S100A8 and periodontal disorder: Calprotectin is a heterogeneous complex of S100A8 and S100A9 and is an inflammation-related protein [12], and calprotectin level in gingival crevicular fluid (GCF) from periodontal sites with periodontal diseases was significantly higher than that of healthy sites; moreover, calprotectin level in GCF was correlated with clinical indicators of periodontal diseases, suggesting that calprotectin is a useful biomarker for periodontal diseases [13–16].