Different PPAR subtypes show distinct tissue distributions.12 Studies have shown that both PPARα and RXR are expressed in the gingival tissue,13 and that PPARα expression is higher in periodontitis and peri-implantitis groups than in healthy patients, whereas RXR shows a reverse pattern to PPARα, higher in healthy individuals than in periodontitis and peri-implantitis patients.14 This evidence concerns the gene PPARA and periodontitis.