The Role of the Oral Microbiota Related to Periodontal Diseases in Anxiety, Mood and Trauma- and Stress-Related Disorders

Antimicrobial management of dental infections: Updated review

Dental infections, which include anything from severe periodontal illnesses and abscess forms to routine tooth caries, are a major public health risk. This review article focuses on the pathophysiology and treatment of dental infections. A narrative review was conducted based on several published articles, relevant journals, and books in Google Scholar PubMed using the keywords dental caries, periodontal disease, gingivitis, and related diseases; we excluded duplicated information. Our review illustrated the types of dental infections and the proper antimicrobial drug that is suitable for this disease. Drawing from recent research findings and clinical evidence, we explore the spectrum of bacteria commonly associated with dental infections and their susceptibility profiles to various antibiotics. Emphasis is placed on understanding the mechanisms of antibiotic action and resistance in the context of dental pathogens, shedding light on optimal treatment regimens and potential challenges in clinical management. Additionally, we go over the clinical consequences of antibiotic therapy in dentistry, taking into account factors like patient selection, dose guidelines, and side effects. The management of dental infections through antimicrobial strategies has undergone significant advancements, as evidenced by this updated review. Besides the normal methods, emerging technologies such as 3D printing for drug delivery of antibiotics and disinfectants hold promise in enhancing treatment efficacy and patient outcomes. By leveraging the precision and customization afforded by 3D printing, dentistry can tailor antimicrobial interventions to individual patient needs, optimizing therapeutic outcomes while minimizing adverse effects.

Adolescent alcohol use is associated with differences in the diversity and composition of the oral microbiome

BACKGROUND

Adolescence is a sensitive stage of oral microbial development that often coincides with the initiation and escalation of alcohol use. Thus, adolescents may be particularly susceptible to alcohol-induced alterations in the oral microbiome, though minimal research has been done in this area. Understanding the connection between the oral microbiome and alcohol use during adolescence is important to understand fully the biological consequences of alcohol use to mitigate potential adverse outcomes.

METHODS

Saliva samples were collected from adolescents aged 17-19 who used alcohol heavily (n = 21, 52.4% female) and those who did not use alcohol or any other substances (n = 18, 44.4% female). We utilized 16S rRNA sequencing to examine differences in microbial diversity and composition between the groups.

RESULTS

For alpha diversity, evenness was significantly lower in the drinking group than the control group as indicated by Pielou's evenness, Shannon, and Simpson indices. There were no statistically significant findings for beta diversity. Differential abundance analyses revealed higher abundances of Rothia and Corynebacterium in the alcohol-using group using both centered-log-ratio and relative abundance normalization. These genera are known for their high capacity to convert alcohol into acetaldehyde, a toxic metabolite reported to play a role in the neurobiological effects of alcohol. An unclassified Clostridia UCG-014, Streptobacillus, Comamonas, unclassified Lachnospiraceae, and Parvimonas were also identified as significantly different between groups when using only one of the normalization techniques.

CONCLUSIONS

This is the first study designed specifically to compare the oral microbiome of adolescents who use alcohol with that of control participants. Our findings reveal distinct alcohol-related differences in microbial composition and taxon abundance, emphasizing the importance of understanding the impact on the oral microbiome of alcohol use during adolescence. Because the oral microbiome is malleable, this study provides foundational work for future prevention and intervention studies.

High-intensity interval training mitigates the progression of periodontitis and improves behavioural aspects in rats

AIM

To investigate the effects of high-intensity interval training (HIIT) on periodontitis (PD) progression and behavioural outcomes.

MATERIALS AND METHODS

Forty-eight Wistar rats were divided into four groups: non-trained (NT); non-trained with PD; HIIT with PD; and HIIT. The HIIT protocol, involving daily treadmill sessions, spanned 8 weeks, with PD induced by ligature after the 6th week. Behavioural tests were conducted to assess anxiety and memory. Post euthanasia, we evaluated the systemic inflammatory profile and oxidative stress markers in the hippocampus and amygdala. A morphological evaluation and elemental composition analysis of the mandibular alveolar bone were performed.

RESULTS

PD exacerbated alveolar bone level, bone surface damage and alterations in calcium and phosphorus percentages on the bone surface (p < .05), while HIIT attenuated these changes (p < .05). HIIT improved systemic inflammatory markers altered by PD (tumour necrosis factor [TNF]-α, interleukin [IL]-10, TNF-α/IL-10 and IL-1β/IL-10 ratios, p < .05). PD animals exhibited lower total antioxidant capacity and levels of thiobarbituric acid reactive substances in the amygdala and hippocampus, respectively (p < .05). HIIT maintained these parameters at levels similar to those in NT animals. HIIT improved anxiety and memory outcomes altered by PD (p < .05).

CONCLUSIONS

HIIT attenuates systemic inflammation, anxiety and memory outcomes promoted by PD.

The role of Toll-like receptors in neuropsychiatric disorders: Immunopathology, treatment, and management

Neuropsychiatric disorders denote a broad range of illnesses involving neurology and psychiatry. These disorders include depressive disorders, anxiety, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, autism spectrum disorders, headaches, and epilepsy. In addition to their main neuropathology that lies in the central nervous system (CNS), lately, studies have highlighted the role of immunity and neuroinflammation in neuropsychiatric disorders. Toll-like receptors (TLRs) are innate receptors that act as a bridge between the innate and adaptive immune systems via adaptor proteins (e.g., MYD88) and downstream elements; TLRs are classified into 13 families that are involved in normal function and illnesses of the CNS. TLRs expression affects the course of neuropsychiatric disorders, and is influenced during their pharmacotherapy; For example, the expression of multiple TLRs is normalized during the major depressive disorder pharmacotherapy. Here, the role of TLRs in neuroimmunology, treatment, and management of neuropsychiatric disorders is discussed. We recommend longitudinal studies to comparatively assess the cell-type-specific expression of TLRs during treatment, illness progression, and remission. Also, further research should explore molecular insights into TLRs regulation and related pathways.

Bibliometric Analysis and Visualization of Clinical Trials on Psychological Stress and Oral Health (1967-2024)

Stress is ubiquitous in modern life, influencing various facets of human health and well-being. While the impact of stress on mental and physical health is well-documented, its effects on oral health have garnered increasing attention in recent years. This bibliometric analysis explores the literature on the impact of stress on oral health. The study utilizes data from the PubMed database, focusing on publication trends, influential contributors and the temporal analysis of their publications, coauthorship analysis of authors and institutions, key thematic clusters, thematic evolution, and collaboration between various countries. Examining clinical trials investigating the impact of stress on oral health unveils significant trends and insights. Over time, there has been a steady rise in publication frequency, although with occasional fluctuations, indicating an increasing interest in the subject. The University of California has been identified as a leading institution, while Psychoneuroendocrinology emerges as a pivotal journal for disseminating research findings in the field. Keyword analysis reveals diverse thematic clusters, reflecting the multifaceted nature of the impact of stress on oral health. The analysis of topic trends showcases significant shifts over different periods, from basic correlations between mental health conditions and physiological indicators to a broader exploration of psychological interventions and social contexts in recent years. Thematic evolution analysis further elucidates this progression, categorizing themes into motor, basic, niche, and emerging or declining categories. Additionally, the analysis of corresponding authors' countries uncovers patterns of collaborative efforts, with the United States leading in collaboration levels. In summary, these analyses collectively highlight an evolving comprehension of the impact of stress on oral health, providing valuable insights for clinical practice and guiding future research endeavors.

Increased IgA-mediated responses to the gut paracellular pathway and blood-brain barrier proteins predict delirium due to hip fracture in older adults

Introduction

Delirium is accompanied by immune response system activation, which may, in theory, cause a breakdown of the gut barrier and blood-brain barrier (BBB). Some results suggest that the BBB is compromised in delirium, but there is no data regarding the gut barrier. This study investigates whether delirium is associated with impaired BBB and gut barriers in elderly adults undergoing hip fracture surgery.

Methods

We recruited 59 older adults and measured peak Delirium Rating Scale (DRS) scores 2-3 days after surgery, and assessed plasma IgG/IgA levels (using ELISA techniques) for zonulin, occludin, claudin-6, β-catenin, actin (indicating damage to the gut paracellular pathway), claudin-5 and S100B (reflecting BBB damage), bacterial cytolethal distending toxin (CDT), LPS-binding protein (LBP), lipopolysaccharides (LPS), Porphyromonas gingivalis, and Helicobacter pylori.

Results

Results from univariate analyses showed that delirium is linked to increased IgA responses to all the self-epitopes and antigens listed above, except for LPS. Part of the variance (between 45-48.3%) in the peak DRS score measured 2-3 days post-surgery was explained by independent effects of IgA directed to LPS and LBP (or bacterial CDT), baseline DRS scores, and previous mild stroke. Increased IgA reactivity to the paracellular pathway and BBB proteins and bacterial antigens is significantly associated with the activation of M1 macrophage, T helper-1, and 17 cytokine profiles.

Conclusion

Heightened bacterial translocation, disruption of the tight and adherens junctions of the gut and BBB barriers, elevated CDT and LPS load in the bloodstream, and aberrations in cell-cell interactions may be risk factors for delirium.

Analysis of influencing factors of anxiety and depression in patients with periodontitis

BACKGROUND

Periodontitis is a chronic oral disease caused by pathogenic microorganisms that corrode tooth tissue, form periodontal pockets, absorb alveolar bone, and finally lead to tooth loss. During treatment, patients are prone to anxiety, tension, and other negative emotions, which affect their ability to face the disease and may also lead to aggravation of the original condition and affect oral health. Therefore, it is important to improve the negative psychology of patients with periodontitis to clarify the factors that may lead to negative psychological emotions.

AIM

To investigate the risk factors that may lead to anxiety and depression in patients with periodontitis.

METHODS

One hundred patients with periodontitis were selected between March 2022 and March 2023 at our hospital. All patients were assessed with the Zung Self-rating Depression Scale (SDS) (≥ 53 points indicate a depressive state) and Zung Self-rating Anxiety Scale (SAS) (≥ 50 points indicates an anxious state). In this study, patients who experienced anxiety or depression were included in the occurrence group and those without anxiety or depression were included in the non-occurrence group. The baseline data of the two groups were compared to explore the risk factors for anxiety and depression in patients with periodontitis.

RESULTS

A total of 100 patients with periodontitis were included in this study. According to the SDS, 38 patients (38.00%) developed depression, with an average SDS score of (68.52 ± 5.85) points. According to the SAS, 40 patients (40.00%) developed anxiety, and the average SAS score was (72.15 ± 4.15) points. In this study, 56 patients with anxiety or depression were included. Compared with the non-occurrence group, the occurrence group had higher ages (≥ 60 years), lower level of hope (low level), educational level (high school or below), disease perception (poor), and sleep disorder (yes). The negative coping dimension scores of the simplified coping style questionnaire (SCSQ) and Dental Fear Scale (DFS) in the occurrence group were higher, whereas the score of the positive coping dimension of the SCSQ was significantly lower (P < 0.05). There were no significant differences in the other data between the groups (P > 0.05). The results of multiple logistics regression analysis showed that age (≥ 60 years), level of hope (low level), educational level (high school or below), disease perception (poor), sleep disorder (yes), high negative coping dimension scores of SCSQ, high score of DFS, and low positive coping dimension scores of SCSQ were all factors contributing to the anxiety and depression in patients with periodontitis (odds ratio > 1, P < 0.05).

CONCLUSION

Age, hope level, educational level, disease perception, sleep disorders, coping style, and dental fear were all associated with anxiety and depression in patients with periodontitis.

Periodontitis salivary microbiota exacerbates colitis-induced anxiety-like behavior via gut microbiota

The gut-brain axis is a bidirectional communication system between the gut and central nervous system. Many host-related factors can affect gut microbiota, including oral bacteria, making the brain a vulnerable target via the gut-brain axis. Saliva contains a large number of oral bacteria, and periodontitis, a common oral disease, can change the composition of salivary microbiota. However, the role and mechanism of periodontitis salivary microbiota (PSM) on the gut-brain axis remain unclear. Herein, we investigated the nature and mechanisms of this relationship using the mice with dextran sulfate sodium salt (DSS)-induced anxiety-like behavior. Compared with healthy salivary microbiota, PSM worsened anxiety-like behavior; it significantly reduced the number of normal neurons and activated microglia in DSS mice. Antibiotic treatment eliminated the effect of PSM on anxiety-like behavior, and transplantation of fecal microbiota from PSM-gavaged mice exacerbated anxiety-like behavior. These observations indicated that the anxiety-exacerbating effect of PSM was dependent on the gut microbiota. Moreover, the PSM effect on anxiety-like behavior was not present in non-DSS mice, indicating that DSS treatment was a prerequisite for PSM to exacerbate anxiety. Mechanistically, PSM altered the histidine metabolism in both gut and brain metabolomics. Supplementation of histidine-related metabolites had a similar anxiety-exacerbating effect as that of PSM, suggesting that histidine metabolism may be a critical pathway in this process. Our results demonstrate that PSM can exacerbate colitis-induced anxiety-like behavior by directly affecting the host gut microbiota, emphasizing the importance of oral diseases in the gut-brain axis.

Salivary signatures of oral-brain communication in sleep bruxers

Introduction

Microbiota and their interaction with hosts have been of great interest in brain research in recent years. However, the role of oral microbiota in mental illness and the underlying mechanism of oral-brain communication remains elusive. Sleep bruxism (SB) is an oral parafunctional activity related to the nervous system and is considered a risk factor for harmful clinical consequences and severe systemic conditions. Exploring the connection between oral microbiota and sleep bruxism may deepen our understanding of the complex relationship between oral-brain axis and provide insights for treatment.

Methods

In this study, salivary samples were collected from 22 individuals with SB and 21 healthy controls, and metagenomics with metabolomics was performed. Nonparametric Wilcoxon test were applied for the statistical analysis between the two groups. Microbial dysbiosis and altered oral metabolites were found in the SB individuals.

Results

The characteristic metabolite N-acetylglucosamine (GlcNAc) (VIP=8.4823, P<0.05) was correlated to a statistically lower Streptococcus mitis level in SB individuals. Salivary IFN-g level and IFN-g/IL-4 ratio were detected with significant changes in a chip assay. Amino acid metabolism pathways were upregulated, and the pathway with the largest number of differentially expressed genes is related to amino-tRNA charging pathway, while the most significantly enriched pathway is related to arginine biosynthesis. Neurotransmitter-associated pathways with glutamatergic and GABAergic synapses and cardiovascular system-related pathways were enriched in the SB group.

Discussion

These results indicate a possible neuroimmune regulatory network of oral-brain communication in SB, which helps explain the mechanism of the oral microbiome with the host in sleep bruxers and provides a reference for early clinical and therapeutic intervention to improve the diagnosis and treatment of SB and similar diseases.

Alterations of the salivary microbiota in gastroesophageal reflux disease

OBJECTIVES

Gastroesophageal reflux disease (GERD) is among the most prevalent gastrointestinal disorders. The oral microbiota plays an important role in human health and may be altered by the presence of GERD. Here, we aimed to investigate the alterations of salivary microbiota in GERD patients.

METHODS

We collected clinical information and salivary samples from 60 individuals. All participants underwent combined pH/impedance monitoring measurement and submitted samples for salivary microbiota sequencing. According to acid exposure time and DeMeester score, participants were divided into two groups: GERD + (Group G) and GERD - (Group C).

RESULTS

There was no significant difference in alpha diversity between study groups. Regarding beta diversity, principal coordinate analysis plots indicated that the microbiota composition data of the participants were grouped within partial overlapping clusters. The statistical analysis of the distance matrices was performed using the Adonis test (p = 0.017). Based on linear discriminant analysis effect size, the relative abundances of the phylum Bacteroidetes, class Bacteroidia, order Bacteroidales, family Prevotellaceae, and genus unidentified_Prevotellaceae were enriched in Group G. Compared with Group C, the phylum Actinobacteria, classes unidentified_Actinobacteria and Bacilli, orders Micrococcales and Lactobacillales, families Micrococcaceae and Streptococcaceae, and genuses Rothia and Streptococcus were decreased in Group G. At the genus level, the abundances of Streptococcus and Rothia were negatively correlated with DeMeester score and acid exposure time.

CONCLUSIONS

This study revealed alterations of the salivary microbiota in GERD patients, suggesting that acid reflux changes the oral ecosystem.

Mendelian randomization studies of depression: evidence, opportunities, and challenges

BACKGROUND

Major depressive disorder (MDD) poses a significant social and economic burden worldwide. Identifying exposures, risk factors, and biological mechanisms that are causally connected to MDD can help build a scientific basis for disease prevention and development of novel therapeutic approaches.

METHODS

In this systematic review, we assessed the evidence for causal relationships between putative causal risk factors and MDD from Mendelian randomization (MR) studies, following PRISMA. We assessed methodological quality based on key elements of the MR design: use of a full instrumental variable analysis and validation of the three key MR assumptions.

RESULTS

We included methodological details and results from 52 articles. A causal link between lifestyle, metabolic, inflammatory biomarkers, particular pathological states and MDD is supported by MR investigations, although results for each category varied substantially.

CONCLUSIONS

While this review shows how MR can offer useful information for examining prospective treatment targets and better understanding the pathophysiology of MDD, some methodological flaws in the existing literature limit reliability of results and probably underlie their heterogeneity. We highlight perspectives and recommendations for future works on MR in psychiatry.

Genetically predicted causal associations between periodontitis and psychiatric disorders

BACKGROUND

Psychiatric disorders have serious harm to individuals' lives with high disease burden. Observational studies reported inconsistent associations between periodontitis and some psychiatric disorders, and the causal correlations between them remain unknown.

OBJECTIVE

This study aims to explore the causal associations between periodontitis and psychiatric disorders.

METHODS

A series of two-sample Mendelian randomisation (MR) analyses were employed using genome-wide association study summary statistics for periodontitis in adults from Gene-Lifestyle Interactions in Dental Endpoints Consortium and 10 psychiatric disorders from Psychiatric Genomics Consortium. Causal effects were primarily estimated using the inverse-variance weighted (IVW) method. Various sensitivity analyses were also conducted to assess the robustness of our results.

FINDINGS

The MR analysis suggested that genetically determined periodontitis was not causally associated with 10 psychiatric disorders (IVW, all p>0.089). Furthermore, the reverse MR analysis revealed that 10 psychiatric disorders had no causal effect on periodontitis (IVW, all p>0.068). We discovered that all the results were consistent in the four MR analytical methods, including the IVW, MR-Egger, weighted median and weighted mode. Besides, we did not identify any heterogeneity or horizontal pleiotropy in the sensitivity analysis.

CONCLUSIONS

These results do not support bidirectional causal associations between genetically predicted periodontitis and 10 common psychiatric disorders. Potential confounders might contribute to the previously observed associations.

CLINICAL IMPLICATIONS

Our findings might alleviate the concerns of patients with periodontitis or psychiatric disorders. However, further research was warranted to delve into the intricate relationship between dental health and mental illnesses.

Association between oral microbial dysbiosis and poor functional outcomes in stroke-associated pneumonia patients

BACKGROUND

Despite advances in our understanding of the critical role of the microbiota in stroke patients, the oral microbiome has rarely been reported to be associated with stroke-associated pneumonia (SAP). We sought to profile the oral microbial composition of SAP patients and to determine whether microbiome temporal instability and special taxa are associated with pneumonia progression and functional outcomes.

METHODS

This is a prospective, observational, single-center cohort study that examined patients with acute ischemic stroke (AIS) who were admitted within 24 h of experiencing a stroke event. The patients were divided into three groups based on the occurrence of pneumonia and the use of mechanical ventilation: nonpneumonia group, SAP group, and ventilator-associated pneumonia (VAP) group. We collected oral swabs at different time points post-admission and analyzed the microbiota using 16 S rRNA high-throughput sequencing. The microbiota was then compared among the three groups.

RESULTS

In total, 104 nonpneumonia, 50 SAP and 10 VAP patients were included in the analysis. We found that SAP and VAP patients exhibited significant dynamic differences in the diversity and composition of the oral microbiota and that the magnitude of this dysbiosis and instability increased during hospitalization. Then, by controlling the potential effect of all latent confounding variables, we assessed the changes associated with pneumonia after stroke and explored patients with a lower abundance of Streptococcus were more likely to suffer from SAP. The logistic regression analysis revealed that an increase in specific taxa in the phylum Actinobacteriota was linked to a higher risk of poor outcomes. A model for SAP patients based on oral microbiota could accurately predict 30-day clinical outcomes after stroke onset.

CONCLUSIONS

We concluded that specific oral microbiota signatures could be used to predict illness development and clinical outcomes in SAP patients. We proposed the potential of the oral microbiota as a non-invasive diagnostic biomarker in the clinical management of SAP patients.

CLINICAL TRIAL REGISTRATION

NCT04688138. Registered 29/12/2020, https://clinicaltrials.gov/ct2/show/NCT04688138 .

Emerging role of the host microbiome in neuropsychiatric disorders: overview and future directions

The human body harbors a diverse ecosystem of microorganisms, including bacteria, viruses, and fungi, collectively known as the microbiota. Current research is increasingly focusing on the potential association between the microbiota and various neuropsychiatric disorders. The microbiota resides in various parts of the body, such as the oral cavity, nasal passages, lungs, gut, skin, bladder, and vagina. The gut microbiota in the gastrointestinal tract has received particular attention due to its high abundance and its potential role in psychiatric and neurodegenerative disorders. However, the microbiota presents in other body tissues, though less abundant, also plays crucial role in immune system and human homeostasis, thus influencing the development and progression of neuropsychiatric disorders. For example, oral microbiota imbalance and associated periodontitis might increase the risk for neuropsychiatric disorders. Additionally, studies using the postmortem brain samples have detected the widespread presence of oral bacteria in the brains of patients with Alzheimer's disease. This article provides an overview of the emerging role of the host microbiota in neuropsychiatric disorders and discusses future directions, such as underlying biological mechanisms, reliable biomarkers associated with the host microbiota, and microbiota-targeted interventions, for research in this field.

The Role of the Gut Microbiome in Bipolar Disorder and its Common Comorbidities

Bipolar disorder is a decidedly heterogeneous and multifactorial disease, with significant psychosocial and medical disease burden. Much difficulty has been encountered in developing novel therapeutics and objective biomarkers for clinical use in this population. In that regard, gut-microbial homeostasis appears to modulate several key pathways relevant to a variety of psychiatric, metabolic, and inflammatory disorders. Microbial impact on immune, endocrine, endocannabinoid, kynurenine, and other pathways are discussed throughout this review. Emphasis is placed on this system's relevance to current pharmacology, diet, and comorbid illness in bipolar disorder. Despite the high level of optimism promoted in many reviews on this topic, substantial obstacles exist before any microbiome-related findings can provide meaningful clinical utility. Beyond a comprehensive overview of pathophysiology, this review hopes to highlight several key areas where progress is needed. As well, novel microbiome-associated suggestions are presented for future research.

Neuroinflammation related to the blood-brain barrier and sphingosine-1-phosphate in a pre-clinical model of periodontal diseases and depression in rats

AIM

To explore the potential mechanisms of neuroinflammation (microglia, blood-brain barrier [BBB] permeability, and the sphingosine-1-phosphate [S1P] pathways) resulting from the association between periodontitis and depression in rats.

MATERIALS AND METHODS

This pre-clinical in vivo experimental study used Wistar rats, in which experimental periodontitis (P) was induced by using oral gavages with Porphyromonas gingivalis and Fusobacterium nucleatum. Then, a chronic mild stress (CMS) model was implemented to induce a depressive-like behaviour, resulting in four groups: P with CMS (P+CMS+), P without CMS (P+CMS-), CMS without P (P-CMS+), and control (P-CMS-). After harvesting brain samples, protein/mRNA expression analyses and fluorescence immunohistochemistry were performed in the frontal cortex (FC). Results were analysed by ANOVA.

RESULTS

CMS exposure increased the number of microglia (an indicator of neuroinflammation) in the FC. In the combined model (P+CMS+), there was a decrease in the expression of tight junction proteins (zonula occludens-1 [ZO-1], occludin) and an increase in intercellular and vascular cell adhesion molecules (ICAM-1, VCAM-1) and matrix metalloproteinase 9 (MMP9), suggesting a more severe disruption of the BBB. The enzymes and receptors of S1P were also differentially regulated.

CONCLUSIONS

Microglia, BBB permeability, and S1P pathways could be relevant mechanisms explaining the association between periodontitis and depression.

Impact of local predisposing/precipitating factors and systemic drivers on peri‐implant diseases

BACKGROUND

Strong evidence suggests the infectious nature of peri-implant diseases occurring in susceptible hosts. Epidemiological reports, though, indicate that peri-implantitis is a site-specific entity. Hence, the significance of local factors that may predispose/precipitate plaque accumulation and the impact of systemic drivers that alter the immune response are relevant in the prevention and management of peri-implant disorders.

PURPOSE

The purpose of the present review is to shed light on the significance of local and systemic factors on peri-implant diseases, making special emphasis on the associations with peri-implantitis.

METHODS

The biologic plausibility and supporting evidence aiming at providing a concluding remark were explored in the recent scientific literature for local predisposing/precipitating factors and systemic drivers related to peri-implant diseases.

RESULTS

Local predisposing factors such as soft tissue characteristics, implant position and prosthetic design proved being strongly associated with the occurrence of peri-implant diseases. Hard tissue characteristics, however, failed to demonstrate having a direct association with peri-implant diseases. Robust data points toward the strong link between residual sub-mucosal cement and peri-implant diseases, while limited data suggests the impact of residual sub-mucosal floss and peri-implantitis. Systemic drivers/habits such as hyperglycemia and smoking showed a strong negative impact on peri-implantitis. However, there is insufficient evidence to claim for any link between metabolic syndrome, atherosclerotic cardiovascular disease, and obesity and peri-implant diseases.

CONCLUSION

Local predisposing/precipitating factors and systemic drivers may increase the risk of peri-implant diseases. Therefore, comprehensive anamnesis of the patients, educational/motivational programs and exhaustive prosthetically-driven treatment planning must be fostered aiming at reducing the rate of biological complications in implant dentistry.

Healthy microbiome – a mere idea or a sound concept?

Hundreds of studies in last decades have aimed to compare the microbiome of patients suffering from diverse diseases with that of healthy controls. The microbiome-related component was additionally identified in pathophysiology of many diseases formerly considered to depend only on the host physiology. This, however, opens important questions like: “What is the healthy microbiome?” or “Is it possible to define it unequivocally?”. In this review, we describe the main hindrances complicating the definition of “healthy microbiome” in terms of microbiota composition. We discuss the human microbiome from the perspective of classical ecology and we advocate for the shift from the stress on microbiota composition to the functions that microbiome ensures for the host. Finally, we propose to leave the concept of ideal healthy microbiome and replace it by focus on microbiome advantageous for the host, which always depends on the specific context like the age, genetics, dietary habits, body site or physiological state.

Healthy microbiome - a mere idea or a sound concept?

Hundreds of studies in last decades have aimed to compare the microbiome of patients suffering from diverse diseases with that of healthy controls. The microbiome-related component was additionally identified in pathophysiology of many diseases formerly considered to depend only on the host physiology. This, however, opens important questions like: "What is the healthy microbiome?" or "Is it possible to define it unequivocally?". In this review, we describe the main hindrances complicating the definition of "healthy microbiome" in terms of microbiota composition. We discuss the human microbiome from the perspective of classical ecology and we advocate for the shift from the stress on microbiota composition to the functions that microbiome ensures for the host. Finally, we propose to leave the concept of ideal healthy microbiome and replace it by focus on microbiome advantageous for the host, which always depends on the specific context like the age, genetics, dietary habits, body site or physiological state.

Mental health and periodontal and peri-implant diseases

Mental health disorders, particularly depression and anxiety, affect a significant number of the global population. Several pathophysiological pathways for these disorders have been identified, including the hypothalamic-pituitary-adrenal axis, autonomic nervous system, and the immune system. In addition, life events, environmental factors, and lifestyle affect the onset, progression, and recurrence of mental health disorders. These may all overlap with periodontal and/or peri-implant disease. Mental health disorders are associated with more severe periodontal disease and, in some cases, poorer healing outcomes to nonsurgical periodontal therapy. They can result in behavior modification, such as poor oral hygiene practices, tobacco smoking, and alcohol abuse, which are also risk factors for periodontal disease and, therefore, may have a contributory effect. Stress has immunomodulatory effects regulating immune cell numbers and function, as well as proinflammatory cytokine production. Stress markers such as cortisol and catecholamines may modulate periodontal bacterial growth and the expression of virulence factors. Stress and some mental health disorders are accompanied by a low-grade chronic inflammation that may be involved in their relationship with periodontal disease and vice versa. Although the gut microbiome interacting with the central nervous system (gut-brain axis) is thought to play a significant role in mental illness, less is understood about the role of the oral microbiome. The evidence for mental health disorders on implant outcomes is lacking, but may mainly be through behaviourial changes. Through lack of compliance withoral hygiene and maintenance visits, peri-implant health can be affected. Increased smoking and risk of periodontal disease may also affect implant outcomes. Selective serotonin reuptake inhibitors have been linked with higher implant failure. They have an anabolic effect on bone, reducing turnover, which could account for the increased loss.

No bidirectional relationship between depression and periodontitis: A genetic correlation and Mendelian randomization study

Background

Observational and in-vivo research suggested a bidirectional relationship between depression and periodontitis. We estimated the genetic correlation and examined directionality of causation.

Methods

The study used summary statistics from published genome wide association studies, with sample sizes ranging from 45,563 to 797,563 individuals of European ancestry. We performed linkage disequilibrium score regression (LDSC) to estimate global correlation and used Heritability Estimation from Summary Statistics (ρ-HESS) to further examine local genetic correlation. Latent Heritable Confounder Mendelian randomization (LHC-MR), Causal Analysis using Summary Effect estimates (CAUSE), and conventional MR approaches assessed bidirectional causation.

Results

LDSC observed only weak genetic correlation (r_g = 0.06, P-Value = 0.619) between depression and periodontitis. Analysis of local genetic correlation using ρ-HESS did not reveal loci of significant local genetic covariance. LHC-MR, CAUSE and conventional MR models provided no support for bidirectional causation between depression and periodontitis, with odds ratios ranging from 1.00 to 1.06 in either direction.

Conclusions

Results do not support shared heritability or a causal connection between depression and periodontitis.

A genetic association study reveals the relationship between the oral microbiome and anxiety and depression symptoms

BACKGROUND

Growing evidence supports that alterations in the gut microbiota play an essential role in the etiology of anxiety, depression, and other psychiatric disorders. However, the potential effect of oral microbiota on mental health has received little attention.

METHODS

Using the latest genome-wide association study (GWAS) summary data of the oral microbiome, polygenic risk scores (PRSs) of 285 salivary microbiomes and 309 tongue dorsum microbiomes were conducted. Logistic and linear regression models were applied to evaluate the relationship between salivary-tongue dorsum microbiome interactions with anxiety and depression. Two-sample Mendelian randomization (MR) was utilized to compute the causal effects between the oral microbiome, anxiety, and depression.

RESULTS

We observed significant salivary-tongue dorsum microbiome interactions related to anxiety and depression traits. Significantly, one common interaction was observed to be associated with both anxiety score and depression score, Centipeda periodontii SGB 224 × Granulicatella uSGB 3289 (P _{depressionscore} = 1.41 × 10^-8, P _anxietyscore = 5.10 × 10^-8). Furthermore, we detected causal effects between the oral microbiome and anxiety and depression. Importantly, we identified one salivary microbiome associated with both anxiety and depression in both the UKB database and the Finngen public database, Eggerthia (P _{IVW - majordepression - UKB} = 2.99 × 10^-6, P _{IVW - Self - reportedanxiety/panicattacks - UKB} = 3.06 × 10^-59, P _{IVW - depression - Finngen} = 3.16 × 10 , - 16 P _{IVW - anxiety - Finngen} = 1.14 × 10^-115).

CONCLUSION

This study systematically explored the relationship between the oral microbiome and anxiety and depression, which could help improve our understanding of disease pathogenesis and propose new diagnostic targets and early intervention strategies.