toothpaste without sodium lauryl sulfate (SLS), also known as sodium dodecyl sulfate (SDS). This molecule, present in most toothpastes, is responsible for the frothy nature of toothpaste once you start brushing. It is good for helping remove oily substances, but is also responsible for leaving a mouth dry.Dry mouths are more prone to developing canker sores. Rembrandt and other companies produce several toothpastes without SDS. Just check the label to make sure.