tissue surrounding a partially erupted tooth. The flap of gum over the tooth traps bacteria, leading to pain, swelling, and sometimes pus. Pericoronitis tends to recur until the tooth is removed.
Other potential complications include cavities forming on the impacted tooth or on the neighboring molar (which is hard to clean properly when crowded), gum disease in the surrounding tissue, cysts that develop around the trapped tooth, and damage to the large nerve that runs through your lower jaw. In rare cases, an infection around an impacted tooth can spread to other parts of the body and become serious. If you notice increasing swelling, fever, or trouble swallowing, that warrants urgent attention.
How Impacted Molars Are Diagnosed
Your dentist can suspect an impaction from a clinical exam, but the definitive diagnosis comes from imaging. A panoramic X-ray, which captures your entire jaw in a single image, is the standard tool. It shows where the tooth sits relative to the jawbone, the neighboring teeth, and the nerve canal. The American Academy of Pediatric Dentistry recommends a panoramic X-ray during late adolescence specifically to assess the position and development of third molars, so many people learn about an impaction before symptoms ever start.
From the X-ray, your dentist or oral surgeon can determine the angle of impaction, how deep the tooth sits, and how close it lies to the nerve. These details directly shape the treatment plan and help predict how straightforward or complex removal will be.
What Removal Involves
If your impacted molar needs to come out, the procedure depends on how deeply the tooth is buried. A partially impacted tooth that’s mostly above the gum line may come out in a relatively simple extraction. A fully impacted tooth, especially one embedded in bone, requires a surgical approach: incisions in the gum to access the tooth, removal of any bone covering it, and often dividing the tooth into smaller sections so it can be taken out in pieces rather than as a whole.
You’ll typically receive local anesthesia at minimum. Many oral surgeons offer sedation ranging from mild (you’re relaxed but awake) to general anesthesia (you’re fully asleep), depending on the complexity and your preference. The procedure itself usually takes 20 to 45 minutes per tooth.
What Recovery Looks Like
The first two days are the most uncomfortable. Expect a blood clot forming in the empty socket, moderate swelling, and some bruising along the cheeks or jaw. Swelling typically peaks around day three to five, then starts to improve. Pain also eases for most people during this window, and a white or yellowish film begins covering the socket. This is a normal protective layer, not a sign of infection.
By days six through fourteen, the gum tissue starts closing over the site. Redness fades, any stitches dissolve or are removed, and eating becomes noticeably easier. By weeks three to four, the socket fills in with new tissue and the gum reshapes to a smooth surface.
During recovery, gentle saltwater rinses starting 24 hours after surgery help keep the area clean (half a teaspoon of salt in eight ounces of warm water, several times a day). The most important thing to avoid in the first week is anything that creates suction in your mouth: straws, vigorous spitting, or forceful rinsing. These can dislodge the blood clot protecting the socket, leading to a painful condition called dry socket, which feels like sudden, sharp pain and exposes bare bone in the extraction site.
Signs that something isn’t healing normally include swelling that worsens after day three instead of improving, thick yellow or green discharge with a foul smell, visible bone in the socket, heavy bleeding that soaks through gauze repeatedly, or spreading facial swelling accompanied by fever.
When Impacted Molars Can Stay
An impacted molar that’s fully buried, causing no symptoms, and showing no signs of cysts or damage to neighboring teeth on X-ray may not need removal. The decision involves weighing the risks of surgery (nerve injury, infection, dry socket) against the risks of leaving it in place. For younger patients, early removal tends to be easier because the roots aren’t fully formed and the bone is less dense, which means quicker healing. For older adults with asymptomatic impactions, monitoring with periodic X-rays is often the more conservative and reasonable approach.