Platelet Rich Fibrine (PRF), which promotes wound healing by supporting angiogenesis, immunity and epithelial proliferation phases. over a decade has since past since PRF was developed and many clinicians now point to the potential use of a liquid version of PRF. a liquid injectable-platelet-rich fibrin (i-PRF) was developed by modifying spin centrifugation forces. At lower centrifugation speeds and by utilizing non-glass centrifugation tubes, the fibrin coagulation could be slowed down at early time points thus generating an injectable PRF. Much like traditional PRF, i-PRF contains an increase in leukocyte number and is further able to stimulate growth factor release.

Lichen planus is a common chronic mucocutaneous inflammatory disorder which generally affect s middle aged adults. Therapeutic methods including topical and systemic corticosteroids for the treatment of oral lichen planus (OLP) are suggested. However, long

-term use of corticosteroids may be associated with local and systemic complications, and moreover, some patients may not be responsive.

The investigators aimed to apply a treatment of autogenous origin (including no foreign products), considering the side effects of our corticosteroids. The study was designed as a split mouth.

The investigators planned to administer I-PRF to one side and intralesional corticosteroid therapy to the other side at patients with bilateral atrophic / erosive oral lichen planus lesions

Lichen planus diagnosis will be made histopathologically. Intraoral photographs and measurements will be taken at the beginning of the treatment and 2 months after the treatment is finished.

Inclusion Criteria:

1. Oral erosive lesions were diagnosed according to Andreasen classification.
2. Histological confirmation of erosive OLP according to the World Health Organization's clinicopathological diagnostic criteria for OLP.
3. No previous treatment of oral lichen planus at least 3 months.
4. Willingness and ability to complete the present clinical trial.
5. Patients of ages above 18 years old without skin involvement.

Exclusion Criteria:

1. Histological signs of dysplasia.
2. Using drugs associated with lichenoid reaction.
3. Pregnant, lactating and smoker patients.
4. Patient with systemic diseases such as diabetes mellitus, immunodysfunction, hematological and hepatological patients or had photosensitivity history.

Investigator, Outcomes Assessor