Temporal trends in cross-country inequalities of permanent caries burden from 1990 to 2021: a secondary analysis of the global burden of disease study 2021.

OBJECTIVE: To evaluate the changes in cross-national disparities in the burden of Permanent caries (PC) from 1990 to 2021. METHODS: We extracted the annual incidence and years lived with disability (YLDs), including their estimated annual percentage changes (EAPCs), categorized by year, age, geographical region, and socio-demographic index (SDI) from the Global Burden of Disease 2021. Correlation analysis was performed to evaluate the relationships among age-standardized rates (ASRs) of incidence, YLDs, and SDI. To assess the distributional inequalities in the burden of PC, we employed both the slope index of inequality (SII) and the concentration index. Furthermore, a frontier analysis was conducted to identify areas needing improvement and to investigate disparities among countries based on their development levels. RESULTS: From 1990 to 2021, the age-standardized incidence rate (ASIR) of PC globally showed an upward trend with an estimated annual percentage change (EAPC) of 0.23% (0.20 to 0.26). In contrast, the age-standardized YLDs for PC remained stable with a corresponding EAPC of -0.03% (-0.08 to 0.02). The SDI was positively correlated with ASIR, while it was negatively correlated with ASR of YLDs. The SII decreased from 9.51 in 1990 to 7.30 and the concentration index increased from 0.04 in 1990 to 0.08 in 2021 for PC. Regardless of their development levels, numerous countries possess substantial potential for decreasing the burden associated with PC. CONCLUSION: Although the ASIR of global PC showed an upward trend from 1990 to 2021, the ASR of YLDs displayed a stable trend, with a more pronounced decrease in high and high-middle SDI regions. This study highlights a persistent, though gradually narrowing, inequality in the global burden of PC over the past 32 years.