Association of dental and periodontal disease with chronic kidney disease in patients of a single, tertiary care centre in Thailand

Fusobacterium nucleatum-infected periodontitis promotes renal interstitial fibrosis in rats through the TGF-β/SMAD2/3 and β-catenin signaling pathways

OBJECTIVES

Periodontitis is associated with Fusobacterium nucleatum (F.n) infection. Although the colonization of renal tissue by F.n is well documented, its specific role in kidney disease has yet to be determined. This study aimed to investigate the potential association between F.n-induced periodontitis and renal interstitial fibrosis.

METHODS

The rat gingival sulcus was injected with F.n suspension, while the control group (NC) was injected with PBS. The levels of total protein (TP), albumin (ALB), creatinine, and urea nitrogen (BUN) in rat serum and/or urine were quantified using the appropriate kits. Renal interstitial fibrosis and epithelial-mesenchymal transition (EMT) were evaluated in rats using Masson staining, Periodic Schiff-Methenamine (PASM) staining, and immunohistochemical staining. The levels of fibrosis- and EMT-related proteins and the TGF-β/SMAD2/3 and β-catenin signaling pathways were determined using Western blot analysis. F.n in the kidney tissues was quantitatively determined using bacterial 16S rRNA technology.

RESULTS

Serum levels of TP, ALB, creatinine, and BUN were not significantly decreased in F.n-infected rats with periodontitis. The levels of creatinine and ALB in the urine were not statistically different between two groups. Masson and PASM staining showed that F.n-induced periodontitis could promote renal interstitial fibrosis in rats. The levels of collagen I, fibronectin (FN), vimentin, and α-SMA were upregulated in the kidney tissues of rats with F.n-induced periodontitis and in F.n-treated HK-2 cells. However, E-cadherin levels were reduced. F.n promoted renal interstitial and HK-2 cell fibrosis in rats by modulating the TGF-β/SMAD2/3 and β-catenin signaling pathways. F.n colonization increased renal interstitial fibrosis in rats.

CONCLUSION

F.n-induced periodontitis promoted EMT by activating the TGF-β/SMAD2/3 and β-catenin signaling pathways, thus promoting renal interstitial fibrosis in rats.

Oral health-related quality of life in chronic kidney disease patients

BACKGROUND

Chronic kidney disease (CKD) is a systemic disease with a major burden on several life aspects, including oral health. As life expectancy has improved in CKD patients, oral health status has become important regarding their quality of life. The aim of this study was to investigate oral health and oral health-related quality of life (OHRQoL) in CKD patients.

MATERIALS AND METHODS

This was a cross-sectional study. Patients' age, gender, and estimated glomerular filtration rate (eGFR) stage were recorded. Oral Health Impact Profile-14 (OHIP-14) was used to evaluate OHRQoL. Decayed, missing, and filled teeth (DMFT) index was utilized to record oral health status. SPSS software was used to analyze data. One-way ANOVA, t-test and Pearson/Spearman correlations were used. P < 0.05 was considered statistically significant.

RESULTS

One hundred and four patients participated; 60.6% male versus 39.4% female. Mean age was 52.1 ± 18.1 years. The most frequent eGFR stage was 5 (41.2%). Mean DMFT score was 18.7 ± 8.5. Mean OHIP-14 score was 14.82 ± 5.86. DMFT score was significantly correlated with OHIP-14 total score as well as its physical domains (P < 0.05). The correlation between eGFR stage and OHIP-14/DMFT score was both statistically significant (P = 0.03/P = 0.02, respectively).

CONCLUSION

DMFT score was significantly correlated with OHRQoL in CKD patients, especially regarding its physical domains. Paying attention to fulfill dental treatment needs seems mandatory to improve OHRQoL and overall quality of life in these patients.

Relationship between chronic periodontitis and inflammatory cytokines in patients undergoing maintenance hemodialysis

OBJECTIVES

To investigate the correlation between serum and gingival crevicular fluid (GCF) levels of inflammatory cytokines and the association with periodontal parameters in patients with maintenance hemodialysis (MHD) and healthy control.

MATERIALS AND METHODS

Patients who were undergoing MHD were enrolled as the MHD group. Healthy individuals who underwent oral examination were selected as the control group after matching for the MHD group. All participants underwent a full-mouth periodontal evaluation, and the levels of eight inflammatory cytokines, including IL-1β, IL-17, IL-6, IL-8, and tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein-1 (MCP-1), matrix metalloproteinase-8 (MMP-8), and C-reactive protein (CRP), in the GCF and serum were measured.

RESULTS

A total of 63 MHD patients and 75 healthy persons were included. The prevalence of moderate/severe periodontitis was significantly higher in the MHD group than in the control group (88.9 vs. 66.7%, P < 0.05). The GCF levels of CRP, TNF-α, MCP-1, and MMP-8 were higher in patients in the MHD group with moderate/severe periodontitis than in the control group (P < 0.05). Serum CRP, MCP-1, TNF-α, and MMP-8 levels were positively correlated with the GCF CRP levels (P < 0.05). The GCF and serum CRP levels were positively correlated with the periodontal clinical parameters (P < 0.05).

CONCLUSIONS

Serum CRP, MCP-1, TNF-α, and MMP-8 may relate with the GCF CRP levels. The GCF and serum CRP levels correlated positively with the periodontal clinical parameters, including the VPI, PPD, and CAL, indicating that CRP may play an important role between periodontitis and ESRD.

CLINICAL RELEVANCE

The present study indicated that GCF and serum CRP levels correlated positively with the periodontal clinical parameters, and the CRP levels may be selected as an indicator to evaluate the severity of inflammation and the effectiveness, prognosis of periodontal treatment in ESRD patients.

Severity of Periodontal Disease in Chronic Kidney Disease Patients: A Hospital-Based Study

Background

Periodontal disease is a chronic inflammatory condition of multifactorial origin. The inflammatory mediators released during the progression of disease may affect all the organs of the body. Renal disease is a chronic systemic disease which may influence the progression of periodontal disease. Therefore, this study was conducted to evaluate and compare the prevalence of periodontal disease among individuals with chronic kidney disease undergoing maintenance hemodialysis with healthy individuals.

Methodology

In this cross-sectional study including 150 participants, 75 patients with different renal diseases undergoing hemodialysis (Group I) and 75 healthy controls (Group II) were included. The general examination of the patients was done. Blood pressure, pulse, and body mass index were recorded, followed by biochemical investigations, in which serum urea, serum creatinine, and random blood sugar were evaluated for each participant. Plaque Index (PI) and Gingival Index (GI) scores were recorded. Probing pocket depth (PPD) and gingival recession GR were measured, and clinical attachment level (CAL) was calculated based on the obtained values. The subjects were then categorized into three groups, namely, no/mild, moderate, and severe periodontitis.

Results

Out of the total study participants, 68% were men and 32% were women, with a mean age of 47 years. Serum markers were significantly elevated in Group I compared to Group II. Poor oral hygiene and periodontitis were observed to be much higher in dialysis patients compared to the control group. The two groups also significantly differed in PI, GI, PPD, GR, and CAL, all of which were higher in Group I.

Conclusions

The results suggest that patients with renal disease must be screened for periodontal disease.

The Impact of Chronic Kidney Disease on Nutritional Status and Its Possible Relation with Oral Diseases

Several studies have demonstrated a strong relation between periodontal diseases and chronic kidney disease (CKD). The main mechanisms at the base of this link are malnutrition, vitamin dysregulation, especially of B-group vitamins and of C and D vitamins, oxidative stress, metabolic acidosis and low-grade inflammation. In particular, in hemodialysis (HD) adult patients, an impairment of nutritional status has been observed, induced not only by the HD procedures themselves, but also due to numerous CKD-related comorbidities. The alteration of nutritional assessment induces systemic manifestations that have repercussions on oral health, like oral microbiota dysbiosis, slow healing of wounds related to hypovitaminosis C, and an alteration of the supporting bone structures of the oral cavity related to metabolic acidosis and vitamin D deficiency. Low-grade inflammation has been observed to characterize periodontal diseases locally and, in a systemic manner, CKD contributes to the amplification of the pathological process, bidirectionally. Therefore, CKD and oral disease patients should be managed by a multidisciplinary professional team that can evaluate the possible co-presence of these two pathological conditions, that negatively influence each other, and set up therapeutic strategies to treat them. Once these patients have been identified, they should be included in a follow-up program, characterized by periodic checks in order to manage these pathological conditions.

Blood and Salivary Inflammatory Biomarkers Profile in Patients with Chronic Kidney Disease and Periodontal Disease: A Systematic Review

Introduction: Periodontitis is the most prevalent inflammatory disease worldwide. Its inflammatory levels spread systemically, which can be associated with chronic kidney disease. Biomarkers have the potential to diagnose and correlate periodontitis and chronic kidney disease, helping to monitor systemic inflammation. Thereby, this study aimed to analyze the association between chronic kidney disease and periodontitis by conducting a biomarker analysis on blood and saliva. Material and methods: An electronic search through PubMed/MEDLINE, EMBASE, and Web of Science databases was conducted to identify clinical studies published in the last ten years, with no language restrictions. Twelve articles met all the inclusion criteria, two randomized controlled trials, one cohort study, and nine observational studies. Results: The studies included a total of 117 patients for saliva biomarkers, with a mean age of approximately 57 years old, and 56.68% of the subjects were female. After analyzing all the included studies, it was possible to verify the following biomarkers assessed: CRP, WBC, fibrinogen, IL-4 and -6, cardiac troponin T, NOx, ADMA, albumin, osteocalcin, cystatin C, PGLYRP1, cholesterol, HDL, LDL, triglycerides, and hemoglobin. Conclusion: A direct cause–effect association between periodontitis and CKD could not be established. However, it was possible to conclude that there was a correlating effect present, through the analyzed biomarkers.

Is there a relationship between oral hygiene and nutritional status in peritoneal dialysis patients?

Brackground: in the early stages of kidney disease, oral manifestations (gingivitis and periodontitis) may cause premature tooth loss and limit food intake. There is scarce evidence of the relationship between oral hygiene and nutritional status in patients on peritoneal dialysis (PD).

OBJECTIVE

we aimed to assess the relationship of oral hygiene with nutritional, clinical, and physical performance parameters in PD patients.

METHODS

this cross-sectional study included outpatients aged 34-69 years. Oral health questionnaire, nutritional, functional, and clinical assessment tools such as malnutrition inflammation score (MIS), subjective global assessment (SGA), handgrip strength, and gastrointestinal symptoms questionnaire (GSQ) were applied. Patients were divided according to debris, calculus, and simplified oral hygiene index (OHI-S) in two groups: "clean-slightly dirty" and "dirty-very dirty".

RESULTS

in total, 41 patients were included, those in the "dirty-very dirty" group had a worse nutritional status with higher scores on the MIS tool and worse nutritional diagnosis with SGA as compared to the "clean-slightly dirty" group. The handgrip strength was higher in patients in the best category of oral hygiene, and those with the worst hygiene presented greater severity of gastrointestinal symptoms. The risks of malnutrition in the three indices of oral hygiene with the worst category were statistically significant.

CONCLUSION

poor oral hygiene was associated with poorer nutritional status, lower handgrip, and worse GSQ. Poor oral hygiene might be related to persistent inflammation status and catabolism that favored protein-energy wasting.

Improved oral hygiene care and chronic kidney disease occurrence: A nationwide population-based retrospective cohort study

Oral diseases or poor oral hygiene have close connections with systemic inflammatory reaction, which is one of major mechanism in the development of chronic kidney disease (CKD). We conducted a research assuming that better oral hygiene care would be negatively related with the risk of developing new-onset CKD.From 2003 to 2004, a total of 158,495 participants from the Korean national health insurance data sharing service which provides health screening data including variables as age, sex, vascular risk factors, medication information, indicators regarding oral hygiene, and laboratory results. The diagnosis of CKD and vascular risk factors were defined according to the International Statistical Classification of Diseases and Related Health Problems codes-10th revision. The follow-up period for the study subject was until the occurrence of CKD, until death, or Dec 31, 2015.Approximately 13.3% of the participants suffered from periodontal disease, and 40.7% brushed their teeth at least three times a day. With a median of 11.6 (interquartile range 11.3-12.2) years' follow-up, the cohort included 3223 cases of incident CKD. The 10-year incidence rate for CKD was 1.80%. In multivariable analysis with adjustment for age, sex, demographics, vascular risk factors, blood pressure, and blood laboratory results, frequent tooth brushing (≥3 times a day) was negatively related to occurrence of CKD (hazard ratio: 0.90, 95% confidence interval [0.83-0.99], P  =  .043, P value for trend  =  .043).Participants with improved oral hygiene (≥3 times a day) have showed less risk of CKD. Additional interventional studies are in need to establish causative relationship between oral hygiene and risk of CKD.

Association between Dental Scaling and Reduced Risk of End-Stage Renal Disease: A Nationwide Matched Cohort Study

Periodontitis is prevalent in patients with chronic kidney disease (CKD) and is also associated with kidney function decline. It is unclear whether dental scaling treatment prevents the progression of CKD. In a nationwide cohort study, Taiwan's National Health Insurance Research Database was used to select people with CKD. Propensity score-matching procedures were performed to compare the long-term risk of end-stage renal disease (ESRD) between CKD patients with and without the receipt of dental scaling. A total of 33,637 matched pairs with CKD were included, with 503,373 person-years of follow-up for analyses. Dental scaling was significantly associated with a lower risk of ESRD (adjusted hazard ratio (aHR): 0.83, 95% confidence interval (CI): 0.77-0.90). In addition, there was a dose-dependent relationship between the frequency of dental scaling and a reduced risk of ESRD. Dental scaling was also linked to reduced risks of major adverse cardiovascular events (aHR: 0.91, 95% CI: 0.87-0.95), sepsis (aHR: 0.81, 95% CI: 0.77-0.85), and all-cause mortality (aHR: 0.81, 95% CI: 0.76-0.87). Dental scaling was significantly associated with lower risks of progression to ESRD in patients with CKD. Regular dental scaling may serve as a prophylactic measure for kidney function decline.

Periodontal disease and risk of mortality and kidney function decline in advanced chronic kidney disease: a nationwide population-based cohort study

OBJECTIVES

Periodontal disease is prevalent in patients with chronic kidney disease (CKD) and potentially associated with kidney function decline. However, it is uncertain whether periodontal disease affects the risk of mortality and morbidity in patients with advanced CKD.

MATERIALS AND METHODS

Taiwan's National Health Insurance Research Database was used to conduct a nationwide population-based cohort study. Propensity score matching procedures were performed to select people with stage 5 CKD and to compare the long-term risk of mortality, end-stage renal disease, and major adverse cardiovascular events (MACE) between people with and without periodontal disease. Multivariable Cox regression analyses were conducted to calculate the adjusted hazard ratio (aHR) with 95% confidence interval (CI) for the outcome of interest.

RESULTS

A total of 8119 subjects with stage 5 CKD were initially included. After matching to demographic and clinical covariates, 1254 subjects with 7099 person-years of follow-up were selected for analyses. Periodontal disease was not associated with long-term risks of all-cause mortality (aHR: 0.77, 95% CI: 0.49-1.22), progression to end-stage renal disease (aHR: 0.91, 95% CI: 0.75-1.10), or MACE (aHR: 1.18, 95% CI: 0.91-1.53). These findings were generally consistent across subgroups of age, sex, comorbid diabetes, uses of systemic antibiotic, and different dental procedures.

CONCLUSIONS

Periodontal disease is not a predictor for long-term mortality or morbidity in patients with advanced CKD.

CLINICAL RELEVANCE

These results provide important evidence to elucidate the relationship between periodontitis and critical clinical outcomes of advanced CKD.

Renal alterations caused by ligature-induced periodontitis persist after ligature removal in rats

BACKGROUND AND OBJECTIVE

Periodontitis may crosstalk with renal diseases, yet that remains unclear. We investigated whether the renal alterations caused by induced periodontitis are reversible after removal of the ligatures in experimental ligature-induced periodontitis.

MATERIAL AND METHODS

Twenty-four female rats were divided into three groups: control (without periodontitis), periodontitis (20 days of ligature-induced periodontitis), and P20-20 (20 days of ligature-induced periodontitis and 20 days after ligature removal). The following periodontal parameters were assessed: gingival bleeding index, probing pocket depth, myeloperoxidase activity, and alveolar bone height. For renal tissues, histopathology, malonaldehyde (MDA) levels, glutathione (GSH) content, and renal weight were evaluated. In the blood, creatinine, uric acid, albumin, total cholesterol, total protein, and glucose levels were assessed. Total protein and creatinine levels in urine were also investigated.

RESULTS

Rat renal tissues did not demonstrate reversal of periodontitis-related changes in the P20-20 group in terms of MDA, GSH, and histopathological evaluations when compared to the periodontitis group. Accordingly, only total cholesterol levels were reversible in the P20-20.

CONCLUSION

Renal alterations caused by ligature-induced periodontitis persisted even after removal of ligatures in rats.

Association among kidney function, frailty, and oral function in patients with chronic kidney disease: a cross-sectional study

Background

Chronic kidney disease (CKD) involves many factors that can cause frailty and oral hypofunction. We aimed to investigate the prevalence of frailty and oral hypofunction and to examine the associations among kidney function, frailty, and oral function in adults with CKD in Japan.

Methods

This cross-sectional study was conducted at two institutions. The participants included 109 patients with CKD stages 3–5 who visited outpatient clinics or were admitted for inpatient treatment. Frailty was evaluated using the Japanese version of the Cardiovascular Health Study frailty criteria. Oral function was evaluated by assessing oral motor skills [oral diadochokinesis (ODK) rate], masticatory ability, and the repetitive saliva swallowing test. The estimated glomerular filtration rate (eGFR) was used to indicate kidney function. We examined the associations among kidney function, frailty, and oral function using binomial logistic regression analysis.

Results

In total, 31 participants (28.4%) were classified as being frail. Univariate analysis showed that age, body mass index, eGFR, and haemoglobin level were significantly associated with frailty. ODK and swallowing function were significantly associated with frailty. Multivariate analysis revealed that frailty was significantly associated with eGFR [odds ratio (OR) 0.96, 95% confidence interval (CI) 0.92–1.00, p = 0.048] and ODK rate (OR 0.68, CI 0.47–0.98, p = 0.038). However, no significant association was found between CKD severity and masticatory or swallowing function.

Conclusion

We found a high prevalence of frailty in patients with CKD and a significant association between frailty and oral motor skills, affecting the swallowing function of patients with nondialysis CKD. The high prevalence of frailty among patients with CKD suggests that routine assessment of frailty is necessary to prevent the development of severe complications. In addition, oral and kidney function should be carefully evaluated, and oral health education and interventions should be performed for patients with CKD.

Periodontal Health of Pre-Dialysis Chronic Kidney Disease Patients in a Northeast Peninsular Malaysia Tertiary Hospital

Introduction

Chronic kidney disease (CKD) is associated with periodontal disease due to its hyperinflammatory state. Limited studies have explored the prevalence of periodontal disease among CKD patients in Malaysia.

Objective

To assess the periodontal status of pre-dialysis CKD patients in Hospital Universiti Sains Malaysia.

Methods

A total of 46 pre-dialysis CKD patients who attended the nephrology clinic at Hospital Universiti Sains Malaysia were enrolled in this study. Periodontal examination was performed using the periodontal probing depth (PPD), clinical attachment loss (CAL) and plaque index.

Results

The majority of the CKD patients were Malay (95.7%) and 80.4% were males. The mean age of the patients was 58.5 years. Using PPD measurement, 37 (74.0%) of the patients had mild periodontitis, 9 (20.0%) had moderate periodontitis and 3 (6.0%) had no periodontitis. Based on CAL measurement, 12 (26%) patients had mild periodontitis, 29 (63.0%) had moderate periodontitis and 5 (11%) had severe periodontitis. The mean (standard deviation [SD]) value of mild and moderate-to-severe periodontitis by PPD measurement were 4.26 (0.26) and 5.24 (0.36), respectively. The mean of mild and moderate-to-severe periodontitis by CAL measurement were 2.66 (0.62) and 4.98 (0.73), respectively. There was no correlation between the periodontal parameters and estimated glomerular filtration rate (PPD: r = −0.160, P = 0.914; CAL: r = −0.135, P = 0.372; plaque index: r = 0.005, P = 0.974).

Conclusion

This study revealed a greater prevalence and severity of chronic periodontitis among CKD patients. Thus, the periodontal health of CKD patients’ needs to be screened and monitored.

Periodontal disease and detection of human herpesviruses in saliva and gingival crevicular fluid of chronic kidney disease patients

BACKGROUND

Patients with chronic kidney disease (CKD) have inability to maintain the normal levels of protein metabolism products, blood pressure and hematocrit. Periodontal disease involves an inflammatory destructive process. Identification of opportunistic viruses is extremely important as they are associated with co-morbidities. The objective of this study was to analyse the presence of human herpesviruses in saliva and gingival crevicular fluid (GCF) from patients with CKD.

METHODS

One hundred and thirty one individuals were divided depending on the stage of CKD: Group 1 (clearance of creatinine > 75 mL/min) patients with no renal disease (n = 24); Group 2 (clearance of creatinine of 11-75 mL/min) patients with renal disease (n = 67); Group 3 (clearance of creatinine < 10 mL/min) patients on hemodialysis (n = 40). The parameters of periodontal disease were evaluated. The viral detection was assessed by PCR.

RESULTS

considering the three groups, the prevalence of herpes simplex virus 1 (HSV-1) were 9% in saliva and 5% in GCF; Epstein-Barr virus 36% in saliva and 39% in GCF; human cytomegalovirus (HCMV) 11% in GCF; varicella zoster virus 6% in saliva and 3% in GCF; of human herpesvirus-6 (HHV-6) 6% in saliva and 2% in GCF; and HHV-7 44% in saliva and 8% in GCF. Of these patients, 46.48% presented with severe periodontitis. A statistically significant association between HSV-1 and HCMV was found in hemodialysis patients and severe periodontitis was also more frequent among them.

CONCLUSION

These findings show the importance of evaluating the periodontal disease and detecting herpesviruses in patients with CKD as the inflammatory process observed in these clinical conditions may worsen the course of both periodontal disease and CKD.

Dysregulated Phosphate Metabolism, Periodontal Disease, and Cancer: Possible Global Health Implications

An association between periodontal disease and cancer has been established in recent studies, but no common etiology has been identified in the hopes of reducing the global burden of these non-communicable diseases. This perspective article hypothesizes that the determinant mediating the association of periodontal disease with cancer is dysregulated phosphate metabolism. Phosphate, an essential dietary micronutrient, is dysregulated in chronic kidney disease, and both cancer and periodontal disease are associated with chronic kidney disease. Reviewed evidence includes the association between phosphate toxicity and cancer development, and the association between periodontal disease and chronic kidney disease-mineral and bone disorder includes conditions such as ectopic calcification and bone resorption, which may be indirectly related to periodontal disease. Dental calculus in periodontal disease contains calcium phosphate crystals that are deposited from excess calcium and phosphate in saliva. Alveolar bone resorption may be linked systemically to release of parathyroid hormone in response to hypocalcemia induced by hyperphosphatemia. More research is needed to examine the role of dysregulated phosphate metabolism in periodontal disease.

An update on possible pathogenic mechanisms of periodontal pathogens on renal dysfunction

Periodontitis is a potential source of permanent systemic inflammation that initiates renal dysfunction and contributes to the development of chronic kidney diseases (CKDs). Although numerous studies have confirmed the bidirectional role of periodontal infection and renal inflammation, no literature has yet highlighted the sophisticated pathogenic mechanisms by which periodontal pathogens, particularly Porphynomonas Gingivalis, induce renal dysfunction and contributed in the development of CKDs. The present review aims to critically analyze and highlight the novel pathogenesis of periodontitis induced CKDs.

The directional and non-directional associations of periodontitis with chronic kidney disease: A systematic review and meta-analysis of observational studies

This systematic review aimed to assess the current evidence on the directional and non-directional associations of periodontitis with chronic kidney disease (CKD). Electronic search for observational studies on the association of periodontitis with CKD was performed in MEDLINE, EMBASE, PubMed, Open GREY and Cochrane library up to June 5, 2017. Two reviewers conducted study selection, data collection and assessment of methodological quality using the original and modified Newcastle-Ottawa Scale. Cohort, case-control and cross-sectional studies were included, which clearly defined periodontitis and CKD or reported acceptable clinical parameters of these 2 diseases in adults. Meta-analysis was employed to estimate the pooled odds ratio on the non-directional association and the incidence rate ratio (IRR) for the directional association. Among 2530 potential eligible articles, 47 were finally included. Most of them investigated a non-directional association of periodontitis with CKD, including 7 case-control studies and 38 cross-sectional studies; 24 studies had statistical analysis on the non-directional association and 75% of them reported significant results, which were supported further by the meta-analysis (random: odds ratio = 2.12, P < .001; χ²  = 25.74, I²  = 88.3%). None of the studies focused on the directional association of CKD (as the exposure) with periodontitis (as the outcome), whereas 2 retrospective cohort studies explored a directional association of periodontitis (as the exposure) with CKD (as the outcome) (random: IRR=2.10, P > .05; fixed: IRR=1.76, P < .05; χ²  = 4.65, I²  = 78.3%). Overall, the high heterogeneity of studies limits the significance of these results. There is substantial evidence on the non-directional association of periodontitis with CKD, while there are limited studies on the directional association. Well-designed prospective studies with longer follow-ups in representative communities are needed to clarify the directional association and enhance the quality of the evidence on this topic.