 This subtype makes up about 10 % of all cases of aphthous stomatitis . It is termed major aphthous ulceration ( MaAU ) or major recurrent aphthous stomatitis ( MaRAS ) . Major aphthous ulcers ( major aphthae ) are similar to minor aphthous ulcers , but are more than 10 mm in diameter and the ulceration is deeper . Because the lesions are larger , healing takes longer ( about twenty to thirty days ) , and may leave scars . Each episode of ulceration usually produces a greater number of ulcers , and the time between attacks is less than seen in minor aphthous stomatitis . Major aphthous ulceration usually affects non keratinized mucosal surfaces , but less commonly keratinized mucosa may also be involved , such as the dorsum ( top surface ) of the tongue or the gingiva ( gums ) . The soft palate or the fauces ( back of the throat ) may also be involved , the latter being part of the oropharynx rather than the oral cavity . Compared to minor aphthous ulceration , major aphthae tend to have an irregular outline . 
