The majority of lesions are found beneath ill-fitting dentures of long use and in patients who do not take their dentures out overnight. The lesion seems to result from a combination of chronic, mild trauma which permit frictional irritation. A poor fitting denture never acquires papillomatosis. However, there must be some unidentified predisposing factors present in those patients who develop the lesion. It is also induced by low-grade infection by bacteria or "Candida" yeast. It is occasionally seen in patients without dentures but with high palatal vaults or those with habit of breathing through the mouth.