Design characteristics of studies evaluating the effect of non-surgical periodontal treatment on systemic health outcomes.

backgroundEvidence for whether and how non-surgical periodontal treatment (NSPT) improves systemic outcomes remains equivocal. Inconclusive findings may in part be due to design variations of randomized controlled trials (RCTs) in this field. The objective of this study was to describe the study design characteristics of RCTs that have evaluated the effect of non-surgical periodontal treatment on systemic health outcomes.

methodsWe searched Medline via Ovid and EMBASE for RCTs published through January 1, 2024, for terms indicating NSPT (i.e., scaling and root planing) and selected chronic diseases. We developed a standardized coding sheet for systematically extracting data from studies, including the definition of periodontal disease (PD) among study participants, the length of study duration, and whether the effect of NSPT was found to have a statistically significant beneficial, detrimental, or null effect on systemic outcomes.

resultsEighty-two RCTs, which reported the effect of NSPT on systemic outcomes in 816 individual analyses, met our inclusion criteria. Fifty-six studies (68.3%) had at least 1 of 4 variations in study design that may contribute to biased results. Studies that restricted their inclusion criteria to participants with severe PD were more likely to measure a beneficial effect than a non-beneficial effect on specific systemic outcomes following NSPT (62.7% vs. 49.2%, p < 0.001).

conclusionVariation in study designs of RCTs may be contributing to mixed and inconclusive findings investigating the effect of NSPT on systemic disease outcomes. PLAIN LANGUAGE SUMMARY: This study reviewed clinical trials to understand why the evidence on whether non-surgical periodontal treatment (NSPT) can improve overall health is inconclusive. Eighty-two clinical trials were analyzed to identify patterns in how these studies were designed. While most trials found that NSPT had some benefits, more than two-thirds of the studies had design features that could skew results. Trials involving participants with severe gum disease were more likely to show benefits than those including people with milder forms. How clinical trials are set up-such as who is included and how long the study lasts-may heavily affect overall findings. The study highlights the need for more standardized approaches to research in this area to better understand whether and how dental treatments can improve overall health. These findings are important for designing future studies and ensuring reliable evidence for medical and dental professionals.