Oral manifestations of type 2 diabetes mellitus are devastating which include gingival and periodontal diseases, bone loss, dental caries, alterations in salivary flow and others. A large evidence base suggests that diabetes is associated with an increased prevalence, extent and severity of gingivitis and periodontitis. The risk of developing periodontitis may be greater in patients with diabetes who have poor glycemic control than that in patients with well-controlled diabetes. Dentists should be aware of the potential influence that poor glycemic control has on the periodontium of patients with diabetes and should also recognize that patients with well-controlled diabetes can have periodontal diseases just as patients with poorly controlled diabetes may have a healthy periodontium.