The multi-center randomized controlled trial (RCT) published by the journal of the American Medical Association (JAMA) on the effect of periodontal therapy on glycated hemoglobin (HbA1c) has fundamental problems.

Subject Participants had type 2 diabetes, were on stable medication regimens, had HbA(1c) levels between 7% and <9%, retained at least 16 natural teeth, and had untreated chronic periodontitis. A total of 514 participants were enrolled between November 2009 and March 2012 from diabetes and dental clinics and communities affiliated with five participating academic medical centers. They were randomized with half (n = 257) allocated to a treatment group and the other half (n = 257) to a control group. Key Exposure/Study Factor The exposure was non-surgical periodontal treatment comprising scaling and root planing, oral hygiene instruction, and oral rinsing with chlorhexidine provided to the treatment group at baseline. Supportive periodontal therapy was also provided at 3 and 6 months. The control group received no treatment for the 6-month duration of the study. Main Outcome Measure The primary outcome measure was "the difference in change in HbA(1c) level from baseline between the two groups at 6 months." Secondary outcomes included changes in periodontal probing depth (PPD), clinical attachment loss, bleeding on probing (BOP), gingival index, fasting glucose level, and Homeostasis Model Assessment (HOMA2) score. Main Results The authors report that enrollment into their Diabetes and Periodontal Therapy Trial (DPTT) was terminated early due to futility. At 6 months, mean HbA1c levels in the periodontal therapy group increased 0.17 (+/- 1.0)%, compared with 0.11 (+/- 1.0)% in the control group, with no significant difference between groups based on a linear regression model adjusting for clinical site (mean difference, -0.05% [95% CI: -0.23% to 0.12%]; p = 0.55). Periodontal measures improved in the treatment group compared with the control group at 6 months, with adjusted between-group differences of 0.28 mm (95% CI: 0.18-0.37) for PPD; 0.25 mm (95% CI: 0.14-0.36) for clinical attachment loss; 13.1% (95% CI: 8.1%-18.1%) for BOP; and 0.27 (95% CI: 0.17-0.37) for gingival index (p < 0.001 for all). Conclusions The authors conclude: "Nonsurgical periodontal therapy did not improve glycemic control in patients with type 2 diabetes and moderate to advanced chronic [GRAPHICS] periodontitis. These findings do not support the use of nonsurgical periodontal treatment in patients with diabetes for the purpose of lowering levels of HbA(1c)."