Increasing Metal-Free-Restorations Insured by Japanese Universal Healthcare System

Objectives: The application of metal-free restoration has increased due to dental alloy allergies, more awareness of dental aesthetics, fluctuations in metal cost, and the introduction of hybrid-CAD/CAM restorations. This study analyzed the transition of the posterior metal inlays to composite fillings.
Methods: Datasets of dental claims of posterior class II metal inlay(PMI) and composite filling(PCF) from 2012 ~ 2018 were obtained from the Japanese Universal Healthcare system's (UHCS) national database in 2020 with approval by Japan’s Ministry of Health, Labor and Welfare. The data were analyzed with factors of frequency for 6 years period, 47 prefectures, state’s GDP, average income per family (AIF), and DCPP (dental cost per person) and the ratio of younger population (YPO) by Spearman’s correlation coefficient.
Results: The numbers of claims for PCF significantly decreased (R: 0.771, p<0.0001) and PMI decreased (R: -0.587, p<0.0001) in the last 6 years. Data from private practices and dental school hospitals revealed the frequency of PCF was significantly increased for both with R: 0.772 and 0.774 respectively (p<0.001). However, PMI decreased significantly only for private offices (R: -0.5865, p<0.0001), but not for dental school hospitals (R: 0.2028, >0.05). The data from 47 states for the past 3 years indicated that average coefficient R was 0.867 (Max: 0.999, Min: 0.032) for PCF and -0.857 (Max: -0.999, Min:-0.289) for PMI. There was a significant correlation between R values (trend of increase and decrease of PCF and PMI), and GDP and YPO only for PCF (table below). A total dental cost of PMI and PCF per year showed no significant difference, while a significant increase was observed in PCF (<0.01).
Conclusions: There was an increase in metal-free restorations insured in Japan and this trend will continuously increase including full coverage posterior restorations.