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Clinical question.
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Do adults with diabetes who receive periodontal therapy experience improved glycemic control compared with similar patients who do not receive periodontal treatment?
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Review methods.
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The authors of this systematic review conducted a search of seven databases with no language restrictions and publication dates from January 1976 to December 2007; they also included unpublished research. They followed a clear protocol, with two independent reviewers identifying studies and extracting data. The authors considered studies for inclusion if they were original interventional investigations and involved human subjects for whom glycosylated hemoglobin (HbA1c) levels were reported. The authors reported the results of the systematic review and meta-analysis. They followed the Quality of Reporting of Meta-analyses (QUOROM) recommendations.1
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Main results.
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The authors of the systematic review included 25 studies with a total of 976 participants. Of these 25 studies, only nine were randomized controlled trials. These nine trials had sample sizes ranging from 22 to 165 participants, and investigators used varied treatment modalities. Overall, the meta-analysis demonstrated a moderate, statistically significant result favoring the therapeutic group (standardized mean difference in HbA1c, 0.46; 95 percent confidence interval [CI], 0.11–0.82; P = .01). This result may be interpreted as a small but statistically significant improvement in glycemic control (0.79 percent; 95 percent CI, 0.19–1.40).
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Conclusion.
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The best information available suggests that scaling and root planing can improve glycemic control. However, caution is advised, because despite the general trend of these results, the studies have shortcomings that may influence the findings.
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COMMENTARY
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Importance and context.
Diabetes affects a substantial (about 8 percent) and growing minority of the U.S. population and can result in serious problems for those with the disease.2 For patients with diabetes, maintaining glycemic control results in a lower risk of developing severe biological complications, such as cardiovascular disease, retinopathy, nephropathy and periodontal disease. Although an association clearly exists between periodontal disease and some types of diabetes,3 Taylor4 and Janket and colleagues5 concluded that the evidence was insufficient to show that periodontal therapy improves glycemic control in patients with diabetes.
Strengths and weaknesses of the systematic review.
The authors followed the QUOROM guidelines1 to search for and select studies. Two independent reviewers extracted data from the studies and followed a procedure for attaining consensus in areas of disagreement. The authors assessed the quality of the studies, evaluated their heterogeneity (from both a statistical and clinical viewpoint) and checked for publication bias. Publication bias occurs when studies with positive results are more likely to be published than are studies with negative results. (Researchers test for publication bias by using a funnel plot of the magnitude of treatment effect against the reciprocal of the standard error.6)
The authors used both fixed- and random-effects methods to calculate the standardized mean difference. They provided a comprehensive list of studies and their characteristics, along with baseline characteristics of participants in the included studies. The authors assessed the scientific merit of the studies, with the exception of one study from the gray literature.7 (Gray literature includes research findings presented in theses, dissertations, reports and symposium proceedings but not published in journals.8 Its evidence is more difficult to locate by using standard search techniques.) The review was not specific in describing the methodological deficiencies that gave rise to the wide variation in quality scores for the studies, and it was weakened by the inclusion of one nonrandomized study in the overall meta-analysis.
Strengths and weaknesses of the evidence.
If the authors had eliminated one study9 from the meta-analysis, there would have been no significant difference between the treatment and control groups. This studydid not randomize assignment of participants to the treatment and control groups, yet the review authors assigned it a weight of 21 percent in the meta-analysis. If this study is eliminated, the conclusion from the meta-analysis becomes equivocal. One study suggesting a positive effect of periodontal treatment was conducted with patients who did not have periodontal disease and sought care at a dental school. The two trials with the strongest designs showed nonsignificant effects of periodontal interventions. Because the evidence is weak, the effect on HbA1c is small and the potential for bias is substantial, this meta-analysis provides insufficient evidence to promote periodontal therapy specifically to improve glycemic control.
Implications for dental practice.
This systematic review provides weak evidence of a small benefit in glycemic control in adults with diabetes who received periodontal therapy. No harms were reported. Any recommendations for periodontal treatment that claim an additional benefit of improving glycemic control in adults with diabetes would exceed the current best evidence, as represented in this systematic review. Nevertheless, the benefit would be substantial if relatively simple, albeit frequent, prophylactic intraoral interventions could prevent more serious medical conditions in patients with diabetes.
TOP
Clinical question.
Review methods.
