Oral biofilms: emerging concepts in microbial ecology

Choline and geranate ionic liquid for subgingival biofilm control

Periodontitis is a chronic inflammatory disease that causes destruction of the periodontium and eventual tooth loss. The priority in the periodontal treatment is to remove the subgingival biofilm. Chemical removal of biofilms using antimicrobial agents has been applied in clinical practice. However, their clinical effect is still limited because the agents must overcome biofilm's significant drug tolerance, which is primarily caused by the extracellular matrix, a physical barrier that attenuates drug diffusion. This study aimed to study the use of ionic liquids (ILs), a new class of biocompatible materials, for controlling subgingival biofilms because of their excellent permeability. Choline and geranate (CAGE) IL was tested for its highly potent antiseptic behavior and permeability. Antibacterial tests revealed that the significant efficacy of CAGE against periodontopathic microorganisms was derived from their ability to destroy cell membrane, as demonstrated by membrane permeability assay and transmission electron microscopy imaging. Antibiofilm tests using two pathogenic biofilm models revealed that CAGE exerted efficacy against the biofilm-embedded bacteria, conspicuously neutralized the biofilms, and eventually destroyed the biofilm structure. Furthermore, the penetration of CAGE into the biofilm was visually confirmed using confocal laser scanning microscopy. This study highlighted the potential of CAGE as a powerful antibiofilm therapeutic.

Novel antibacterial orthodontic elastomeric ligature with oral biofilm-regulatory ability to prevent enamel demineralization

OBJECTIVES

To synthesize a novel antibacterial orthodontic elastomeric ligature incorporating dimethylaminohexadecyl methacrylate (DMAHDM) for the first time to prevent enamel demineralization during orthodontic therapy.

METHODS

Various mass fractions of DMAHDM (ranging from 0 % to 20 %) were grafted onto commercial elastomeric ligatures using an ultraviolet photochemical grafting method and were characterized. The optimal DMAHDM concentration was determined based on biocompatibility and mechanical properties, and the antibacterial efficacy was evaluated in a whole-plaque biofilm model. TaqMan real-time polymerase chain reaction and fluorescence in situ hybridization were used to assess the microbial regulatory ability of the multispecies biofilms. Furthermore, an in vitro tooth demineralization model was established to explore its preventive effects on enamel demineralization. Statistical analysis involved a one-way analysis of variance and LSD post hoc tests at a significance level of 0.05.

RESULTS

The elastomeric ligature containing 2 % mass fraction of DMAHDM exhibited excellent mechanical properties, favorable biocompatibility, and the most effective antibacterial ability against microorganisms, which decreased by almost two logarithms (P < 0.05). It significantly reduced the proportion of Streptococcus mutans in the multispecies plaque biofilm by 25 % at 72 h, leading to an enhanced biofilm microenvironment. Moreover, the novel elastomeric ligature demonstrated an obvious preventive effect on enamel demineralization, with an elastic modulus 30 % higher and hardness 62 % higher than those of the control group within 3 months (P < 0.05).

SIGNIFICANCE

The integration of DMAHDM with an elastomeric ligature holds significant promise for regulating biofilms and preventing enamel demineralization in orthodontic applications.

Update on Focal Infection Management: A Czech Interdisciplinary Consensus

BACKGROUND

The focal infection theory has been used to explain several chronic systemic diseases in the past. Systemic diseases were thought to be caused by focal infections, such as caries and periodontal diseases, and dentists were held responsible for these diseases due to the spread of oral infections. As knowledge of the interrelationship between oral microorganisms and the host immune response has evolved over the last few decades, the focal infection theory has been modified in various ways. The relationship between oral and systemic health appears to be more complex than that suggested by the classical theory of focal infections. Indeed, the contribution of the oral microbiota to some systemic diseases is gaining acceptance, as there are strong associations between periodontal disease and atherosclerotic vascular disease, diabetes, and hospital-associated pneumonia, amongst others. As many jurisdictions have various protocols for managing this oral-systemic axis of disease, we sought to provide a consensus on this notion with the help of a multidisciplinary team from the Czech Republic.

METHODS

A multidisciplinary team comprising physicians/surgeons in the specialities of dentistry, ear-nose and throat (ENT), cardiology, orthopaedics, oncology, and diabetology were quetioned with regard to their conceptual understanding of the focal infection theory particularly in relation to the oral-systemic axis. The team also established a protocol to determine the strength of these associations and to plan the therapeutic steps needed to treat focal odontogenic infections whenever possible.

RESULTS

Scoring algorithms were devised for odontogenic inflammatory diseases and systemic risks, and standardised procedures were developed for general use.

CONCLUSIONS

The designed algorithm of the oral-systemic axis will be helpful for all health care workers in guiding their patient management protocol.

Topical oxygen therapy as a novel strategy to promote wound healing and control the bacteria in implantology, oral surgery and periodontology: A review

Globally, oral infections and inflammatory lesions persist as substantial public health concerns, necessitating the introduction of novel oral treatment protocols. Oral diseases are linked to various causative factors, with dental plaque/biofilm resulting from inadequate hygiene practices playing a predominant role. The strategic implementation of novel topical therapies holds promise for effectively controlling the biofilms, addressing oral infections and promoting enhanced oral wound healing. This review aims to providing a comprehensive overview of the available evidence pertaining to the potential efficacy of topical oxygen and lactoferrin-releasing biomaterials, exemplified by the blue®m formula, as novel oral care interventions within the scope of contemporary implantology, oral surgery and periodontology.

3Y-TZP/Ta Biocermet as a Dental Material: An Analysis of the In Vitro Adherence of Streptococcus Oralis Biofilm and an In Vivo Pilot Study in Dogs

The surface adhesion of bacterial cells and the in vivo biocompatibility of a new ceramic-metal composite made of zirconium dioxide and tantalum were evaluated. Within the framework of an in vitro study using the crystal violet staining and colony counting methods, a relatively similar adhesion of Streptococcus oralis to the 3Y-TZP/Ta biocermet (roughness Ra = 0.12 ± 0.04 µm) and Ti-Al6-V4 titanium alloy (Ra = 0.04 ± 0.01 µm) was found. In addition, in an in vivo preliminary study focused on the histological analysis of a series of rods implanted in the jaws of beagle dogs for a six-month period, the absence of any fibrous tissue or inflammatory reaction at the interface between the implanted 3Y-TZP/Ta biocermets and the new bone was found. Thus, it can be concluded that the developed ceramic-metal biocomposite may be a promising new material for use in dentistry.

Evaluation of extracellular polymeric substances matrix volume, surface roughness and bacterial adhesion property of oral biofilm

Background/purpose

Oral biofilms are highly structured bacterial colonies embedded in a highly hydrated extracellular polymeric substances (EPS) matrix. This study aimed to investigate the characteristics of oral biofilm at different stages of maturation.

Materials and methods

Oral multispecies biofilms were grown anaerobically from plaque bacteria on collagen coated hydroxyapatite discs in brain heart infusion broth for one and three weeks. The volume of live bacteria and EPS matrix of the biofilms were determined by using corresponding fluorescent probes and confocal laser scanning microscopy. Atomic force microscopy (AFM) was used to quantitatively probe and correlate cell surface adhesion force of biofilms. The surface roughness was quantified in terms of the root mean square average of the height deviations. Adhesion was measured from force-distance data for the retraction of the cell from the surface.

Results

The volume of live bacteria and EPS of 3-week-old biofilms was higher than 1-week-old biofilms. The surface roughness value in 1-week-old biofilms was significantly higher than that in 3-week-old biofilms. AFM force-distance curve results showed that the adhesion force at the cell-cell interface was significantly more at-tractive than those at bacterial cells surface of both stages biofilms. Adhesion forces between the AFM tip and the surface of bacterial cell were fairly constant, whereas the cell-cell interface experienced greater adhesion forces in the biofilm's development.

Conclusion

As oral biofilms become mature, EPS volume and cell-cell adhesion forces increase while the surface roughness decreases.

The Effect of Centella asiatica Methanolic Extract on Expression of IL-1β Proinflammatory Cytokines in Severe Early Childhood Caries

OBJECTIVE

 This article analyzes the role of C. asiatica extract in reducing the proinflammatory cytokine interleukin (IL)-1β produced by salivary neutrophils.

MATERIAL AND METHODS

 Selected kindergartens in the Surabaya area provided samples. The sample was initially checked for dental caries by measuring its def-t index, and then the participants who satisfied the requirements for severe caries with a def-t of greater than 6 were chosen. At the time of sampling, all of the individuals were between the ages of 4 and 6. The sampling was performed by researchers and certified persons using well-known methodologies. For 60 minutes before to sampling, respondents were not allowed to eat, drink, chew gum, or brush their teeth. For analysis, the samples were collected and then frozen at -80°C.

RESULTS

 The administration of methanolic extract C. asiatica decreased the expression of the proinflammatory cytokine IL-1β on the surface of salivary neutrophils on S-ECC; The administration of C. asiatica methanol extract resulted in a decrease in the expression of the proinflammatory cytokine IL-1β on the surface of salivary neutrophils in S-ECC.

CONCLUSION

 C. asiatica extract has the effect of reducing the proinflammatory cytokine IL-1β produced by salivary neutrophils on S-ECC via inhibiting nuclear factor kappa B and mitogen-activated protein kinase signaling pathway activation and suggest that C. asiatica is a possible candidate for treating S-ECC.

A randomized double-blind clinical trial evaluating comparative plaque and gingival health associated with commercially available stannous fluoride-containing dentifrices as compared to a sodium fluoride control dentifrice

BACKGROUND

Gingivitis is a non-specific inflammatory lesion in response to the accumulation of oral biofilm and is a necessary precursor to periodontitis. Enhanced oral hygiene practices, including utilization of a dentifrice that could significantly improve plaque accumulation and gingival inflammation, is desirable to prevent and treat gingivitis and potentially prevent progression to periodontitis. This clinical study aimed to investigate the effect of a new stannous fluoride-containing dentifrice with 2.6% ethylenediamine tetra acetic acid (EDTA) as an anti-tartar agent to reduce plaque index and gingival index over a 3-month study period compared to other commercially-available fluoride-containing dentifrices.

METHODS

This double-blind, randomized controlled clinical study evaluated plaque, gingival inflammation, and sulcular bleeding in patients using one of five commercially available fluoride-containing dentifrices The dentifrices tested contained: 0.454% stannous fluoride and 2.6% EDTA (D1), 0.24% sodium fluoride (C), and 0.454% stannous fluoride (D2-D4). One hundred fifty subjects participated over a 3-month period. Co-primary endpoints were improvements in plaque index (PI) and modified gingival index (mGI) from baseline values. No professional cleaning was performed during the study period.

RESULTS

All subjects in the study demonstrated statistically significant improvements in all measures of oral hygiene over the 3-month study period. Subjects using dentifrice 1 (D1) showed statistically significantly greater reductions in PI, mGI, and modified sulcular bleeding index (mSBI) compared with all other commercially-available dentifrices tested (p < 0.00001).

CONCLUSIONS

A new dentifrice with 0.454% stannous fluoride and 2.6% EDTA demonstrated significant improvements in clinical parameters associated with gingivitis compared to other sodium and stannous fluoride containing dentifrices.

Effects of Tea Polyphenols and Theaflavins on Three Oral Cariogenic Bacteria

In order to investigate the antibacterial mechanism of tea polyphenols and theaflavins against oral cariogenic bacteria, the pH value of the culture medium, the number of bacteria adhering to the smooth glass tube wall, and the electrical conductivity value within 10 h were measured, respectively. The effects of four concentrations of tea polyphenols and theaflavins below the MIC value were studied on acid production, adhesion, and electrical conductivity of oral cariogenic bacteria. The live/dead staining method was used to observe the effects of four concentrations of tea polyphenols and theaflavins below the MIC value on the biofilm formation of oral cariogenic bacteria under a laser scanning confocal microscope. With the increase in concentrations of tea polyphenols and theaflavins, the acid production and adhesion of the cariogenic bacteria gradually decreased, and the conductivity gradually increased. However, the conductivity increase was not significant (p < 0.05). Compared with the control group, the 1/2MIC and 1/4MIC tea polyphenols and theaflavins treatments significantly reduced the biomass of the cariogenic biofilm (p < 0.05). The confocal laser scanning microscope showed that the integrated optical density of green fluorescence of the cariogenic biofilm gradually decreased with the increase in agent concentration after the action of tea polyphenols and theaflavins.

Saliva biomarkers in oral disease

Saliva is a versatile biofluid that contains a wide variety of biomarkers reflecting both physiologic and pathophysiologic states. Saliva collection is noninvasive and highly applicable for tests requiring serial sampling. Furthermore, advances in test accuracy, sensitivity and precision for saliva has improved diagnostic performance as well as the identification of novel markers especially in oral disease processes. These include dental caries, periodontitis, oral squamous cell carcinoma (OSCC) and Sjögren's syndrome (SS). Numerous growth factors, enzymes, interleukins and cytokines have been identified and are the subject of much research investigation. This review highlights current procedures for successful determination of saliva biomarkers including preanalytical factors associated with sampling, storage and pretreatment as well as subsequent analysis. Moreover, it provides an overview of the diagnostic applications of these salivary biomarkers in common oral diseases.

Oropharyngeal microbiome composition as a possible diagnostic marker for true psychosis in a forensic psychiatric setting: A narrative literature review and an opinion

The malingered psychosis has increasingly occurred over the past few years due to the tendency towards care in the community and the closures of long-stay psychiatric institutions. Thus, it is required to identify malingered psychosis to reach accurate forensic assessments and inhibit misuse of restricted healthcare resources and miscarriages of justice. Despite the fact that some practical psychometric tools and strategies have been proposed for diagnosing true psychosis over the past decades, the differentiation between true psychosis and malingered psychosis is still sometimes challenging. Accordingly, it seems crucial to identify innovative and reliable diagnostic alternatives. Hence, the present article summarizes a collection of evidence that can be used by researchers to improve future assessment of oropharyngeal microbiome composition as a feasible diagnostic marker for true psychosis in a forensic psychiatric setting.

Lippia origanoides derivatives in vitro evaluation on polymicrobial biofilms: Streptococcus mutans, Lactobacillus rhamnosus and Candida albicans

OBJECTIVE

This work evaluated the Lippia origanoides derivatives in vitro effect on polymicrobial biofilms of Streptococcus mutans, Lactobacillus rhamnosus and Candida albicans. Additionally, the cytotoxic effect of the oils on human skin keratinocytes (HaCaT) and fibroblasts of the periodontal ligament (FLP) cell lines was evaluated.

DESIGN

The minimum inhibitory concentration, the inhibitory activity on monomicrobial (S. mutans) and polymicrobial biofilm (S. mutans, L. rhamnosus and C. albicans) of L. origanoides four essential oils and terpenes (thymol and carvacrol) were evaluated. The cytotoxic effect of each one of the compounds was measured, and all the tests were compared against chlorhexidine.

RESULTS

All the evaluated compounds reached an inhibition percentage of S. mutans monomicrobial biofilms formation of 100 % at 600 µg/mL (p < 0.0001). The highest concentration (2 MIC) eradicated 100 % of S. mutans-preformed biofilms after 5 min L. origanoides carvacrol + thymol and thymol chemotypes showed marked reductions in topography, the number of microbial cells and extracellular matrix on polymicrobial biofilm. The cytotoxic effect of the compounds was very similar to chlorhexidine.

CONCLUSIONS

L. origanoides essential oils have an inhibitory effect on mono and polymicrobial biofilms. The oils present a similar cytotoxic effect to chlorhexidine on HaCaT and FLP cell lines. However, including these compounds in formulations for clinical use is an exciting proposal yet to be investigated.

Better living through chemistry? A randomized, double-blind controlled study evaluating the efficacy of plaque control and gingival health impacts of a novel stannous fluoride-containing gel

BACKGROUND

Gingivitis is a nonspecific inflammatory lesion in response to the accumulation of oral biofilm and is a necessary precursor to periodontitis. Enhanced oral hygiene practices are necessary to reverse gingivitis and a dentifrice that could provide significant clinical reductions in plaque accumulation and gingival inflammation would be desirable to treat gingivitis and potentially prevent progression to periodontitis. This clinical study aimed to investigate the effect of a novel stannous fluoride-containing dentifrice with 2.6% ethylenediamine tetra-acetic acid (EDTA) as an antitartar agent to reduce Plaque Index (PI) and Gingival Index over a 3-month study period.

METHODS

This double-blind, randomized controlled clinical study evaluated plaque, gingival inflammation, and sulcular bleeding in patients using either a novel dental gel containing 0.454% stannous fluoride and 2.6% EDTA or a dentifrice with 0.24% sodium fluoride. Sixty subjects participated over a 3-month period. Co-primary endpoints were improvements in PI and Modified Gingival Index (mGI) from baseline values. No professional cleaning was performed during the study period.

RESULTS

All subjects in the study demonstrated statistically significant improvements in all measures of oral hygiene over the 3-month study period. Subjects using the novel dental gel showed statistically significantly greater reductions in PI (ΔPI) [(-1.43 ± 0.34; -0.49 ± 0.13) (p < 0.00001)], mGI (ΔmGI) [(-1.11 ± 0.22; -0.16 ± 0.12) (p < 0.00001)], and modified sulcular bleeding index (ΔmSBI) [(-1.15 ± 0.18; -0.20 ± 0.07) (p < 0.00001)].

CONCLUSIONS

The novel dental gel demonstrated significant improvements in clinical parameters associated with gingivitis compared to a commercially available sodium fluoride dentifrice.

Sulfate-Reducing Bacteria in Patients Undergoing Fixed Orthodontic Treatment

OBJECTIVES

The oral microbiological environment may be implicated in the corrosion of orthodontic metals. This study aimed to examine the prevalence of sulfate-reducing bacteria (SRB) in orthodontic patients undergoing fixed appliance treatment.

METHODS

Sixty-nine orthodontic and 69 healthy non-orthodontic participants were enrolled in the study. Supragingival and subgingivaloral biofilm were collected and tested for the presence of SRB. The DNA extraction, polymerase chain reaction (PCR), and 16sRNA Sanger sequencing method was performed from the SRB-positive samples. The sequenced PCR products were analysed and compared with databases to identify the bacterial genus.

RESULTS

Amongst 69 orthodontic patients, characteristic black precipitates developed in 14, indicating the presence of iron sulfides which demonstrates the likelihood of SRB. Alternatively, 2 out of 69 showed the presence of SRB in healthy non-orthodontic participants (controls). Desulfovibrio spp was confirmed by analyses of 16sRNA sequencing, which revealed that the SRB prevalence was 20% in the examined participants with orthodontic appliances.

CONCLUSIONS

The prevalence of SRB was found to be significantly higher amongst orthodontic patients compared to non-orthodontic participants. Presence of stainless steel in the oral environment may have facilitated the colonisation of SRB.

The Oral Microbiota in Valvular Heart Disease: Current Knowledge and Future Directions

Oral microbiota formation begins from birth, and everything from genetic components to the environment, alongside the host's behavior (such as diet, smoking, oral hygiene, and even physical activity), contributes to oral microbiota structure. Even though recent studies have focused on the gut microbiota's role in systemic diseases, the oral microbiome represents the second largest community of microorganisms, making it a new promising therapeutic target. Periodontitis and dental caries are considered the two main consequences of oral bacterial imbalance. Studies have shown that oral dysbiosis effects are not limited locally. Due to technological advancement, research identified oral bacterial species in heart valves. This evidence links oral dysbiosis with the development of valvular heart disease (VHD). This review focuses on describing the mechanism behind prolonged local inflammation and dysbiosis, that can induce bacteriemia by direct or immune-mediated mechanisms and finally VHD. Additionally, we highlight emerging therapies based on controlling oral dysbiosis, periodontal disease, and inflammation with immunological and systemic effects, that exert beneficial effects in VHD management.

Influence of Environmental Factors on Salivary Microbiota and Their Metabolic Pathway: Next-Generation Sequencing Approach

The current study aimed to investigate the effect of periodontitis and long-term heavy metal (HM) exposure on the salivary microbiome. The patients were divided into four groups as Wu Wei control (WWC) group involved healthy individuals, Wu Wei periodontitis (WWP) patients having periodontitis, Jing Chang with metal pollution periodontally healthy individuals (JCP), and Kuang periodontitis (KP). The most abundant bacteria identified at the phylum level in the WWC group were Bacteroides, Firmicutes, and Fusobacteria. Firmicutes were observed in a significantly higher proportion in the KP group than in the WWC, WWP, and JCP. At the genus level, the WWC has major dominating bacterial genera (such as Leptotrichia, Neisseria, and Fusobacterium) which were similar to WWP and KP group. The significant difference (p < 0.05) was found in alpha diversity while in beta diversity, the significant (p = 0.005) results were found among the four groups. The correlation of oral microbiota revealed that HMs present in the soil (Cr, Ni, and Cu) are associated with the growth of Capnocytophaga, Selenomonas, Aggregatibacter, and Campylobacter. The bacterial functions in the KP group were higher in translation and nucleotide metabolism than in the WWP group. This demonstrated that long-term exposure to HMs can influence the salivary microbiota which can alter the functioning, and diversity of bacteria.

Sphingosine kinase activity and sphingosine-1-phosphate in the inflamed human periodontium

OBJECTIVES

This study evaluated changes in the levels of Sphingosine-1-Phosphate (S1P) and Sphingosine Kinase (SPHK) activity in response to non-surgical periodontal treatment in humans.

METHODS

Diseased (n = 65) and healthy sites (n = 72) were screened in 18 patients with localized periodontitis stage II or III. Periodontal clinical parameters were recorded, and the gingival crevicular fluid (GCF) collected at baseline, 30 and 90 days of non-surgical treatment. Internal control sites without attachment loss/bleeding were sampled at baseline and after 90 days of treatment. SPHK activity and S1P levels and SPHK 1/2 isoforms were determined in the GCF at different time points using ELISA.

RESULTS

Non-surgical treatment caused significant improvement in all periodontal clinical parameters (p < 0.01). Activity of SPHK and S1P levels was decreased (p < 0.05) 30 days after treatment and continued up to 90 days (p < 0.01); control sites remained unchanged throughout the study and resembled treated sites at 3 months (p > 0.05). SPHK1 levels presented decrease after periodontal treatment (p < 0.001). SPHK2 levels were lower than SPHK1 (p < 0.001) and remained unchanged.

CONCLUSIONS

S1P levels and SPHK activity decreased within 3 months of non-surgical periodontal treatment, which were correlated with improvements in periodontal parameters. Only SPHK1 levels varied significantly in the states of health and disease.

Characterization of the oral microbiome of children with type 1 diabetes in the acute and chronic phases

Background and Aim

The relationship between the oral microbiota and type 1 diabetes (T1D) remains unclear. We aimed to evaluate the variations in the oral microbiome in T1D and identify potentially associated bacterial factors.

Methods

We performed high-throughput sequencing of the V3-V4 area of the 16S rRNA gene to profile the oral bacterial composition of 47 healthy children (CON group), 46 children with new-onset T1D in the acute phase (NT1D group), and 10 children with T1D in the chronic phase receiving insulin treatment (CT1D group). Multivariate statistical analysis of sequencing data was performed.

Results

Compared to the CON group, the NT1D group was characterized by decreased diversity and increased abundance of genera harboring opportunistic pathogens, while this trend was partially reversed in the CT1D group. Differential genera between groups could distinguish the NT1D group from the CON group (AUC = 0.933) and CT1D group (AUC = 0.846), respectively. Moreover, T1D-enriched genera were closely correlated with HbA1c, FBG and WBCs levels.

Conclusion

Our results showed that the acute phase of T1D was characterized by oral microbiota dysbiosis, which could be partially ameliorated via glycemic control. The possible role of oral microbiota dysbiosis on oral health and systemic metabolic status in T1D warrants further mechanistic investigation.

Diurnal changes of the oral microbiome in patients with alcohol dependence

Background

Saliva secretion and oral microbiota change in rhythm with our biological clock. Dysbiosis of the oral microbiome and alcohol consumption have a two-way interactive impact, but little is known about whether the oral microbiome undergoes diurnal changes in composition and function during the daytime in patients with alcohol dependence (AD).

Methods

The impact of alcohol consumption on the diurnal salivary microbiome was examined in a case-control study of 32 AD patients and 21 healthy control (HC) subjects. We tested the changes in microbial composition and individual taxon abundance by 16S rRNA gene sequencing.

Results

The present study is the first report showing that alcohol consumption enhanced the richness of the salivary microbiome and lowered the evenness. The composition of the oral microbiota changed significantly in alcohol-dependent patients. Additionally, certain genera were enriched in the AD group, including Actinomyces, Leptotrichia, Sphaerochaeta and Cyanobacteria, all of which have pathogenic effects on the host. There is a correlation between liver enzymes and oral microbiota. KEGG function analysis also showed obvious alterations during the daytime.

Conclusion

Alcohol drinking influences diurnal changes in the oral microbiota, leading to flora disturbance and related functional impairment. In particular, the diurnal changes of the oral microbiota may open avenues for potential interventions that can relieve the detrimental consequences of AD.

Microbiome and Human Health: Current Understanding, Engineering, and Enabling Technologies

The human microbiome is composed of a collection of dynamic microbial communities that inhabit various anatomical locations in the body. Accordingly, the coevolution of the microbiome with the host has resulted in these communities playing a profound role in promoting human health. Consequently, perturbations in the human microbiome can cause or exacerbate several diseases. In this Review, we present our current understanding of the relationship between human health and disease development, focusing on the microbiomes found across the digestive, respiratory, urinary, and reproductive systems as well as the skin. We further discuss various strategies by which the composition and function of the human microbiome can be modulated to exert a therapeutic effect on the host. Finally, we examine technologies such as multiomics approaches and cellular reprogramming of microbes that can enable significant advancements in microbiome research and engineering.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

Correlation between Streptococcus mutans levels in dental plaque and saliva of children

PURPOSE

This study was designed to compare the levels of Streptococcus mutans (S. mutans) in saliva with those in occlusal plaque on posterior teeth at different stages of dentition, and to explore the correlation with caries experience to determine the most suitable source of S. mutans for research.

METHODS

Samples of saliva and occlusal plaque were collected from 83 patients (aged 3-17 years) over three months. S. mutans levels were determined by culture-based selective plating, morphological identification, and S.mutans-specific monoclonal antibody labeling.

RESULTS

The mean age of the participants was 8.8 (±3.7) years, and 74.7% of them were Hispanic. Mean caries experience for children with primary, mixed, and permanent dentition was 5.2 (±4.7), 4.0 (±3.3), and 0.8 (±1.3), respectively. Children with primary and mixed dentition had a higher caries experience than children with permanent dentition (P < 0.01), despite having similar S. mutans levels and total bacteria. A positive correlation was observed between S. mutans levels in plaque and those in saliva, but not between S. mutans levels and caries experience. It was noteworthy that plaque samples harbored higher S. mutans levels (>10⁵ CFU/mL) than saliva samples.

CONCLUSION

Both plaque and saliva samples are useful sources for S. mutans isolation. S. mutans levels from both sources were not significantly correlated with caries experience, but occlusal plaque had greater sensitivity for quantification of high S. mutans levels.

The use of Trojan-horse drug delivery system in managing periodontitis

The aim of this review is to evaluate the possibility of delivering a silver-acid complex via a Trojan-horse mechanism for managing periodontits. We theroised that the complex could be an effective treatment option for bacterial inflammatory processes in the oral cavity. Searches were conducted using MEDLINE, Embase, Web of Science Core Collection, and Google Scholar search engines. We also reviewed several reference lists of the included studies or relevant reviews identified by the search. By using Medical Subject Headings (MeSH) terminology, a comprehensive search was performed for the following keywords: silver, folic acid, periodontitis, macrophages, Trojan-horse mechanism, toxicity, and targeting. Using the keywords mentioned earlier, we selected 110 articles and after appropriate elimination the review was written based on 37 papers. Accordingly the we noted that silver isons were an effective approach to kill oral pathogens. Secondly the Trojan-horse mechanism. could be used by macrophages (as the Trojan horse) to deliver silver ions in large quantities to the inflammatory focus to kill the periodontopathogens. The Trojan-horse mechanism has never been described in the field of dentistry before. The proposed novel approach using the principle of Trojan Horse delivery of drugs/chemicals could be used to manage oral inflammatory conditions. This method can be used to supplement regular treatments.

Highly Targeted Electrochemical Disruption of Microbes with Minimal Disruption to Pulp Cells

INTRODUCTION

Pulpitis results from the infiltration of mixed populations of bacteria which trigger inflammation in the dental pulp, causing significant disruption to these tissues. Clinically, pulpitis frequently leads to devitalization or extraction, as disinfection of the dental pulp while maintaining its vitality is extremely difficult. Here we describe the use of an electrocatalytic titanium dioxide (TiO₂)-based apparatus adapted from water purification technology, which can efficiently deliver anti-microbial oxidants (e.g., hydroxyl radicals) when low voltages are applied. As these oxidants are also potentially harmful to pulp cells, oxidant exposure protocols that disrupt oral bacteria, yet are innocuous to dental pulp cells must be established.

METHODS

Stem cells from Human Exfoliated Deciduous teeth (SHEDs) and mixed salivary bacteria were exposed to apparatus generated oxidants for time points of 15, 100 or 300 seconds. SHED apoptosis, necrosis, and vitality post exposure were analyzed by florescent marker staining and flow cytometry. Destruction of mixed salivary bacteria was analyzed by post exposure counts of adherent bacterial cells.

RESULTS

When applied to SHEDs the apparatus generated oxidants do not significantly induce apoptosis or necrosis at any exposure time. SHED cell vitality is not decreased with apparatus exposure. Exposure to apparatus generated oxidants destroys mixed salivary bacteria, with significant destruction seen at 15 seconds and maximal destruction achieved at 100 seconds.

CONCLUSIONS

This technology has the potential to be useful in the disinfection of deep lesions and pulp tissues, efficiently producing oxidants which eliminate bacteria but do not harm native pulp cells after relatively brief exposures.

CLINICAL SIGNIFICANCE

Incomplete disinfection of inflamed dental pulp is a significant cause of pulp destruction, leading to devitalization or extraction. Novel technology which enhances the disinfection of the pulp may provide clinicians with treatments options that preserve pulp vitality and tooth structure.

Dysbiosis and Predicted Functions of the Dental Biofilm of Dairy Goats with Periodontitis

Periodontitis is a polymicrobial biofilm-induced inflammatory disease associated with a dysbiotic microbial community and severely affects the health and welfare of animals. However, little is known regarding the dental microbiota associated with this disease in goats. In this study, we used high-throughput sequencing, network analysis, and predicted functions to investigate the microbiota of clinically healthy goats and those with periodontitis and identify possible pathogens and proteins associated with the disease. Dental microbiomes of goats with periodontitis were richer, and network analyses showed that the number of negative interactions was higher in the networks of animals with periodontitis. Based on the interrelationships, Porphyromonas, Fusobacterium, and Prevotella were suggested to play an important role in the dental microbiota associated with goat periodontitis. Protein families linked to translation, cytoplasmatic translation, and rRNA processing were more abundant in the dental microbiota of goats with periodontitis. In conclusion, the dental biofilm microbiota associated with goat periodontitis seems to be dysbiotic and has significant antagonistic interactions, which discriminate healthy animals from diseased animals and highlight the importance of key bacteria. Thus, these novel findings contribute to the evolution of knowledge regarding the etiopathogenesis of goat periodontitis and possibly to the development of periodontitis control measures.

Hydroxyapatite Pellets as Versatile Model Surfaces for Systematic Adhesion Studies on Enamel: A Force Spectroscopy Case Study

Research into materials for medical application draws inspiration from naturally occurring or synthesized surfaces, just like many other research directions. For medical application of materials, particular attention has to be paid to biocompatibility, osseointegration, and bacterial adhesion behavior. To understand their properties and behavior, experimental studies with natural materials such as teeth are strongly required. The results, however, may be highly case-dependent because natural surfaces have the disadvantage of being subject to wide variations, for instance in their chemical composition, structure, morphology, roughness, and porosity. A synthetic surface which mimics enamel in its performance with respect to bacterial adhesion and biocompatibility would, therefore, facilitate systematic studies much better. In this study, we discuss the possibility of using hydroxyapatite (HAp) pellets to simulate the surfaces of teeth and show the possibility and limitations of using a model surface. We performed single-cell force spectroscopy with single Staphylococcus aureus cells to measure adhesion-related parameters such as adhesion force and rupture length of cell wall proteins binding to HAp and enamel. We also examine the influence of blood plasma and saliva on the adhesion properties of S. aureus. The results of these measurements are matched to water wettability, elemental composition of the samples, and the change in the macromolecules adsorbed over time on the surface. We found that the adhesion properties of S. aureus were similar on HAp and enamel samples under all conditions: Significant decreases in adhesion strength were found equally in the presence of saliva or blood plasma on both surfaces. We therefore conclude that HAp pellets are a good alternative for natural dental material. This is especially true when slight variations in the physicochemical properties of the natural materials may affect the experimental series.

Characterization of Acidic Mammalian Chitinase as a Novel Biomarker for Severe Periodontitis (Stage III/IV): A Pilot Study

Periodontitis is a chronic inflammatory condition characterized by gingival infection, periodontal pocket formation, and alveolar bone loss. Acidic mammalian chitinase (AMCase), an active chitinase enzyme, increased its expression under severe inflammation and related systemic disorders. However, AMCase expression and molecular mechanism in periodontal inflammation, have not been elucidated yet. This study was aimed to characterize AMCase in severe periodontitis patients compare to those in periodontally healthy subjects. In total, 15 periodontally healthy subjects and 15 severe (stage III/IV) periodontitis patients were enrolled with their informed consent. Tissue samples were collected and analyzed using Western blot and enzyme-linked immunosorbent assay (ELISA). AMCase protein expressions in periodontal patients were significantly more increased than those of periodontally healthy individuals. ELISA resulted in median values (first quartile to third quartile) of the periodontally healthy group 0.654 ng/mL (range, 0.644−0.827 ng/mL) and the periodontitis group 0.965 ng/mL (range, 0.886−1.165 ng/mL). AMCase was expressed significantly higher levels in periodontitis patients than in periodontally healthy individuals (p < 0.05). This suggests that AMCase may play a potential role as a biomarker for the screening and early diagnosis of severe periodontitis.

Oral Microbiome: Getting to Know and Befriend Neighbors, a Biological Approach

The oral microbiome, forming a biofilm that covers the oral structures, contains a high number of microorganisms. Biofilm formation starts from the salivary pellicle that allows bacterial adhesion–colonization–proliferation, co-aggregation and biofilm maturation in a complex microbial community. There is a constant bidirectional crosstalk between human host and its oral microbiome. The paper presents the fundamentals regarding the oral microbiome and its relationship to modulator factors, oral and systemic health. The modern studies of oral microorganisms and relationships with the host benefits are based on genomics, transcriptomics, proteomics and metabolomics. Pharmaceuticals such as antimicrobials, prebiotics, probiotics, surface active or abrasive agents and plant-derived ingredients may influence the oral microbiome. Many studies found associations between oral dysbiosis and systemic disorders, including autoimmune diseases, cardiovascular, diabetes, cancers and neurodegenerative disorders. We outline the general and individual factors influencing the host–microbial balance and the possibility to use the analysis of the oral microbiome in prevention, diagnosis and treatment in personalized medicine. Future therapies should take in account the restoration of the normal symbiotic relation with the oral microbiome.

Is There a Link between Oropharyngeal Microbiome and Schizophrenia? A Narrative Review

The study aimed to examine the impact of the oropharyngeal microbiome in the pathophysiology of schizophrenia and to clarify whether there might be a bidirectional link between the oral microbiota and the brain in a context of dysbiosis-related neuroinflammation. We selected nine articles including three systemic reviews with several articles from the same research team. Different themes emerged, which we grouped into 5 distinct parts concerning the oropharyngeal phageome, the oropharyngeal microbiome, the salivary microbiome and periodontal disease potentially associated with schizophrenia, and the impact of drugs on the microbiome and schizophrenia. We pointed out the presence of phageoma in patients suffering from schizophrenia and that periodontal disease reinforces the role of inflammation in the pathophysiology of schizophrenia. Moreover, saliva could be an interesting substrate to characterize the different stages of schizophrenia. However, the few studies we have on the subject are limited in scope, and some of them are the work of a single team. At this stage of knowledge, it is difficult to conclude on the existence of a bidirectional link between the brain and the oral microbiome. Future studies on the subject will clarify these questions that for the moment remain unresolved.

Microbiota analysis of peri-implant mucositis in patients with periodontitis history

OBJECTIVES

To investigate the bacterial diversity in peri-implant plaques and the effect of periodontitis history on the occurrence of peri-implant mucositis.

MATERIALS AND METHODS

Three groups of subgingival plaques were collected from peri-implant sulci in the first molar area. The three groups included healthy implants in patients without periodontitis (NH implant), healthy implants in patients with periodontitis history (PH implant), and peri-implant mucositis implants in patients with periodontitis history (PM implant). Subgingival plaques in periodontal pockets of contralateral natural first molars were also collected. Bacterial DNA was extracted and the V4 region of the 16S rDNA sequence was amplified and sequenced on an Illumina HiSeq platform. The operational taxonomic units obtained from amplicon sequencing were used to analyze the prevalence and identity of bacteria based on public databases and advanced techniques.

RESULTS

Analysis of similarities indicated a significant difference in bacterial structures between the NH implant and PM implant groups. Additionally, a significantly higher relative abundance of the genera Actinomyces and Streptococcus was found in the samples of the NH implant group. The genera Fusobacterium and Prevotella could be considered as potential biomarkers for peri-implant mucositis. Moreover, more gram-negative anaerobic bacteria (Porphyromonas and Prevotella) were detected in the samples from patients with periodontitis history.

CONCLUSIONS

The increased accumulation of Fusobacterium and Prevotella is associated with a higher risk of peri-implant mucositis. In addition, patients with periodontal history may be more likely to develop peri-implant mucositis.

CLINICAL RELEVANCE

The increase in periodontal pathogens and the decrease in health-associated bacteria in patients with periodontitis history may be more likely to develop peri-implant mucositis. These results provide a bacteriological basis for the prevention and treatment of peri-implant mucositis in patients with periodontitis history.

Effect of Cavity Cleanser With Long-Term Antibacterial and Anti-Proteolytic Activities on Resin-Dentin Bond Stability

Objective

Secondary caries caused by oral microbiome dysbiosis and hybrid layer degradation are two important contributors to the poor resin-dentin bond durability. Cavity cleansers with long-term antimicrobial and anti-proteolytic activities are in demand for eliminating bacteria-induced secondary caries and preventing hybrid layers from degradation. The objectives of the present study were to examine the long-term antimicrobial effect and anti-proteolytic potential of poly(amidoamine) dendrimers with amino terminal groups (PAMAM-NH₂) cavity cleanser.

Methods

Adsorption tests by attenuated total reflectance-infrared (ATR-IR) spectroscopy and confocal laser scanning microscopy (CLSM) were first performed to evaluate whether the PAMAM-NH₂ cavity cleanser had binding capacity to dentin surface to fulfill its relatively long-term antimicrobial and anti-proteolytic effects. For antibacterial testing, Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis were grown on dentin surfaces, prior to the application of cavity cleanser. Colony-forming unit (CFU) counts and live/dead bacterial staining were performed to assess antibacterial effects. Gelatinolytic activity within the hybrid layers was directly detected by in situ zymography. Adhesive permeability of bonded interface and microtensile bond strength were employed to assess whether the PAMAM-NH₂ cavity cleanser adversely affected resin-dentin bonding. Finally, the cytotoxicity of PAMAM-NH₂ was evaluated by the Cell Counting Kit-8 (CCK-8) assay.

Results

Adsorption tests demonstrated that the binding capacity of PAMAM-NH₂ on dentin surface was much stronger than that of 2% chlorhexidine (CHX) because its binding was strong enough to resist phosphate-buffered saline (PBS) washing. Antibacterial testing indicated that PAMAM-NH₂ significantly inhibited bacteria grown on the dentin discs as compared with the control group (p < 0.05), which was comparable with the antibacterial activity of 2% CHX (p > 0.05). Hybrid layers conditioned with PAMAM-NH₂ showed significant decrease in gelatin activity as compared with the control group. Furthermore, PAMAM-NH₂ pretreatment did not adversely affect resin-dentin bonding because it did not decrease adhesive permeability and microtensile strength. CCK-8 assay showed that PAMAM-NH₂ had low cytotoxicity on human dental pulp cells (HDPCs) and L929.

Conclusions

PAMAM-NH₂ cavity cleanser developed in this study could provide simultaneous long-term antimicrobial and anti-proteolytic activities for eliminating secondary caries that result from a dysbiosis in the oral microbiome and for preventing hybrid layers from degradation due to its good binding capacity to dentin collagen matrix, which are crucial for the maintenance of resin-dentin bond durability.

A New pH-Responsive Nano Micelle for Enhancing the Effect of a Hydrophobic Bactericidal Agent on Mature Streptococcus mutans Biofilm

The bactericidal effect on biofilm is the main challenge currently faced by antibacterial agents. Nanoscale drug-delivery materials can enhance biofilm penetrability and drug bioavailability, and have significant applications in the biomedical field. Dental caries is a typical biofilm-related disease, and the acidification of biofilm pH is closely related to the development of dental caries. In this study, a pH-responsive core-shell nano micelle (mPEG-b-PDPA) capable of loading hydrophobic antibacterial agents was synthesized and characterized, including its ability to deliver antibacterial agents within an acidic biofilm. The molecular structure of this diblock copolymer was determined by hydrogen-1 nuclear magnetic resonance (¹H-NMR) and gel permeation chromatography (GPC). The characters of the micelles were studied by dynamic light scattering (DLS), TEM, pH titration, and drug release detection. It was found that the hydrophilic micelles could deliver bedaquiline, a hydrophobic antibacterial agent on S. mutans, in acidic environments and in mature biofilm. No cytotoxic effect on the periodontal cells was detected within 48 h. This pH-responsive micelle, being able to load hydrophobic antibacterial agent, has good clinical application potential in preventing dental caries.

Challenges and solutions in polymer drug delivery for bacterial biofilm treatment: A tissue-by-tissue account

To tackle the emerging antibiotic resistance crisis, novel antimicrobial approaches are urgently needed. Bacterial communities (biofilms) are a particular concern in this context. Biofilms are responsible for most human infections and are inherently less susceptible to antibiotic treatments. Biofilms have been linked with several challenging chronic diseases, including implant-associated osteomyelitis and chronic wounds. The specific local environments present in the infected tissues further contribute to the rise in antibiotic resistance by limiting the efficacy of systemic antibiotic therapies and reducing drug concentrations at the infection site, which can lead to reoccurring infections. To overcome the shortcomings of systemic drug delivery, encapsulation within polymeric carriers has been shown to enhance antimicrobial efficacy, permeation and retention at the infection site. In this Review, we present an overview of current strategies for antimicrobial encapsulation within polymeric carriers, comparing challenges and solutions on a tissue-by-tissue basis. We compare challenges and proposed drug delivery solutions from the perspective of the local environments for biofilms found in oral, wound, gastric, urinary tract, bone, pulmonary, vaginal, ocular and middle/inner ear tissues. We will also discuss future challenges and barriers to clinical translation for these therapeutics. The following Review demonstrates there is a significant imbalance between the research focus being placed on different tissue types, with some targets (oral and wound biofims) being extensively more studied than others (vaginal and otitis media biofilms and endocarditis). Furthermore, the importance of the local tissue environment when selecting target therapies is demonstrated, with some materials being optimal choices for certain sites of bacterial infection, while having limited applicability in others.

Local/Topical Antibiotics for Peri-Implantitis Treatment: A Systematic Review

Most studies indicate that the mechanical removal of the bacterial biofilm from the implant surface is the central goal of peri-implantitis therapy. However, controversial results in the treatment of peri-implantitis have led to the consideration of additional strategies that include surgical approaches and chemical adjuvants. Local/topical antibiotics, such as minocycline, azithromycin, tetracycline, amoxicillin, doxycycline, and metronidazole, may improve the efficacy of the definitive treatment of the disease, but the lack of conclusive findings prevents their use in clinical practice. This systematic review aimed to evaluate the effect of local/topical antibiotics for peri-implantitis treatment. Randomised controlled studies (RCT) on patients with peri-implantitis and comparing the efficacy of local/topical antibiotics vs. placebo or mechanical debridement were included. A systematic search strategy was carried out using three registered databases (PubMed, Web of Science, and Scopus). RoB2 was used to assess risk of bias. Five RCTs were identified (n = 250 patients and 333 implants). Contrast results emerged among the included studies, and a high heterogeneity level was observed. Risk of bias revealed some concerns for three studies out of five, while one study was judged at high risk. Only one study analysed the limitations of its findings. Overall, local antibiotic use can be considered a valid approach in the treatment of peri-implantitis. Therefore, future long-term clinical trials with standardised protocols and antibiotics with similar biological activity profiles should be tested to achieve a valid and definitive conclusion.

Dynamic Change in Oral Microbiota of Children With Cleft Lip and Palate After Alveolar Bone Grafting

To investigate the longitudinal influence of alveolar bone grafting on the oral microbiota of children with cleft lip and palate (CLP).

Twenty-eight children with nonsyndromic CLP were recruited and underwent secondary alveolar bone grafting at the first time. Unstimulated saliva and plaque samples were collected from the subjects preoperatively and at 2 days, 1 month, and 3 months postoperatively. The v3-v4 hypervariable regions of the 16S rRNA gene from bacterial DNA were sequenced using the Illumina MiSeq sequencing platform.

The alpha diversity of the saliva and plaque microbiota was significantly decreased at 2 days postoperatively and then increased at 1 and 3 months postoperatively. The saliva and plaque microbiota compositions at 2 days postoperatively differed from those at the other time points, and the microbiota compositions at 1 and 3 months postoperatively showed a gradual shift toward the preoperative composition. The saliva, but not plaque, microbiota composition 3 months postoperatively was similar to that preoperatively.

The effect of secondary alveolar bone grafting on the plaque microbiota in children with CLP lasted longer than the saliva microbiota. Alveolar bone grafting altered the saliva microbiota in children with CLP within 3 months postoperatively.

Effects of brief sodium fluoride treatments on the growth of early and mature cariogenic biofilms

Although fluoride has been widely used as a preventive agent for dental caries, the effects of fluoride on the activities of biofilms in different stages of cariogenic biofilm formation are less studied. This study was designed to investigate the antibiofilm activity of sodium fluoride during the early and mature stages of Streptococcus mutans (S. mutans) biofilm formation. S. mutans biofilms were formed on saliva-coated hydroxyapatite disks. In the early (0-46 h) and mature (46-94 h) biofilm stages, the biofilms were treated with different concentrations of fluoride (250, 500, 1000, 2000 ppm; 5 times in total, 1 min/treatment). Acidogenicity, dry weight, colony-forming units (CFUs), water-soluble/insoluble extracellular polysaccharides (EPSs), and intracellular polysaccharides were analysed, and confocal laser scanning microscopy images were obtained of the two stages of biofilms to determine antibiofilm activities of fluoride at varying concentrations during the formation of early and mature biofilms. In the early stages of cariogenic biofilm formation, test groups with all fluoride concentrations significantly inhibited the growth of S. mutans biofilms. The antibiofilm and anti-EPS formation activities of the brief fluoride treatments increased with a concentration-dependent pattern. At the mature biofilm stage, only the 2000 ppm fluoride treatment group significantly inhibited biofilm accumulation, activity, and intracellular/extracellular polysaccharide content compared with those of the control and other fluoride treatment groups. The antimicrobial effect of fluoride treatment on the growth of S. mutans biofilms was linked with the stage of cariogenic biofilm formation. The inhibition of S. mutans biofilm growth by fluoride treatment was easier in the early formation stage than in the mature stage. Fluoride treatment in the early stage of cariogenic biofilm formation may be an effective approach to controlling cariogenic biofilm development and preventing dental caries.

[Design, screening and antibacterial activity evaluation of the novel antibacterial peptide KR-1]

OBJECTIVE

To design novel antimicrobial peptides with high activity and low toxicity and evaluate their effect against Streptococcus mutans and other oral bacteria for prevention and treatment of dental caries.

OBJECTIVE

We synthesized two antimicrobial peptides (KR-1 and KR-2) using Dhvar4 (a histatins5 mimic) as the template. The antimicrobial peptides with high activity and low toxicity were screened using minimal inhibitory concentration (MIC) test, hemolysis test, and CCK-8 assay. Streptococcus mutans biofilms cultured in 96-well plates were divided into experimental group (KR-1) and positive control group (CHX) and treated with concentration gradients (0.6×, 0.8×, 1× and 2× MICs) of KR-1 and CHX, respectively. Crystal violet staining was used for quantitative analysis of the changes of the biofilms after the treatments. The structural changes of the biofilms were observed with laser confocal microscopy after KR-1 treatment at 10 × MIC. The antimicrobial activity of KR-1 against oral Streptococcus was analyzed based on the time required for sterilization after KR-1 treatment.

OBJECTIVE

The MIC of KR-1 and KR-2 for S. mutans was 3.2 μmol/L and 12.8 μmol/L, respectively. Under the effective concentration, KR-1 and KR-2 resulted in hemolysis rates of 0.35% and 48.8% in rabbit red blood cells and lowered the survival rates of gingival fibroblasts to 88.7% and 21.94%, respectively. KR-1 treatment significantly reduced biofilm formation with a minimum biofilm inhibition concentration (MBIC₅₀) lower than 1.92 μmol/L, and showed an even stronger antimicrobial than CHX at the concentration of 2.56 μmol/L (P=0.001). Confocal laser scanning microscopy revealed that the biofilm structure became loosened after KR-1 treatment, which was capable of killing about 90% of the bacteria within 5 min.

OBJECTIVE

The antimicrobial peptide KR-1 has a stronger antibacterial activity and a low toxicity with a good inhibitory effect against S. mutans biofilm.

Dynamic Observation of the Effect of Maternal Caries on the Oral Microbiota of Infants Aged 12-24 Months

Aim

To provide a dynamic description of the oral microbial composition in mothers with and without dental caries and their children aging 12-24 months.

Methodology

A total of 20 pairs of mothers and their children aged 12 months were included and followed up at 18 and 24 months of age. Ten mothers with dental caries(MEG) and their children(CEG) were in the exposure group, and ten caries-free mothers(MCG) and their children(CCG)in control group. Supragingival plaque biofilm samples were collected and DNA was extracted for bacterial 16S rRNA gene sequencing.

Results

A total of 18 pairs completed follow-ups. At a 3% divergence level, the number of common operational taxonomic units found between the mothers and children increased as the children aged. Proteobacteria, Bacteroidetes, Firmicutes, Fusobacteria, and Actinobacteria accounted for more than 80% phyla of each group. A microbial community structure analysis showed that the differences between mothers and children were significant in all groups except for the MEG24 and CEG24 groups.

Conclusions

Oral microbiota of children was more like their mothers' with increasing age, regardless of whether the mothers had dental caries. Mothers with dental caries may have a greater influence on the oral microbiota of children's than those without dental caries as children age.

Oxyresveratrol promotes biofilm formation, cell attachment and aggregation of Streptococcus gordonii in the presence of sucrose

Streptococcus gordonii is a commensal colonizer of oral cavity that initiates the formation of dental plaque. Oxyresveratrol is a natural purification from plants with antibacterial effects on various oral bacteria including Streptococcus mutans. The aim of this study was to investigate the effects of oxyresveratrol on S. gordonii. The basic viability, biofilm formation and cell aggregation of S. gordonii treated with oxyresveratrol were investigated. Oxyresveratrol dose-dependently inhibited the growth of S. gordonii in the absence of sucrose. However, in the presence of sucrose, it promoted biofilm formation under MIC. Both the biofilm formation and extracellular polysaccharides synthesis reached the maximum level at ½ MIC (250 μg/mL) oxyresveratrol. The gene expressions of abpA, abpB, scaA, gtfG, hsa, cshA, cshB, ccpA, srtA and sspB were upregulated when treated with 62.5 and 125 μg/mL oxyresveratrol. A total eight of the ten genes were significantly upregulated at 250 μg/mL oxyresveratrol except abpB and sspB, which were downregulated at 250 μg/mL without significance. In conclusion, oxyresveratrol has dual-effects on S. gordonii. Considering its specific biofilm suppressive effect on S. mutans, it might be a candidate for bacterial interspecies modulator applied in caries prevention.

Recent Advances of Therapeutic Targets for the Treatment of Periodontal Disease

Periodontal disease is primarily associated with bacterial infection such as dental plaque. Dental plaque, an oral biofilm harboring a complex microbial community, can cause various inflammatory reactions in periodontal tissue. In many cases, the local bacterial invasion and host-mediated immune responses lead to severe alveolar bone destruction. To date, plaque control, non-surgical, and surgical interventions have been the conventional periodontal treatment modalities. Although adjuvant therapies including antibiotics or supplements have accompanied these procedures, their usage has been limited by antibiotic resistance, as well as their partial effectiveness. Therefore, new strategies are needed to control local inflammation in the periodontium and host immune responses. In recent years, target molecules that modulate microbial signaling mechanisms, host inflammatory substances, and bone immune responses have received considerable attention by researchers. In this review, we introduce three approaches that suggest a way forward for the development of new treatments for periodontal disease; (1) quorum quenching using quorum sensing inhibitors, (2) inflammasome targeting, and (3) use of FDA-approved anabolic agents, including Teriparatide and sclerostin antibody.

Reverse Actuation of Polyelectrolyte Effect for In Vivo Antifouling

Zwitterionic polymers have extraordinary properties, that is, significant hydration and the so-called antipolyelectrolyte effect, which make them suitable for biomedical applications. The hydration induces an antifouling effect, and this has been investigated significantly. The antipolyelectrolyte effect refers to the extraordinary ion-responsive behavior of particular polymers that swell and hydrate considerably in physiological solutions. This actuation begins to attract attention to achieve in vivo antifouling that is challenging for general polyelectrolytes. In this study, we established the sophisticated cornerstone of the antipolyelectrolyte effect in detail, including (i) the essential parameters, (ii) experimental verifications, and (iii) effect of improving antifouling performance. First, we find that both osmotic force and charge screening are essential factors. Second, we identify the antipolyelectrolyte effect by visualizing the swelling and hydration dynamics. Finally, we verify that the antifouling performance can be enhanced by exploiting the antipolyelectrolyte effect and report reduction of 85% and 80% in ex and in vivo biofilm formation, respectively.

Longitudinal Multi-omics and Microbiome Meta-analysis Identify an Asymptomatic Gingival State That Links Gingivitis, Periodontitis, and Aging

A significant portion of world population still fails to brush teeth daily. As a result, the majority of the global adult population is afflicted with chronic gingivitis, and if it is left untreated, some of them will eventually suffer from periodontitis.

Most adults experience episodes of gingivitis, which can progress to the irreversible, chronic state of periodontitis, yet roles of plaque in gingivitis onset and progression to periodontitis remain elusive. Here, we longitudinally profiled the plaque metagenome, the plaque metabolome, and salivary cytokines in 40 adults who transited from naturally occurring gingivitis (NG) to healthy gingivae (baseline) and then to experimental gingivitis (EG). During EG, rapid and consistent alterations in plaque microbiota, metabolites, and salivary cytokines emerged as early as 24 to 72 h after oral-hygiene pause, defining an asymptomatic suboptimal health (SoH) stage of the gingivae. SoH features a swift, full activation of 11 salivary cytokines but a steep synergetic decrease of plaque-derived betaine and Rothia spp., suggesting an anti-gum inflammation mechanism by health-promoting symbionts. Global, cross-cohort meta-analysis revealed, at SoH, a greatly elevated microbiome-based periodontitis index driven by its convergence of both taxonomical and functional profiles toward the periodontitis microbiome. Finally, post-SoH gingivitis development accelerates oral microbiota aging by over 1 year within 28 days, with Rothia spp. depletion and Porphyromonas gingivalis elevation as hallmarks. Thus, the microbiome-defined, transient gum SoH stage is a crucial link among gingivitis, periodontitis, and aging.

Diagnosis of Biofilm-Associated Peri-Implant Disease Using a Fluorescence-Based Approach

Dental implants have become a routine component of daily dental practice and the demand for dental implants is expected to increase significantly in the future. Despite the high success rates of dental implants, failures do occur, resulting in discomfort, rampant destruction of the oral health, or painful and costly surgical replacement of a failed implant. Peri-implant diseases are inflammatory conditions affecting the soft/hard tissues surrounding a functional dental implant. Plenty of experimental evidence indicates that the accumulation of dental plaque at the soft tissue-implant interface and the subsequent local inflammatory response seems to be key in the pathogenesis of the peri-implant mucositis. Such peri-implant-soft tissue interface is less effective than natural teeth in resisting bacterial invasion, enhancing vulnerability to subsequent peri-implant disease. Furthermore, in certain individuals, it will progress to peri-implantitis, resulting in alveolar bone loss and implant failure. Although early diagnosis and accurate identification of risk factors are extremely important to effectively prevent peri-implant diseases, current systematic reviews revealed that a uniform classification and diagnostic methodology for peri-implantitis are lacking. Recent progress on fluorescence-based technology enabled rapid diagnosis of the disease and effective removal of plaques. Here, we briefly review biofilm-associated peri-implant diseases and propose a fluorescence-based approach for more accurate and objective diagnoses. A fluorescence-based diagnosis tool through headlights combined with special-filtered dental loupes may serve as a hands-free solution for both precise diagnosis and effective removal of plaque-biofilms.

Periodontitis Deteriorates Cognitive Function and Impairs Neurons and Glia in a Mouse Model of Alzheimer's Disease

BACKGROUND

Although periodontitis is reportedly associated with increased cognitive decline in Alzheimer's disease, the mechanisms underlying this process remain unknown. Porphyromonas gingivalis lipopolysaccharide (P.g-LPS) is an endotoxin associated with periodontal disease.

OBJECTIVE

We investigated the effect of periodontitis on learning capacity and memory of amyloid-β protein precursor (AβPP)/presenilin (PS1) transgenic mice along with the mechanisms underlying these effects.

METHODS

Mice were randomly assigned to three groups, namely AβPP/PS1 (control), P.g-LPS Injection, and P.g-LPS Injection + Ligation. Mice from the P.g-LPS Injection group were injected with P.g-LPS in the periodontal tissue three times per week for 8 weeks, while mice from the P.g-LPS Injection + Ligation group were injected with P.g-LPS and subjected to ligation of the gingival sulcus of the maxillary second molar.

RESULTS

Expression of gingival proinflammatory cytokines as well as alveolar bone resorption in P.g-LPS-injected and ligatured mice was increased compared to that in control mice. Mice in the P.g-LPS Injection + Ligation group exhibited cognitive impairment and a significant reduction in the number of neurons. Glial cell activation in the experimental groups with significantly increased amyloid-β (Aβ) levels was more pronounced relative to the control group. Induction of periodontitis was concurrent with an increase in cyclooxygenase-2, inducible nitric oxide synthase, AβPP, and beta-secretase 1 expression and a decrease in A disintegrin and metalloproteinase domain-containing protein 10 expression.

CONCLUSION

These findings indicated that periodontitis exacerbated learning and memory impairment in AβPP/PS1 mice and augmented Aβ and neuroinflammatory responses. Our study provides a theoretical basis for risk prediction and early intervention of Alzheimer's disease and periodontitis.

Oral infectious bacteria in dental plaque and saliva as risk factors in patients with esophageal cancer

BACKGROUND

High levels of periodontopathic bacteria as well as Streptococcus anginosus were detected in cancer tissue from patients with esophageal cancer. An association between oral infectious bacteria and esophageal cancer has been reported.

METHODS

Characteristics of the oral microbiota and periodontal conditions were studied as clinicopathologic factors in patients with esophageal cancer. The study included 61 patients with esophageal cancer and 62 matched individuals without any cancers. Samples of subgingival dental plaque and unstimulated saliva were collected to evaluate the prevalence and abundance of the following oral bacteria using a real-time polymerase chain reaction assay: Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, Treponema denticola, and S. anginosus.

RESULTS

In the cancer group, the prevalence of all bacteria, with the exception of F. nucleatum, in dental plaque; the prevalence of A. actinomycetemcomitans in saliva; the abundance of all bacteria, with the exception of F. nucleatum and P. intermedia, in dental plaque; and the abundance of A. actinomycetemcomitans and S. anginosus in saliva were significantly higher. Furthermore, a logistic regression analysis suggested that the prevalence of T. forsythia and S. anginosus in dental plaque and of A. actinomycetemcomitans in saliva, as well as a drinking habit, were associated with a high risk of esophageal cancer, with a high odds ratio.

CONCLUSIONS

The current findings have potential implications for the early diagnosis of esophageal cancer.

Effect of xylitol tablets with and without red propolis on salivary parameters, dental biofilm and sensory acceptability of adolescents: a randomized crossover clinical trial

The effect of xylitol tablets with (XPT) and without (XT) red propolis on salivary parameters, dental biofilm and acceptability of adolescents was evaluated through a blinded randomized crossover clinical trial. Healthy volunteers were allocated in the XPT and XT groups with a 30-day washout period for consumption of two tablets/dayfor seven days. An increase in salivary parameters was only observed immediately after tablet consumption, without differences between XPT and XT. The results for total microorganisms were similar, but XT was better in controlling Streptococcus spp. Rothia dentocariosa and Streptococcus salivarius were the most frequent in the biofilm and saliva, respectively. XPT and XT showed similar acceptability, with the highest purchase intention for XT. Although propolis did not enhance the properties of XT, further studies testing different protocols and follow-up are necessary; XT controlled Streptococcus spp. in biofilms, which demonstrate its potential for clinical application.