Abstract: We included two RCTs in the review. One study focused on the primary prevention of CVD, and the other addressed secondary prevention. We evaluated both as being at high risk of bias. Our primary outcomes of interest were death (all-cause and CVD-related) and all cardiovascular events, measured at one-year follow-up or longer. For primary prevention of CVD in participants with periodontitis and metabolic syndrome, one study (165 participants) provided very low-certainty evidence. There was only one death in the study; we were unable to determine whether scaling and root planning plus amoxicillin and metronidazole could reduce incidence of all-cause death (Peto odds ratio (OR) 7.48, 95% confidence interval (CI) 0.15 to 376.98), or all CVD-related death (Peto OR 7.48, 95% CI 0.15 to 376.98). We could not exclude the possibility that scaling and root planning plus amoxicillin and metronidazole could increase cardiovascular events (Peto OR 7.77, 95% CI 1.07 to 56.1) compared with supragingival scaling measured at 12-month follow-up. For secondary prevention of CVD, one pilot study randomised 303 participants to receive scaling and root planning plus oral hygiene instruction (periodontal treatment) or oral hygiene instruction plus a copy of radiographs and recommendation to follow-up with a dentist (community care). As cardiovascular events had been measured for different time periods of between 6 and 25 months, and only 37 participants were available with at least one-year follow-up, we did not consider the data to be sufficiently robust for inclusion in this review. The study did not evaluate all-cause death and all CVD-related death. We are unable to draw any conclusions about the effects of periodontal therapy on secondary prevention of CVD. For primary prevention of cardiovascular disease (CVD) in people diagnosed with periodontitis and metabolic syndrome, very low-certainty evidence was inconclusive about the effects of scaling and root planning plus antibiotics compared to supragingival scaling. There is no reliable evidence available regarding secondary prevention of CVD in people diagnosed with chronic periodontitis and CVD. Further trials are needed to reach conclusions about whether treatment for periodontal disease can help prevent occurrence or recurrence of CVD.

Plain-language summary: We searched for scientific research studies known as 'randomised controlled trials', up to 17 September 2019. In this type of study, participants are assigned in a random way to an experimental or control group. People in the experimental group receive the treatment being tested, and people in the control group usually receive either no treatment, placebo (fake treatment), another type of treatment or routine care. We found two studies to include in our review. One study assessed 165 participants who did not have cardiovascular diseases, but had metabolic syndrome (a combination of risk factors for cardiovascular disease, such as obesity, high blood pressure, and high blood sugar). The other study started off with 303 participants who had cardiovascular diseases, but after a year, only 37 participants were assessed and so we thought the results were not be reliable enough to be used. Both studies had problems with their design, and we judged them to be at high risk of bias. For people who have metabolic syndrome but no cardiovascular diseases, we were unable to determine whether treating chronic periodontitis, by removing the plaque and tartar ('scaling') from the roots of teeth and giving antibiotics, reduced the risk of dying or having cardiovascular attacks when compared with scaling the teeth from above the gumline only. For people with cardiovascular diseases and chronic periodontitis, we found no reliable evidence about the effects of periodontal treatment. We classified the evidence as 'very low certainty'. We are uncertain about the findings because there are only two small studies, at high risk of bias, with very imprecise results. Overall, we cannot draw any reliable conclusions from the findings. Further research is needed.