Does the national dental scaling policy reduce inequalities in dental scaling usage? A population-based quasi-experimental study

BACKGROUND: In 2013, the national dental scaling insurance policy was introduced in South Korea. The purpose of this study is to determine the impact of the policy on inequalities in dental scaling usage. METHODS: Data of a nationally representative sample of 1,517,097 people over the age of 20 were obtained from the 2010–2016 Community Health Survey. Respondents who reported that they had not received dental scaling in the past year were defined as dental scaling non-users. The excess prevalence and relative prevalence ratio of dental scaling non-users were calculated for the pre-policy (2010–2012) and post-policy periods (2014–2016) using monthly household income levels. Additionally, trends of dental scaling inequalities were shown as concentration indexes. RESULTS: The prevalence of dental scaling non-users declined from 58.0 to 48.7% in the highest income group and from 86.3 to 78.8% in the lowest income group. However, the adjusted excess prevalence for the lowest income group compared with the highest had increased from 11.9 (95% CI: 11.9–11.9) to 15.5 (95% CI: 15.5–15.5)%, and the adjusted prevalence ratio increased from 1.19 (95% CI: 1.19–1.20) to 1.29 (95% CI: 1.29–1.30). Absolute and relative concentration indexes of dental scaling non-users increased after policy implementation. CONCLUSIONS: The national dental scaling insurance policy has increased socioeconomic inequalities in dental scaling usage. Because dental care access generally requires high individual agency, expanded dental coverage may have had limited effects in attenuating inequalities and inadvertently widened the gap. To reduce dental care inequalities, universal access with universal dental coverage should be considered. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12903-019-0881-7) contains supplementary material, which is available to authorized users.