PADI4 and periodontitis: However, the protein expressions of both PAD2 (mean score 2.16 ± 0.87 for periodontitis and 1.74 ± 0.62 for healthy controls) and PAD4 (mean score 2.18 ± 0.66 for periodontitis and 1.54 ± 0.55 for healthy) were significantly higher (p < 0.05 and p < 0.01, respectively) in the gingival connective tissue of patients with periodontitis compared to healthy controls (Fig. 4a, b, respectively).