Poor oral hygiene is associated with an increased risk for oral cancer
Luis Monteiro, Lorena C. Mariano, Saman Warnakulasuriya and Beatrice Lauby-Secretan, 
UNIPRO, (IUCS-CESPU), Oporto, Portugal; WHO Collaborating Centre for Oral Cancer, King's College London, UK, and  IARC Lyon, France
Background: Poor oral hygiene is particularly prevalent in low- and middle-income countries, and is linked to cardiovascular disease, diabetes, and some human cancers. Objectives: We investigated the role of poor oral hygiene and oral cancer risk. Methods: A systematic review and meta- analysis was performed following the PRISMA and the MOOSE guidelines. A total of 15 studies carried out from 1989 to 2020 in populations from Asia (6), Europe (2), Latin America (5), North America (1), and Oceania (1) were included in the study. Results: The meta-analysis assessing the association between toothbrushing frequency and oral cancer risk encompassed 13 studies. We also investigated any association of oral cancer with the frequency of visits to a dentist. Based on a fixed- effects model, poor oral hygiene significantly increased the risk for oral cancer, with a meta-OR of 1.85 (95% CI, 1.06–3.22) for individuals practicing toothbrushing < 1/day or never compared to toothbrushing once a day or more. Toothbrushing < 2/day compared with ≥ 2/day also showed a positive association with oral cancer risk, with an OR of 1.32 (95% CI, 1.17–1.48). Visiting a dentist for regular examinations and oral care was found to have a protective effect. Conclusions / Implications: The study reinforces the importance of good oral health as a preventive measure in the control of oral cancer. Toothbrushing twice or more daily and regular dental visits could be recommended to reduce oral cancer risk. In future studies investigating risk factors for oral cancer, it is prudent to assess and adjust for oral hygiene by including toothbrushing habits.