Periodontal Care and HbA1c: Critical Response to JAMA Study


The debate continues around the effect of nonsurgical periodontal therapy on HbA1C levels in persons with type 2 diabetes and chronic periodontitis. Now, a critical review of the study that triggered the controversy.

Past research has suggested that eliminating oral infections and effectively treating periodontitis may be one tool that can improve HbA1c (A1c) levels. Recent months, though, have witnessed a controversy sparked by publication of the largest randomized controlled trial (RCT) to date to study the issue. The results were reported in the Journal of the American Medical Association in December 2013 and questions revolve around the role of nonsurgical periodontal treatment in glycemic control of patients with T2DM.1

Many in the dental community were dumbfounded by the study’s results, and pointed to various flaws in experimental design that may have influenced results. The European Federation of Periodontology quickly issued a statement about the results, and pointed out that the majority of past studies have suggested improvements in A1c with nonsurgical periodontal treatment.2 This controversy was covered, here, in January 2014.  

Now a group of researchers has come out with a critical review,3 currently in press in the Journal of Evidence Based Dental Practice, that highlights three main concerns regarding the JAMA study:

  * Baseline HbA1c levels already near goal: Most study participants had A1c levels below 8.0%, making a further decrease unlikely and limiting the benefit of any additional therapy.

  * Periodontal treatment did not reach the accepted standard of care: Lack of clinically effective periodontal treatment and clinical improvement left “considerable” inflammation and high plaque levels, which likely prevented any reduction in A1c levels.

  * “Prominent” obesity in the treatment group:  The effects of periodontal therapy were masked. Obesity-associated systemic inflammation was a potential confounder. Enrolling non-obese individuals with diabetes would have corrected for this effect.

The issue in obese patients is that periodontal disease constitutes a relatively small portion of the overall systemic inflammation associated with obesity, explained review author Iain Chapple, PhD, professor of periodontology at the University of Birmingham (UK). Periodontitis is independently associated with obesity and metabolic syndrome, Chapple added, and obese patients have higher levels of periodontitis.

Effectively treating periodontal disease in obese individuals may reduce systemic inflammation, but by such a modest amount relative to the level already associated with the obesity, that it would have a small impact on general inflammation measures. A1c levels likewise do not always improve following periodontal therapy in obese diabetes patients.

“That is not to say that nonsurgical periodontal treatment, consisting of scaling and root planning, or ‘deep cleaning,’ does not work in obese patients,” Chapple said. “It may well be effective in controlling local gum disease.  But there is limited data on that at present.”

According to Chapple, the current standard of periodontal care includes:

  * Pocket depth: Targeted average reduction of 1 to2 mm, depending upon baseline levels of disease, with an ideal periodontal pocket depth of less than 4mm

  * Plaque scores:  Targeted to below 20%

  * Gingival bleeding after probing: Targeted to below 10%.

Reducing plaque scores and bleeding, is “challenging,” Chapple commented, because it requires good home oral hygiene habits. He also pointed out, however, that clinically relevant reductions have been obtained in most smaller studies and are linked to “far better clinical outcomes” among the majority of patients with T2DM.

“The systematic reviews all show that periodontal treatment does improve A1c by about 0.4 percentage points, which is equivalent to adding a second oral antidiabetic medication or metformin,” Chapple emphasized. 

Chapple recommends that practicing clinicians follow the joint European/American Consensus Report on Periodontitis and Systemic Diseases published in 2013 in the Journal of Clinical Periodontology.4 The report includes recommendations for medical professionals regarding their patients with diabetes. 

To definitively answer the question on the impact of periodontal therapy on A1c, a similar, large RCT needs to be conducted, but one that ensures effective periodontal treatment, and shows improvement in periodontal disease among participants. Patients would need to be treated to a defined endpoint, Chapple said, that is consistent with “successful” periodontal care in agreement with the evidence base.

“However, these are very expensive studies,” Chapple says. “And this one may be the nail in the coffin for future similar studies in the US.


  • Engebretson SP, Hyman LG, Michalowicz BS, et al. The effect of nonsurgical periodontal therapy on hemoglobin A1c in persons with type 2 diabetes and chronic periodontitis: a randomized clinical trial.  JAMA.  2013;310:2523-2532. doi: 10.1001/jama.2013.282431.
  • European Federation of Periodontology. Official Statement on NIH Study.  Dec 18, 2013.  Personal email communication with Iaian Chapple.
  • Borgnakke WS, Chapple ILC, Genco RJ, et al.  The randomized controlled trial RCT published by the Journal of the American Medical Association (JAMA) on the impact of periodontal therapy on glycated hemoglobin (HbA1c) has fundamental flaws.  J Evid Base Dent Pract. 2014; doi: 10.1016.j.jebdp.2014.04.017
  • Chapple ILC, Genco R, and the working group 2 of the joint EFP/AAP workshop. Diabetes and periodontal diseases: consensus report of the Joint EFP/AAP Workshop on Periodontitis and Systemic Diseases. J Periodontol. 2013;84(4 Suppl):S106-S112 doi:10.1902/jop.2013.134001.  Accessed online on July 11 2014 at:


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