Recent evidence has suggested that poor glycaemic control increases the risk of periodontal disease and that periodontal disease can itself cause deterioration in glycaemic control.
The Cochrane review examined seven studies of people with type-1 or type-2 diabetes with periodontitis.
Patients in the studies were treated using mechanical therapy with or without adjunctives and oral hygiene education.
Compared with no treatment, scaling or root planing and oral hygiene with or without antibiotics, was associated with a 0.4 percentage point drop in HbA1c.
But there were few trials examining the effect, the researchers said.
In addition, each of the studies was, on its own, too small to detect a statistical difference from treatment.
The researchers concluded: 'Improving periodontal health is an important objective in itself. But to understand the potential of this treatment to improve glycaemic control among people with diabetes, larger, carefully conducted and reported studies are needed.'