Periodontal disease as a possible cause for Alzheimer's disease

Membrane-anchoring selenophene viologens for antibacterial photodynamic therapy against periodontitis via restoring subgingival flora and alleviating inflammation

Antibacterial photodynamic therapy (aPDT) has emerged as a promising strategy for treating periodontitis. However, the weak binding of most photosensitizers to bacteria and the hypoxic environment of periodontal pockets severely hamper the therapeutic efficacy. Herein, two novel oxygen-independent photosensitizers are developed by introducing selenophene into viologens and modifying with hexane chains (HASeV) or quaternary ammonium chains (QASeV), which improve the adsorption to bacteria through anchoring to the negatively charged cell membrane. Notably, QASeV binds only to the bacterial surface of Porphyromonas gingivalis and Fusobacterium nucleatum due to electrostatic binding, but HASeV can insert into their membrane by strong hydrophobic interactions. Therefore, HASeV exhibits superior antimicrobial activity and more pronounced plaque biofilm disruption than QASeV when combined with light irradiation (MVL-210 photoreactor, 350-600 nm, 50 mW/cm2), and a better effect on reducing the diversity and restoring the structure of subgingival flora in periodontitis rat model was found through 16S rRNA gene sequencing analysis. The histological and Micro-CT analyses reveal that HASeV-based aPDT has a better therapeutic effect in reducing periodontal tissue inflammation and alveolar bone resorption. This work provides a new strategy for the development of viologen-based photosensitizers, which may be a favorable candidate for the aPDT against periodontitis.

The importance of mechanosensitive cell mediated prostaglandin and nitric oxide synthesis in the pathogenesis of apical periodontitis: comparative with chronic periodontitis

OBJECTIVES

Mechano-sensitive odontoblast cells, which sense mechanical loading and various stresses in the tooth structure, synthesize early signaling molecules such as prostaglandin E2 (PGE2) and nitric oxide (NO) as an adaptive response. It is thought that these synthesized molecules can be used for the diagnosis and treatment of periodontal and periapical diseases. The aim of this study was to investigate the relationship between the severity of apical periodontitis (AP) and chronic periodontitis (CP) and serum (s) TNF-α, IL-10, PGE2 and NO levels, as well as PGE2 and NO levels in gingival crevicular fluid (GCF) samples.

MATERIALS & METHODS

A total of 185 subjects were divided into three categories: AP group (n = 85), CP group (n = 50) and healthy control group (n = 50). The AP group was divided into 3 subgroups according to abscess scoring (AS-PAI 1, 2 and 3) based on the periapical index. The CP group was divided into 4 subgroups according to the periodontitis staging system (PSS1, 2,3 and 4). After recording the demographic and clinical characteristics of all participants, serum (s) and gingival crevicular fluid (GCF) samples were taken. TNF-α, IL-10, PGE2 and NO levels were measured in these samples.

RESULTS

Unlike serum measurements (sTNF-α, sIL-10, sNO and sPGE2), GCF-NO and GCF-PGE levels of the AP group were significantly higher than the control group in relation to abscess formation (54.4 ± 56.3 vs. 22.5 ± 12.6 µmol/mL, p < 0.001 and 100 ± 98 vs. 41 ± 28 ng/L, p < 0.001, respectively). Confirming this, the GCF-NO and GCF-PGE levels of the AS-PAI 1 group, in which abscesses have not yet formed, were found to be lower than those in AS-PAI 2 and 3, which are characterized by abscess formation [(16.7(3.7-117.8), 32.9(11.8-212.8) and 36.9(4.3-251.6) µmol/mL, p = 0,0131; 46.0(31.4-120.0), 69.6(40.3-424.2) and 74.4(32.1-471.0) ng/L, p = 0,0020, respectively]. Consistent with the increase in PSS, the levels of sTNF [29.8 (8.2-105.5) vs. 16.7(6.3-37.9) pg/mL, p < 0.001], sIL-10 [542(106-1326) vs. 190(69-411) pg/mL, p < 0.001], sNO [182.1(36.3-437) vs. 57.0(15.9-196) µmol/mL, p < 0.001], sPGE2 [344(82-1298) vs. 100(35-1178) ng/L, p < 0.001], GCF-NO [58.9 ± 33.6 vs. 22.5 ± 12.6 ng/L, p < 0.001] and GCF-PGE2 [ 99(37-365) vs. 30(13-119), p < 0.001] in the CP group were higher than the control group. Comparison ROC analysis revealed that the GCF-PGE2 test had the best diagnostic value for both AP and CP (sensitivity: 94.1 and 88.0; specificity: 64.0 and 78.0, respectively; p < 0.001).

CONCLUSIONS

GCF-PE2 and GCF-NO have high diagnostic value in the determination of AP and CP, and can be selected as targets to guide treatment. In addition, the measurements of PGE2 and NO in GCF can be used as an important predictor of pulpal necrosis leading to abscess in patients with AP.

CLINICAL RELEVANCE

In this article, it is reported that syntheses of early signaling molecules such as PGE2 and NO can be used for the diagnosis and treatment target of periapical and periodontal infections.

The impact of systemic administration of polyphenols on periodontitis associated with diabetes mellitus: a systematic review

OBJECTIVE

The aim of this work was to explore the potential of polyphenol supplement consumption in enhancing the treatment of periodontitis and diabetes mellitus in both diabetic animals and humans.

MATERIALS AND METHODS

A comprehensive search across eight databases (MEDLINE, EBSCO, Taylor & Francis, PRIMO, Web of Science, Wiley Online Library, ScienceDirect, and SAGE Journals) and two registers (ClinicalTrials.gov and Cochrane Library Trials) was conducted. Methodological quality assessment employed the Cochrane Collaboration Risk of Bias Assessment Tool for randomised controlled trials and the Systematic Review Centre for Laboratory Animal Experimentation Risk of Bias Tool for experimental animal studies.

RESULTS

Ten articles meeting inclusion criteria were identified. Three clinical studies demonstrated significant reductions in probing depth (PD) and clinical attachment loss (CAL). Ginger supplementation showed a decrease in CAL (-0.57 ± 0.50 vs. -0.14 ± 0.35, p = 0.003) and PD (-0.52 ± 0.51 vs. -0.19 ± 0.51, p = 0.04), while resveratrol supplementation exhibited a reduction in PD (-1.1 ± 0.58 vs. -0.6 ± 0.47, p < 0.001). Additionally, cranberry juice supplementation led to a decrease in PD (-0.56 ± 0.03, p < 0.001). However, there was no significant improvement in inflammation status. Although polyphenol supplementation did not impact fasting blood glucose levels, it did result in improved insulin resistance (3.66 ± 0.97 vs. 4.49 ± 1.56, p = 0.045). In diabetic animals, six studies reported a significant reduction (p < 0.05) in bone loss along with marked improvements in inflammation status.

CONCLUSIONS

Despite the promising results observed in the included studies, the overall evidence supporting the positive effects of polyphenols on periodontal and diabetes mellitus status, along with their anti-inflammatory properties, remains inadequate.

Patient awareness of the association between periodontal and systemic diseases in an academic setting

BACKGROUND

Periodontal diseases (PD) have been increasingly associated with several systemic conditions such as cardiovascular disease (CVD), diabetes mellitus (DM), rheumatoid arthritis (RA), and Alzheimer's disease (AD). This study aimed to gain insight into patients' awareness of the association between PD and systemic diseases.

METHODS

A survey was developed to analyze patient awareness of the association between PD and systemic diseases. Descriptive and categorical variables were summarized with counts and percentages. Chi-squared tests were used to evaluate differences between variables. A linear logistical regression model was used to assess the simultaneous, independent association between each variable.

RESULTS

Data from 161 completed surveys were analyzed. The majority of the participants (61.49%) reported awareness of symptoms of PD, but only 36.36% identified all its major symptoms. Individuals reporting awareness of the association between PD and systemic diseases was 48.4%, 31.7%, 14.9%, and 9.9% for CVD, DM, RA, and AD, respectively. Patients aged ≥51 years and males were more aware of the association between PD and CVD. Increased awareness of an association between PD and DM was observed among patients who had a higher frequency of dental visits and those with a self-reported history of DM.

CONCLUSIONS

This study provides insight that, even with the vast amount of scientific knowledge on the inter-relationships that exist between PD and systemic diseases, most patients are still unaware of these associations. This research identified that improvement of health literacy surrounding PD, their symptoms, and their association with systemic diseases may be warranted.

Periodontitis and brain magnetic resonance imaging markers of Alzheimer's disease and cognitive aging

INTRODUCTION

We examined the association of clinical, microbiological, and host response features of periodontitis with MRI markers of atrophy/cerebrovascular disease in the Washington Heights Inwood Columbia Aging Project (WHICAP) Ancillary Study of Oral Health.

METHODS

We analyzed 468 participants with clinical periodontal data, microbial plaque and serum samples, and brain MRIs. We tested the association of periodontitis features with MRI features, after adjusting for multiple risk factors for Alzheimer's disease/Alzheimer's disease-related dementia (AD/ADRD).

RESULTS

In fully adjusted models, having more teeth was associated with lower odds for infarcts, lower white matter hyperintensity (WMH) volume, higher entorhinal cortex volume, and higher cortical thickness. Higher extent of periodontitis was associated with lower entorhinal cortex volume and lower cortical thickness. Differential associations emerged between colonization by specific bacteria/serum antibacterial IgG responses and MRI outcomes.

DISCUSSION

In an elderly cohort, clinical, microbiological, and serological features of periodontitis were associated with MRI findings related to ADRD risk. Further investigation of causal associations is warranted.

Modulation of myeloid-derived suppressor cell functions by oral inflammatory diseases and important oral pathogens

The oral cavity presents a diverse microbiota in a dynamic balance with the host. Disruption of the microbial community can promote dysregulation of local immune response which could generate oral diseases. Additionally, alterations in host immune system can result in inflammatory disorders. Different microorganisms have been associated with establishment and progression of the oral diseases. Oral cavity pathogens/diseases can modulate components of the inflammatory response. Myeloid-derived suppressor cells (MDSCs) own immunoregulatory functions and have been involved in different inflammatory conditions such as infectious processes, autoimmune diseases, and cancer. The aim of this review is to provide a comprehensive overview of generation, phenotypes, and biological functions of the MDSCs in oral inflammatory diseases. Also, it is addressed the biological aspects of MDSCs in presence of major oral pathogens. MDSCs have been mainly analyzed in periodontal disease and Sjögren's syndrome and could be involved in the outcome of these diseases. Studies including the participation of MDSCs in other important oral diseases are very scarce. Major oral bacterial and fungal pathogens can modulate expansion, subpopulations, recruitment, metabolism, immunosuppressive activity and osteoclastogenic potential of MDSCs. Moreover, MDSC plasticity is exhibited in presence of oral inflammatory diseases/oral pathogens and appears to be relevant in the disease progression and potentially useful in the searching of possible treatments. Further analyses of MDSCs in oral cavity context could allow to understand the contribution of these cells in the fine-tuned balance between host immune system and microorganism of the oral biofilm, as well as their involvement in the development of oral diseases when this balance is altered.

Small Extracellular Vesicles Laden Oxygen-Releasing Thermosensitive Hydrogel for Enhanced Antibacterial Therapy against Anaerobe-Induced Periodontitis Alveolar Bone Defect

Periodontitis is a bacterially induced chronic destructive inflammatory disease that leads to irreversible destruction of the tooth supporting structure, including connective tissue destruction, bone resorption, and even tooth loss. Until now, there has been no effective treatment to repair inflammatory bone loss in periodontitis. Recently, small extracellular vesicles (sEVs) emerged as the essential paracrine factors of mesenchymal stem cells (MSCs) that mediated tissue regeneration. However, limitations of antimicrobial activity associated with the use of sEVs have led to the urgency of new alternative strategies. Currently, we investigated the potential of a biocompatible oxygen-releasing thermosensitive hydrogel laded with sEVs secreted by bone marrow MSCs (BMMSCs) for the alveolar bone defect in periodontitis. The hydrogel composed of different polymers such as chitosan (CS), poloxamer 407 (P407), and cross-linked hyaluronic acid (c-HA) conglomerating is a kind of nanoporous structure material. Then, the gel matrix further encapsulated sEVs and calcium peroxide nanoparticles to realize the control of sEVs and oxygen release. Furthermore, ascorbic acid was added to achieve the REDOX equilibrium and acid-base equilibrium. The experiments in vivo and in vitro proved its good biocompatibility and effectively inhibited the growth of the periodontal main anaerobe, relieved periodontal pocket anaerobic infections, and promoted the periodontal defect regeneration. Therefore, this finding demonstrated that it was a promising approach for combating anaerobic pathogens with enhanced and selective properties in periodontal diseases, even in other bacteria-induced infections, for future clinical application.

Lipoxin A4 levels predict site-specific clinical improvements post scaling and root planing and correlate negatively with periodontal pathogens in severe periodontitis

BACKGROUND

Serving as a stop signal of inflammation, the role of lipoxin A4 (LXA4) in periodontitis remains to be clarified. This study is aimed to examine the changes in LXA4 levels in gingival crevicular fluid (GCF) after scaling and root planing (SRP) and to determine the relationship between LXA4 levels and treatment outcomes and periodontal pathogens in severe periodontitis.

METHODS

A total of 74 GCF samples were collected from 21 severe periodontitis participants at the deepest affected sites. These sites were re-sampled at 1, 3, and 6 months after SRP. Besides, GCF samples were also collected from 25 periodontally healthy participants. Clinical parameters including probing depth (PD) and clinical attachment level (CAL) in periodontitis group were recorded. LXA4 levels and periodontal pathogens in the GCF were analyzed by ELISA and PCR, respectively. Correlations between GCF LXA4 levels and treatment effect and periodontal pathogens were assessed.

RESULTS

LXA4 levels in GCF significantly increased after SRP (p < 0.05), but remained lower than those observed in healthy individuals (p < 0.05). Sites with lower baseline LXA4 concentrations were more likely to experience greater improvements in PD at 6 months post-SRP (area under the curve [AUC] = 0.792), and the improvements were positively correlated with the increase of LXA4 at these sites post-treatment (p < 0.05). Furthermore, more elevated LXA4 levels were observed in sites that became negative for Prevotella intermedia or Tannerella forsythia after SRP.

CONCLUSION

Baseline LXA4 in GCF has the potential to predict the site-specific response of severe periodontal lesions to SRP. The increase of LXA4 levels after treatment was positively correlated with clinical improvements and negatively correlated with the presence of Prevotella intermedia or Tannerella forsythia.

[Teeth and oral cavity at the heart of systemic health]

Research into the interrelationships between oral and systemic diseases has been growing exponentially for over 20 years. Teeth and their supporting tissues can be affected by pathologies, particularly infectious ones, the consequences of which are felt locally in the oral cavity and at a distance in the body. Oral diseases frequently lead to the maintenance of an inflammatory state in oral bones and mucosa, which complicates the treatment of systemic inflammatory pathologies. The aim of this review is to take stock of current knowledge concerning the interrelationships that may exist between the oral environment and other organs, in both adults and children.

High-Throughput Combined Analysis of Saliva Microbiota and Metabolomic Profile in Chinese Periodontitis Patients: A Pilot Study

The onset and progression of periodontitis involves complicated interactions between the dysbiotic oral microbiota and disrupted host immune-inflammatory response, which can be mirrored by the changes in salivary metabolites profile. This pilot study sought to examine the saliva microbiome and metabolome in the Chinese population by the combined approach of 16s rRNA sequencing and high-throughput targeted metabolomics to discover potential cues for host-microbe metabolic interactions. Unstimulated whole saliva samples were collected from eighteen Stage III and IV periodontitis patients and thirteen healthy subjects. Full-mouth periodontal parameters were recorded. The taxonomic composition of microbiota was obtained by 16s rRNA sequencing, and the metabolites were identified and measured by ultra-high performance liquid chromatography and mass spectrometry-based metabolomic analysis. The oral microbiota composition displayed marked changes where the abundance of 93 microbial taxa differed significantly between the periodontitis and healthy group. Targeted metabolomics identified 103 differential metabolites between the patients and healthy individuals. Functional enrichment analysis demonstrated the upregulation of protein digestion and absorption, histidine metabolism, and nicotinate and nicotinamide metabolism pathways in the dysbiotic microbiota, while the ferroptosis, tryptophan metabolism, glutathione metabolism, and carbon metabolism pathways were upregulated in the patients. Correlation analysis confirmed positive relationships between the clinical parameters, pathogen abundances, and disease-related metabolite levels. The integral analysis of the saliva microbiome and metabolome yielded an accurate presentation of the dysbiotic oral microbiome and functional alterations in host-microbe metabolism. The microbial and metabolic profiling of the saliva could be a potential tool in the diagnosis, prognosis evaluation, and pathogenesis study of periodontitis.

Novel benzothiazole derivatives as multitargeted-directed ligands for the treatment of Alzheimer's disease

Neurodegenerative diseases such as Alzheimer's disease (AD) are multifactorial with several different pathologic mechanisms. Therefore, it is assumed that multitargeted-directed ligands (MTDLs) which interact with different biological targets relevant to the diseases, might offer an improved therapeutic alternative than using the traditional "one-target, one-molecule" approach. Herein, we describe new benzothiazole-based derivatives as a privileged scaffold for histamine H₃ receptor ligands (H₃R). The most affine compound, the 3-(azepan-1-yl)propyloxy-linked benzothiazole derivative 4b, displayed a K_i value of 0.012 μM. The multitargeting potential of these H₃R ligands towards AChE, BuChE and MAO-B enzymes was evaluated to yield compound 3s (pyrrolidin-1-yl-(6-((5-(pyrrolidin-1-yl)pentyl)oxy)benzo[d]thiazol-2-yl)methanone) as the most promising MTDL with a K_i value of 0.036 μM at H₃R and IC₅₀ values of 6.7 µM, 2.35 µM, and 1.6 µM towards AChE, BuChE, and MAO-B, respectively. These findings suggest that compound 3s can be a lead structure for developing new multi-targeting anti-AD agents.

The Effects of Antimicrobial Mouthwashes on Systemic Disease: What Is the Evidence?

The potential association between antimicrobial mouthwash use and systemic health has gained attention in recent years with reports highlighting how some common systemic conditions are influenced by the use of different types of mouthwashes. In this context, links between mouthwash use and cardiovascular disease, diabetes mellitus, oral cancer, Alzheimer's disease, and preeclampsia have been proposed, albeit with limited levels of evidence. Chlorhexidine mouthwash in particular has been the most widely studied agent while available data on other types of over-the-counter mouthwashes are generally scarce. Furthermore, there is currently no evidence-based recommendations on the appropriate use of mouthwashes during pregnancy. This article will present the current evidence on the association between mouthwash use and the aforementioned conditions with emphasis on the mechanisms that may underlie such an association.

Bacterial growth stage determines the yields, protein composition, and periodontal pathogenicity of Porphyromonas gingivalis outer membrane vesicles

Introduction

P. gingivalis (W83), as the keystone pathogen in chronic periodontitis, has been found to be tightly bound to systemic diseases. Outer membrane vesicles (OMVs) produced by P. gingivalis (W83) are thought to serve key functions in bacterial virulence and pathogenicity. This study aims to comprehend the biological functions of P. gingivalis OMVs isolated from different growth stages by comparing their physicochemical properties and pathogenicity.

Methods

Protein composition was analyzed via isotope-labeled relative and absolute quantification (iTRAQ). Macrophage polarization and the expression of IL-6 and IL-1β were detected. The proliferation, migration, osteogenic differentiation, and IL-1b/NLRP3 expression of periodontal ligament stem cells (PDLSCs) were evaluated. P. gingivalis/P. gingivalis OMVs-induced periodontal models were also constructed in Sprague Dawley rats.

Results

The protein composition of P. gingivalis OMVs isolated from different growth stages demonstrated obvious differences ranging from 25 KDa to 75 KDa. In the results of flow cytometry, we found that in vitro experiments the M1 subtype of macrophages was more abundant in the late-log OMVs and stationary OMVs groups which boosted the production of inflammatory cytokines more than pre-log OMVs. Compared to pre-log OMVs, late-log OMVs and stationary OMVs had more pronounced inhibitory effects on proliferation, migration, and early osteogenesis of PDLSCs. The NLRP3 inflammasome was activated to a larger extent in the stationary OMVs group. Micro-computed tomography (Micro CT), hematoxylin-eosin staining (HE), and tartrate acid phosphatase (TRAP) results showed that the periodontal damage in the stationary OMVs group was worse than that in the pre-log OMVs and late-log OMVs group, but almost equal to that in the positive control group (P. gingivalis).

Discussion

In general, both in vivo and in vitro experiments showed that late-log OMVs and stationary OMVs have more significant pathogenicity in periodontal disease.

The role of periodontitis-associated bacteria in Alzheimer's disease: A narrative review

Alzheimer's disease causes memory loss and dementia in older adults through a neurodegenerative mechanism. Despite the pathophysiological clarification of this cognitive disorder, novel molecular and cellular pathways should be identified to determine its exact mechanism. Alzheimer's disease (AD) is pathologically characterized by senile plaques comprising beta-amyloid and neurofibrillary tangles (NFTs) formed by hyperphosphorylated tau as a microtubule-associated protein with a key role in the pathogenesis of AD. Periodontitis through inflammatory pathways is a risk factor for deteriorating cognitive impairment in AD patients. Poor oral hygiene coupled with immunocompromised status in older adults causes periodontal diseases and chronic inflammations through an oral bacterial imbalance. Toxic bacterial products, including bacteria themselves, can reach the central nervous system through the bloodstream and evoke inflammatory responses. The present review was conducted to investigate relationships between AD and periodontitis-involved bacteria as a risk factor.

Effect of Periodontal Disease on Alzheimer's Disease: A Systematic Review

The aim of this review was to evaluate the relationship between periodontal disease (PD) and the onset and progression of Alzheimer's disease (AD) and to determine whether patients with PD would be at greater risk of developing AD compared to periodontally healthy subjects. This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. An electronic search for cross-sectional, cohort, or case-control studies was conducted on five databases (PubMed, ScienceDirect, EBSCO, Web of Science, and Scopus). No restrictions were applied to the language and year of publication. Exposure was PD, and the outcome of interest was the onset and/or progression of AD. The risk of bias of the included studies was assessed using the Newcastle-Ottawa Scale (NOS) designed for non-randomized studies. Six studies fulfilling the selection criteria were included in this systematic review. Four of the studies were of cohort design and two were of case-control design. All except one showed a significant association between PD and the risk of AD onset and progression. According to the NOS bias risk assessment, three studies were found to be of good quality, and three other cohort studies were of low quality. Data from this systematic review indicate that patients with PD present a significantly higher risk of AD compared to individuals with healthy periodontium. However, results should be interpreted with caution given the methodological limitations found. For future research, powerful and comparable epidemiological studies are needed to evaluate the relationship between PD and AD.

Associations of Dental Health With the Progression of Hippocampal Atrophy in Community-Dwelling Individuals: The Ohasama Study

BACKGROUND AND OBJECTIVES

Although tooth loss and periodontitis have been considered risk factors of Alzheimer disease, recent longitudinal researches have not found a significant association with hippocampal atrophy. Therefore, this study aimed to clarify a longitudinal association between the number of teeth present (NTP) and hippocampal atrophy dependent on the severity of periodontitis in a late middle-aged and older adult population.

METHODS

This study included community-dwelling individuals aged 55 years or older who had no cognitive decline and had undergone brain MRI and oral and systemic data collection twice at 4-year intervals. Hippocampal volumes were obtained from MRIs by automated region-of-interest analysis. The mean periodontal probing depth (PD) was used as a measure of periodontitis. Multiple regression analysis was performed with the annual symmetric percentage change (SPC) of the hippocampal volume as the dependent variable and including an interaction term between NTP and mean PD as the independent variable. The interaction details were examined using the Johnson-Neyman technique and simple slope analysis. The 3-way interaction of NTP, mean PD, and time on hippocampal volume was analyzed using a linear mixed-effects model, and the interaction of NTP and time was examined in subgroups divided by the median mean PD. In all models, dropout bias was adjusted by inverse probability weighting.

RESULTS

Data of 172 participants were analyzed. The qualitative interaction between NTP and the mean PD was significant for the annual SPC in the left hippocampus. The regression coefficient of the NTP on the annual SPC in the left hippocampus was positive (B = 0.038, p = 0.026) at the low-level mean PD (mean -1 SD) and negative (B = -0.054, p = 0.001) at the high-level mean PD (mean +1 SD). Similar results were obtained in the linear mixed-effects model; the interaction of NTP and time was significant in the higher mean PD group.

DISCUSSION

In a late middle-aged and older cohort, fewer teeth were associated with a faster rate of left hippocampal atrophy in patients with mild periodontitis, whereas having more teeth was associated with a faster rate of atrophy in those with severe periodontitis. The importance of keeping teeth healthy is suggested.

Periodontal health status of people with dementia - A systematic review of case-control studies

Background

The number of older people increases globally, so is the risk of cognitive impairment. Periodontal diseases are common among older adults with significant tooth loss and periodontal problems. Thus, this review explored the periodontal disease conditions among individuals with and without dementia.

Methods

Available databases such as Medline/Pubmed, Web of Science, Scopus, Cochrane Library and Embase/OVID were used in the search. Case-control studies reporting on periodontal disease and dementia parameters were selected based on PICO (Population, Intervention, Comparison and Outcomes) framework. A Newcastle-Ottawa Scale (NOS) was used to assess the quality reporting of the studies and PRISMA guideline was used for screening.

Results

A total of ten studies were identified for analysis. Most studies reported higher plaque index score (PI), bleeding on probing (BoP), pocket depth (PD) and clinical attachment loss (CAL) among individuals diagnosed with dementia or Alzheimer's disease compared with clinically healthy controls or individual diagnosed without dementia. A higher prevalence of subjects with severe periodontal disease was also observed in individuals diagnosed with dementia/Alzheimer's disease. The quality of the studies was found to be moderate with lower comparability and ascertainment criteria scores.

Conclusion

This qualitative analysis has shown poor periodontal health and increased inflammatory mediators in case groups compared to the control groups. Thus, more quality studies and novel intervention are warranted to reduce the impact of periodontal health on dementia globally.

Microbiome Alterations and Alzheimer's Disease: Modeling Strategies with Transgenic Mice

In the last decade, the role of the microbiota-gut-brain axis has been gaining momentum in the context of many neurodegenerative and metabolic disorders, including Alzheimer's disease (AD) and diabetes, respectively. Notably, a balanced gut microbiota contributes to the epithelial intestinal barrier maintenance, modulates the host immune system, and releases neurotransmitters and/or neuroprotective short-chain fatty acids. However, dysbiosis may provoke immune dysregulation, impacting neuroinflammation through peripheral-central immune communication. Moreover, lipopolysaccharide or detrimental microbial end-products can cross the blood-brain barrier and induce or at least potentiate the neuropathological progression of AD. Thus, after repeated failure to find a cure for this dementia, a necessary paradigmatic shift towards considering AD as a systemic disorder has occurred. Here, we present an overview of the use of germ-free and/or transgenic animal models as valid tools to unravel the connection between dysbiosis, metabolic diseases, and AD, and to investigate novel therapeutical targets. Given the high impact of dietary habits, not only on the microbiota but also on other well-established AD risk factors such as diabetes or obesity, consistent changes of lifestyle along with microbiome-based therapies should be considered as complementary approaches.

Age- and sex-related differences of periodontal bone resorption, cognitive function, and immune state in APP/PS1 murine model of Alzheimer's disease

BACKGROUND

The existence of an interconnected mechanism between cognitive disorders and periodontitis has been confirmed by mounting evidence. However, the role of age or sex differences in this mechanism has been less studied. This study aims to investigate sex and age differences in the characterization of periodontal bone tissue, immune state and cognitive function in amyloid precursor protein/presenilin 1(APP/PS1) murine model of Alzheimer's disease (AD).

METHODS

Three- and twelve-month-old male and female APP/PS1 transgenic mice and wild-type (WT) littermates were used in this study. The Morris water maze (MWM) was used to assess cognitive function. The bone microarchitecture of the posterior maxillary alveolar bone was evaluated by microcomputed tomography (micro-CT). Pathological changes in periodontal bone tissue were observed by histological chemistry. The proportions of helper T cells1 (Th1), Th2, Th17 and regulatory T cells (Tregs) in the peripheral blood mononuclear cells (PBMCs) and brain samples were assessed by flow cytometry.

RESULTS

The learning ability and spatial memory of 12-month-old APP/PS1 mice was severely damaged. The changes in cognitive function were only correlated with age and genotype, regardless of sex. The 12-month-old APP/PS1 female mice exhibited markedly periodontal bone degeneration, evidenced by the decreased bone volume/total volume (BV/TV), trabecular thickness (Tb.Th), and bone mineral density (BMD), and the increased trabecular separation (Tb.Sp). The altered periodontal bone microarchitecture was associated with genotype, age and females. The flow cytometry data showed the increased Th1 and Th17 cells and the decreased Th2 cells in the brain and PBMC samples of 12-month-old APP/PS1 mice, compared to age- and sex-matched WT mice. However, there was no statistical correlation between age or sex and this immune state.

CONCLUSIONS

Our data emphasize that age and sex are important variables to consider in evaluating periodontal bone tissue of APP/PS1 mice, and the cognitive impairment is more related to age. In addition, immune dysregulation (Th1, Th2, and Th17 cells) was found in the brain tissue and PBMCs of APP/PS1 mice, but this alteration of immune state was not statistically correlated with sex or age.

The Potential of a Saliva Test for Screening of Alveolar Bone Resorption

Oral health screening is important for maintaining and improving quality of life. The present study aimed to determine whether patients with a certain level of alveolar bone resorption could be screened by salivary bacterial test along with their background information. Saliva samples were collected from 977 Japanese patients, and the counts of each red-complex, that is, Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia, were measured using quantitative polymerase chain reaction analysis. Mean bone crest levels (BCLs) were measured using a full-mouth periapical radiograph. Multiple logistic regression analysis was used to determine associations between BCLs (1.5-4.0 mm in 0.5 mm increments) and explanatory variables, such as the number of each red-complex bacteria and the patients' age, sex, number of teeth, stimulated saliva volume, and smoking habits. When the cutoff BCL value was set at 3.0 mm, the area under the curve, sensitivity, and specificity values were optimal at 0.86, 0.82, and 0.76, respectively. In addition, all tested explanatory variables, except sex and T. denticola count, were significantly associated with BCLs according to a likelihood ratio test (p < 0.05). Additionally, the odds ratio (OR) was substantially increased when a patient was >40 years old and the bacterial count of P. gingivalis was >10⁷ cells/µL (OR: >6). Thus, P. gingivalis count and patients' background information were significantly associated with the presence of a certain amount of bone resorption, suggesting that it may be possible to screen bone resorption without the need for radiography or oral examination.

A systematic review of the protein composition of whole saliva in subjects with healthy periodontium compared with chronic periodontitis

CONTEXT

Periodontitis is a chronic multifactorial inflammatory disease linked to oral microbiota dysbiosis. This disease progresses to infection that stimulates a host immune/inflammatory response, with progressive destruction of the tooth-supporting structures.

OBJECTIVE

This systematic review aims to present a robust critical evaluation of the evidence of salivary protein profiles for identifying oral diseases using proteomic approaches and summarize the use of these approaches to diagnose chronic periodontitis.

DATA SOURCES

A systematic literature search was conducted from January 1st, 2010, to December 1st, 2022, based on PICO criteria following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and by searching the three databases Science Direct, Scopus, and Springer Link.

STUDY SELECTION

According to the inclusion criteria, eight studies were identified to analyze the proteins identified by proteomics.

RESULTS

The protein family S100 was identified as the most abundant in patients with chronic periodontitis. In this family, an increased abundance of S100A8 and S100A9 from individuals with the active disease was observed, which strongly relates to the inflammatory response. Moreover, the ratio S100A8/S100A9 and the metalloproteinase-8 in saliva could differentiate distinct periodontitis groups. The changes in protein profile after non-surgical periodontal therapy improved the health of the buccal area. The results of this systematic review identified a set of proteins that could be used as a complementary tool for periodontitis diagnosis using salivary proteins.

CONCLUSION

Biomarkers in saliva can be used to monitor an early stage of periodontitis and the progression of the disease following therapy.

Poor Oral Health and Risk of Incident Dementia: A Prospective Cohort Study of 425,183 Participants

BACKGROUND

The association between poor oral health and the risk of incident dementia remains unclear.

OBJECTIVE

To investigate the associations of poor oral health with incident dementia, cognitive decline, and brain structure in a large population-based cohort study.

METHODS

A total of 425,183 participants free of dementia at baseline were included from the UK Biobank study. The associations between oral health problems (mouth ulcers, painful gums, bleeding gums, loose teeth, toothaches, and dentures) and incident dementia were examined using Cox proportional hazards models. Mixed linear models were used to investigate whether oral health problems were associated with prospective cognitive decline. We examined the associations between oral health problems and regional cortical surface area using linear regression models. We further explored the potential mediating effects underlying the relationships between oral health problems and dementia.

RESULTS

Painful gums (HR = 1.47, 95% CI [1.317-1.647], p <  0.001), toothaches (HR = 1.38, 95% CI [1.244-1.538], p <  0.001), and dentures (HR = 1.28, 95% CI [1.223-1.349], p <  0.001) were associated with increased risk of incident dementia. Dentures were associated with a faster decline in cognitive functions, including longer reaction time, worse numeric memory, and worse prospective memory. Participants with dentures had smaller surface areas of the inferior temporal cortex, inferior parietal cortex, and middle temporal cortex. Brain structural changes, smoking, alcohol drinking, and diabetes may mediate the associations between oral health problems and incident dementia.

CONCLUSION

Poor oral health is associated with a higher risk of incident dementia. Dentures may predict accelerated cognitive decline and are associated with regional cortical surface area changes. Improvement of oral health care could be beneficial for the prevention of dementia.

Microcontact-Imprinted Optical Sensors for Virulence Factors of Periodontal Disease

Periodontitis (gum disease) is a common biofilm-mediated oral condition, with around 7% of the adult population suffering from severe disease with risk for tooth loss. Moreover, periodontitis virulence markers have been found in atherosclerotic plaque and brain tissue, suggesting a link to cardiovascular and Alzheimer's diseases. The lack of accurate, fast, and sensitive clinical methods to identify patients at risk leads, on the one hand, to patients being undiagnosed until the onset of severe disease and, on the other hand, to overtreatment of individuals with mild disease, diverting resources from those patients most in need. The periodontitis-associated bacterium, Porphyromonas gingivalis, secrete gingipains which are highly active proteases recognized as key virulence factors during disease progression. This makes them interesting candidates as predictive biomarkers, but currently, there are no methods in clinical use for monitoring them. Quantifying the levels or proteolytic activity of gingipains in the periodontal pocket surrounding the teeth could enable early-stage disease diagnosis. Here, we report on a monitoring approach based on high-affinity microcontact imprinted polymer-based receptors for the Arg and Lys specific gingipains Rgp and Kgp and their combination with surface plasmon resonance (SPR)-based biosensor technology for quantifying gingipain levels in biofluids and patient samples. Therefore, Rgp and Kgp were immobilized on glass coverslips followed by microcontact imprinting of poly-acrylamide based films anchored to gold sensor chips. The monomers selected were N-isopropyl acrylamide (NIPAM), N-hydroxyethyl acrylamide (HEAA) and N-methacryloyl-4-aminobenzamidine hydrochloride (BAM), with N,N'-methylene bis(acrylamide) (BIS) as the crosslinker. This resulted in imprinted surfaces exhibiting selectivity towards their templates high affinity and selectivity for the templated proteins with dissociation constants (K _d) of 159 and 299 nM for the Rgp- and Kgp-imprinted, surfaces respectively. The former surface displayed even higher affinity (K _d = 71 nM) when tested in dilute cell culture supernatants. Calculated limits of detection for the sensors were 110 and 90 nM corresponding to levels below clinically relevant concentrations.

Profiling the oral microbiomes in patients with Alzheimer's disease

OBJECTIVES

To analyse the characteristics of the oral microbiomes and expected to find biomarkers about Alzheimer's disease (AD).

SUBJECTS AND METHODS

AD patients (n = 26) and cognitive intact people (n = 26) were examined for cognition, depression, oral health and collected saliva and gingival crevicular fluid (GCF) in the morning. Full-length 16S rRNA gene was amplified and sequencing was performed using the PacBio platform.

RESULTS

The predominant bacterium of salivary microbiome and periodontal microbiome from AD patients was Streptococcus oralis and Porphyromonas gingivalis, respectively. With respect to β diversity analysis, there was a significance difference in periodontal microbiome between AD patients and cognitively intact subjects. The relative abundance of Veillonella parvula significantly increased in oral microbiomes from AD patients. Interestingly, the dominant species were different between early-onset AD and late-onset AD patients. Moreover, the predominant species were changed as the clinical severity of AD. Furthermore, the correlation analysis revealed that V. parvula was associated with AD in both saliva and GCF and that P. gingivalis was associated with AD only in GCF.

CONCLUSIONS

In this study, the microbiome community of oral microbes was altered in AD patients and periodontal microbiome was sensitive to cognition changes. Moreover, V. parvula and P. gingivalis were associated with AD.

Confounding in observational studies evaluating the association between Alzheimer's disease and periodontal disease: A systematic review

Background

Studies investigating the association between periodontitis and Alzheimer's disease (AD) suggested indirect (periodontitis would increase the circulation of inflammation-inducible molecules) and direct (periodontopathogens might colonize brains affected by Alzheimer's disease) pathways. While there seems to be a positive relationship between periodontitis and AD, concerns have been raised about the role of confounding.

Aim

To systematically review the literature to assess confounding and their level of heterogeneity in the association between periodontitis and AD. Also, to examine data reporting and interpretation regarding confounding bias.

Methods

This review followed the PRISMA guidelines and was registered within PROSPERO. Electronic searches were performed in seven main databases and three others to capture the "grey literature". The PECO strategy was used to identify observational studies (cross-sectional, case-control, or cohort studies) assessing the association between periodontal disease and AD without restricting publication language and year. Critical appraisal was performed according to the Joanna Briggs Institute guidelines. Confounders were evaluated following a two-step approach.

Results

A total of 3255 studies were found, of which 18 (13 case-control, four cross-sectional, and one cohort) met the eligibility criteria. Participants with AD were 1399 (mean age 64 ± 9 to 84.8 ± 5.6 years), whereas those without AD were 1730 (mean age 62.6 ± 7.1 to 81.4 ± 4.6). Female patients composed most of the sample for both groups. The confounding variables "age" and "sex" were present in all studies. Four studies used the 2017 AAP/EFP periodontal classification. Most studies had a low risk of bias. Fifty percent of the articles did not consider confounding; variation in the adjustment approaches was observed. Additionally, 62% of the studies did not mention bias, and 40% did not discuss any limitations about confounders.

Conclusions

Given the study's limitations, caution must be taken to properly interpret the association between periodontitis and AD.Registration: CRD42022293884.

Periodontal Inflamed Surface Area (PISA) associates with composites of salivary cytokines

BACKGROUND

Periodontal disease (PerioD) is a chronic, complex inflammatory condition resulting from the interaction between subgingival dysbiotic bacteria and the host immune response leading to local inflammation. Since periodontal inflammation is characterized by multiple cytokines effects we investigated whether Periodontal Inflamed Surface Area (PISA), a continuous measure of clinical periodontal inflammation is a predictor of composite indexes of salivary cytokines.

METHODS AND FINDINGS

In a cross-sectional study of 67 healthy, well-educated individuals, we evaluated PISA and several cytokines expressed in whole stimulated saliva. Two salivary cytokine indexes were constructed using weighted and unweighted approaches based on a Principal Component Analysis [named Cytokine Component Index (CCI)] or averaging the (standardized) level of all cytokines [named Composite Inflammatory Index (CII)]. In regression analysis we found that PISA scores were significantly associated with both salivary cytokine constructs, (CCI: part R = 0.51, p<0.001; CII: part R = 0.40, p = 0.001) independent of age, gender and BMI showing that single scores summarizing salivary cytokines correlated with severity of clinical periodontal inflammation.

CONCLUSIONS

Clinical periodontal inflammation may be reflected by a single score encompassing several salivary cytokines. These results are consistent with the complexity of interactions characterizing periodontal disease. In addition, Type I error is likely to be avoided.

The impact of study factors in the association of periodontal disease and cognitive disorders: systematic review and meta-analysis

AIM

The aim was to assess study factors that impact the association of cognitive disorders in people with periodontal disease (PD).

METHOD

Medline, EMBASE and Cochrane databases were searched until February 2022 using keywords and MeSH: (periodon* OR tooth loss OR missing teeth) AND (dementia OR Alzheimer's Disease OR cognitive*). Observational studies reporting prevalence or risk of cognitive decline, dementia or Alzheimer's disease (AD) in people with PD compared with healthy controls were included. Meta-analysis quantified the prevalence and risk (relative risk[RR]) of cognitive decline, dementia/AD, respectively. Meta-regression/subgroup analysis explored the impact of study factors including PD severity and classification type, and gender.

RESULTS

Overall, 39 studies were eligible for meta-analysis: 13 cross-sectional and 26 longitudinal studies. PD demonstrated increased risks of cognitive disorders (cognitive decline-RR = 1.33, 95% CI = 1.13-1.55; dementia/AD-RR = 1.22, 95% CI = 1.14-1.31). Risk of cognitive decline increased with PD severity (moderate-[RR] = 1.14, 95% confidence interval [CI] = 1.07-1.22; severe-RR = 1.25, 95% CI = 1.18-1.32). For every 10% population increase in females, the risk of cognitive decline increased by 34% (RR = 1.34, 95% CI = 1.16-1.55). Self-reported PD showed a lower risk of cognitive disorders compared with clinical classification (cognitive decline-RR = 0.77, 95% CI = 0.65-0.91; dementia/AD-RR = 0.86, 95% CI = 0.77-0.96).

CONCLUSION

The prevalence and risk estimates of cognitive disorders in association with PD can be influenced by gender, the disease classification of PD and its severity. Further homologous evidence taking these study factors into consideration is needed to form robust conclusions.

Studying ancient human oral microbiomes could yield insights into the evolutionary history of noncommunicable diseases

Noncommunicable diseases (NCDs) have played a critical role in shaping human evolution and societies. Despite the exceptional impact of NCDs economically and socially, little is known about the prevalence or impact of these diseases in the past as most do not leave distinguishing features on the human skeleton and are not directly associated with unique pathogens. The inability to identify NCDs in antiquity precludes researchers from investigating how changes in diet, lifestyle, and environments modulate NCD risks in specific populations and from linking evolutionary processes to modern health patterns and disparities. In this review, we highlight how recent advances in ancient DNA (aDNA) sequencing and analytical methodologies may now make it possible to reconstruct NCD-related oral microbiome traits in past populations, thereby providing the first proxies for ancient NCD risk. First, we review the direct and indirect associations between modern oral microbiomes and NCDs, specifically cardiovascular disease, diabetes mellitus, rheumatoid arthritis, and Alzheimer's disease. We then discuss how oral microbiome features associated with NCDs in modern populations may be used to identify previously unstudied sources of morbidity and mortality differences in ancient groups. Finally, we conclude with an outline of the challenges and limitations of employing this approach, as well as how they might be circumvented. While significant experimental work is needed to verify that ancient oral microbiome markers are indeed associated with quantifiable health and survivorship outcomes, this new approach is a promising path forward for evolutionary health research.

Impact of oral microbiota on pathophysiology of GVHD

Allogeneic transplantation of hematopoietic cells is the only curative therapy for several hematopoietic disease in which patients receive cytotoxic conditioning regimens followed by infusion of hematopoietic stem cells. Although the outcomes have improved over the past decades, graft-versus-host-disease (GVHD), the most common life-threatening complication, remains a major cause of non-relapse morbidity and mortality. Pathophysiology of acute GVHD characterized by host antigen-presenting cells after tissue damage and donor T-cells is well studied, and additionally the importance of recipient microbiota in the intestine is elucidated in the GVHD setting. Oral microbiota is the second most abundant bacterial flora in the body after the intestinal tract, and it is related to chronic inflammation and carcinogenesis. Recently, composition of the oral microbiome in GVHD related to transplantation has been characterized and several common patterns, dysbiosis and enrichment of the specific bacterial groups, have been reported. This review focuses on the role of the oral microbiota in the context of GVHD.

Oral environment and cerebral blood flow in patients with neurodegenerative dementia: comparison of Alzheimer type dementia and dementia with Lewy bodies

BACKGROUND

The number of patients with dementia is increasing worldwide. Modifying risk factors may significantly reduce the prevalence and cost of dementia. The number of remaining teeth, occlusal force, denture use, and periodontal disease status are associated with the risk of developing dementia. The oral environment may be a risk factor for dementia. This study aimed to investigate the association between the oral environment and cerebral blood flow in patients with mild cognitive impairment and dementia (either Alzheimer type dementia (ATD) or dementia with Lewy bodies (DLB)). We aimed to identify differences in the oral environment according to the underlying neurodegenerative disease.

METHODS

The participants were 25 patients with ATD and 25 patients with DLB who visited the Department of Dementia and Geriatric Medicine, Kanagawa Dental University Hospital. Patients were diagnosed with ATD and DLB by well-trained specialists certified by the Japanese Dementia Society and categorised as Level 3 or 4 by the Functional Assessment Staging of Alzheimer Disease scale. The correlation between oral environment (number of teeth, periodontal tissue, and oral function) and cerebral blood flow in each brain area calculated by single photon emission computed tomography was examined.

RESULTS

The DLB group showed a significant correlation between masticatory performance and cerebral blood flow in some areas, while no such correlation was observed in the ATD group. Significant correlations were found between periodontal pocket depth and bleeding on probing and cerebral blood flow in some areas in both groups, although the correlation was considerable in the ATD group.

CONCLUSIONS

The results of this study suggest that the association between changes in the oral environment and cerebral blood flow may differ among patients with ATD and DLB, depending on the underlying causative disease.

The effect of the "Oral-Gut" axis on periodontitis in inflammatory bowel disease: A review of microbe and immune mechanism associations

Periodontitis and inflammatory bowel diseases (IBD) are inflammatory diseases of the gastrointestinal tract that share common features of microbial-induced ecological dysregulation and host immune inflammatory response. The close relationship between periodontitis and IBD is characterized by a higher prevalence of IBD in patients with periodontitis and a higher prevalence and severity of periodontitis in patients with IBD, indicating that periodontitis and IBD are different from the traditional independent diseases and form an "Oral-Gut" axis between the two, which affect each other and thus form a vicious circle. However, the specific mechanisms leading to the association between the two are not fully understood. In this article, we describe the interconnection between periodontitis and IBD in terms of microbial pathogenesis and immune dysregulation, including the ectopic colonization of the gut by pathogenic bacteria associated with periodontitis that promotes inflammation in the gut by activating the host immune response, and the alteration of the oral microbiota due to IBD that affects the periodontal inflammatory response. Among the microbial factors, pathogenic bacteria such as Klebsiella, Porphyromonas gingivalis and Fusobacterium nucleatum may act as the microbial bridge between periodontitis and IBD, while among the immune mechanisms, Th17 cell responses and the secreted pro-inflammatory factors IL-1β, IL-6 and TNF-α play a key role in the development of both diseases. This suggests that in future studies, we can look for targets in the "Oral-Gut" axis to control and intervene in periodontal inflammation by regulating periodontal or intestinal flora through immunological methods.

Studying ancient human oral microbiomes could yield insights into the evolutionary history of noncommunicable diseases

Noncommunicable diseases (NCDs) have played a critical role in shaping human evolution and societies. Despite the exceptional impact of NCDs economically and socially, little is known about the prevalence or impact of these diseases in the past as most do not leave distinguishing features on the human skeleton and are not directly associated with unique pathogens. The inability to identify NCDs in antiquity precludes researchers from investigating how changes in diet, lifestyle, and environments modulate NCD risks in specific populations and from linking evolutionary processes to modern health patterns and disparities. In this review, we highlight how recent advances in ancient DNA (aDNA) sequencing and analytical methodologies may now make it possible to reconstruct NCD-related oral microbiome traits in past populations, thereby providing the first proxies for ancient NCD risk. First, we review the direct and indirect associations between modern oral microbiomes and NCDs, specifically cardiovascular disease, diabetes mellitus, rheumatoid arthritis, and Alzheimer's disease. We then discuss how oral microbiome features associated with NCDs in modern populations may be used to identify previously unstudied sources of morbidity and mortality differences in ancient groups. Finally, we conclude with an outline of the challenges and limitations of employing this approach, as well as how they might be circumvented. While significant experimental work is needed to verify that ancient oral microbiome markers are indeed associated with quantifiable health and survivorship outcomes, this new approach is a promising path forward for evolutionary health research.

Antibacterial Effect of Zirconia Nanoparticles on Polyethyl Methacrylate Resin for Provisional Crowns

Objective

Mid-to-long term use of provisional crowns in the oral cavity is associated with bacterial adhesion and biofilm formation, thus necessitating provisional crowns exhibiting antibacterial properties to prevent the occurrence of gingivitis and periodontal disease. This study aimed to evaluate the antibacterial effect of zirconia nanoparticle-containing polyethyl methacrylate (PEMA) resin for provisional restorations.

Methods

Zirconia nanoparticles were added to the monomer of PEMA resin for provisional restorations, and the mixture was stirred for 2 h using a magnetic stirrer. Disk-shaped specimens were prepared by mixing the polymer with the nanoparticle solution. The control group contained pure PEMA resin samples, and the experimental groups Group Z2, Group Z4, and Group Z8 included PEMA resin specimens containing 2, 4, and 8% w/v zirconia nanoparticles, respectively. After analyzing the sample surfaces, the antibacterial effect of the specimens was evaluated using Streptococcus mutans. Statistical analysis was performed using Tukey's test and Mann-Whitney U-test, according to the normality result in the Shapiro-Wilk test.

Results

FE-SEM and EDX analyses revealed the successful addition of zirconia nanoparticles. Results showed no significant difference in the measured values for surface roughness and contact angle between the experimental and control groups; however, adhesion and biofilm thickness of S. mutans were significantly decreased in Group Z2, Group Z4, and Group Z8 compared to the control group (P < 0.05, P < 0.01, P < 0.01, respectively).

Conclusion

The addition of zirconia nanoparticles can lower the incidence of adhesion and biofilm thickness of S. mutans on PEMA resin used for provisional crowns. Thus, incorporating zirconia nanoparticles in repair materials for provisional crowns and PEMA resin can produce an antibacterial effect and prevent gingivitis, periodontal disease, and dental caries.

Is Periodontitis Associated with Age-Related Cognitive Impairment? The Systematic Review, Confounders Assessment and Meta-Analysis of Clinical Studies

It has been suggested that molecular pathological mechanisms responsible for periodontitis can be linked with biochemical alterations in neurodegenerative disorders. Hypothetically, chronic systemic inflammation as a response to periodontitis plays a role in the etiology of cognitive impairment. This study aimed to determine whether periodontitis (PDS) is a risk factor for age-related cognitive impairment (ACI) based on evidence of clinical studies. A comprehensive, structured systematic review of existing data adhering to the Preferred Reporting Items for Systematic Review and Meta Analyses (PRISMA) guidelines was carried out. Five electronic databases, PubMed, Embase, Scopus, Web of Science, and Cochrane, were searched for key terms published in peer-reviewed journals until January 2021. The Newcastle-Ottawa scale was used to assess the quality of studies and risk of bias. The primary and residual confounders were explored and evaluated. A meta-analysis synthesizing quantitative data was carried out using a random-effects model. Seventeen clinical studies were identified, including 14 cohort, one cross-sectional, and two case-control studies. Study samples ranged from 85 to 262,349 subjects, with follow-up between 2 and 32 years, and age above 45 years, except for two studies. The findings of studies suggesting the PDS-ACI relationship revealed substantial differences in design and methods. A noticeable variation related to the treatment of confounders was observed. Quality assessment unveiled a moderate quality of evidence and risk of bias. The subgroups meta-analysis and pooled sensitivity analysis of results from seven eligible studies demonstrated overall that the presence of PDS is associated with an increased risk of incidence of cognitive impairment (OR = 1.36, 95% CI 1.03-1.79), particularly dementia (OR = 1.39, 95% CI 1.02-1.88) and Alzheimer's disease (OR = 1.03 95% CI 0.98-1.07)). However, a considerable heterogeneity of synthesized data (I2 = 96%) and potential publication bias might affect obtained results. While there is a moderate statistical association between periodontitis and dementia, as well as Alzheimer's disease, the risk of bias in the evidence prevents conclusions being drawn about the role of periodontitis as a risk factor for age-related cognitive impairment.

Treponema denticola Induces Neuronal Apoptosis by Promoting Amyloid-β Accumulation in Mice

Background: Neuronal apoptosis is a major contributor to Alzheimer's disease (AD). Periodontitis is a significant risk factor for AD. The periodontal pathogens Porphyromonas gingivalis and Treponema denticola have been shown to initiate the hallmark pathologies and behavioral symptoms of AD. Studies have found that T. denticola infection induced Tau hyperphosphorylation and amyloid β accumulation in the hippocampi of mice. Aβ accumulation is closely associated with neuronal apoptosis. However, the roles of T. denticola in neuronal apoptosis remain unclear and its roles in AD pathology need further study. Objective: This study aimed to investigate whether oral infection with T. denticola induced alveolar bone loss and neuronal apoptosis in mice. Methods: C57BL/6 mice were orally administered with T. denticola, Micro-CT was employed to assess the alveolar bone resorption. Western blotting, quantitative PCR, and TUNEL staining were utilized to detect the apoptosis-associated changes in mouse hippocampi. N2a were co-cultured with T. denticola to verify in vivo results. Results: Mice infected with T. denticola exhibited more alveolar bone loss compared with the control mice. T. denticola oral infection induced neuronal apoptosis in hippocampi of mice. Consistent results of the apoptosis-associated protein expression were observed in N2a cells treated with T. denticola and Aβ_1-42 in vitro. However, the Aβ inhibitor reversed these results, suggesting that Aβ_1-42 mediates T. denticola infection-induced neuronal apoptosis. Conclusions: This study found that oral infected T. denticola caused alveolar bone loss, and induced neuronal apoptosis by promoting Aβ accumulation in mice, providing evidence for the link between periodontitis and AD.

Dementia Prevention in Clinical Practice

Over 55 million people globally are living with dementia and, by 2050, this number is projected to increase to 131 million. This poses immeasurable challenges for patients and their families and a significant threat to domestic and global economies. Given this public health crisis and disappointing results from disease-modifying trials, there has been a recent shift in focus toward primary and secondary prevention strategies. Approximately 40% of Alzheimer's disease (AD) cases, which is the most common form of dementia, may be prevented or at least delayed. Success of risk reduction studies through addressing modifiable risk factors, in addition to the failure of most drug trials, lends support for personalized multidomain interventions rather than a "one-size-fits-all" approach. Evolving evidence supports early intervention in at-risk patients using individualized interventions directed at modifiable risk factors. Comprehensive risk stratification can be informed by emerging principals of precision medicine, and include expanded clinical and family history, anthropometric measurements, blood biomarkers, neurocognitive evaluation, and genetic information. Risk stratification is key in differentiating subtypes of dementia and identifies targetable areas for intervention. This article reviews a clinical approach toward dementia risk stratification and evidence-based prevention strategies, with a primary focus on AD.

Machine Learning Analysis Reveals Biomarkers for the Detection of Neurological Diseases

It is critical to identify biomarkers for neurological diseases (NLDs) to accelerate drug discovery for effective treatment of patients of diseases that currently lack such treatments. In this work, we retrieved genotyping and clinical data from 1,223 UK Biobank participants to identify genetic and clinical biomarkers for NLDs, including Alzheimer's disease (AD), Parkinson's disease (PD), motor neuron disease (MND), and myasthenia gravis (MG). Using a machine learning modeling approach with Monte Carlo randomization, we identified a panel of informative diagnostic biomarkers for predicting AD, PD, MND, and MG, including classical liver disease markers such as alanine aminotransferase, alkaline phosphatase, and bilirubin. A multinomial model trained on accessible clinical markers could correctly predict an NLD diagnosis with an accuracy of 88.3%. We also explored genetic biomarkers. In a genome-wide association study of AD, PD, MND, and MG patients, we identified single nucleotide polymorphisms (SNPs) implicated in several craniofacial disorders such as apnoea and branchiootic syndrome. We found evidence for shared genetic risk loci among NLDs, including SNPs in cancer-related genes and SNPs known to be associated with non-brain cancers such as Wilms tumor, leukemia, and colon cancer. This indicates overlapping genetic characterizations among NLDs which challenges current clinical definitions of the neurological disorders. Taken together, this work demonstrates the value of data-driven approaches to identify novel biomarkers in the absence of any known or promising biomarkers.

Association of periodontitis with tinnitus: A population-based cohort study in Taiwan

AIM

Tinnitus, ringing in the ears, is speculated to be driven by inflammation. This study examined whether periodontitis is a risk factor for tinnitus using Taiwan's National Health Insurance Research Database.

MATERIALS AND METHODS

Among the 79,456 patients who visited for dental concerns, 11,055 patients who were diagnosed with periodontitis and underwent periodontal treatment between 2000 and 2015 were enrolled in Group 1. After matching for sex, age, and index year, 11,055 patients with periodontitis who received no treatment were enrolled in Group 2. Similarly, 11,055 participants without periodontitis were included as controls.

RESULTS

At the end of the follow-up, 412 and 404 participants in the two periodontitis groups and 321 participants in the control group had tinnitus. Cumulative risk for tinnitus in Group 1 or 2 was significantly greater than in the control group. More periodontitis patients than controls developed tinnitus (adjusted hazard ratios were 1.71 (95% confidence interval [CI]: 1.49-1.97, p < .001) and 1.64 (95% CI: 1.37-1.86, p < .001) in Groups 1 and 2, respectively). The risks were not significantly different between Groups 1 and 2. Similar findings were obtained after excluding data for the first 1 or 5 years.

CONCLUSIONS

The study findings indicate that periodontitis is associated with tinnitus.

Dual Inhibitory Activity of Petroselinic Acid Enriched in Fennel Against Porphyromonas gingivalis

Increasing evidence has shown that a major periodontal pathobiont, Porphyromonas gingivalis, triggers oral dysbiosis leading to deterioration not only of periodontal health, but also of several systemic conditions. In the present study we identified remarkable anti-P. gingivalis activity of Foeniculum vulgare (fennel), an herbal plant used in Asian cuisine as well as in traditional medicine, by screening of 92 extracts prepared from 23 edible plants. The n-hexane-extracted fennel (HEF) showed a rapid lethal action toward P. gingivalis, while it was rather ineffective with a wide range of other oral commensal bacterial species. Morphological analysis using both high-speed atomic force microscopy and field emission scanning electron microscopy revealed that a low concentration of HEF (8 μg/mL) resulted in formation of protruding nanostructures composed of outer membrane vesicle (OMV)-like particles, while a high concentration of HEF (64 μg/mL) induced bacteriolysis with overproduction of OMVs with unusual surface properties. Interestingly, HEF treatment resulted in deprivation of two outer membrane transporter proteins, RagA and RagB, which is essential for nutrient acquisition in P. gingivalis, by extracellularly releasing RagA/RagB-enriched OMVs. Furthermore, HEF showed gingipain-inhibitory activity toward both arginine-specific (Rgps) and lysine-specific (Kgp) gingipains, resulting in blocking oral epithelial cell rounding and the subsequent detachment from culture dishes. Finally, we isolated petroselinic acid as a major bactericide as well as a gingipain inhibitor through a bioassay-guided fractionation of HEF. Taken together, our findings suggest clinical applicability of HEF and petroselinic acid for periodontitis therapy to eliminate P. gingivalis and its major virulence factors on the basis of the dual anti-P. gingivalis activity, i.e., rapid bacteriolysis and gingipain inhibition.

Does Dementia Have a Microbial Cause?

The potential contribution of pathogenic microbes to dementia-inducing disease is a subject of considerable importance. Alzheimer’s disease (AD) is a neurocognitive disease that slowly destroys brain function, leading to cognitive decline and behavioral and psychiatric disorders. The histopathology of AD is associated with neuronal loss and progressive synaptic dysfunction, accompanied by the deposition of amyloid-β (Aβ) peptide in the form of parenchymal plaques and abnormal aggregated tau protein in the form of neurofibrillary tangles. Observational, epidemiological, experimental, and pathological studies have generated evidence for the complexity and possible polymicrobial causality in dementia-inducing diseases. The AD pathogen hypothesis states that pathogens and microbes act as triggers, interacting with genetic factors to initiate the accumulation of Aβ, hyperphosphorylated tau protein (p-tau), and inflammation in the brain. Evidence indicates that Borrelia sp., HSV-1, VZV (HHV-2), HHV-6/7, oral pathogens, Chlamydophila pneumoniae, and Candida albicans can infect the central nervous system (CNS), evade the immune system, and consequently prevail in the AD brain. Researchers have made significant progress in understanding the multifactorial and overlapping factors that are thought to take part in the etiopathogenesis of dementia; however, the cause of AD remains unclear.

Periostin regulates LPS-induced apoptosis via Nrf2/HO-1 pathway in periodontal ligament fibroblasts

OBJECTIVE

Periostin is important for the maintenance of periodontal tissue, but its role in periodontitis is controversial. This research investigated the effect of periostin in periodontitis and the underlying mechanism.

DESIGN

Mouse periodontitis models in vivo and inflammation model in vitro which were induced by Porphyromonas gingivalis lipopolysaccharide were established to evaluate periostin expression. Human periodontal ligament fibroblasts (PDLFs) were treated with lipopolysaccharide and N-acetylcysteine, fluorescence staining, flow cytometry, western blot, and qRT-PCR were used to detect reactive oxygen species (ROS), periostin expression, and apoptosis-related makers. The periostin gene was successfully transfected into PDLFs to verify the effect of periostin on apoptosis. Then, the Nrf2 inhibitor was added to clarify the mechanism.

RESULTS

Periostin expression decreased in the periodontal ligaments of mouse periodontitis models and lipopolysaccharide-induced PDLFs. Lipopolysaccharide promoted the activation of ROS and apoptosis in PDLFs, whereas N-acetylcysteine reversed this condition. Overexpression of periostin suppressed apoptosis of PDLFs and reversed the inhibitory effect of lipopolysaccharide on nuclear Nrf2 expression. Moreover, the Nrf2 inhibitor attenuated the protective effect of periostin on lipopolysaccharide-induced apoptosis.

CONCLUSIONS

Lipopolysaccharide induced apoptosis in PDLFs by inhibiting periostin expression and thus Nrf2/HO-1 pathway, indicating that periostin could be a potential therapeutic target for periodontitis.

Waste Clearance in the Brain and Neuroinflammation: A Novel Perspective on Biomarker and Drug Target Discovery in Alzheimer's Disease

Alzheimer’s disease (AD) is a multifactorial disease with a heterogeneous etiology. The pathology of Alzheimer’s disease is characterized by amyloid-beta and hyperphosphorylated tau, which are necessary for disease progression. Many clinical trials on disease-modifying drugs for AD have failed to indicate their clinical benefits. Recent advances in fundamental research have indicated that neuroinflammation plays an important pathological role in AD. Damage- and pathogen-associated molecular patterns in the brain induce neuroinflammation and inflammasome activation, causing caspase-1-dependent glial and neuronal cell death. These waste products in the brain are eliminated by the glymphatic system via perivascular spaces, the blood-brain barrier, and the blood–cerebrospinal fluid barrier. Age-related vascular dysfunction is associated with an impairment of clearance and barrier functions, leading to neuroinflammation. The proteins involved in waste clearance in the brain and peripheral circulation may be potential biomarkers and drug targets in the early stages of cognitive impairment. This short review focuses on waste clearance dysfunction in AD pathobiology and discusses the improvement of waste clearance as an early intervention in prodromal AD and preclinical stages of dementia.

Oral microbiota in human systematic diseases

Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment. The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling, hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician’s understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases, and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health.

The Brain-Nose Interface: A Potential Cerebrospinal Fluid Clearance Site in Humans

The human brain functions at the center of a network of systems aimed at providing a structural and immunological layer of protection. The cerebrospinal fluid (CSF) maintains a physiological homeostasis that is of paramount importance to proper neurological activity. CSF is largely produced in the choroid plexus where it is continuous with the brain extracellular fluid and circulates through the ventricles. CSF movement through the central nervous system has been extensively explored. Across numerous animal species, the involvement of various drainage pathways in CSF, including arachnoid granulations, cranial nerves, perivascular pathways, and meningeal lymphatics, has been studied. Among these, there is a proposed CSF clearance route spanning the olfactory nerve and exiting the brain at the cribriform plate and entering lymphatics. While this pathway has been demonstrated in multiple animal species, evidence of a similar CSF egress mechanism involving the nasal cavity in humans remains poorly consolidated. This review will synthesize contemporary evidence surrounding CSF clearance at the nose-brain interface, examining across species this anatomical pathway, and its possible significance to human neurodegenerative disease. Our discussion of a bidirectional nasal pathway includes examination of the immune surveillance in the olfactory region protecting the brain. Overall, we expect that an expanded discussion of the brain-nose pathway and interactions with the environment will contribute to an improved understanding of neurodegenerative and infectious diseases, and potentially to novel prevention and treatment considerations.

Do Periodontal Pathogens or Associated Virulence Factors Have a Deleterious Effect on the Blood-Brain Barrier, Contributing to Alzheimer's Disease?

The central nervous system (CNS) is protected by a highly selective barrier, the blood-brain barrier (BBB), that regulates the exchange and homeostasis of bloodborne molecules, excluding xenobiotics. This barrier forms the first line of defense by prohibiting pathogens from crossing to the CNS. Aging and chronic exposure of the BBB to pathogens renders it permeable, and this may give rise to pathology in the CNS such as Alzheimer's disease (AD). Researchers have linked pathogens associated with periodontitis to neuroinflammation and AD-like pathology in vivo and in vitro. Although the presence of periodontitis-associated bacteria has been linked to AD in several clinical studies as DNA and virulence factors were confirmed in brain samples of human AD subjects, the mechanism by which the bacteria traverse to the brain and potentially influences neuropathology is unknown. In this review, we present current knowledge about the association between periodontitis and AD, the mechanism whereby periodontal pathogens might provoke neuroinflammation and how periodontal pathogens could affect the BBB. We suggest future studies, with emphasis on the use of human in vitro models of cells associated with the BBB to unravel the pathway of entry for these bacteria to the CNS and to reveal the molecular and cellular pathways involved in initiating the AD-like pathology. In conclusion, evidence demonstrate that bacteria associated with periodontitis and their virulence factors are capable of inflecting damage to the BBB and have a role in giving rise to pathology similar to that found in AD.

Current Considerations for Clinical Management and Care of People with HIV: Findings from the 11th Annual International HIV and Aging Workshop

The number of people with HIV (PWH) aged 50 years or older continues to steadily increase. The convergence of age- and HIV-related complications in these individuals presents a challenge for both patients and clinicians alike. New findings continue to emerge, as numerous researchers evaluate the combined impact of these two factors on quality of life, physiological systems, and mental health in PWH. Since its first occurrence in 2009, the International Workshop on HIV and Aging has served as a multidisciplinary meeting to share basic biomedical data, clinical trial results, treatment strategies, and epidemiological recommendations, toward better understanding and outcomes among like-minded scientific professionals. In this article, we share a selection of key findings presented in plenary talks at the 11th Annual International Workshop on HIV and Aging, held virtually from September 30, 2020 to October 2, 2020. We will also address the future directions of HIV and aging research, to further assess how the aging process intersects with chronic HIV.

Periodontitis and Gestational Diabetes Mellitus: A Potential Inflammatory Vicious Cycle

Periodontitis is a chronic inflammatory immune disease associated with a dysbiotic state, influenced by keystone bacterial species responsible for disrupting the periodontal tissue homeostasis. Furthermore, the severity of periodontitis is determined by the interaction between the immune cell response in front of periodontitis-associated species, which leads to the destruction of supporting periodontal tissues and tooth loss in a susceptible host. The persistent bacterial challenge induces modifications in the permeability and ulceration of the sulcular epithelium, which facilitates the systemic translocation of periodontitis-associated bacteria into distant tissues and organs. This stimulates the secretion of pro-inflammatory molecules and a chronic activation of immune cells, contributing to a systemic pro-inflammatory status that has been linked with a higher risk of several systemic diseases, such as type 2 diabetes mellitus (T2DM) and gestational diabetes mellitus (GDM). Although periodontitis and GDM share the common feature of systemic inflammation, the molecular mechanistic link of this association has not been completely clarified. This review aims to examine the potential biological mechanisms involved in the association between periodontitis and GDM, highlighting the contribution of both diseases to systemic inflammation and the role of new molecular participants, such as extracellular vesicles and non-coding RNAs, which could act as novel molecular intercellular linkers between periodontal and placental tissues.

What is the future of Periodontal Medicine?

In the last five decades, considerable progress has been made towards understanding the etiology and pathogenesis of periodontal diseases and their interactions with the host. The impact of an individual periodontal condition on systemic homeostasis became more evident because of this knowledge and prompted advances in studies that associate periodontitis with systemic diseases and conditions. The term Periodontal Medicine describes how periodontal infection/inflammation can affect extraoral health. This review presents the current scientific evidence on the most investigated associations between periodontitis and systemic diseases and conditions, such as cardiovascular diseases, diabetes, preterm birth and low birth weight, and pneumonia. Additionally, other associations between periodontitis and chronic inflammatory bowel disease, colorectal cancer, and Alzheimer's disease that were recently published and are still poorly studied were described. Thus, the aim of this review was to answer the following question: What is the future of Periodontal Medicine? Epidemiological evidence and the evidence of biological plausibility between periodontitis and general health reinforce the rationale that the study of Periodontal Medicine should continue to advance, along with improvements in the epidemiological method, highlighting the statistical power of the studies, the method for data analysis, the case definition of periodontitis, and the type of periodontal therapy to be applied in intervention studies.

Porphyromonas Gingivalis as a Risk Factor to Alzheimer's Disease: A Systematic Review

BACKGROUND

Alzheimer's disease (AD) is a chronic neurodegenerative disease that accounts for more than 50% of all dementia cases worldwide. There is wide consensus on the risk factors of AD; however, a clear etiology remains unknown. Evidence suggests that the inflammatory-mediated disease model, such as that found with periodontal disease due to Porphyromonas gingivalis (P. gingivalis), plays a role in AD progression.

OBJECTIVE

This study aims to systematically review the literature on the association between P. gingivalis to AD, and to identify the homogeneity of the methods used across studies to measure P. gingivalis involvement in AD.

METHODS

We systematically searched studies on Cochrane library, Ovid Medline, PubMed, Web of Science, WHOLIS, Google Scholar databases, and reference lists of identified studies.

RESULTS

6 studies out of 636 identified records fulfilled all eligibility criteria. Results showed no clear pathophysiology of AD due to P. gingivalis and its various virulence factors. No consensus was found in the literature pertaining to the method of measurement of AD or P. gingivalis and its virulence factors.

CONCLUSION

The included studies suggest that P. gingivalis bacteria play a role in the process of systemic inflammation which leads to cerebrospinal fluid inflammation and indirectly cause hastening of AD onset and progression. Our included studies revealed heterogeneity in the methodologies of measurement of AD and/or P. gingivalis and its virulence factors, which opens discussion about the benefits and weakness of possible standardization.