The mRNA expression levels of GRP78, ATF6, PERK, and XBP1 were highest in DM, followed by IG, and the lowest in CG. Hyperglycaemia activates ER stress. DM and IG microscopic observations showed disorganised cell arrangement in PDL, necrotic tissue, inflammatory cells, inflammation, granulation tissue hyperplasia, and disordered fibroblasts. This evidence concerns the gene XBP1 and diabetes mellitus.