Social Inequalities in Dental Implant Use Among Older Japanese

Objectives: Social inequalities in oral health service utilization have been reported, however data on the direct association between socio-economic status (SES) and dental implant use (DIU) is scarce. Universal health care insurance in Japan covers most of dental care except for dental implants. We examined the association between SES and DIU in older Japanese.
Methods: In 2016, a self-reported questionnaire was mailed to subjects aged 65 years or older living in 39 different municipalities across Japan as part of the ongoing Japan Gerontological Evaluation Study (JAGES project). We used data from 86,634 respondents having 19 or fewer teeth. After multiple imputation analysis to deal with missing data, logistic regressions estimated the association of DIU with equivalised income level and years of formal education. Covariates were age, sex, density of dental clinics in the residential area, number of teeth, smoking status, and general health status such as diabetes, musculoskeletal disease, and ability of daily living.
Results: Overall, 3.09% of respondents had dental implants. Higher DIU was observed in females, younger age groups, groups having more teeth, participants who did not need assistance in their daily life, non-smokers and non-diabetics. In the fully adjusted model that included both income and education and all covariates, participants in the highest income group (=>54,000 USD/year) showed 5.38 (4.38-6.61) times significantly higher odds of DIU compared to those in the lowest income group (<11,000 USD/year). Also those in the highest educated group (=>13 years of formal education) showed 3.38 (1.90-7.72) times significantly higher odds of DIU compared to the lowest educated group (<6 years of formal education).
Conclusions: A clear social gradient was observed in DIU favoring the higher SES groups, especially the highest income level group. Relevant dental health policies are needed to address this severe social inequality.