The biggest clusters in dogs with oral diseases were: (i) periodontal diseases: ARHGDIB, LCP1, LYZ, PPRC1, S100A8, S100A9, S100A12, and TLR4 [associated with ‘defense response to bacterium’]; (ii) dental calculus: HSPA8, PHLPP1, and PLEKHA5; and (iii) oral tumors: CEP192, DNAH11, ESRRA, INVS, KAT2B, PPRC1, SENP7, TERF2IP, and TRRAP [involved in ‘positive regulation of transcription, DNA-templated]. The gene discussed is S100A9; the disease is periodontal disorder.