Not Medical Advice: According to the book: "Ask a Nurse: From Home Remedies to Hospital Care," in addition to over-the-counter treatments, you can gargle with Epsom salts and a cup of warm water.
To help relieve pain and speed healing, consider these tips from Mayo Clinic:
Rinse your mouth. Use salt water or baking soda rinse (dissolve 1 teaspoon of baking soda in 1/2 cup warm water).
Dab a small amount of milk of magnesia on your canker sore a few times a day.
Avoid abrasive, acidic or spicy foods that can cause further irritation and pain.
Apply ice to your canker sores by allowing ice chips to slowly dissolve over the sores.
Brush your teeth gently, using a soft brush and foaming-agent-free toothpaste such as Biotene or Sensodyne ProNamel.
The exact cause of most canker sores is unknown. Stress or tissue injury is thought to be the cause of simple canker sores. Certain foods including citrus or acidic fruits and vegetables (such as lemons, oranges, pineapples, apples, figs, tomatoes, and strawberries) can trigger a canker sore or make the problem worse. Sometimes a sharp tooth surface or dental appliance, such as braces or ill-fitting dentures, might also trigger canker sores.
Learn more about canker sores, its symptoms and how can it be treated and prevented, all at WebMD.