There are many common risk factors for the occurrence and progression of CP and CKD (including age and environmental factors).The risk of the occurrence of severe periodontal disease increases as CKD progresses to ESRD[12].There are many reasons for susceptibility to periodontal disease in ESRD patients.To prevent overload volume,dialysis patients need to restrict fluid intake and use diuretics as adjuvant therapy,especially patients with residual renal function; thus,xerostomia becomes the most common oral symptom[7][21].On the other hand,uremia alters the inflammatory response to bacterial plaques in gingival tissue,and reduced salivation can further lead to plaque formation[7].Currently, the proportion of regular stomatology follow-up in ESRD patients is very low[9].Negligence of oral hygiene is one of the main causes of a higher prevalence and severity of CP[7][22][23].Numerous studies have shown that the prevalence of moderate or severe periodontitis in PD patients was significantly higher than that in those without CKD,and CP was widespread in patients with renal replacement therapy.Patients with CKD stage 3 or higher also had a significantly increased prevalence of CP[7][12][22][24].
Similar results were obtained in this study. Based on the collected periodontal clinical data, patients’ GI, PLI and BOP(+)% were high, indicating poor oral hygiene and gingival status. PPD and CAL are the most important parameters for periodontitis.PPD is closely related to subgingival plaque biofilms and inflammatory status, representing the current CP condition.CAL is an indicator of previous cumulative tissue destruction[7].Our study found that all PD patients had different degrees of CP(mild: 9.2%, moderate: 72.4%, severe 18.4%),and more than 90% of patients had moderate/severe CP.The mean value of CAL reached 3.91 mm.Ibrahim et al.[7] reported that the mean CAL reached 3.97 mm in predialysis patients.Kristine Sun et al.[24] found that there were significant differences in CAL between PD patients and healthy patients, indicating more severe periodontitis in PD patients.
In a previous study of serological examination in dialysis patients,the serum CRP levels in hemodialysis patients with CP were significantly higher than those without CP.The serum CRP levels significantly decreased after periodontal treatment[25][26].Kristine Sun et al.[24] showed that various inflammatory factors (including IL-6, IL-8, hs-CRP, etc.) in gingival crevicular fluid were correlated with the degree of periodontitis and were much higher than those in healthy people.This phenomenon was related to periodontal tissue destruction caused by severe periodontal disease in PD patients.This study found a positive correlation between CRP and CAL, indicating that periodontitis was probably an important source of systemic inflammation in PD patients.Hypoalbuminemia not only is an indicator of malnutrition but also is related to clinical complications, influencing the prognosis[27][28].This study showed a weak negative correlation between PPD and Alb (r=-0.235, p = 0.041),probably because persistent inflammatory reactions and reduced oral intake are associated with malnutrition[9][24][26].Periodontal status can affect nutritional parameters,and periodontal treatment can improve periodontal status as well as inflammatory status and the nutritional state[19].However, some studies found no statistically significant association between Alb and the severity of periodontitis.In addition to nutritional status,these studies suggested that Alb is regulated by other factors,such as protein loss caused by peritoneal dialysis and gastric anorexia caused by inadequate dialysis[26][28].Increased calcium in the saliva can promote dental calculus formation[7],which may be supported by the positive correlation between PLI and serum Ca in this study.On the other hand,secondary hyperparathyroidism can alter the levels of serum calcium and phosphorus metabolism and PTH, which are common complications observed in dialysis patients[22]. Kristine Sun et al.[24] and Naghsh N et al.[28] reported a positive correlation between PTH and alveolar bone loss and suggested that CKD-mineral and bone disorder (MBD) was an important risk factor for alveolar bone loss.Furthermore, alveolar bone loss can be improved by increasing calcium intake and worsened by a high-phosphorus diet[12][29].This study found only a weak correlation between Ca and PPD,while several studies showed that there were no statistically significant differences in Ca,P and PTH between PD patients with or without CP[26][28][29].Therefore,we need further randomized controlled intervention trials to prove that periodontitis is correlated with secondary hyperparathyroidism and calcium and phosphorus metabolism.Hematopoietic raw material,nutritional status and inflammatory states result in anemia in dialysis patients.This study showed no significant correlation between serum Hb and periodontitis,which is consistent with the results of most recent studies[28].
The presence of microinflammatory status in dialysis can lead to an increased risk for cardiovascular and infectious disease, seriously affecting the quality of life and prognosis[2][7]. Some studies have suggested that the degree of CP is positively related to inflammatory parameters (including hs-CRP,etc.) and atherosclerosis risk factors[20][25].The relationship between periodontitis and systemic inflammation includes the cytokine response in the gingival epithelium caused by bacterial plaque, bacteremia caused by oral bacteria, circulating oral microbial toxins and immune responses to oral microorganisms[23].Bacteremia and the systemic inflammatory response associated with CP are not only initiating factors for vascular endothelial lesions but also important factors of the vascular wall inflammatory process[20][21].Patients with CKD and CP as comorbidities can experience the progression of renal and cardiovascular disease due to systemic chronic inflammation[12].This study also found a correlation between CAL and CRP.However, there were no significant differences in any periodontal parameters between patients with and those without CCEs.Tasdemir Z et al.[30] reported that periodontal therapy can reduce the systemic inflammatory response,thus contributing to a reduction in the risk of cardiovascular and cerebrovascular disease.However,evidence that CP determines the long-term effects on CCEs is still limited,and there is little evidence that periodontal treatment can prevent atherosclerosis or change its prognosis[20][31].Further intervention studies are needed to confirm the relationship between CP and CCEs in dialysis patients.
Currently,there are few studies on the correlation between oral infection and dialysis-related infection.Research on dialysis-related infections mostly focuses on the analysis of infectious pathogens and lacks research data on oral health conditions and oral microorganisms. No studies have reported the association between periodontitis and PDAP. ISPD guidelines[32] reported that oral streptococci can cause PDAP.Hideaki Oka et al.[23] suggested that better oral hygiene habits were associated with a lower incidence of PDAP and streptococcal infection.At present, the risk factors for PDAP are considered to include age, hypoalbuminemia,DM,etc.[19].Moreover,a long dialysis vintage can aggravate periodontal damage[24].In this study,all variables were included in the univariate analysis,and we found statistically significant differences in CAL, PPD, PLI, CRP and long PD vintage between the occurrences of PDAP and non-PDAP.Then, these statistically significant variables were included in the multivariate regression analysis,revealing that CAL was a risk factor for PDAP.
Bacteremia caused by invasive dental manipulation is considered one of the secondary causes of PDAP[23]. Oka H et al.[23] reported that oral streptococci can be found in PD effluent from some PDAP patients,and streptococci in the oral cavity was the most important bacterial cause of PDAP in the oral cavity.The study also summarized other previous studies to prove the theory that oral splash contamination leads to PDAP.To prevent exogenous peritonitis,the study recommended hand washing and wearing a face mask before fluid exchange.At the same time,the positive culture rate of gram-negative Enterobacteriaceae was 1.2–3.2% on the tongue and in saliva and gingival crevicular fluid,indicating that gram-negative Enterobacteriaceae derives from the gastrointestinal tract but also comes from the oral cavity as the main pathogenic bacteria.However, the main causal organisms of PDAP are still gram-positive bacteria, and staphylococci,as the most common bacteria found in PDAP patients,are not oral colonization bacteria[17].In our study, gram-positive bacteria were the predominant pathogens (57.8%), with staphylococci and streptococci each accounting for 24.4% of infections.Unfortunately, we were not able to detect the presence of oral flora,so the relationship between oral pathogens and PDAP pathogens requires further study.
In addition,periodontitis can lead to poor glycemic control, consequently increasing the risk of other complications of DM[20].After treatment,the inflammatory markers in PD patients,especially those with DM,are slightly reduced, and blood glucose control also improves[7][20].These results suggest that periodontal disease is the main source of inflammation in PD patients with DM.Due to the small sample of DM patients,the daily glucose levels of patients during follow-up were not accurately recorded,so data on the correlation between periodontitis and glycemic control were not available.
The main limitation of this study is that this is an observational cohort study with no periodontal therapy intervention,a lack of long-term control,a small sample size,and a short follow-up duration.Although our study found that CP can influence systemic inflammatory status and nutritional condition,which is a risk factor for PDAP,it is not certain whether the improvement in periodontitis reduces systemic inflammation,improves nutritional status,slows the process of alveolar bone loss and reduces the incidence of PDAP and CCEs.The answers to these questions need to be confirmed by further prospective randomized controlled studies.