Oral submucous fibrosis since 25 years without any history of smoking, tobacco, pan, nut. Patient has no complaints. How common is Oral submucous fibrosis in such cases (without cause).

In how many years Oral submucous fibrosis turns into malignancy and what is the percentage of converting into Malignancy. Do such persons need to have frequent oral monitoring or just avoid particular food like chilly, hot drinks etc. Any particular treatment like B complex etc?