Gum swollen at back of mouth

Swelling behind the last molar can come from an erupting wisdom tooth, trapped food, gum disease or a dental infection.

The area may be the gum over a partially erupted third molar, called a pericoronal flap. Bacteria and food can collect beneath it, while a cavity, gum pocket or infection at the tooth root can also enlarge nearby tissue.

Gently clean the back molar with a soft brush and rinse with warm salt water without forcing anything under the gum. Choose softer foods, avoid smoking, and do not squeeze the swelling or place chemicals on it.

Book an examination if swelling lasts, recurs, bleeds, produces a bad taste, or makes chewing difficult. Get urgent help if it spreads into the cheek or neck, or causes fever, difficulty swallowing, breathing difficulty or restricted mouth opening.

Ask whether the wisdom tooth is erupting normally and whether an examination or panoramic radiograph is needed. Ask if cleaning, gum treatment, restoration, extraction or another procedure addresses the identified cause.