CASP8 and chronic periodontitis: Elevated levels of receptor-interacting protein serine-threonine kinases -1 (RIPK1), phosphorylated RIPK3, mixed lineage kinase domain-like protein (MLKL), phosphorylated MLKL and FLIPL were observed in gingival tissues collected from patients with untreated chronic periodontitis; whereas no difference in caspase 8 was observed between the periodontitis and healthy control group.