Oral lichen planus (OLP) is a chronic inflammatory disease that affects the mucosal membrane. T-cell mediated damage against the mucosal epithelial cells is implicated in the pathogenesis of OLP, although the exact mechanism is unknown.

Sulfasalazine is extensively used in inflammatory bowel disease and is effective on immune-related inflammatory disease such as Crohn's disease, rheumatoid arthritis, and Behcet's disease. In spite of its effectiveness, the anti-inflammatory mechanism is not clearly understood.

• Patients will be recruited in a consecutive manner from the outpatient Diagnostic center, Faculty of Dentistry, Cairo University.
• A total number of 46 patients will be included in this study. The 23 patients categorized as study group (S group) will use topical sulfasalazine prepared by dissolving one tablet of commercially available (COLOSALAZINE - EC 500 MG 20 TAB, manufactured by: Alexandria Company for Pharmaceuticals & Chemical Industries, Alexandria) in 100 ml of distilled water 4 times per day as a mouth wash combined with topical corticosteroids 4 times per day as a topical gel in an alternate sequence. There are no expected side effects of this treatment due to its topical application however, the patient will be instructed to stop the treatment if any adverse reactions occur such as allergy and coming to the clinic next day.
• The 23 patients categorized as control group (C group) will receive topical corticosteroids gel only 4 times per day. The treatment regimen will be continued for 4 weeks with follow up visits one per week.
• Medical history will be taken, thorough oral examination will be done, and a full questionnaire will be filled for each patient.
• All participants in the study groups will undergo adequate oral hygiene performance measures with complete removal of plaque and calculus as they implement intraoral inflammation and intensify both extension and symptoms of OLP lesions. Patients will be advised to evade accidental trauma on soft tissues using soft bristles toothbrush. Acidic, spicy, hard, hot food and beverages will be avoided.

Inclusion Criteria:

• - Patients with 30-65 years old
• Patents with atrophic OLP

Exclusion Criteria:

• - Smokers
• pregnant or lactating ladies and
• Patients under topical or systemic steroids during the last two months
• Patients using lichenoid reaction-inducing drugs,
• Patients with positive hepatitis C virus (HCV) antibodies, diabetes and hypertension
• Patients having amalgam filling adjacent lesions will not also be included

Because the research not published yet.