Grading evidence concerning bidirectional diabetes

March 10, 2014
Many dental hygienists, dentists, and periodontists have been lecturing or writing about the bidirectional diabetes link to periodontal disease.

By Lynne Slim, RDH, BSDH, MSDH

Many dental hygienists, dentists, and periodontists have been lecturing or writing about the bidirectional diabetes link to periodontal disease. It's easy to get excited about many of the oral/systemic links because we're eager to promote the mouth-body connection.

We know that the mouth is the gateway to the body. In the last 10 years or so, we've witnessed an escalating interest in possible links between oral and body health. According to a consumer adviser for the American Dental Association, adults with periodontitis are more likely to have a chronic medical condition, and she cites one recent study.1 WebMD also talks about how oral inflammation compounds systemic inflammation, and many of us are communicating this message to our patients.


Other articles by Slim


I can recall how the medical profession used to recommend hormone replacement therapy (HRT) to postmenopausal women based on epidemiological studies, demonstrating that women who took HRT also had lower-than-average incidence of coronary heart disease (CHD). (HRT use and CHD were linked.) The strong epidemiological link led doctors to believe that HRT was protective against CHD.

When data were reanalyzed from epidemiological studies, it was observed that the women who showed less CHD also came from higher than average socioeconomic groups. These women had better than average diets and exercise regimens, and had better access to physicians for routine preventive care. When clinical investigations in the Women's Health Initiative (WHI) began to test the benefits of HRT in large clinical trials, the studies were abruptly halted because researchers were shocked to learn that women receiving hormone therapy had more heart attacks, strokes, blood clots, and breast cancer than the control groups who were taking a placebo drug.

It may seem logical to us that treating periodontal disease in an adult patient with diabetes will improve glycemic control. Speculation about causality between periodontal disease and improved diabetes glycemic control continues to be tested by researchers. For clinicians, the ability to track and critically appraise and incorporate this body of evidence into one's clinical operatory comes next.

In an attempt to summarize the strength of the evidence to date surrounding this particular link, only the highest quality evidence will be presented and that includes randomized clinical trials, and systematic reviews. The evidence surrounding this and every other link will eventually be graded by experts who will translate clinical research to patient care.

Clinicians must learn to understand and critically analyze the results of clinical studies. Due to the increasing production of scientific data and the complexity of interpreting it and applying it to daily practice, grading systems will become a useful tool that will help dental hygienists and dentists identify strength of the evidence from an article in a peer-reviewed journal. You can learn more about grading systems by subscribing to the Journal of Evidence-Based Dental Practice.

In 2012, I was part of a team of academic dental hygienists led by Frieda Pickett, RDH, MS, who reviewed the strength of the evidence for a variety of oral/systemic links, including the bidirectional relationship of diabetes and periodontal disease.2 Authors Linda Boyd, RDH, RD, EdD, Lori Giblin, RDH, BA, and Dianne Chadbourne, RDH, MDH, found that individuals with type 2 diabetes seem to have a 2.6 to 4 times greater risk for more severe periodontal disease.2 Meta-analyses also report statistically significant differences in clinical attachment levels for persons with type 2 diabetes compared to individuals without type 2 diabetes. Range of CAL was reported as ≈ 0.612 to 1 mm.2

Since a lower risk for progression of periodontal disease and less severe periodontal disease is associated with tightly controlled diabetes, researchers have also suggested that the level of glycemia is an important mediator of the relationship between diabetes and risk of periodontal disease.3 Trying to find cause/effect between periodontal disease and diabetes has been "observational, limited, and inconsistent."3 Even though there are about four meta-analyses and systematic reviews of research related to how treatment of periodontal disease affects glycemic control of diabetes, most results showing a decrease in HbA1c following periodontal therapy did not reach statistical significance.2

Several small interventional clinical studies found an insignificant decrease of HbA1c levels of 0.38% three months after periodontal therapy, and one trial showed a 0.65% nonsignificant reduction of HbA1c levels four months after periodontal therapy. That particular study was considered underpowered, which means the number of subjects in the study was too low to support the probability of detecting an effect of practical importance.3

In continuing to answer the question about the relationship between periodontal therapies and possible improvement of glycemic control in individuals with type 2 diabetes having periodontal disease, a large, adequately powered (90%), multicentered, randomized clinical trial (The Diabetes and Periodontal Therapy Trial or DPTT) was designed and implemented. The results were published in the Journal of the Medical Association (JAMA) in Dec. 2013.3

Results from this particular trial may disappoint many dental hygienists. If that is the case, we must learn to think like scientists. Scientists go to a lot of trouble to make sure their studies remain completely objective and free from observer bias. Conclusions need to be based on repeatability, not conjecture, as well as not trying to find facts to support preconceived conclusions.

The easiest way for me to describe this study is by copying the multicenter trial abstract (see Table 1) and making a few comments. Information not in the abstract is that the treatment group received initial scaling/root planing, using both ultrasonic and hand instruments for a minimum of 160 minutes (average was 190 minutes). The treatment was repeated after three months and six months for a minimum of 60 minutes. The work of the initial operator was verified by a periodontist for completion. Subjects were given oral hygiene education and used chlorhexidine rinse for two months. Read the abstract in Table I for remaining trial details. Even though clinical periodontal outcomes improved as a result of the periodontal therapy, nonsurgical periodontal therapy did not improve glycemic control in patients with type 2 diabetes and moderate to severe periodontal disease.3

As with all clinical trials, this one had some limitations and strengths. Limitations discussed were lack of systemic or topical antibiotics and nonsurgical vs. surgical treatment of periodontitis. Systemic antibiotics were not included so as not to confound the effects of the study intervention. RDH magazine readers may want to read the entire research report in JAMA as referenced below.

I commend the take-home message given by Boyd, Giblin, and Chadbourne in their Canadian Journal of Dental Hygiene (CJDH) narrative review about the bidirectional relationship between type 2 diabetes and periodontal disease.2 They recommend collaboration between medical and dental professionals as paramount when treating these patients. Conducting a thorough medical history review, taking vital signs, and consulting with a medical provider to gather information about glycemic control and associated medical conditions is essential before planning dental hygiene care for the patient.2 Educating the medical provider is also needed, especially if the infection is in the form of periodontitis or a periapical infection that could possibly impact diabetes management.2

In a 2013 position statement (medical care standards) from the American Diabetes Association, diabetes "control" testing should be performed within the health-care setting because of the need for follow-up and discussion of abnormal results.4

"Community screening outside a health-care setting is not recommended because people with positive tests may not seek, or have access to, appropriate follow-up testing and care. Conversely, there may be failure to ensure appropriate repeat testing for individuals who test negative. Community screening may also be poorly targeted; i.e., it may fail to reach the groups most at risk and inappropriately test those at low risk (the worried well) or even those already diagnosed."4

Study professional guidelines for diabetes and question patients about diabetes prevention and management. This includes positive lifestyle changes in addition to strict HbA1c and other metabolic measure control.2 Set a good example for patients and show them how a combination of regular physical activity, modest weight loss, healthy food choices, and prevention/management of dental caries/periodontal disease can improve quality of life.2

Table 1


"The Effect of Nonsurgical Periodontal Therapy on Hemoglobin A1c Levels in Persons With Type 2 Diabetes and Chronic Periodontitis: A Randomized Clinical Trial"


Chronic periodontitis, a destructive inflammatory disorder of the supporting structures of the teeth, is prevalent in patients with diabetes. Limited evidence suggests that periodontal therapy may improve glycemic control.


To determine if nonsurgical periodontal treatment reduces levels of glycated hemoglobin (HbA1c) in persons with type 2 diabetes and moderate to advanced chronic periodontitis.

Design, setting, and participants

The Diabetes and Periodontal Therapy Trial (DPTT), a 6-month, single-masked, multicenter, randomized clinical trial. Participants had type 2 diabetes, were taking stable doses of medications, had HbA1c levels between 7% and less than 9%, and untreated chronic periodontitis. 514 participants were enrolled between November 2009 and March 2012 from diabetes and dental clinics and communities affiliated with five academic medical centers.


The treatment group (n = 257) received scaling and root planing plus chlorhexidine oral rinse at baseline and supportive periodontal therapy at 3 and 6 months. The control group (n = 257) received no treatment for 6 months.

Main outcomes and measures

Difference in change in HbA1c level from baseline between groups at 6 months. Secondary outcomes included changes in probing pocket depths, clinical attachment loss, bleeding on probing, gingival index, fasting glucose level, and Homeostasis Model Assessment (HOMA2) score.


Enrollment was stopped early because of futility. At 6 months, mean HbA1c levels in the periodontal therapy group increased 0.17%(SD, 1.0), compared with 0.11% (SD, 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 = .55). Periodontal measures improved in the treatment group compared with the control group at 6 months, with adjusted between-group differences of 0.28mm (95%CI, 0.18 to 0.37) for probing depth, 0.25mm (95%CI, 0.14 to 0.36) for clinical attachment loss, 13.1% (95%CI, 8.1% to 18.1%) for bleeding on probing, and 0.27% (95%CI, 0.17 to 0.37) for gingival index (P < .001 for all).

Conclusions and relevance

Nonsurgical periodontal therapy did not improve glycemic control in patients with type 2 diabetes and moderate to advanced chronic periodontitis. These findings do not support the use of nonsurgical periodontal treatment in patients with diabetes for the purpose of lowering levels of HbA1c.

Source: JAMA. 2013;310(23):2523-2532. doi:10.1001/jama.2013.282431

LYNNE SLIM, RDH, BSDH, MSDH, is an awardwinning writer who has published extensively in dental/dental hygiene journals. Lynne is the CEO of Perio C Dent, a dental practice management company that specializes in the incorporation of conservative periodontal therapy into the hygiene department of dental practices. Lynne is also the owner and moderator of the periotherapist yahoo group: Lynne speaks on the topic of conservative periodontal therapy and other dental hygiene-related topics. She can be reached at [email protected] or


2. Boyd LD, Giblin L, Chadbourne D. Bidirectional relationship between diabetes mellitus and periodontal disease: state of the evidence. Can J Dental Hygiene 2012; 46 (2): 93-102.
3. Engebretson et al. The effect of nonsurgical periodontal therapy on Hemoglobin A1c levels in persons with type 2 diabetes and chronic periodontitis: a randomized clinical trial. JAMA Dec 18, 2013; 310(23): 2523-2532.

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