Social inequality in tooth loss: separate and joint effects of household income and dental visits

Objective: The aim of the study was to investigate the separate and joint effects of household income and dental visits on tooth loss. Basic research design: Participants from the Social Inequality in Cancer Cohort (SIC) were followed in registers for household income (2000), dental visits (2002-2009) and tooth loss (2010-2016). Logistic regression was used to assess the effect of household income and dental visits on tooth loss, and linear models were applied to assess the separate and joint effects of household income and dental visits. Results: In total, 10.8% of the participants had tooth loss (<15 teeth present). Low household income and irregular dental visits showed significantly higher odds ratios for tooth loss. Compared to regular dental visits, irregular dental visits accounted for 923 (95% CI 840 – 1,005) extra cases of tooth loss per 10,000 persons, and compared to high household income, low household income accounted for 1,294 (95% CI 1,124 – 1,464) additional cases of tooth loss per 10,000 persons. Further, due to household income-dental visit interaction, we observed 581 (95% CI 233 – 928) extra cases of tooth loss per 10,000 persons. Conclusion: Low household income and irregular dental visits are important in relation to social inequality in tooth loss. Irregular dental visits are associated with higher risk of tooth loss among persons with low household income compared to persons with high household income. Such interaction may be explained by differences in susceptibility to tooth loss across household income groups. Keywords: Social inequality, Tooth loss, Household Income, Dental visits, Interaction