Cinemagic

Oral mucosal lesions can appear white because of thickening of the epithelium (acanthosis), the production of excess keratin on the epithelial surface (hyperkeratosis), or accumulations of surface organisms or debris (pseudomembranes).

Thrush has the following:

Multiple, nonadherent (will rub off), white plaques on the surface of the epithelium
Removal of the white plaques reveals an erythematous mucosal surface
Can occur on any oral mucosal site (most often on the buccal mucosa, tongue, and palate).
Acute onset.
Patients may complain of a dry mouth and bad taste.
Acute pseudomembranous candidiasis is associated with a number of predisposing factors including systemic antibiotic therapy, topical and systemic corticosteroid therapy, dentures, chronic dry mouth, endocrine diseases (especially diabetes mellitus), and immunosuppression.
Persistent or recurrent episodes of acute pseudomembranous candidiasis may indicate that the patient's immune status is compromised.
Because the white plaques of acute pseudomembranous candidiasis can be rubbed off, this condition is infrequently confused with other white lesions .