Comparison of therapeutic effect of nigella sativa and corticosterioid in orabase on oral erosive atrophic lichen planus

INTERVENTION: Intervention 1: In intervention group patients will use nigella sativa orabase (5%) 3 times a day for one month. Intervention 2: Control group: In this group patients will receive routine treatment which is orabase containing corticosteroid (Triamcinolone 0‐1%) 3 time a day topically for one month. CONDITION: lichen planus. ; Lichen planus PRIMARY OUTCOME: Severity of oral lesion. Timepoint: weekly up to one month. Method of measurement: tongprasom scale. SECONDARY OUTCOME: Burning sensation. Timepoint: Pain and burning sensation will be measured before intervention and then weekly for one month. Method of measurement: Visual Analogue Scale. INCLUSION CRITERIA: patient with oral lichen planus two oral lesions maximum 3 cm diameter