Root canal treatment is needed when the nerve tissue inside a tooth becomes inflamed or infected, often due to deep decay, trauma, or repeated dental work. Common signs include lingering pain after hot or cold, spontaneous toothache, pain when biting, gum swelling, or changes seen on X-rays. Treatment can often be completed in one visit, though sometimes a temporary medication is placed for 1–2 weeks. Afterward, a temporary filling is used, and a permanent restoration or crown is usually recommended.