Relationship between dental factors and risk of upper aerodigestive tract cancer

We examined the relationship between dental health variables and risk of upper aerodigestive tract (UADT) cancers in a casecontrol study in Southern Brazil. The study population included 717 cases of cancers of the mouth, pharynx, and larynx and 1434 controls matched on age, gender, period of admission and study site. The association with dental factors was investigated by conditional logistic regression using extensive adjustment for a priori and empirical confounders, including tobacco and alcohol consumption, diet and sociodemographic variables. Lifetime use of dentures was not associated with risk of any UADT cancer, but history of oral sores secondary to ill-fitting dentures was associated with cancers of the mouth (odds ratio [OR] = 2.3, 95% confidence interval [CI] 1.2-4.6) and of the pharynx (OR = 2.7, 95% CI 1.1-6.2) among those using dentures. The association for mouth cancers was restricted primarily to an increased risk of tongue neoplasms (OR = 9.1, 95% CI 1.9-43.4). Less than daily tooth brushing frequency was also associated with risk of cancer of the tongue (OR = 2.1, 95% CI 1.0-4.3) and of other parts of the mouth (OR = 2.4, 95% CI 1.0- 5.4). Having broken teeth was not significantly associated with risk of UADT cancer of any site. We conclude that poor oral hygiene due to infrequent tooth brushing and sores caused by dentures are risk factors for cancer of the mouth and that these associations are unlikely to be due to insufficient control of confounding.