Effect of non-surgical periodontal therapy on the serum and crevicular fluid interleukin-10 levels in chronic periodontitis - A systematic review and meta-analysis

Introduction

Chronic periodontitis is a long standing immune disease that causes destruction of periodontal tissue, including connective tissue, periodontal ligament, cementum, and alveolar bone.[1] At the outset and initiation of periodontitis, a biofilm is formed and microbial products from it, such as lipopolysaccharides and toxins interacts with Toll-like receptors and trigger intracellular signaling pathways that culminate in an inflammatory cytokine response leading to release of various inflammatory mediators (such as prostaglandin E2) and cytokines such as interleukins (ILs) and tumor necrosis factor alpha (TNF-α) as well as proteolytic enzymes including matrix metal loproteinases (MMPs). The recent paradigm states that relative levels of pro- and anti-inflammatory cytokines regulate the cytokine balance in the local environment of the disease lesion.[2,3]

IL-10 is a pleiotropic and an immunoregulatory cytokine that has been discovered recently. It is involved in the reduction of IL-1, IL-6, IL-8, TNF-α, and MMPs and inhibition of bone resorption.[4,5] This cytokine originates from immune cells such as monocytes, macrophages, and T and B-cells and acts by reducing the synthesis of the pro-inflammatory cytokines. It downregulates the macrophage activation and impacts the immune response by limiting the duration and extent of inflammation.[6] Therefore, IL-10 is documented to have a modulatory role on inflamed and progressive periodontal disease sites.[7]

Periodontal treatment consists of the mechanical scaling and root planning (SRP) of the surfaces to reduce the bacterial load and change the environmental conditions for microbial niches, reducing the host inflammatory response.[8] In patients with periodontitis, resolution of inflammation after non-surgical periodontal therapy (NSPT) along with improvement in clinical parameters has been reported in the previous investigation. For histological parameters, although a decrease was seen in the amount of inflammatory cell infiltrate some amount was still present in the connective tissue, together with the presence of pro-inflammatory cytokines, such as IL-1β. Moreover, when the concentration of IL-1β was evaluated in the gingival crevicular fluid (GCF) after the treatment, a slight increase was noticed.[9] Detection of molecular biomarkers in clinical practice may provide an insight into the degree of success of treatment outcomes after NSPT.[10]

Thus, the evaluation of cytokine levels before and after periodontal treatment may provide a mechanism to evaluate the treatment outcome. Hence, the present review was aimed to critically appraise the available literature on the impact of NSPT on IL-10 levels in GCF, saliva and serum of chronic periodontitis patients.

Methods

Information sources and search

For the present meta-analysis, a comprehensive search was carried out by utilizing relevant key terms and search strategy in PubMed, Embase, and Scopus [Figure 1] supplemented by a grey literature search and manual search through libraries and cross references.The search words used were “Chronic Periodontitis or Chronic Periodontitides or Periodontitides, Chronic or Periodontitis, Chronic or Adult Periodontitis or Adult Periodontitides or Periodontitides, Adult or Periodontitis, Adult,” “Interleukin-10 or IL-10 or CSIF-10 or Cytokine Synthesis Inhibitory Factor,” “Non-surgical periodontal therapy.” During the search, the criteria for selection was based on full text articles, peer reviewed, randomized and non-randomized, controlled clinical trials. The studies measuring the levels of IL-10 before and after NSPT among patients with chronic periodontitis were selected.

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Figure 1

Flow diagram of the literature search for the systematic review and meta-analysis

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Results

Quality assessment results

All randomized as well as non-randomized interventional studies were assessed by Cochrane’s Risk of bias Tool for Quality assessment [Figure 2a and b] and all the included studies had low risk of bias.

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Figure 2

(a) ROBVIS presentation for quality assessment results (interventional studies). (b) ROBVIS presentation for quality assessment results (Randomized controlled trials)

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General study characteristics

Table 1 provides the descriptive analysis of all the studies included in systematic Review. 3 articles had randomized controlled trial design[4,8,14] while 14 articles were non-randomized interventional designs.[7,10,15-26]

Table 1 Characteristics of studies included

Of all the studies, 12 studies measured IL-10 in GCF, four used serum as a diagnostic fluid and three studies used saliva as the diagnostic fluid wherein we analyzed the change in levels of IL-10 pre- and post-NSPT in chronic periodontitis patients.

Age groups for all the studies fall under the range of 25–75 years with an average of 35 years.

There are two studies each for follow-up intervals at 15 days, 1, 1.5, 4, and 6 months in GCF. For follow-up at 2 and 3 months, four studies for GCF were available whereas at 8 and 12 months, one study could be found. For serum and saliva at 1 and 1.5 months, there was one study whereas at an interval of 3 and 6 months, two for serum and one for saliva were found.

There was observed great deal of variation in the included studies but in general most of them involved the recording of attachment loss, deep probing depth, and bleeding on probing.

From a total of 395 patients, the results showed that NSPT increases the value of IL-10 in GCF at 1, 3, and 4 months post-therapy but decrease was seen at 6 months. Some of the studies documented a decrease in levels of IL-10 at 15 days interval, 1.5 and 2 months post-therapy.

In serum, an opposite trend was seen as there was an increase in IL-10 levels at 6 months and at 1, 1.5 months a decrease in its level was noticed. For the interval of 3 months, both increase and decrease were seen in different studies.

The descriptive analysis of studies regarding saliva showed an increase was seen at 1 and 1.5 months post-NSPT whereas a subsequent decrease at 3 and 6 months.

Results of meta-analysis

The GCF samples for IL-10 level among patients suffering with periodontitis at baseline relative to their levels at 3 months following NSPT showed the standard mean difference of 6.994 pg/ml (0.922; 13.066). This is suggestive of an increase in IL-10 level in patients after NSPT which shows that the intervention was favorable, and the overall result was statistically significant (P = 0.024). A random effect model [Figure 3] was used to assess the effect size as heterogeneity of studies came out to be statistically significant (I^2: 98.37%; P < 0.0001).

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Figure 3

Forest plot assessing the standardized mean difference of IL-10 levels pre and post NSPT in GCF at 3 months

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The standard mean difference in GCF samples for IL-10 level among patients suffering with periodontitis at baseline relative to their levels at 4 months following NSPT was 0.634 pg/ml (–1.204; 2.473) suggestive of an increase in IL-10 level in patients after NSPT. This reflects that the intervention was favorable, but the overall result was found to be statistically non-significant (P = 0.498). A random effect model [Figure 4] was used for the existing high heterogeneity of studies (I^2: 93.62 %; P = 0.0001).

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Figure 4

Forest plot assessing standardized mean difference of IL-10 levels pre- and post-NSPT in GCF at 4 months

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For GCF 6 month subgroup analysis, a fixed effect model [Figure 5] was used, as the heterogeneity of studies came out to be 0 (I2:0.00%; P = 0.4830) whereas the standard mean difference in GCF samples for IL-10 level among patients suffering with periodontitis at baseline relative to their levels at 6 months following NSPT was –0.612 pg/ml (–0.836; –0.388) which was found to be statistically significant. This suggests that the NSPT could have raised the levels of IL-10 post-therapy and the effect could not be sustained for longer duration (6 months).

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Figure 5

Forest plot assessing standardized mean difference of IL-10 levels pre- and post-NSPT in GCF at 6 months

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The subgroup analysis of IL-10 values in serum samples at baseline and at 6 months showed the standard mean difference of 3.676 pg/ml (1.797; 5.555) suggestive of an increase in IL-10 level in patients after NSPT which reflects that the intervention was favorable, and here the overall result was also found to be statistically significant (P < 0.001). A random effect model [Figure 6] was used due to high heterogeneity of studies (I^2: 81.82%; P = 0.0190). Based on the small number of studies in the meta-analysis (i.e., <10), funnel plots were not included to display publication bias.

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Figure 6

Forest plot assessing standardized mean difference IL-10 levels pre- and post-NSPT in serum at 6 months

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Discussion

As periodontal diseases are prevalent both in developed and developing countries and affect about 20–50% of global population, thus high prevalence of periodontal disease in adolescents, adults, and older individuals makes it a public health concern.[27]

IL-10 is a pluripotent cytokine with effects on numerous cell populations, in particular circulating and resident immune cells as well as epithelial cells. With its potent immunoregulatory capacities, its main biological function seems to be the limitation and termination of inflammatory responses.[28]

The primary aim of the systematic review was to evaluate the effect of Non-Surgical Periodontal therapy on the level of anti-inflammatory cytokine IL-10 in GCF, serum and saliva samples in Chronic Periodontitis patients. The systematic review identified 17 controlled trials assessing the use of SRP for management of chronic periodontitis with follow-ups ranging from 15 days to 12 months. The results of meta-analysis including five studies for GCF and 2 for serum could be pooled for analysis, whereas there were relatively inadequate and heterogeneous studies of small duration that analyzed the levels of IL-10 in saliva so that was not pooled.

To the best of our knowledge, this is the first systematic review and meta-analysis exploring the GCF, serum and saliva IL-10 cytokine levels in chronic periodontitis disease pre- and post-NSPT.

The results from the systematic review demonstrated that NSPT significantly affects the level of IL-10 in GCF and increases the level of this cytokine post-therapy. The effect was consistent at three and 4 months; however, there was observed a decrease at 6 months of duration.

To compensate the small number of studies available, separate clinical procedure employed in the particular RCTs has been considered as separate treatment units. This could be a cause of weakness because it reduced the independent inclusion of clinical studies not designed to answer the direct research question. Nevertheless, the strict inclusion criteria and absence of significant differences between treatment arms and methods of evaluation, the approach adopted was deemed reasonable. The same approach had been utilized previously by other authors conducting analysis for similar situations.[29] Very stringently, clinical trials reporting the concentration of IL-10 only were included in the meta-analysis, rather than the total activity pre- and post-treatment as reported in the original studies were excluded.[7,10,16,18,19,24] Further the method of estimation of the cytokine was by ELISA technique in majority of the studies which added to the methodological similarity of analysis. As there is only one reported systematic review and meta-analysis by Stadler et al., 2016, which has evaluated GCF levels of cytokines and chemokines in chronic periodontitis after NSPT and non-significant increase has been revealed regarding IL-10, the findings of the studies have been compared to RCTs published earlier.

Studies by Andrade et al., 2017, Ribeiro et al., 2008, Grover et al., 2016; and Hamoudi et al., 2020; have reported an increased level of GCF IL-10 at 3 months after non-surgical periodontal therapy which are in agreement with the results of current meta-analysis also. Grover et al., 2016, Dede et al., 2017, and Goutoudi et al., 2004 depicted an increase in GCF levels of IL-10 following NSPT at 1, 1.5.4 months, respectively. The increase in concentration of anti-inflammatory cytokines seems plausible as IL-10 might have an important regulatory role in limiting the duration and extent of the acute inflammatory response. In addition, it has been suggested that IL-10 increases the synthesis of tissue inhibitors of metal loproteinases in macrophages which, in turn, inhibit MMP production thus representing itself as an important matrix protective cytokine during inflammation.[30,31]

Studies mentioning values of IL-10 in GCF at 6 months by Ribeiro et al., 2008, and Fu et al., 2013, showed a decrease in its value comparable to baseline significantly.

IL-10 levels in serum samples that showed increased IL-10 levels in chronic periodontitis after NSPT at 3 and 6 months stated that NSPT has been regulating the overall circulating inflammatory status. And this increased level of IL10 is indicative of its antiinflammatory role that has been implicated in the suppression of tissue destruction. Moreover it inhibits the synthesis of monocyte-derived pro-inflammatory cytokines such as IL-1, IL-6, IL-8, and TNF-α thus enhancing the production of the IL-1 receptor antagonist in polymorphonuclear leukocytes stimulated with lipopolysaccharide.[32,33]

A key observation from the identified studies showed that there is a clear-cut lack of defined value or range of IL-10 levels in GCF, as only a few studies reporting on the levels of the cytokines were found in literature. Further the range observed by Fenol et al., 2014, in a total of 91 subjects was: 260.0 ± 1728.0 pg/ml (periodontitis group), 1128 ± 532.9 (Gingivitis group); 648 ± 505.75 (healthy group), wherein pocket depth ≥5 mm and CAL ≥3 mm was taken as the diagnostic criteria for periodontitis group and in another study by Gamonal et al., 2000: Range was 23.1–241 pg/ml which showed that the levels of IL-10 was usually variable among the studies.[26,34]

The strengths of our review include it’s novelty and potential clinical relevance as IL-10 is a primary anti-inflammatory cytokine in the local milieu determinant of the clinical status and response of periodontal tissues to therapy. IL-1β and IL-10 ratios have been documented to be significantly altered in response to therapy in cases of chronic and aggressive periodontitis.[35] Further we have limited our meta-analysis to clinical trials at specific time point durations of 3 and 6 months of observations which are clinically relevant as supportive periodontal therapy intervals to provide clinically meaningful answers.

Furthermore, a number of limitations are there in our reviewed and identified literature as there is significant heterogeneity among studies (statistical, clinical, and methodological) which results from multiple factors associated with the study design. These include aspects related to patient population and characteristics, variation in the SRP procedures, oral hygiene instructions, the baseline gingivitis, and plaque levels.

This could not be controlled and contributed to the heterogeneity that was observed. The follow-up durations for the pooled analysis in the included studies were limited to 6 months which may be considered short. It should be remembered that there could be differences in the self-performed infection control and distribution of modifying factors too.

While the overall risk of bias for included studies was found to be low, most were institutional and were performed in well-controlled environment in patient samples. Hence, the present review probably describes the efficacy rather than the effectiveness of intervention.

In conclusion and within the limitations of the present review a comprehensive search and analysis of the available literature based upon controlled trials within 15 days, 1, 1.5, 2, 3, 4, 6, 8, 9, 12 months follow-up duration demonstrated that non-surgical periodontal therapy significantly alters the levels of anti-inflammatory cytokines IL-10 in GCF and serum and there is inconclusive data regarding the same when evaluated in saliva. Reporting of results has been described on the basis of GRADE guidelines and suggests a moderate evidence of recommendation for the study results owing to low imprecision, indirectness, and inconsistency found in the literature.

Future RCTs providing insight into IL-10 levels must be registered on the publicly accessible database before commencement and be appropriately designed with longer duration of follow-ups and defined outcome measures. It is important that the baseline clinical characteristics and diagnosis should be recorded based on uniform disease definition criteria to provide best available evidence based on clinically relevant answers to improve the patient outcomes.

Conclusion

Within the limitations of the current analysis, there is moderate evidence to suggest that the NSPT affects significantly the levels of IL-10 in GCF, serum and saliva in chronic periodontitis patients. Increased levels of IL-10 at 3 months for GCF, 6 months for serum, was seen whereas a decrease was evident in its level at 6 months in GCF, 3 and 6 months for saliva. Due to much variable heterogenous data available, more well-designed randomized trials on this cytokine needs to be conducted in the future.

Clinical Relevance

Authors’ Declaration Statements

Competing Interests

The authors do not report any conflicts of interest.

Funding Statement

None.

Authors’ Contributions

Vishakha Grover: Conceptualization; Methodology; validation, visualization, data curation, Formal analysis and investigation: Writing - original draft preparation: Jyoti Gupta: Conceptualization; Methodology; validation, visualization, Formal analysis and investigation: Writing - original draft preparation: Suhani Maheshwari; data curation, writing, (pre liminary and original draft preparation), protocol writing; Narinder Kumar: statistical analysis; Ashish Jain: Conceptualization; Methodology; validation, visualization.