KRT4 and periodontitis: Other results obtained by similar proteomics research closely overlap with our findings, reporting all the eight types of keratins (KRT13, KRT14, KRT16, KRT19, KRT1, KRT4, KRT76, KRT6A) as decreased in GCF samples from severe chronic periodontitis [40,44]; KRT1 was also confirmed by Choi et al. [39].