IL4 and periodontitis: Twelve of the 32 studies were case–control studies that compared periodontitis prevalence and its severity, serum urea, serum creatinine, eGFR, genetic polymorphisms (monocyte chemoattractant protein-1 gene, interleukin-1, and interleukin-4), oral microbial diversity, and serum ions (calcium, potassium, phosphorus, and bicarbonate) between participants with and without CKD of different stages, including patients on kidney replacement therapy (Table 2) [45–56].