How do you prevent mouthsores?

What's diagnosis? Get examined please. Canker sores are common aphthous ulcers of mouth that occur situationally, often in response to stressors, are bacterial or viral, & can be treated topically with many otc products that reduce local discomfort & potentially speed healing. However, oral/dental problems & a number of systemic diseases cause canker sore-like lesions--crohn's, behcet's, std (sexually transmitted).