Impact of Oral Hygiene Practices in Reducing Cardiometabolic Risk, Incidence, and Mortality: A Systematic Review
Cardiometabolic diseases encompass a group of interrelated conditions including cardiovascular disease (CVD), diabetes mellitus (DM), and chronic kidney disease (CKD) , and are increasingly occurring in combination . These conditions are the leading cause of death and disability worldwide , and collectively were responsible for almost half of all Australian deaths in 2022 . Cardiometabolic diseases share many highly publicised, modifiable risk factors, including tobacco and alcohol consumption, diet, and sedentary lifestyle . However, oral disease, specifically periodontal disease, (PD)  which is another important modifiable risk factor, is seldom mentioned . Categorised as gingivitis or periodontitis, PD affects 90% of any population . The more severe form of PD, periodontitis, which affects between 20 and 50% of the global population , has strong associations with CVD  and a well-established bi-directional relationship with DM ; and there is also emerging evidence of a bi-directional link with CKD . Preventing PD and other oral disease  begins with simple oral hygiene practices including toothbrushing (TB) with toothpaste, interdental cleaning, and, under certain circumstances, mouthwash use which together maintain a healthy oral biofilm . Poor oral hygiene practices allow bacterial deposits to accumulate on the soft and hard tissues of the oral cavity resulting in PD. A biofilm that remains stagnant for 24–48 h, initiates a host immune response, triggering a local inflammatory reaction which in turn initiates systemic inflammation . The local vasodilation enables bacteria within stagnant biofilm to enter the bloodstream  and reach distant organs such as the heart and pancreas . Inflammation is therefore the mechanism that links the more severe form of PD, namely periodontitis, and cardiometabolic conditions such as CVD, CKD, and type 2 diabetes mellitus (T2DM) . Whilst previous studies investigated oral hygiene practices in combination with other therapies , or focus on a single cardiometabolic condition , this study is the first systematic review to evaluate the effect oral hygiene practices alone may have on a range of cardiometabolic conditions. The aim of this review is to identify the impact of oral hygiene practices on the risk, incidence, and/or mortality rate of CVD, T2DM, and CKD. 

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement . The review protocol is registered with an international register of systematic reviews (PROSPERO ID: CRD42021269584). 2.1. Inclusion and Exclusion Criteria Peer-reviewed randomized controlled trials (RCTs), quasi-RCTs, observational, cohort, case–control, and cross-sectional studies were eligible for inclusion meeting the following criteria: adults ≥18 years, examined the influence of oral hygiene practices (toothbrushing, interdental cleaning, mouthwash, or toothpaste use, either alone or in combination) on cardiometabolic disease, specifically CVD, CKD, and/or T2DM. Conference abstracts, case-studies/series, letters to the editors, editorials, and animal studies were excluded. Studies which reviewed scaling and root debridement/planning, periodontal surgery, or other dental treatments alone, or focused on other cardiometabolic conditions or non-cardiometabolic diseases were excluded. 2.2. Search Strategy The initial search was performed on 27 July 2021 and repeated in 2022 and 2023. The final search, occurring on 10 July 2024, was carried out on the following electronic databases: MEDLINE, Embase, Scopus, and CINHAL. No restrictions were placed on language or publication period, and no human filter was applied. Mirroring terms were used for electronic databases; Google Scholar was explored for grey literature. Citation lists of relevant studies were also examined. The search strategy included Boolean operators, medical subject headings, and truncations, and included terms relating to, or describing, oral health practices and cardiometabolic diseases, including CVD, T2DM, and CKD. Every attempt was made to retrieve inaccessible studies. For the full search strategy, see . 2.3. Data Extraction and Synthesis A data extraction tool developed within Covidence was completed independently by LC and one of five other reviewers (BS, KC, KF, JM, RB). Key characteristics extracted were author[s], publication year, country, study design, aim[s], setting, age, sex, oral hygiene practices, disease biomarkers, and oral health status. Due to the heterogeneity in included study designs and outcomes, a meta-analysis was not feasible. Data synthesis has been presented narratively with reference to . 2.4. Quality Appraisal and Risk of Bias Study quality was assessed independently by LC and one of five other reviewers (BS, KC, KF, JM, RB). RCT quality (n = 3) was assessed using an adapted Cochrane’s risk of bias tool . The Newcastle–Ottawa Scale (NOS)  was used for all other included studies (n = 52). Any disagreements were resolved via open discussion and where consensus was unsuccessful a third investigator (SK or NM) was involved. 

Peer-reviewed randomized controlled trials (RCTs), quasi-RCTs, observational, cohort, case–control, and cross-sectional studies were eligible for inclusion meeting the following criteria: adults ≥18 years, examined the influence of oral hygiene practices (toothbrushing, interdental cleaning, mouthwash, or toothpaste use, either alone or in combination) on cardiometabolic disease, specifically CVD, CKD, and/or T2DM. Conference abstracts, case-studies/series, letters to the editors, editorials, and animal studies were excluded. Studies which reviewed scaling and root debridement/planning, periodontal surgery, or other dental treatments alone, or focused on other cardiometabolic conditions or non-cardiometabolic diseases were excluded. 

The initial search was performed on 27 July 2021 and repeated in 2022 and 2023. The final search, occurring on 10 July 2024, was carried out on the following electronic databases: MEDLINE, Embase, Scopus, and CINHAL. No restrictions were placed on language or publication period, and no human filter was applied. Mirroring terms were used for electronic databases; Google Scholar was explored for grey literature. Citation lists of relevant studies were also examined. The search strategy included Boolean operators, medical subject headings, and truncations, and included terms relating to, or describing, oral health practices and cardiometabolic diseases, including CVD, T2DM, and CKD. Every attempt was made to retrieve inaccessible studies. For the full search strategy, see . 

A data extraction tool developed within Covidence was completed independently by LC and one of five other reviewers (BS, KC, KF, JM, RB). Key characteristics extracted were author[s], publication year, country, study design, aim[s], setting, age, sex, oral hygiene practices, disease biomarkers, and oral health status. Due to the heterogeneity in included study designs and outcomes, a meta-analysis was not feasible. Data synthesis has been presented narratively with reference to . 

Study quality was assessed independently by LC and one of five other reviewers (BS, KC, KF, JM, RB). RCT quality (n = 3) was assessed using an adapted Cochrane’s risk of bias tool . The Newcastle–Ottawa Scale (NOS)  was used for all other included studies (n = 52). Any disagreements were resolved via open discussion and where consensus was unsuccessful a third investigator (SK or NM) was involved. 

3.1. Selection Process Using systematic review software Covidence , 8659 citations were imported into the program, 4280 duplicates were removed and 4379 were screened. Title and abstract screening, followed by full-text screening, was completed independently by two reviewers from a pool of eight (BS, KC, KF, JM, LC, NM, RB, SK). A total of 55 studies (32 cohort , 13 cross-sectional studies , 3 case–control , 1 prospective , 2 observational , 1 quasi-experimental , and 3 RCTs ) met the inclusion criteria. See for the PRISMA flow diagram. Conflicts arising during the screening process were resolved via group discussion. 3.2. Characteristics Fifty-five studies spanning between 2003 and 2024 were identified, taking place in Europe , Asia , United States , South America , and the Middle East . Study populations ranged from n = 60 to n = 487,198; the mean and median age ranges were 41.5 ± 9.3–67.71 ± 10.6 and 63–68, respectively. Eleven studies had a majority of female participants, twenty-eight had a majority of male participants, two included only male participants and four did not disclose sex. Thirty-four studies focused on CVD , twenty-three on DM , and nine on CKD . Oral hygiene practices investigated included TB , interdental cleaning , mouthwash , and fluoridated toothpaste use . See for study characteristics. Two studies reported oral hygiene practices as a proxy for oral hygiene status score , thus not directly relating specific practices with the disease outcome. Additionally, two discussed the relationship of oral hygiene practice to oral conditions (non-defined periodontal symptoms and tooth loss) , which were associated with the disease outcome; see for study findings. Of the total studies, thirty-nine  were considered good quality, eight  were considered fair, and the remaining five  were rated poor quality; see for NOS quality assessment. The RCTs’ overall risk of bias was determined high [n = 1]  and low [n = 2] ; see RoB in . Created using the robvis tool with permission . 3.3. Toothbrushing Frequency Forty-three studies examined TB practices reported as daily frequency , device used , technique , time of day , and/or duration . Increased TB frequency (ranging from sometimes/daily—≥3× daily) was linked to reduced risk of developing CVD  and/or hypertension.  It was also shown to reduce the risk of stroke , atrial fibrillation , and/or heart failure (HF) occurrence , cardiovascular events , including death , and all-cause deaths . Seven studies reported no link between low TB frequency (ranging from never to 2× daily) and increased risk of hypertension , acute coronary syndrome , cardiovascular death , subarachnoid haemorrhage, ischemic heart disease , haemorrhagic stroke , or other CVD outcomes . For individuals living with DM, higher daily TB frequency was found to significantly lower the risk of cerebral or myocardial infarction  as well as HF . One study found lower daily TB frequency was a risk factor for developing DM in males, but not females , whilst two discussed no relationship between TB frequency and T2DM . Several studies highlighted either increased DM prevalence associated with lower TB frequency  or reduced DM incidence associated with higher TB frequency . Similarly, in those living with end-stage kidney disease (ESKD), individuals with higher TB frequency had lower prevalence of hypertension, DM , rates of hospitalisations , and longer all-cause survival ; however, there was no impact on cardiovascular death risk. Conversely, one study reported that TB frequency was most the important factor for all-cause peritonitis, streptococcal peritonitis, CHF, and pneumonia in individuals with ESKD . Two  found no association between TB frequency and CKD, whilst another reported an inverse relationship between TB frequency and developing CKD . Interestingly, one study concluded TB only 1–2× daily was associated with better kidney function . Twenty studies reported on biomarkers linked to CVD, DM, and CKD. These included C-reactive protein (CRP) or high-sensitivity C-reactive protein (hs-CRP), interleukin (IL), blood glucose, cholesterol, lipids, and others. Seven studies reported a significant inverse relationship between TB frequency and circulating CRP/hs-CRP . One study linked TB frequency with undefined periodontal symptoms, which were found to be associated with higher glycated haemoglobin (HbA1c) levels . The other studies reported lower Hb1Ac , fasting plasma glucose (FPG) , or fasting blood glucose (FBGL)  with more frequent TB. One study concluded those who did not brush daily had a 79% increased risk of higher HbA1c , similar to another study . Biomarkers related to dyslipidaemia are heavily involved with cardiometabolic conditions and were discussed in seven studies . Whilst one study reported total cholesterol was not significantly impacted by TB frequency , others found that less frequent TB was associated with elevated total cholesterol , lower HDL , high LDL , and high triglycerides . Two studies found reduced TB frequency was associated with dyslipidaemia . Interestingly; however, one found frequency was linked to developing the condition in females only . The impact of TB frequency on other cardiometabolic disease biomarkers had similar results. Less frequent TB was associated with increased concentrations of white blood cells , adiponectin , fibrinogen, higher levels of IL-1β, and a trend toward an association with a higher level of tissue plasminogen activator inhibitor-1 (tPAI-1) . A better oral hygiene score was significantly associated with lower albumin levels  and had an inverse correlation with oral innate immunity marker salivary lysozyme . Additionally, increased TB frequency was associated with higher estimated glomerular filtration rate [eGFR] and milder stage of CKD compared to less frequent TB . 3.4. Toothbrushing Device Three studies examined the impacts of TB devices on CVD, whilst one focused on T2DM. One study found, compared to controls, participants living with stroke were less likely to use a toothbrush, leading to poor oral health status and increased periodontal disease . Another reported that the use of other toothbrushing devices such as a neem stick or miswak increased the risk of developing CHD , whilst using an electric toothbrush was found to be associated with a decrease in non-specified CVD outcomes and better survival when combined with other oral hygiene practices . When comparing electric and manual tooth brushes, one study found significant reduction in HbA1c in both study arms at the final follow-up; however, no significant reductions in CRP and IL-β levels were found . 3.5. Toothbrushing Technique Toothbrushing technique (non-rolling or rolling stroke) had no significant effect on self-reported periodontal symptoms  and no significant differences were detected between individuals living with or without stroke in terms of their toothbrushing technique (horizontal or other) . 3.6. Timing The timing of toothbrushing was assessed in three studies. When defined as before or after meals, one study found no association with toothbrush timing and individuals living with stroke, compared to those without stroke . Defined as brushing before bed (sometimes/no or always) in a T2DM cohort, those who brushed their teeth every night before bed had lower BMI and LDL than those who did not brush nightly . The third study categorised TB timing as Group MN (morning and night)/Group M (morning only)/Group Night (night only)/Group None (not brushing) and reported higher survival estimates following cardiovascular events in Group MN and Group N . 3.7. Duration The duration of TB was assessed in two studies. In individuals living with ESKD, there was an association between longer survival and lower risk of cardiovascular death when TB for ≥2 min . For individuals living with CVD, brushing < 2× daily for <2 min was associated higher risk of cardiovascular events compared to those TB for ≥2 min ≥2× daily . However, no differences were detected for cardiovascular events when comparing brushing < 2× daily for <2× min with brushing either twice daily or for two minutes. 3.8. Interdental Cleaning Interdental cleaning was evaluated in fourteen studies. As the primary focus of , dental floss use was associated with lower HbA1c levels  and lower risk of elevated CRP , and its lack of use was associated with an increased risk for patient mortality . As a proxy for remaining teeth, seldom/occasional dental floss use before bed was indirectly linked to higher risk of stroke . Secondary to other oral hygiene practices, dental floss or interdental brush use was associated with reduced hospitalisations , decreased risk of CVD mortality , increased adiponectin and fibrinogen levels , and longer survival rates if living with ESKD . In contrast, less-frequent flossing was associated with elevated mean arterial pressure. Increased daily use of dental floss in a diabetic population was indirectly linked to the decrease in FPG and HbA1c . Furthermore, the use of dental floss was linked to health outcomes when grouped with other practices to develop an oral hygiene score . For individuals living with CKD completing peritoneal dialysis, an oral hygiene score of ≥7 was associated with lower hospitalisation and mortality rates . One study reported individuals who had a high oral hygiene score had a 79% decreased risk of CVD morality . Similarly, when grouped with other dental products, one study reported an association with interdental cleaning and stroke . 3.9. Mouthwash and Toothpaste Daily mouth wash use was discussed in twelve studies. Three incorporated the practice with either auxiliary products  or other practices , indirectly linking its use to improved glycaemic control , reduced CVD admissions, and mortality rates , as well as an association with stroke . Significant reductions in H1bAc levels at follow-up were reported by one study when using mouthwash via a water flosser and a powered brush twice daily ; however, no significant reductions were reported in CRP or IL-β. Two studies found mouthwash use corresponded with better survival  and lower hospitalisations  in individuals living with ESKD and CKD. Two studies  found that its use was associated with a 55% and 85% higher risk of developing new-onset DM or hypertension, respectively, as well as increased blood pressure . However, other studies found no independent link between mouthwash use and CVD outcomes . One study included both mouthwash and toothpaste use, though it did not link them to HbA1c . Two  found no independent link with toothpaste use and disease outcomes. 

Using systematic review software Covidence , 8659 citations were imported into the program, 4280 duplicates were removed and 4379 were screened. Title and abstract screening, followed by full-text screening, was completed independently by two reviewers from a pool of eight (BS, KC, KF, JM, LC, NM, RB, SK). A total of 55 studies (32 cohort , 13 cross-sectional studies , 3 case–control , 1 prospective , 2 observational , 1 quasi-experimental , and 3 RCTs ) met the inclusion criteria. See for the PRISMA flow diagram. Conflicts arising during the screening process were resolved via group discussion. 

Fifty-five studies spanning between 2003 and 2024 were identified, taking place in Europe , Asia , United States , South America , and the Middle East . Study populations ranged from n = 60 to n = 487,198; the mean and median age ranges were 41.5 ± 9.3–67.71 ± 10.6 and 63–68, respectively. Eleven studies had a majority of female participants, twenty-eight had a majority of male participants, two included only male participants and four did not disclose sex. Thirty-four studies focused on CVD , twenty-three on DM , and nine on CKD . Oral hygiene practices investigated included TB , interdental cleaning , mouthwash , and fluoridated toothpaste use . See for study characteristics. Two studies reported oral hygiene practices as a proxy for oral hygiene status score , thus not directly relating specific practices with the disease outcome. Additionally, two discussed the relationship of oral hygiene practice to oral conditions (non-defined periodontal symptoms and tooth loss) , which were associated with the disease outcome; see for study findings. Of the total studies, thirty-nine  were considered good quality, eight  were considered fair, and the remaining five  were rated poor quality; see for NOS quality assessment. The RCTs’ overall risk of bias was determined high [n = 1]  and low [n = 2] ; see RoB in . Created using the robvis tool with permission . 

Forty-three studies examined TB practices reported as daily frequency , device used , technique , time of day , and/or duration . Increased TB frequency (ranging from sometimes/daily—≥3× daily) was linked to reduced risk of developing CVD  and/or hypertension.  It was also shown to reduce the risk of stroke , atrial fibrillation , and/or heart failure (HF) occurrence , cardiovascular events , including death , and all-cause deaths . Seven studies reported no link between low TB frequency (ranging from never to 2× daily) and increased risk of hypertension , acute coronary syndrome , cardiovascular death , subarachnoid haemorrhage, ischemic heart disease , haemorrhagic stroke , or other CVD outcomes . For individuals living with DM, higher daily TB frequency was found to significantly lower the risk of cerebral or myocardial infarction  as well as HF . One study found lower daily TB frequency was a risk factor for developing DM in males, but not females , whilst two discussed no relationship between TB frequency and T2DM . Several studies highlighted either increased DM prevalence associated with lower TB frequency  or reduced DM incidence associated with higher TB frequency . Similarly, in those living with end-stage kidney disease (ESKD), individuals with higher TB frequency had lower prevalence of hypertension, DM , rates of hospitalisations , and longer all-cause survival ; however, there was no impact on cardiovascular death risk. Conversely, one study reported that TB frequency was most the important factor for all-cause peritonitis, streptococcal peritonitis, CHF, and pneumonia in individuals with ESKD . Two  found no association between TB frequency and CKD, whilst another reported an inverse relationship between TB frequency and developing CKD . Interestingly, one study concluded TB only 1–2× daily was associated with better kidney function . Twenty studies reported on biomarkers linked to CVD, DM, and CKD. These included C-reactive protein (CRP) or high-sensitivity C-reactive protein (hs-CRP), interleukin (IL), blood glucose, cholesterol, lipids, and others. Seven studies reported a significant inverse relationship between TB frequency and circulating CRP/hs-CRP . One study linked TB frequency with undefined periodontal symptoms, which were found to be associated with higher glycated haemoglobin (HbA1c) levels . The other studies reported lower Hb1Ac , fasting plasma glucose (FPG) , or fasting blood glucose (FBGL)  with more frequent TB. One study concluded those who did not brush daily had a 79% increased risk of higher HbA1c , similar to another study . Biomarkers related to dyslipidaemia are heavily involved with cardiometabolic conditions and were discussed in seven studies . Whilst one study reported total cholesterol was not significantly impacted by TB frequency , others found that less frequent TB was associated with elevated total cholesterol , lower HDL , high LDL , and high triglycerides . Two studies found reduced TB frequency was associated with dyslipidaemia . Interestingly; however, one found frequency was linked to developing the condition in females only . The impact of TB frequency on other cardiometabolic disease biomarkers had similar results. Less frequent TB was associated with increased concentrations of white blood cells , adiponectin , fibrinogen, higher levels of IL-1β, and a trend toward an association with a higher level of tissue plasminogen activator inhibitor-1 (tPAI-1) . A better oral hygiene score was significantly associated with lower albumin levels  and had an inverse correlation with oral innate immunity marker salivary lysozyme . Additionally, increased TB frequency was associated with higher estimated glomerular filtration rate [eGFR] and milder stage of CKD compared to less frequent TB . 

Three studies examined the impacts of TB devices on CVD, whilst one focused on T2DM. One study found, compared to controls, participants living with stroke were less likely to use a toothbrush, leading to poor oral health status and increased periodontal disease . Another reported that the use of other toothbrushing devices such as a neem stick or miswak increased the risk of developing CHD , whilst using an electric toothbrush was found to be associated with a decrease in non-specified CVD outcomes and better survival when combined with other oral hygiene practices . When comparing electric and manual tooth brushes, one study found significant reduction in HbA1c in both study arms at the final follow-up; however, no significant reductions in CRP and IL-β levels were found . 

Toothbrushing technique (non-rolling or rolling stroke) had no significant effect on self-reported periodontal symptoms  and no significant differences were detected between individuals living with or without stroke in terms of their toothbrushing technique (horizontal or other) . 

The timing of toothbrushing was assessed in three studies. When defined as before or after meals, one study found no association with toothbrush timing and individuals living with stroke, compared to those without stroke . Defined as brushing before bed (sometimes/no or always) in a T2DM cohort, those who brushed their teeth every night before bed had lower BMI and LDL than those who did not brush nightly . The third study categorised TB timing as Group MN (morning and night)/Group M (morning only)/Group Night (night only)/Group None (not brushing) and reported higher survival estimates following cardiovascular events in Group MN and Group N . 

The duration of TB was assessed in two studies. In individuals living with ESKD, there was an association between longer survival and lower risk of cardiovascular death when TB for ≥2 min . For individuals living with CVD, brushing < 2× daily for <2 min was associated higher risk of cardiovascular events compared to those TB for ≥2 min ≥2× daily . However, no differences were detected for cardiovascular events when comparing brushing < 2× daily for <2× min with brushing either twice daily or for two minutes. 

Interdental cleaning was evaluated in fourteen studies. As the primary focus of , dental floss use was associated with lower HbA1c levels  and lower risk of elevated CRP , and its lack of use was associated with an increased risk for patient mortality . As a proxy for remaining teeth, seldom/occasional dental floss use before bed was indirectly linked to higher risk of stroke . Secondary to other oral hygiene practices, dental floss or interdental brush use was associated with reduced hospitalisations , decreased risk of CVD mortality , increased adiponectin and fibrinogen levels , and longer survival rates if living with ESKD . In contrast, less-frequent flossing was associated with elevated mean arterial pressure. Increased daily use of dental floss in a diabetic population was indirectly linked to the decrease in FPG and HbA1c . Furthermore, the use of dental floss was linked to health outcomes when grouped with other practices to develop an oral hygiene score . For individuals living with CKD completing peritoneal dialysis, an oral hygiene score of ≥7 was associated with lower hospitalisation and mortality rates . One study reported individuals who had a high oral hygiene score had a 79% decreased risk of CVD morality . Similarly, when grouped with other dental products, one study reported an association with interdental cleaning and stroke . 

Daily mouth wash use was discussed in twelve studies. Three incorporated the practice with either auxiliary products  or other practices , indirectly linking its use to improved glycaemic control , reduced CVD admissions, and mortality rates , as well as an association with stroke . Significant reductions in H1bAc levels at follow-up were reported by one study when using mouthwash via a water flosser and a powered brush twice daily ; however, no significant reductions were reported in CRP or IL-β. Two studies found mouthwash use corresponded with better survival  and lower hospitalisations  in individuals living with ESKD and CKD. Two studies  found that its use was associated with a 55% and 85% higher risk of developing new-onset DM or hypertension, respectively, as well as increased blood pressure . However, other studies found no independent link between mouthwash use and CVD outcomes . One study included both mouthwash and toothpaste use, though it did not link them to HbA1c . Two  found no independent link with toothpaste use and disease outcomes. 

This systematic review is the first to assess the impact of oral hygiene practices on the risk, incidence, and/or mortality rate of cardiometabolic conditions CVD, T2DM, and CKD, and highlights the significant effects some of these practices have on cardiometabolic disease outcomes. 4.1. Main Findings Frequency of TB was the primary focus of most studies . Although there were some conflicting results , the overwhelming consensus was that increased TB frequency had positive impacts on CVD , DM , and CKD  outcomes. These findings support the role oral bacteria play in cardiometabolic disease if allowed to remain stagnant. Furthermore, the combination of increased TB frequency and daily interdental cleaning was associated with a further decrease in CVD mortality risk compared to brushing alone . This result is likely due to interdental cleaning reaching areas where toothbrushes cannot . Increased frequency of oral hygiene practices was also found to reduce inflammatory markers such as CRP , further supporting the role of oral bacteria in driving systemic inflammation. Elevation of CRP levels are associated with the development of cardiometabolic conditions , having detrimental consequences for those already living with CVD , DM , and CKD . Interestingly, for individuals living with CKD, there were contradictory findings. Two studies found TB ≥ 3 times daily had positive CKD outcomes , whilst another reported TB after every meal was more detrimental to kidney function than TB 1–2× daily . This may be due to disruption of the oral microbiome as overbrushing has been reported to reduce beneficial bacteria . The other studies involving CKD do not define TB frequency  or incorporate it into an oral hygiene score , and as such, additional studies with standardised TB frequency categories are required to clarify these opposing findings. The benefits of mouthwash use on cardiometabolic disease outcomes is inconclusive with studies reporting positive , neutral , and negative  health outcomes. The indeterminate bactericidal nature of mouthwash which can disrupt the healthy oral microbiome is thought to be the reason for the negative health outcomes. The oral microbiome is a complex mix of beneficial bacteria and other microorganisms residing in the oral cavity . This microbiome, as well as protective enzymes in saliva , make up part of a nonimmune defence system against invasion from harmful bacteria and pathogens . Mouthwash use disrupts the oral microbiome by eliminating both beneficial and harmful bacteria  and may explain why ≥2× daily use was found to increase the risk of hypertension and DM . 4.2. Risk Factor Comparison Diet and exercise are well-known modifiable risk factors for cardiometabolic diseases . Recent literature found individuals with a higher diet score (≥5) were at a lower risk of mortality (HR 0.70;0.63–0.77), CVD (HR 0.82; 0.75–0.91), MI (HR 0.86; 0.75–0.99) and stroke (HR 0.81; 0.71–0.93) ; having a combination of a healthy diet and active lifestyle significantly lowered the risk of all-cause mortality (HR 0.74; 0.65–0.86) and CVD deaths (HR 0.79; 0.73 to 0.86) . Similar HRs were found in the included studies, reporting that individuals with increased oral hygiene practices had a lower risk of all-cause death (HR 0.76; 0.58–0.99) , CVD mortality (HR 0.25; 0.07–0.89) , MI (HR: 0.76; 0.62–0.94), and cerebral infarction (HR: 0.81, 95% CI: 0.69–0.94) . However, oral health education is rarely provided for chronic disease management, and easily accessible information is scarce . 

Frequency of TB was the primary focus of most studies . Although there were some conflicting results , the overwhelming consensus was that increased TB frequency had positive impacts on CVD , DM , and CKD  outcomes. These findings support the role oral bacteria play in cardiometabolic disease if allowed to remain stagnant. Furthermore, the combination of increased TB frequency and daily interdental cleaning was associated with a further decrease in CVD mortality risk compared to brushing alone . This result is likely due to interdental cleaning reaching areas where toothbrushes cannot . Increased frequency of oral hygiene practices was also found to reduce inflammatory markers such as CRP , further supporting the role of oral bacteria in driving systemic inflammation. Elevation of CRP levels are associated with the development of cardiometabolic conditions , having detrimental consequences for those already living with CVD , DM , and CKD . Interestingly, for individuals living with CKD, there were contradictory findings. Two studies found TB ≥ 3 times daily had positive CKD outcomes , whilst another reported TB after every meal was more detrimental to kidney function than TB 1–2× daily . This may be due to disruption of the oral microbiome as overbrushing has been reported to reduce beneficial bacteria . The other studies involving CKD do not define TB frequency  or incorporate it into an oral hygiene score , and as such, additional studies with standardised TB frequency categories are required to clarify these opposing findings. The benefits of mouthwash use on cardiometabolic disease outcomes is inconclusive with studies reporting positive , neutral , and negative  health outcomes. The indeterminate bactericidal nature of mouthwash which can disrupt the healthy oral microbiome is thought to be the reason for the negative health outcomes. The oral microbiome is a complex mix of beneficial bacteria and other microorganisms residing in the oral cavity . This microbiome, as well as protective enzymes in saliva , make up part of a nonimmune defence system against invasion from harmful bacteria and pathogens . Mouthwash use disrupts the oral microbiome by eliminating both beneficial and harmful bacteria  and may explain why ≥2× daily use was found to increase the risk of hypertension and DM . 

Diet and exercise are well-known modifiable risk factors for cardiometabolic diseases . Recent literature found individuals with a higher diet score (≥5) were at a lower risk of mortality (HR 0.70;0.63–0.77), CVD (HR 0.82; 0.75–0.91), MI (HR 0.86; 0.75–0.99) and stroke (HR 0.81; 0.71–0.93) ; having a combination of a healthy diet and active lifestyle significantly lowered the risk of all-cause mortality (HR 0.74; 0.65–0.86) and CVD deaths (HR 0.79; 0.73 to 0.86) . Similar HRs were found in the included studies, reporting that individuals with increased oral hygiene practices had a lower risk of all-cause death (HR 0.76; 0.58–0.99) , CVD mortality (HR 0.25; 0.07–0.89) , MI (HR: 0.76; 0.62–0.94), and cerebral infarction (HR: 0.81, 95% CI: 0.69–0.94) . However, oral health education is rarely provided for chronic disease management, and easily accessible information is scarce . 

This review has highlighted that simple oral hygiene practices are associated with better cardiometabolic health outcomes and can reduce systemic inflammation. Therefore, non-dental clinicians are encouraged to recommend daily interdental cleaning followed by ≥2× daily TB to for at least two minutes for patients living with cardiometabolic conditions. 

The strength of this systematic review is that it is the first review to summarise the impact oral health practices have on the risk, incidence, and mortality rate of CVD, DM, and/or CKD. This review followed a PROSPERO registered protocol. Two thirds of the included studies were rated as good quality. The global origin of the literature enables this review to be more generalisable. Although there was heterogeneity when reporting TB frequency, the overwhelming consensus found increased TB frequency (≥2× daily) and daily interdental cleaning had a positive effect on cardiometabolic disease outcomes. However, there are limitations which need to be considered when interpreting the results. Many of the studies that reported on DM did not specify the type; it is therefore possible that the impact of oral hygiene varies depending on the condition of DM. Although the literature is global in nature, this review does not account for individual countries’ healthcare and belief systems, which may influence oral hygiene practices. Reporting bias is a part of all the included studies, as they relied on self-report data for oral hygiene practices. Furthermore, due to the heterogeneity within the study data collection and reporting, there is a need for further research using standardised oral hygiene questionnaires. Finally, and importantly, only three RCTs were identified. This highlights a great need for further clinical research to better understand causal relationships between oral health and cardiometabolic disease. 

This systematic review has highlighted that for individuals living with or at risk of CVD, T2DM, and/or CKD, increased daily TB frequency (≥2× daily) as well as daily interdental cleaning is associated with reduced systemic inflammation, better health outcomes, and a lowered mortality risk. Cardiometabolic diseases are the leading causes of death and disability worldwide, and as such, provision of basic oral hygiene advice should be included in chronic disease prevention programs. Furthermore, development and implementation of interventional research involving cardiometabolic diseases and oral hygiene practices are needed to further strengthen the findings of this review. 

