Ulcers are not caused by toothpastes in itself. Second thing, toothpaste will NOT heal ulcers as well! Mouth ulcers can be caused due to various reasons. You need to give a complete history online to a dentist or you can visit a clinic. Make sure you check your iron levels and also
vitamin deficiency. Get it checked and start the supplements if needed.
You can apply any over the counter mouth gel for ulcers and make sure to avoid spicy and hot foods for a few days.
Stress also plays a major role in development of ulcers. We need to have every possibility ruled out before a proper treatment is given.