In a prospective clinical trial we will (1) measure the saliva levels of S100A7 in patients with oral leukoplakia treated with chemoprevention approaches prior to during and after therapy and determine whether there is any association between salivary S100A7 level and progression to oral cancer; and (2) measure the pre-treatment, immediate post-treatment and follow-up levels of salivary S100A7 to determine whether there is any association with the level of S100A7 and local recurrence. This evidence concerns the gene S100A7 and Oral leukoplakia.