Patterns of periodontal disease progression based on linear mixed models of clinical attachment loss

A multi-platform analysis of human gingival crevicular fluid reveals ferroptosis as a relevant regulated cell death mechanism during the clinical progression of periodontitis

Ferroptosis is implicated in the pathogenesis of numerous chronic-inflammatory diseases, yet its association with progressive periodontitis remains unexplored. To investigate the involvement and significance of ferroptosis in periodontitis progression, we assessed sixteen periodontitis-diagnosed patients. Disease progression was clinically monitored over twelve weeks via weekly clinical evaluations and gingival crevicular fluid (GCF) collection was performed for further analyses. Clinical metrics, proteomic data, in silico methods, and bioinformatics tools were combined to identify protein profiles linked to periodontitis progression and to explore their potential connection with ferroptosis. Subsequent western blot analyses validated key findings. Finally, a single-cell RNA sequencing (scRNA-seq) dataset (GSE164241) for gingival tissues was analyzed to elucidate cellular dynamics during periodontitis progression. Periodontitis progression was identified as occurring at a faster rate than traditionally thought. GCF samples from progressing and non-progressing periodontal sites showed quantitative and qualitatively distinct proteomic profiles. In addition, specific biological processes and molecular functions during progressive periodontitis were revealed and a set of hub proteins, including SNCA, CA1, HBB, SLC4A1, and ANK1 was strongly associated with the clinical progression status of periodontitis. Moreover, we found specific proteins - drivers or suppressors - associated with ferroptosis (SNCA, FTH1, HSPB1, CD44, and GCLC), revealing the co-occurrence of this specific type of regulated cell death during the clinical progression of periodontitis. Additionally, the integration of quantitative proteomic data with scRNA-seq analysis suggested the susceptibility of fibroblasts to ferroptosis. Our analyses reveal proteins and processes linked to ferroptosis for the first time in periodontal patients, which offer new insights into the molecular mechanisms of progressive periodontal disease. These findings may lead to novel diagnostic and therapeutic strategies.

Epidemiology of mid-buccal gingival recessions according to the 2018 Classification System in South America: Results from two population-based studies

AIM

The aim of this investigation was to estimate the prevalence, severity and extent of mid-buccal gingival recessions (GRs; classified according to the 2018 Classification System) and to identify their risk indicators in the South American population.

MATERIALS AND METHODS

Epidemiological data from two cross-sectional studies-performed on 1070 South American adolescents and 1456 Chilean adults-were obtained. All participants received a full-mouth periodontal examination by calibrated examiners. GR prevalence was defined as the presence of at least one mid-buccal GR ≥ 1 mm. GRs were also categorized into different recession types (RTs) according to the 2018 World Workshop Classification System. Analyses for RT risk indicators were also performed. All analyses were carried out at the participant level.

RESULTS

The prevalence of mid-buccal GRs was 14.1% in South American adolescents and 90.9% in Chilean adults. In South American adolescents, the prevalence of RTs was 4.3% for RT1 GRs, 10.7% for RT2 GRs and 1.7% for RT3 GRs. In Chilean adults, the prevalence of RT1 GRs was 0.3%, while the prevalence of RT2 and RT3 GRs was 85.8% and 77.4%, respectively. Full-Mouth Bleeding Score (FMBS; <25%) was associated with the presence of RT1 GRs in adolescents. The risk indicators for RT2/RT3 GRs mainly overlapped with those for periodontitis.

CONCLUSIONS

Mid-buccal GRs affected 14.1% of South American adolescents, whereas they affected most of the Chilean adult population (>90%). While RT1 GRs are more commonly observed in a non-representative cohort of South American adolescents (when compared to Chilean adults), the majority of Chilean adults exhibit RT2/RT3 GRs.

Pursuing new periodontal pathogens with an improved RNA-oligonucleotide quantification technique (ROQT)

OBJECTIVE

The aim of this study was to optimize the sensitivity, specificity and cost-effectiveness of the RNA-Oligonucleotide Quantification Technique (ROQT) in order to identify periodontal pathogens that remain unrecognized or uncultured in the oral microbiome.

DESIGN

Total nucleic acids (TNA) were extracted from subgingival biofilm samples using an automated process. RNA, DNA and Locked Nucleic Acid (LNA) digoxigenin-labeled oligonucleotide probes targeting 5 cultivated/named species and 16 uncultivated or unnamed bacterial taxa were synthesized. Probe specificity was determined by targeting 96 oral bacterial species; sensitivity was assessed using serial dilutions of reference bacterial strains. Different stringency temperatures were compared and new standards were tested. The tested conditions were evaluated analyzing samples from periodontally healthy individuals, and patients with moderate or severe periodontitis.

RESULTS

The automated extraction method at 63⁰C along with LNA-oligunucleotides probes, and use of reverse RNA sequences for standards yielded stronger signals without cross-reactions. In the pilot clinical study, the most commonly detected uncultivated/unrecognized species were Selenomonas sp. HMT 134, Prevotella sp. HMT 306, Desulfobulbus sp. HMT 041, Synergistetes sp. HMT 360 and Bacteroidetes HMT 274. In the cultivated segment of the microbiota, the most abundant taxa were T. forsythia HMT 613 and Fretibacterium fastidiosum (formerly Synergistetes) HMT 363.

CONCLUSIONS

In general, samples from severe patients had the greatest levels of organisms. Classic (T. forsythia, P. gingivalis) and newly proposed (F. alocis and Desulfobulbus sp. HMT 041) pathogens were present in greater amounts in samples from severe periodontitis sites, followed by moderate periodontitis sites.

Subgingival host-microbiome metatranscriptomic changes following scaling and root planing in grade II/III periodontitis

AIM

To assess the effects of scaling and root planing (SRP) on the dynamics of gene expression by the host and the microbiome in subgingival plaque samples.

MATERIALS AND METHODS

Fourteen periodontitis patients were closely monitored in the absence of periodontal treatment for 12 months. During this period, comprehensive periodontal examination and subgingival biofilm sample collection were performed bi-monthly. After 12 months, clinical attachment level (CAL) data were compiled and analysed using linear mixed models (LMM) fitted to longitudinal CAL measurements for each tooth site. LMM classified the sites as stable (S), progressing (P), or fluctuating (F). After the 12-month visit, subjects received SRP, and at 15 months they received comprehensive examination and supportive periodontal therapy. Those procedures were repeated at the 18-month visit, when patients were also sampled. Each patient contributed with one S, one P, and one F site collected at the 12- and 18-month visits. Samples were analysed using Dual RNA-Sequencing to capture host and bacterial transcriptomes simultaneously.

RESULTS

Microbiome and host response behaviour were specific to the site's progression classification (i.e., S, P, or F). Microbial profiles of pre- and post-treatment samples exhibited specific microbiome changes, with progressing sites showing the most significant changes. Among them, Porphyromonas gingivalis was reduced after treatment, while Fusobacterium nucleatum showed an increase in proportion. Transcriptome analysis of the host response showed that interleukin (IL)-17, TNF signalling pathways, and neutrophil extracellular trap formation were the primary immune response activities impacted by periodontal treatment.

CONCLUSIONS

SRP resulted in a significant "rewiring" of host and microbial activities in the progressing sites, while restructuring of the microbiome was minor in stable and fluctuating sites.

Maladaptive trained immunity and clonal hematopoiesis as potential mechanistic links between periodontitis and inflammatory comorbidities

Periodontitis is bidirectionally associated with systemic inflammatory disorders. The prevalence and severity of this oral disease and linked comorbidities increases with aging. Here, we review two newly emerged concepts, trained innate immunity (TII) and clonal hematopoiesis of indeterminate potential (CHIP), which together support a potential hypothesis on how periodontitis affects and is affected by comorbidities and why the susceptibility to periodontitis and comorbidities increases with aging. Given that chronic diseases are largely triggered by the action of inflammatory immune cells, modulation of their bone marrow precursors, the hematopoietic stem and progenitor cells (HSPCs), may affect multiple disorders that emerge as comorbidities. Such alterations in HSPCs can be mediated by TII and/or CHIP, two non-mutually exclusive processes sharing a bias for enhanced myelopoiesis and production of innate immune cells with heightened proinflammatory potential. TII is a state of elevated immune responsiveness based on innate immune (epigenetic) memory. Systemic inflammation can initiate TII in the bone marrow via sustained rewiring of HSPCs, which thereby display a skewing toward the myeloid lineage, resulting in generation of hyper-reactive or "trained" myeloid cells. CHIP arises from aging-related somatic mutations in HSPCs, which confer a survival and proliferation advantage to the mutant HSPCs and give rise to an outsized fraction of hyper-inflammatory mutant myeloid cells in the circulation and tissues. This review discusses emerging evidence that supports the notion that TII and CHIP may underlie a causal and age-related association between periodontitis and comorbidities. A holistic mechanistic understanding of the periodontitis-systemic disease connection may offer novel diagnostic and therapeutic targets for treating inflammatory comorbidities.

Viruses, periodontitis, and comorbidities

Seminal studies published in the 1990s and 2000s explored connections between periodontal diseases and systemic conditions, revealing potential contributions of periodontal diseases in the initiation or worsening of systemic conditions. The resulting field of periodontal medicine led to the publication of studies indicating that periodontal diseases can influence the risk of systemic conditions, including adverse pregnancy outcomes, cardiovascular and respiratory diseases, as well as Alzheimer disease and cancers. In general, these studies hypothesized that the periodontal bacterial insult and/or the associated proinflammatory cascade could contribute to the pathogenesis of these systemic diseases. While investigations of the biological basis of the connections between periodontal diseases and systemic conditions generally emphasized the bacteriome, it is also biologically plausible, under an analogous hypothesis, that other types of organisms may have a similar role. Human viruses would be logical "suspects" in this role, given their ubiquity in the oral cavity, association with periodontal diseases, and ability to elicit strong inflammatory response, compromise immune responses, and synergize with bacteria in favor of a more pathogenic microbial consortium. In this review, the current knowledge of the role of viruses in connecting periodontal diseases and systemic conditions is examined. We will also delve into the mechanistic basis for such connections and highlight the importance of those relationships in the management and treatment of patients.

Knowledge, Attitude, Access and Confidence in Evidence-based practice amongst French dental undergraduates: A transcultural adaptation and psychometrics analysis of French version of the KACE questionnaire

OBJECTIVE

The aim of this study was to provide a reliable instrument to assess evidence-based practice (EBP) dimensions in French-speaking dental students. To do so, a transcultural adaptation into French of the self-administered KACE questionnaire (Knowledge, Attitude, Access and Confidence Evaluation) and the evaluation of its psychometric properties in a sample of French dental students and teachers were performed. The effects of individual and academic factors on student performance in the KACE were also investigated.

METHOD

Teachers and fourth-year students completed once the translated KACE and fifth-year students completed twice the questionnaire before and after an epidemiology course. Cronbach's alpha coefficient analysis, Kruskal-Wallis and post hoc Dunn's tests, paired samples Wilcoxon tests and a generalised linear mixed model were performed to assess the psychometric properties (reliability, internal consistency, discriminant validity and responsiveness) of the questionnaire and to identify the factors associated with KACE scores, respectively.

RESULTS

186 participants completed the survey. Cronbach's alpha ranged from 0.06 to 0.48 for Knowledge, 0.21 to 0.59 for Attitude, 0.42 to 0.76 for Access and 0.82 to 0.93 for Confidence. The discriminant value and sensitivity of the French KACE revealed significant differences amongst students and teachers and accurately identified the effect the training course had on the students who had completed it. Preparing for a residency programme or having received add-on modules in science improved the students' performance in the test. Being female negatively impacted the KACE Confidence score.

CONCLUSION

This version of the KACE is appropriate to assess EBP dimensions in French dental students. Academic background and gender may affect test performance.

Oral Microbiome and Gingival Gene Expression of Inflammatory Biomolecules With Aging and Periodontitis

Although data describe the presence and increase of inflammatory mediators in the local environment in periodontitis vs. health in humans, details regarding how these responses evolve in the transition from health to disease, changes during disease progression, and features of a resolved lesion remain unknown. This study used a nonhuman primate model of ligature-induced periodontitis in young, adolescent, adult, and aged animals to document features of inflammatory response affected by age. Rhesus monkeys had ligatures tied and provided gingival tissue biopsy specimens at baseline, 0.5, 1, and 3 months of disease and at 5 months of the study, which was 2 months post-ligature removal for clinically resolved tissues. The transcriptome was assessed using microarrays for chemokine (n = 41), cytokine (n = 45), chemokine receptor (n = 21), cytokine receptor (n = 37), and lipid mediator (n = 31) genes. Limited differences were noted in healthy tissues for chemokine expression with age; however, chemokine receptor genes were decreased in young but elevated in aged samples. IL1A, IL36A, and IL36G cytokines were decreased in the younger groups, with IL36A elevated in aged animals. IL10RA/IL10RB cytokine receptors were altered with age. Striking variation in the lipid mediator genes in health was observed with nearly 60% of these genes altered with age. A specific repertoire of chemokine and chemokine receptor genes was affected by the disease process, predominated by changes during disease initiation. Cytokine/cytokine receptor genes were also elevated with disease initiation, albeit IL36B, IL36G, and IL36RN were all significantly decreased throughout disease and resolution. Significant changes were observed in similar lipid mediator genes with disease and resolution across the age groups. Examination of the microbiome links to the inflammatory genes demonstrated that specific microbes, including Fusobacterium, P. gingivalis, F. alocis, Pasteurellaceae, and Prevotella are most frequently significantly correlated. These correlations were generally positive in older animals and negative in younger specimens. Gene expression and microbiome patterns from baseline were distinctly different from disease and resolution. These results demonstrate patterns of inflammatory gene expression throughout the phases of the induction of a periodontal disease lesion. The patterns show a very different relationship to specific members of the oral microbiome in younger compared with older animals.

Subgingival Microbiota and Cytokines Profile Changes in Patients with Periodontitis: A Pilot Study Comparing Healthy and Diseased Sites in the Same Oral Cavities

Periodontitis is a common condition characterized by an exacerbated pro-inflammatory response, which leads to tissue destruction and, ultimately, alveolar bone loss. In this pilot study, we assess the microbiota composition and cytokine profile changes in patients with stage III/IV, grade B/C periodontitis, specifically by comparing healthy and diseased sites in the same oral cavity. Overall, we found that microbiota architecture was significantly disrupted between diseased and healthy sites, and that the clustering was driven, in part, by the increased relative abundances of Synergistetes in diseased sites, as well as the increased abundances of Firmicutes in healthy sites. We also observed that diseased sites were enriched in Synergistetes, TM7, SR1, Spirochaetes, Bacteroidetes and Fusobacteria, and depleted in Firmicutes, Proteobacteria, Tenericutes and Actinobacteria compared to healthy sites. We found that Interleukin-1b, Interleukin-4, Interleukin-10, and Interleukin-17A were significantly overexpressed in diseased sites, whereas Interleukin-6 and TNF-alpha do not differ significantly between healthy and diseased sites. Here, we observed concomitant changes in the subgingival plaque microbiota and cytokines profile, suggesting that this combined alteration could contribute to the pathobiology of periodontitis.

Long-term dynamics of the human oral microbiome during clinical disease progression

BACKGROUND

Oral microbiome dysbiosis is linked to overt inflammation of tooth-supporting tissues, leading to periodontitis, an oral condition that can cause tooth and bone loss. Microbiome dysbiosis has been described as a disruption in the symbiotic microbiota composition's stability that could adversely affect the host's health status. However, the precise microbiome dynamics that lead to dysbiosis and the progression of the disease are largely unknown. The objective of our study was to investigate the long-term dynamics of periodontitis progression and its connection to dysbiosis.

RESULTS

We studied three different teeth groups: sites that showed disease progression, sites that remained stable during the study, and sites that exhibited a cyclic deepening followed by spontaneous recovery. Time-series analysis revealed that communities followed a characteristic succession of bacteria clusters. Stable and fluctuating sites showed high asynchrony in the communities (i.e., different species responding dissimilarly through time) and a reordering of the communities where directional changes dominated (i.e., sample distance increases over time) in the stable sites but not in the fluctuating sites. Progressing sites exhibited low asynchrony and convergence (i.e., samples distance decreases over time). Moreover, new species were more likely to be recruited in stable samples if a close relative was not recruited previously. In contrast, progressing and fluctuating sites followed a neutral recruitment model, indicating that competition between closely related species is a significant component of species-species interactions in stable samples. Finally, periodontal treatment did not select similar communities but stabilized α-diversity, centered the abundance of different clusters to the mean, and increased community rearrangement.

CONCLUSIONS

Here, we show that ecological principles can define dysbiosis and explain the evolution and outcomes of specific microbial communities of the oral microbiome in periodontitis progression. All sites showed an ecological succession in community composition. Stable sites were characterized by high asynchrony, a reordering of the communities where directional changes dominated, and new species were more likely to be recruited if a close relative was not recruited previously. Progressing sites were characterized by low asynchrony, community convergence, and a neutral model of recruitment. Finally, fluctuating sites were characterized by high asynchrony, community convergence, and a neutral recruitment model.

Impact of interproximal composite restorations on periodontal tissue health: Clinical and cytokine profiles from a pre-post quasi-experimental study

BACKGROUND

The aim of this study is to clinically and molecularly evaluate the effect of an interproximal iuxta/subgingival direct composite restoration on periodontal tissue healing.

METHODS

Individuals in need of a posterior iuxta/subgingival interproximal restoration were consecutively enrolled. After enrollment, a test (site with tooth decay) and a control site (intact contralateral tooth) were identified. After a periodontal examination (probing depth [PD], clinical attachment level, recession, plaque, and bleeding on probing [BOP]) and a sampling of gingival crevicular fluid, the composite restoration was performed (T₀ ). Clinical and molecular assessments were repeated at 3 (T₃ ), 6 (T₆ ), and 12 (T₁₂ ) months after the restoration. Intragroup pre-post comparisons for quantitative variables were performed either through one-way ANOVA or Kruskal-Wallis test. A multivariate linear regression analysis was then modeled. With α = 0.05, a power of 80% will be reached with the inclusion of 41 individuals.

RESULTS

Biometric parameters demonstrated an increased mean PD (ΔPDT₀ -T₁₂ = -0.83 mm; P = 0.001) and loss of attachment (AL) (ΔCALT₀ -T₁₂ = -0.91 mm; P = 0.005) in the test site at 12 months. Accordingly, in the final multivariate regression model the radiographic distance between the bone crest and the restorative margin at baseline accounted for the dependent variable "attachment loss (AL)" (ΔCALT₀ -T₁₂ ) (P <0.05).

CONCLUSIONS

Iuxta/subgingival interproximal restorative margins jeopardized clinically and molecularly the periodontal tissue healing at least up to 1 year of follow-up.

Subgingival microbiome is associated with alveolar bone loss measured 5 years later in postmenopausal women

BACKGROUND

The aim of this study was to quantify the association between subgingival microbiota and periodontal disease progression in older women, for which limited published data exist.

METHODS

A total of 1016 postmenopausal women, aged 53 to 81 years, completed baseline (1997 to 2001) and 5-year (2002 to 2006) dental exams that included probing depth, clinical attachment level, gingival bleeding, and radiographic alveolar crestal height (ACH). Baseline microbiota were measured in subgingival plaque using 16S rRNA sequencing. Associations between 52 microbiota we previously found statistically significantly associated with clinical periodontal disease at baseline, were examined with disease progression. The traditional Socransky microbiota complexes also were evaluated. Side-by-side radiograph comparisons were used to define progression as ≥2 teeth with ≥1 mm ACH loss or ≥1 new tooth loss to periodontitis. The association between baseline centered log(2) ratio transformed microbial relative abundances and 5-year periodontal disease progression was measured with generalized linear models.

RESULTS

Of 36 microbiota we previously showed were elevated in moderate/severe disease at baseline, 24 had statistically significantly higher baseline mean relative abundance in progressing compared with non-progressing women (P < .05, all); which included all Socransky red bacteria (P. gingivalis, T. forsythia, T. denticola). Of 16 microbiota elevated in none/mild disease at baseline, five had statistically significantly lower baseline abundance in non-progressing compared with progressing women (P < 0.05, all), including one Socransky yellow bacteria (S. oralis). When adjusted for baseline age, socioeconomic status, and self-rated general health status, odds ratios for 5-year progression ranged from 1.18 to 1.51 (per 1-standard deviation increment in relative abundance) for microbiota statistically significantly (P < 0.05) positively associated with progression, and from 0.77 to 0.82 for those statistically significantly (P < 0.05) inversely associated with progression. These associations were similar when stratified on baseline levels of pocket depth, gingival bleeding, ACH, and smoking status.

CONCLUSIONS

These prospective results affirm clearly that subgingival microbiota are measurably elevated several years prior to progression of alveolar bone loss, and include antecedent elevations in previously undocumented taxa additional to known Socransky pathogenic complexes.

Metabolomics of gingival crevicular fluid to identify biomarkers for periodontitis: A systematic review with meta-analysis

The present systematic review aimed to examine periodontitis-specific biomarkers in the gingival crevicular fluid (GCF) that could have a diagnostic relevance, and to provide a qualitative assessment of the current literature. Metabolites are reliable indicators of pathophysiological statuses, and their quantification in the GCF can provide an outlook of the changes associated with periodontitis and have diagnostic value. Relevant studies identified from PubMed, Embase, Cochrane Library, and Scopus databases were examined to answer the following PECO question: "In systemically healthy individuals, can concentration of specific metabolites in the GCF be used to discriminate subjects with healthy periodontium (H) or gingivitis from patients with periodontitis (P) and which is the diagnostic accuracy?" Quality of included studies was rated using a modified version of the QUADOMICS tool. Meta-analysis was conducted whenever possible. After the screening of 1,554 titles, 15 studies were selected, with sample size ranging from 30 to 93 subjects. Eleven studies performed targeted metabolomics analysis and provided data for 10 metabolites. Among the most consistent markers, malondialdehyde levels were found higher in the P group compared with H group (SMD = 2.86; 95% CI: 1.64, 4.08). Also, a significant increase of 8-hydroxy-deoxyguanosine, 4-hydroxynonenal, and neopterin was detected in periodontally diseased sites, while glutathione showed an inverse trend. When considering data from untargeted metabolomic analysis in four studies, more than 40 metabolites were found significantly discriminant, mainly related to amino acids and lipids degradation pathways. Notably, only one study reported measures of diagnostic accuracy. Several metabolites were differentially expressed in GCF of subjects across different periodontal conditions, having a major potential for investigating periodontal pathophysiology and for site-specific diagnosis. Oxidative stress-related molecules, such as malondialdehyde and 8-hydroxy-deoxyguanosine, were the most consistently associated to periodontitis (PROSPERO CRD42020188482).

Oral microbiome interactions with gingival gene expression patterns for apoptosis, autophagy and hypoxia pathways in progressing periodontitis

Oral mucosal tissues must react with and respond to microbes comprising the oral microbiome ecology. This study examined the interaction of the microbiome with transcriptomic footprints of apoptosis, autophagy and hypoxia pathways during periodontitis. Adult Macaca mulatta (n = 18; 12-23 years of age) exhibiting a healthy periodontium at baseline were used to induce progressing periodontitis through ligature placement around premolar/molar teeth. Gingival tissue samples collected at baseline, 0·5, 1 and 3 months of disease and at 5 months for disease resolution were analysed via microarray. Bacterial samples were collected at identical sites to the host tissues and analysed using MiSeq. Significant changes in apoptosis and hypoxia gene expression occurred with initiation of disease, while autophagy gene changes generally emerged later in disease progression samples. These interlinked pathways contributing to cellular homeostasis showed significant correlations between altered gene expression profiles in apoptosis, autophagy and hypoxia with groups of genes correlated in different directions across health and disease samples. Bacterial complexes were identified that correlated significantly with profiles of host genes in health, disease and resolution for each pathway. These relationships were more robust in health and resolution samples, with less bacterial complex diversity during disease. Using these pathways as cellular responses to stress in the local periodontal environment, the data are consistent with the concept of dysbiosis at the functional genomics level. It appears that the same bacteria in a healthy microbiome may be interfacing with host cells differently than in a disease lesion site and contributing to the tissue destructive processes.

Biosensor and Lab-on-a-chip Biomarker-identifying Technologies for Oral and Periodontal Diseases

Periodontitis is a complex multifactorial disease that can lead to destruction of tooth supporting tissues and subsequent tooth loss. The most recent global burden of disease studies highlight that severe periodontitis is one of the most prevalent chronic inflammatory conditions affecting humans. Periodontitis risk is attributed to genetics, host-microbiome and environmental factors. Empirical diagnostic and prognostic systems have yet to be validated in the field of periodontics. Early diagnosis and intervention prevents periodontitis progression in most patients. Increased susceptibility and suboptimal control of modifiable risk factors can result in poor response to therapy, and relapse. The chronic immune-inflammatory response to microbial biofilms at the tooth or dental implant surface is associated with systemic conditions such as cardiovascular disease, diabetes or gastrointestinal diseases. Oral fluid-based biomarkers have demonstrated easy accessibility and potential as diagnostics for oral and systemic diseases, including the identification of SARS-CoV-2 in saliva. Advances in biotechnology have led to innovations in lab-on-a-chip and biosensors to interface with oral-based biomarker assessment. This review highlights new developments in oral biomarker discovery and their validation for clinical application to advance precision oral medicine through improved diagnosis, prognosis and patient stratification. Their potential to improve clinical outcomes of periodontitis and associated chronic conditions will benefit the dental and overall public health.

Cytokine profiles of healthy and diseased sites in individuals with periodontitis

OBJECTIVE

The aims of this study were: 1) to compare the levels of cytokines between healthy and diseased sites, in patients with untreated periodontitis; 2) to correlate cytokine levels with each other and with key periodontal pathogens, in healthy and diseased sites.

METHODS

Paired gingival crevicular fluid (GCF) samples were obtained from two healthy (probing depth (PD) and clinical attachment level (CAL) ≤3 mm without bleeding) and two diseased sites (PD and CAL ≥5 mm with bleeding on probing [BoP]) of patients with generalized stage III/IV grade B/C periodontitis. GCF levels of eighteen cytokines and subgingival levels of seven periodontal pathogens were assessed by multiplex immunoassay and qPCR, respectively.

RESULTS

A total of 112 subjects and 448 GCF samples were analyzed. The GCF levels of GM-CSF, IL-17, IL-1β, IL-2, IL-21, IL-23 and TGF-β were significantly higher in the diseased than in the healthy sites (p < 0.05). Levels of IL-8 and MIP-1α were significantly higher in the healthy than in the diseased sites (p < 0.05). In the healthy sites, IL-8 and MIP-1α formed an independent cluster of cytokines and, MIP-1α positively correlated with Porphyromonas gingivalis (p < 0.05). In deep sites, smoking negatively associated with GM-CSF, IL-10, IL-17, IL-23, IL-5, IL-6, IL-7, IL-8 and MIP-1α levels (p < 0.05).

CONCLUSIONS

Diseased sites exhibited increased levels of T helper 17-related cytokines and TGF-β while healthy sites presented increased levels of the chemokines, IL-8 and MIP-1α. Patients with periodontitis may not only have inflammation in diseased deep sites, but also present significant hidden subclinical inflammation in their shallow clinically healthy sites.

Determinants of Periodontal/Periapical Lesion Stability and Progression

Periodontal and periapical lesions are infectious inflammatory osteolitytic conditions in which a complex inflammatory immune response mediates bone destruction. However, the uncertainty of a lesion's progressive or stable phenotype complicates understanding of the cellular and molecular mechanisms triggering lesion activity. Evidence from clinical and preclinical studies of both periodontal and periapical lesions points to a high receptor activator of NF-κB ligand/osteoprotegerin (RANKL/OPG) ratio as the primary determinant of osteolytic activity, while a low RANKL/OPG ratio is often observed in inactive lesions. Proinflammatory cytokines directly modulate RANKL/OPG expression and consequently drive lesion progression, along with pro-osteoclastogenic support provided by Th1, Th17, and B cells. Conversely, the cooperative action between Th2 and Tregs subsets creates an anti-inflammatory and proreparative milieu associated with lesion stability. Interestingly, the trigger for lesion status switch from active to inactive can originate from an unanticipated RANKL immunoregulatory feedback, involving the induction of Tregs and a host response outcome with immunological tolerance features. In this context, dendritic cells (DCs) appear as potential determinants of host response switch, since RANKL imprint a tolerogenic phenotype in DCs, described to be involved in both Tregs and immunological tolerance generation. The tolerance state systemically and locally suppresses the development of exacerbated and pathogenic responses and contributes to lesions stability. However, immunological tolerance break by comorbidities or dysbiosis could explain lesions relapse toward activity. Therefore, this article will provide a critical review of the current knowledge concerning periodontal and periapical lesions activity and the underlying molecular mechanisms associated with the host response. Further studies are required to unravel the role of immunological responsiveness or tolerance in the determination of lesion status, as well as the potential cooperative and/or inhibitory interplay among effector cells and their impact on RANKL/OPG balance and lesion outcome.

Periodontal disease and its impact on general health in Latin America. Section IV: Diagnosis

The art of diagnosis is of great importance in the management of any disease. This includes preventive and therapeutic strategies. To make an accurate and effective diagnosis, knowledge about the health-disease process is fundamental. This paper reviews the important aspects for periodontal diagnosis in a contemporary approach, and endeavors to establish challenges for improving periodontal diagnosis, especially in Latin America. Considering that contemporary periodontal diagnosis should be based on knowledge of the etiopathogenesis of periodontal diseases, this paper highlights that the recently proposed classification system for periodontal diseases and conditions was based on the best available evidence. This system was conceived for individual diagnosis, therefore, its use in research and epidemiological settings might be limited. The system leads to a practical implication that stresses the importance of interviewing the patient, thorough periodontal charting, and requesting any imaging and other complementary tests necessary. An important observation is that partial periodontal data recordings usable for screening are not diagnostic methods and might underestimate disease. The goals of utmost importance for Latin America are to increase the awareness of both the population and the profession and to prioritize correct periodontal diagnosis. In addition, learning how to use the new classification system will help with diagnosing periodontal diseases.

Pathogen profile and MMP-3 levels in areas with varied attachment loss in generalized aggressive and chronic periodontitis

Introduction

The progression of periodontitis depends on the changes in bone and connective tissue homeostasis and the imbalance of the biofilm and the host immunoinflammatory response, particularly matrix metalloproteinases (MMP).

Aim of the study

To assess the probable relation between subgingival anaerobic flora and the expression of MMP-3 in patients with generalized aggressive periodontitis (AgP), chronic periodontitis (CP) and healthy subjects, and to evaluate these levels according to varied tissue loss severity.

Material and methods

The plaque index (PI), gingival index (GI), probing depth (PD) and clinical attachment levels (CAL) were evaluated. MMP levels obtained from gingival sulcus fluid (GCF) were measured with Enzyme Linked Immuno Assay (ELISA). The bacterial counts were determined with Parocheck^®.

Results

Higher levels of MMP-3 in patients with AgP compared to subjects with CP and healthy individuals were observed. The microorganisms responsible of possible tissue destruction in both AgP and CP are red complex bacteria. T. denticola, T. forsythia, P. intermedia and F. nucleatum show positive correlation with MMP-3 levels.

Conclusions

MMP-3 is a biomarker associated with AgP, and red complex bacteria levels are correlated with increasing periodontal tissue loss in both periodontitis forms. The diagnosis of aggressive periodontitis, or site-specific treatment strategies can be orchestrated based on the evaluation of MMP-3 and the bacterial counts in patients with periodontitis.

Long-term assessment of periodontal disease progression after surgical or non-surgical treatment: a systematic review

The primary aim of this systematic review was to assess the evidence on periodontal disease progression after treatment in patients receiving supportive periodontal therapy (SPT) and to identify predictors of clinical attachment level (CAL) loss. A protocol was developed to answer the following focused question: In adult patients treated for periodontitis, what is the disease progression in terms of CAL loss after surgical or non-surgical treatment? Randomized controlled clinical trials, prospective cohort studies, and longitudinal observational human studies with a minimum of 5 years of follow-up after surgical or non-surgical treatment that reported CAL and probing depth changes were selected. Seventeen publications reporting data from 14 investigations were included. Data from 964 patients with a follow-up range of 5-15 years was evaluated. When the CAL at the latest follow-up was compared to the CAL after active periodontal therapy, 10 of the included studies reported an overall mean CAL loss of ≤0.5 mm, 3 studies reported a mean CAL loss of 0.5-1 mm, and 4 studies reported a mean CAL loss of >1 mm. Based on 7 publications, the percentage of sites showing a CAL loss of ≥2 mm varied from 3% to 20%, and a high percentage of sites with CAL loss was associated with poor oral hygiene, smoking, and poor compliance with SPT. The outcomes after periodontal therapy remained stable over time. Disease progression occurred in a reduced number of sites and patients, mostly associated with poor oral hygiene, poor compliance with SPT, and smoking.