Oral potentially malignant disorders, such as oral leukoplakia, are clearly associated to oral cancer development. Mitotic checkpoint complex, including proteins such as BubR1, has an important role in preventing chromosomal instability. Our aim is to evaluate the expression of BubR1 in oral potentially malignant disorders and assess their potential predictive value of malignant transformation. Firstly, we will analyse the clinical and morphological characteristics of oral potentially malignant disorders and compare with the outcome of the lesions (recurrence and malignant transformation). Secondly, we will evaluate the expression of BubR1 by immunohistochemistry in these lesions analysing the significance of this expression on clinical, morphological and patient outcome. At last we will evaluate this protein as a biomarker of malignant transformation comparing with other classic markers such as dysplasia grade, or other classic proteins such as Ki-67 or PCNA. Our results could bring a useful biomarker for clinical use as a predictive diagnosis tool for oral potentially malignant disorders.