Can canker sores be caused by grinding ones teeth?

No. No, but emotional stress can cause both canker sores and grinding of teeth. See dentist for help. http://www.mayoclinic.org/diseases-conditions/canker-sore/basics/causes/con-20021262.
Unlikely. These are aphthous ulcers and the exact cause of these aphthae is not clear. Many things have been associated with them and they are very common. We also se them rarely associated with certain systemic diseases. When you are evaluated you will checked for causes such as trauma, citrus fruits, stress, lack of sleep etc. Rarely do they indicate a serius systemic disease.
Canker sores/teeth. Grinding teeth can occur in reaction to stress. Stress, not grinding teeth, can cause canker sores.