The main objective is to evaluate the effect of nonsurgical periodontal treatment on serum levels of HbA1c in patients with type 2 diabetes mellitus (T2DM). This study is a 6-month, single-masked, randomized clinical trial.A total of 90 patients with diabetes and chronic generalized periodontal disease will be randomly divided into 2 groups: Treatment Group, Control Group.

Background: Periodontitis and diabetes are both highly prevalent conditions, and the association between these two common diseases has been recognised by dental professionals for many years.

Aim: The main objective is to evaluate the effect of nonsurgical periodontal treatment on serum levels of HbA1c in patients with type 2 diabetes mellitus (T2DM).

Methods: This study is a 6-month, single-masked, randomized clinical trial.A total of 90 patients with diabetes and chronic generalized periodontal disease will be randomly divided into 2 groups: Treatment Group (TG) (Oral Hygiene Instructions (OHI) + scaling and root planing (RAR) using ultrasound device and Gracey curettes); Control Group (CG) (OHI + supragingival removal of plaque and calculus with ultrasonic device). CG patients receive salvage therapy if a significant worsening of their periodontal status and / or metabolic observed. Periodontal assesment (probing pocket depth (PPD), gingival index (GI), and plaque index (PI)) and systemic assesment (random blood sugar, glycosylated hemoglobin (HbA1C), and salivary cytokines) and bacterial asessment at baseline and 3, 6 months after treatment is performed. There will be a single examiner, blind and calibrated to improve reproducibility. The investigators' hypothesis is that non-surgical periodontal treatment reduces HbA1c, improving metabolic control in patients with DM

Inclusion criteria were:

• Diagnostic of T2DM (diagnosed at least 1'5 years prior the study).
• Presence of generalized chronic periodontitis (With at least 9 teeth present and more than 30% of locations with probing depth (PD) and clinical attachment level (CAL) ≥4mm).

Exclusion criteria included:

• Patients who received antibiotics the last 15 days, or for a period longer than 10 days the last three months.
• Having received non-surgical periodontal treatment within the past 6 months.
• Pregnancy
• Significant change of medication for diabetes during the course of the study
• Evidence of other serious systemic disease (ASA III or IV) which may influence periodontal disease.