BackgroundThis study investigates the influence of insulin on pulp tissue healing after pulp capping in diabetic dogs.MethodsDiabetes mellitus was induced in four dogs, and their blood glucose levels were adjusted by insulin to normoglycemic level in two dogs (normoglycemic group) and to hyperglycemic level in two dogs (hyperglycemic group). Class V buccal cavities were performed in 15 teeth in each diabetic dog and two normal dogs (control group). The three groups (30 teeth each) were divided according to the capping materials into three subgroups (10 teeth each) including: subgroup A ‐ mineral trioxide aggregate (MTA), subgroup B ‐ bioaggregate (BA), and subgroup C ‐ calcium hydroxide (Ca(OH)2). Each subgroup was divided into two subdivisions according to the evaluation period, subdivision 1: 1 month and subdivision 2: 2 months. Qualitative and quantitative evaluations of the inflammation and dentine bridge formation were assessed histologically.ResultsThe hyperglycemic diabetic group exhibited significant higher inflammatory cell count and scores and lower dentine bridge thickness than those of the normoglycemic diabetic and control groups (P < .05). There were no significant differences in these parameters between the normoglycemic diabetic and control groups (P > .05).ConclusionInsulin has favourable effects on the pulp tissue healing after pulp capping in diabetic dogs.