Treatment of periodontitis for glycaemic control in people with diabetes mellitus: a Cochrane review

BACKGROUND Glycaemic control is a key component in diabetes mellitus (diabetes) management. Periodontitis is the inflammation and destruction of the underlying supporting tissues of the teeth. Some studies have suggested a bidirectional relationship between glycaemic control and periodontitis. Treatment for periodontitis involves subgingival instrumentation, which is the professional removal of plaque, calculus, and debris using hand or ultrasonic instruments, known as scaling and root planing, mechanical debridement, or non-surgical periodontal treatment. Subgingival instrumentation is sometimes accompanied by local or systemic antimicrobials, and occasionally by surgical intervention when periodontitis is severe. This review is part one of an update of a review published in 2010 and first updated in 2015, and evaluates periodontal treatment versus no intervention or usual care. OBJECTIVES To investigate the effects of periodontal treatment on glycaemic control in people with diabetes mellitus and periodontitis. SEARCH METHODS An information specialist searched six bibliographic databases up to 7 September 2021 and additional search methods were used to identify published, unpublished, and ongoing studies. SELECTION CRITERIA AND OUTCOMES A search was performed concerning randomised controlled trials (RCTs) of people with type 1 or type 2 diabetes mellitus and a diagnosis of periodontitis that compared subgingival instrumentation (sometimes with surgical treatment or adjunctive antimicrobial therapy or both) to no active intervention or usual care (oral hygiene instruction, education or support interventions, and/or supragingival scaling). To be included, the RCTs had to have lasted at least 3 months and have measured HbA1c (glycated haemoglobin). At least two review authors independently examined the titles and abstracts retrieved by the search, selected the included trials, extracted data from included trials, and assessed included trials for risk of bias. Where necessary and possible, an attempt to contact study authors was performed. The primary outcomes was blood glucose levels measured as glycated (glycosylated) haemoglobin assay (HbA1c), which can be reported as a percentage of total haemoglobin or as millimoles per mole (mmol/mol). The secondary outcomes included adverse effects, periodontal indices (bleeding on probing, clinical attachment level, gingival index, plaque index, and probing pocket depth), quality of life, cost implications, and diabetic complications. MAIN RESULTS 35 studies were included, which randomised 3249 participants to periodontal treatment or control. All studies used a parallel-RCT design and followed up participants for between 3 and 12 months. The studies focused on people with type 2 diabetes, other than one study that included participants with type 1 or type 2 diabetes. Most studies were mixed in terms of whether metabolic control of participants at baseline was good, fair, or poor. Most studies were carried out in secondary care. Two studies were assessed as being at low risk of bias, 14 studies at high risk of bias, and the risk of bias in 19 studies was unclear. Moderate-certainty evidence from 30 studies (2443 analysed participants) showed an absolute reduction in HbA1c of 0.43% at 3-4 months after treatment of periodontitis. Similarly, after 6 months, the absolute reduction in HbA1c was of 0.30%, while, after 12 months, the absolute reduction was of 0.50%. Studies that measured adverse effects generally reported that no or only mild harms occurred, and any serious adverse events were similar in intervention and control arms. However, adverse effects of periodontal treatments were not evaluated in most studies. AUTHORS' CONCLUSIONS This update has doubled the number of included studies and participants, which has led to a change in conclusions about the primary outcome of glycaemic control and in our level of certainty in this conclusion. There is now moderate-certainty evidence that periodontal treatment using subgingival instrumentation improves glycaemic control in people with both periodontitis and diabetes by a clinically significant amount when compared to no treatment or usual care. Further trials evaluating periodontal treatment versus no treatment/ usual care are unlikely to change the overall conclusion reached in this review.