Swelling behind back tooth
Swelling behind a back tooth can come from an erupting wisdom tooth, gum inflammation, trapped debris, infection, or a nearby salivary tissue.
The short answer
Swelling behind a back tooth is commonly related to inflamed gum over an erupting wisdom tooth, food trapped beneath the gum, a cavity or infection in the tooth, or irritation from biting. The cause is identified by examining the gum and tooth and, when needed, taking a dental X-ray.
What is the gum flap behind a partly erupted tooth?
The area behind the last molar may contain a partially erupted wisdom tooth and a gum flap called an operculum. That flap can trap plaque and food, while a decayed or cracked molar can inflame the surrounding tissues and produce swelling near the cheek or jaw.
How can you keep the area behind a back tooth clean?
Rinse gently with warm water, brush the area carefully with a small-headed brush, and keep food from packing around the tooth. Do not cut the gum, squeeze a lump, or place aspirin directly on the tissue; a dentist may irrigate the pocket, treat decay, or plan wisdom-tooth care after examination.
Which symptoms behind a back tooth need urgent care?
Seek urgent care for spreading facial swelling, fever, pus, worsening pain, reduced mouth opening, or difficulty swallowing or breathing. Arrange a dental appointment even without those signs if the swelling lasts, recurs, or is attached to a tooth that cannot be cleaned properly.
What should you ask about swelling behind the tooth?
Ask whether the swelling is over a wisdom tooth, around a decayed molar, or in another tissue. Ask whether an X-ray is needed, how the area should be cleaned, and whether treatment requires drainage, restoration, gum-flap care, or removal of a tooth.
Frequently asked questions
Can trapped food cause a lump there?
Yes. Food and plaque beneath an inflamed gum flap can make the tissue swollen and tender, although a tooth infection must also be considered.
Should I pop the swelling?
No. Squeezing or puncturing it can injure tissue and may spread contamination; examination is needed to identify the source.
Who wrote this page
This library is published by Dental Nation, a licensed dental group practising in the United Arab Emirates. Pages are written and overseen by the same clinical team that treats patients in our clinics, and are held to a fixed editorial standard for safety and accuracy.
This page is patient education, not medical advice, and cannot replace an examination. Anything urgent — facial swelling, trauma, uncontrolled bleeding or severe pain — needs a dentist or emergency care now.