Diabetes mellitus (DM) is a common endocrine disorder in dogs, with a strong breed disposition. The disease is associated with significant morbidity and death when left untreated, and tight control of blood glucose levels is crucial in avoiding the harmful effects of long-standing hyperglycemia. Insulin administration, appropriate diet, and treatment of concurrent diseases which interfere with insulin actions constitute the cornerstones of treatment. Among the various diseases in humans which affect treatment success, periodontal disease (PD) adversely affects glycemic control, and periodontal treatment leads to improvement in diabetic control. Periodontal disease is a multi-factorial, bacterial disease of dental supporting tissues. A common occurrence in dogs, its incidence increases with age, and most dogs over the age of five are afflicted by PD to variable extent. Beyond the local consequences of PD on dental and gingival health, PD induces a systemic inflammatory reaction, which purportedly accounts for its detrimental effects on diabetic control. In veterinary medicine, only few case reports and small experimental studies, involving 1 to 4 dogs, investigated the role of periodontal treatment (PT) on diabetic control. This study will investigate the effects of PT on diabetic control in a larger cohort of dogs through a prospective, clinical study. The investigators will also examine possible associations between PT, diabetic control and markers of systemic inflammation to elucidate possible mechanisms which may shed light on the relationship between the two conditions.