A case-control study of oral cancer was conducted in Beijing, People's Republic of China. The study was hospitalbased and controls were hospital in-patients matched to the cases by age and gender. A total of 404 case/control pairs were interviewed. This paper provides data regarding oral conditions as risk factors for oral cancer, with every patient having an intact mouth examined (pre-operation among cases) using a standard examination completed by trained oral physicians. After adjustment for tobacco smoking and alcohol consumption, poor dentition--as reflected by missing teeth--emerged as a strong risk factor for oral cancer: the odds ratio (OR) for those who had lost 15 -32 teeth compared to those who had lost none was 5.3 for men and 7.3 for women and the trend was significant (P < 0.01) in both genders. Those who reported that they did not brush their teeth also had an elevated risk (OR = 6.9 for men, 2.5 for women). Compared to those who had no oral mucosal lesions on examination (OR --1.0), persons with leukoplakia and lichen planus also showed an elevated risk of oral cancer among men and women.
Denture wearing per se did not increase oral cancer risk (OR = 1.0 for men, 1.3 for women) although wearing metal dentures augmented risk (OR = 5.5 for men). These findings indicate that oral hygiene and several oral conditions are risk factors for oral cancer, independently of the known risks associated with smoking and drinking.