Scholars had carried out extensive research of oral leukoplakia (oral leukoplakia, OLK) and published a number of papers, however, the aetiology of OLK did not reach a consensus. We collected eligible studies for reviewing and analyzing to explore the aetiological factor of OLK. According to the requisition of systematic evaluation, we formulated detailed standardization of the inclusion and exclusion criteria including contents of research, OLK diagnosed by histopathology and associated with aetiological factor of OLK. We retrieved articles from Pubmed, CNKI and Wanfang data base and found 406 articles related to OLK from January 2012 to July 2016. Retrieving part of the cited references in some literature, we downloaded and comprehended 103 which were consistent with the requirements of our research to analysis. The following search terms were used: "oral leukoplakia" AND "aetiological factors". The research indicated that the duration of smoking habits, the amount of cigarettes smoked and alcohol drank per day were significantly associated with the presence of oral leukoplakia. Local stimulation can cause damage of the oral mucosa and chronic inflammation leading to OLK. Candida infection and human papilloma virus (HPV) infection may lead to OLK and cause epithelial dysplasia of oral mucosa. Systemic factors such as saliva flora, trace elements, radiation, microcirculation changes and genetic factors can increase the risk of OLK.

Leukoplakia, oral; Aetiological factor; Cases analysis; Oral mucosa