Summarize this article:

Sodium lauryl sulfate (SLS) can be found in some commercial toothpastes and mouthwashes. SLS is often used as a cheap filler to help toothpaste thicken and foam up. But this additive has been shown to increase the likelihood of developing canker sores in your mouth. Read the labels on toothpastes and mouthwashes to make sure they are free of SLS before you use them or search online for brands that specifically do not contain SLS. You can also follow good oral hygiene by choosing a soft bristle toothbrush to clean your teeth. Try to brush your teeth twice a day and after every meal. This will reduce the presence of bacteria and food particles that may cause canker sores to develop. Using a soft bristle brush will also prevent irritation in your mouth. Irritating your mouth with hard brushes can lead to the development of canker sores. Floss once each day to prevent food particles from staying in your mouth. These food particles can lead to oral health issues, including canker sores.  Get in the habit of flossing before bed as well so your mouth is clean and free of bacteria or food particles. Flossing more than once daily can be harmful to your gums. If you have braces or a retainer, make sure it is not rubbing or scratching the inside of your mouth. Poorly fitting dental equipment can lead to the development of canker sores. Talk to your dentist if you feel your dental equipment is irritating your mouth. If you have braces that are rubbing against your mouth and causing sores, try using dental wax to cover sharp edges.

Summary:
Use toothpaste that does not contain sodium lauryl sulfate. Brush with a soft bristle brush. Floss once daily. Make sure your dental equipment fits properly.