There is nothing like a permanent cure from oral ulcers..all will have this at any point of their life time...
The thing is to identify the cause and treat it..
Those who use to have lot of spicy food, dentures, sharp tooth, are prone to have frequent mouth ulcers ,but for them it may settle subsequently with conservative treatment...
But, if u have associated, joint pain, rashes...should evaluate properly, since this recurrent oral ulcers are also associated with some systemic diseases.
Next Steps
may need work up...consult nearby health care center