An umbrella review of systematic reviews examining the relationship between type 2 diabetes and periodontitis: Position paper from the Canadian Dental Hygienists Association.

Previous research has confirmed strong associations between periodontitis and diabetes mellitus (DM), supporting DM as a risk factor for periodontal disease and suggesting a bidirectional relationship. Causal relationships have not been confirmed. Aim The aim of this paper is to review the most current evidence of the nature of this relationship and examine whether non-surgical periodontal therapy (NSPT) significantly lowers glycemic (HbA1c) control. Methods The PICO question was, "For individuals with type 2 diabetes mellitus (T2DM) and periodontitis, will non-surgical periodontal therapy (NSPT), as compared to no treatment, improve the individual's glycemic control as measured by HbA1c." Only systematic reviews (SRs) with or without a meta-analysis (MA) of randomized controlled trials (RCTs) or umbrella reviews of SRs and MAs of RCTs published in the English language between 2007 and 2019 were included. Several databases were searched as per their protocols. Quality assessments were conducted by both authors using the PRISMA checklist. The Bradford Hill criteria were used to determine evidence for causality. Results Of 54 records retrieved, after elimination of duplicates and studies not meeting inclusion criteria, 5 SRs/MAs and 3 umbrella reviews of SRs/MAs were selected. All 5 SRs/MAs reported reductions in HbA1c levels 3 months following NSPT, but effect sizes were small and 2 were not statistically significant. The 3 umbrella reviews consistently reported small reductions in HbA1c, but high levels of heterogeneity and moderate to high risk of bias. The Bradford Hill criteria failed to support a causal relationship between periodontitis and T2DM. Conclusions Whether NSPT compared with no treatment in persons with T2DM improves the individual HbA1c remains unclear as does the exact nature of the relationship between periodontitis and T2DM.