Long-Term Effect of Periodontal Therapy on HbA1c Changes in Type 2 Diabetes

Although prior studies have assessed the effect of nonsurgical periodontal therapy (NSPT) on glycemic management, most are short term and do not account for changes in diabetes medication. This longitudinal cohort study assessed the effect of NSPT on HbA1c levels and clinical periodontal measures of type 2 diabetes (T2D) patients with periodontitis. Medication changes up to 1 y prior to and 1 y after commencing NSPT were considered. A total of 154 nonsmoking T2D patients with periodontitis received initial periodontal treatment (professional mechanical plaque removal, subgingival instrumentation, root surface debridement) and oral hygiene instructions at baseline. Supportive periodontal care with repeated subgingival instrumentation for residual pockets was provided at 3, 6, 9, and 12 mo. A full-mouth periodontal examination assessing plaque, bleeding on probing, gingival suppuration, clinical attachment loss, and periodontal inflamed surface area (PISA) was conducted at baseline and at the follow-up visits. Glycemic management was monitored via point-of-care HbA1c testing at each follow-up, with HbA1c records up to 12 mo before NSPT obtained from patients. Linear mixed-effects models were applied to assess the effect of NSPT on HbA1c over time, controlling for important confounding effects such as medical history and changes in diabetes medications. The mean HbA1c at baseline was 8.4% ± 1.6%. Compared with baseline, HbA1c was lower by 0.70%, 0.73%, 0.68%, and 0.77% at 3, 6, 9, and 12 mo, respectively. PISA was reduced by 352.7 mm² after 12 mo. Moreover, other periodontal health parameters (clinical attachment loss, probing pocket depth, and full-mouth bleeding score) were significantly reduced at 3 mo and sustained at 6, 9, and 12 mo. Participants were stratified by baseline HbA1c into "acceptable" (≤8.0%, n = 77) and "unacceptable" (>8.0%, n = 77) groups. The "unacceptable" group showed an HbA1c reduction of 1.31% at 12-mo follow-up compared with 0.24% in the "acceptable" group. The present study demonstrated that NSPT including maintenance significantly improved glycemic outcomes in T2D patients, particularly those with baseline HbA1c >8.0%.