Does treatment for gum disease help people with diabetes control blood sugar levels?

Review question

The main question addressed by this review is: how effective is gum disease (periodontitis) treatment for controlling blood sugar levels (known as glycaemic control) in people with diabetes, compared to no active treatment or usual care?


The aim of treating periodontitis is to reduce swelling and infection and stabilise the condition of the gums and supporting bone. The level of sugar in the blood is too high in people with diabetes, so keeping blood sugar levels under control is a key issue. Some clinical research suggests a relationship exists between gum disease treatment and glycaemic control. 

Glycaemic control can be measured in different ways. For this review, we focused on HbA1c, which shows average blood glucose levels over the preceding 3 months. It can be reported as a percentage (of total haemoglobin) or as mmol/mol (millimoles per mole). Excellent glycaemic control in a diabetic person might be around 6.5% or 48 mmol/mol.

This review was carried out by authors working with the Cochrane Oral Health and is part one of an update of a review previously published in 2010 and 2015. This review evaluates gum disease treatment versus no active treatment or usual care. Part two of the review will compare different types of periodontal treatment. We carried out this review as it is important to discover if gum disease treatment does improve glycaemic control in order to ensure best use of clinical resources. 

Study characteristics

We searched six research databases and found 35 relevant trials where people with diabetes and periodontitis were randomly allocated to an experimental group or a control group. The experimental groups received gum disease treatment called 'subgingival instrumentation', also known as scaling and root planing or deep cleaning. In some experimental groups, the deep cleaning was supplemented with instructions for cleaning teeth properly ('oral hygiene instruction'), or other gum treatments, for example, antimicrobials, which are used to treat infections. Control groups received no active treatment or 'usual care', which was oral hygiene instruction, support with oral hygiene, and/or removal of plaque above the gumline. 

The trials randomised 3249 participants in total. Almost all participants had type 2 diabetes, with a mix of good, fair, and poor diabetic control. Most of the studies were carried out in hospitals. The studies followed up participants for between 3 and 12 months.

Key results

Evidence from 30 trials (results from 2443 participants) showed that periodontitis treatment reduces blood sugar levels (measured by HbA1c) in diabetic patients on average by 0.43 percentage points (e.g. from 7.43% to 7%; 4.7 mmol/mol) 3 to 4 months after receiving the treatment compared with no active treatment or usual care. A difference of 0.30% (3.3 mmol/mol) was seen after 6 months (12 studies), and 0.50% (5.4 mmol/mol) at 12 months (one study).

There were not enough studies measuring side effects to be able to evaluate the risk of harm from gum disease treatments.

Certainty of the evidence

Most of the studies were conducted in a way that meant they were at a high risk of bias or did not provide enough information for us to make a judgement on this. However, the consistency of our findings suggests they are reliable and future research is not likely to change them. 

In summary, currently there is moderate-certainty evidence to support gum disease treatment (known as subgingival instrumentation) for controlling blood sugar levels in people with periodontitis (gum disease) and diabetes up to 12 months after the start of the periodontal treatment.

Date of the search

The evidence is current up to 7 September 2021.

Authors' conclusions: 

Our 2022 update of this review has doubled the number of included studies and participants, which has led to a change in our conclusions about the primary outcome of glycaemic control and in our level of certainty in this conclusion. We now have 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.

Read the full abstract...

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 from below the gumline using hand or ultrasonic instruments. This is known variously 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 to cut away gum tissue 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. 


To investigate the effects of periodontal treatment on glycaemic control in people with diabetes mellitus and periodontitis.

Search strategy: 

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: 

We searched for 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 (also known as PMPR, professional mechanical plaque removal)). To be included, the RCTs had to have lasted at least 3 months and have measured HbA1c (glycated haemoglobin).

Data collection and analysis: 

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, we attempted to contact study authors.

Our primary outcome 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).

Our 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: 

We included 35 studies, 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. 

We assessed two studies as being at low risk of bias, 14 studies at high risk of bias, and the risk of bias in 19 studies was unclear. We undertook a sensitivity analysis for our primary outcome based on studies at low risk of bias and this supported the main findings.

Moderate-certainty evidence from 30 studies (2443 analysed participants) showed an absolute reduction in HbA1c of 0.43% (4.7 mmol/mol) 3 to 4 months after treatment of periodontitis (95% confidence interval (CI) -0.59% to -0.28%; -6.4 mmol/mol to -3.0 mmol/mol). Similarly, after 6 months, we found an absolute reduction in HbA1c of 0.30% (3.3 mmol/mol) (95% CI -0.52% to -0.08%; -5.7 mmol/mol to -0.9 mmol/mol; 12 studies, 1457 participants), and after 12 months, an absolute reduction of 0.50% (5.4 mmol/mol) (95% CI -0.55% to -0.45%; -6.0 mmol/mol to -4.9 mmol/mol; 1 study, 264 participants).

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.