Effect of Novel and Traditional Intracanal Medicaments on Biofilm Viability and Composition.

INTRODUCTION: The aim of this study was to test the hypothesis that a combination of D-amino acids (DAA) and trans-cinnamaldehyde (TC) demonstrates superior antibiofilm activity to calcium hydroxide (CH) and untreated controls. METHODS: In this 3-part in vitro study, the concentration of DAAs (D-methionine, D-leucine, D-tyrosine, and D-tryptophan) that would significantly decrease Enterococcus faecalis and Actinomyces naeslundii biofilm biomass was first determined. Then, the effect of TC + selected DAAs on polymicrobial biofilms was characterized by quantifying the biomass and biofilm viability. Finally, the antibiofilm effects of TC+DAA was compared with CH and untreated controls by (i) determining bacterial viability and (ii) quantifying biofilm matrix composition using selective fluorescence-binding analysis. Statistical analysis was performed using one-way ANOVA and appropriate multiple comparisons test, with P<.05 considered as statistically significant. RESULTS: TC (0.06%) + D-tyrosine (1 mM) + D-tryptophan (25 mM) significantly reduced the biomass and biofilm viability compared to the control (P<.05). While no significant difference was observed between TC+DAA and CH in the cultivable bacterial counts (P>.05), confocal microscopy demonstrated a significantly greater percentage of dead bacteria in TC+DAA-treated biofilms compared to CH and the control (P<.05). TC+DAA significantly decreased the biovolume and all the examined components of the biofilm matrix quantity compared to the control, while CH significantly reduced only the exopolysaccharide quantity (P<.05). CONCLUSION: TC + D-tyrosine + D-tryptophan demonstrated superior antibiofilm activity (biofilm bacterial killing and reduction of matrix quantity) to CH and has potential to be developed as an intracanal medicament.

The Prevalence of Candida albicans and Malassezia globosa in Preschool Children with Severe Early Childhood Caries: A Case-Control Study.

Background: This cross-sectional study aimed to identify the prevalence of Candida albicans and Malassezia globosa in children with severe early childhood caries and caries-free children in Hong Kong. Methods: This study first recruited a total of 80 children aged between 48 and 72 months old, 40 children with severe early childhood caries, and 40 caries-free children. The children were then further divided into four groups, with 20 children in each group: Group 1: Severe early childhood caries-C. albicans, Group 2: Severe early childhood caries-M. globosa, Group 3: Caries-free-C. albicans and Group 4: Caries-free-M. globosa. Saliva, plaque, and caries lesion samples were collected from participants with severe early childhood caries, while only saliva and plaque samples were collected from caries-free participants. Caries status of the primary molars was assessed using WHO's decayed, missing, and filled tooth index, and the severity of cavitated lesions was determined based on International Caries Diagnosis and Assessment System criteria as caries code 5 or 6. The samples were analyzed using an Internal Transcribed Space and Quantitative Real-Time Polymerase Chain Reaction. Results:C. albicans was more prevalent in saliva and plaque samples of severe early childhood caries than in the caries-free group. Proportion of C. albicans in both saliva and plaque samples differed significantly between severe early childhood caries and caries-free groups (p < 0.05). Within the severe early childhood caries group, the proportion of children with C. albicans varied between 6 and 46%. No significant difference in M. globosa load was found between plaque samples of the severe early childhood caries and caries-free groups (p = 0.159). Conversely, no significant difference in M. globosa load was observed between saliva samples of severe early childhood caries and caries-free groups (p = 0.051). Conclusions: This study demonstrated a strong association between C. albicans and severe early childhood caries. M. globosa was detected in both the caries-free and severe early childhood caries groups, albeit at low levels.

Satisfaction with government recommended pre-procedural mouth rinses in the mitigation of Covid-19 in Hong Kong SAR: A triple blind randomized controlled clinical trial.

OBJECTIVE: To evaluate satisfaction and acceptability with three pre-procedural mouthrinses recommended by the Government of Hong Kong Special Administrative Region (HKSAR) during the COVID-19 pandemic. MATERIAL AND METHODS: A triple-blind parallel-arm randomised controlled clinical trial was conducted. Following eligibility assessment, participants were block-randomised to the three intervention pre-procedural mouthrinses groups: Povidone-iodine, Hydrogen Peroxide and Chlorhexidine Digluconate. Participants rinsed with one of the mouthrinses assigned prior to any dental treatment. Participants, operators and assessors were blind to the assigned mouthrinses (triple blind). Satisfaction ratings were assessed on a 10 cm visual analogue scale (VAS) and acceptability of the mouthrinses were determined. RESULTS: Following clinical screening, 228 participants were involved in the trial. The mean overall VAS satisfaction was 7.35 (SD 1.68). There was no significant difference in VAS satisfaction ratings among the three groups (p>0.05) nor in between groups. Acceptability of the mouthrinses was high with the vast majority (89.5 %, 204) willing to use the mouthrinses again if pre-procedural mouthrinsing is required. There was no significant difference in acceptability ratings (p>0.05). There were some aspects such as taste and smell that participants commented on (on average, 24.6 %, 56), although no significant difference in prevalence of reports among groups (p>0.05). CONCLUSIONS: There were high rates of satisfaction and acceptability of the HKSAR Government recommended pre-procedural mouthrinses for the mitigation of COVID-19 transmission in the dental setting. There was no significant difference in satisfaction and acceptability rates among the three recommended pre-procedural mouthrinses. CLINICAL RELEVANCE: The high satisfaction and acceptability rates of the HKSAR Government recommended pre-procedural mouthrinses in the mitigation of COVID-19 in this clinical trial lends support for the HKSAR's policy on pre-procedural mouthrinses in the dental setting and this has implications for practice and policy during pandemics.

Harnessing antimicrobial peptides in endodontics.

Endodontic therapy includes various procedures such as vital pulp therapy, root canal treatment and retreatment, surgical endodontic treatment and regenerative endodontic procedures. Disinfection and tissue repair are crucial for the success of these therapies, necessitating the development of therapeutics that can effectively target microbiota, eliminate biofilms, modulate inflammation and promote tissue repair. However, no current endodontic agents can achieve these goals. Antimicrobial peptides (AMPs), which are sequences of amino acids, have gained attention due to their unique advantages, including reduced susceptibility to drug resistance, broad-spectrum antibacterial properties and the ability to modulate the immune response of the organism effectively. This review systematically discusses the structure, mechanisms of action, novel designs and limitations of AMPs. Additionally, it highlights the efforts made by researchers to overcome peptide shortcomings and emphasizes the potential applications of AMPs in endodontic treatments.

Penetration of Calcium Silicate and Epoxy Resin Sealers Into the Lateral Canals.

OBJECTIVES: The aim of this research was to compare the penetration ability of calcium silicate-based sealers (iRoot SP and TotalFill BC HiFlow) and an epoxy resin-based sealer (AH Plus) into the lateral canals using the single-cone (SC) or continuous wave compaction (CW) obturation techniques. METHODS: Ninety single-rooted human teeth received canal instrumentation and diaphanisation before artificial lateral canals were created at 3 different root levels. The specimens were randomly allocated into 6 groups based on the combination of obturation technique and sealer used. Radiographic and photographic measurements evaluated the percentage of sealer penetration. Statistical analysis was performed to compare the penetration ability amongst different types of sealers, obturation methods, and root levels. RESULTS: Although TotalFill BC HiFlow sealer combined with the CW technique demonstrated greater sealer penetration at the coronal level (P < .05), the overall penetration ability of iRoot SP, TotalFill BC HiFlow, and AH Plus was not significantly different. The deepest sealer penetration was observed at the apical root level. CONCLUSIONS: All sealers showed similar penetration abilities into the lateral canals using the SC or CW techniques in vitro. Calcium silicate-based sealers have comparable penetration ability into lateral canals compared to epoxy resin-based sealers using SC or CW obturation techniques.

Mouthwashes: Alternatives and Future Directions.

This narrative review summarises "alternative" or "natural" over-the-counter (OTC) mouthwashes not covered elsewhere in this supplement and newly emerging products, as potential mouthwashes of the future. The "natural" mouthwashes reviewed include saltwater, baking soda, coconut oil, charcoal, propolis, seaweeds, and probiotics. Other than essential oils, it is apparent that their clinical effectiveness is still under debate, but there is some evidence to suggest that propolis reduces plaque and gingivitis. This review also covers the host immune response, via novel anti-inmmunomodulant mouthwashes, such as erythropoietin to reduce inflammation with oral mucositis (OM) after radiotherapy. The emerging concept of nanoparticle-containing mouthwashes, such as iron oxide, is further discussed for OM, this agent having the potential for more targeted delivery of chemical antimicrobials. Unfortunately, there are impacts on the environment of widening mouthwash use with more new products, including increased use of packaging, antimicrobial resistance, and possible detrimental effects on marine life. Further, there are roadblocks, relating to regularly approvals and side effects, that still need to be overcome for any OTC deivered immunomodulant or nanoformulation mouthwashes. Despite these caveats, there are many new mouthwashes under development, which could help manage major oral diseases such as caries, gingivitis, and periodontal disease.

Tissue Stabilization, Bacterial Adhesion, and Stem Cell Viability in Trans-cinnamaldehyde-conditioned Dentin.

INTRODUCTION: This laboratory study aimed to evaluate the effect of trans-cinnamaldehyde (TC) conditioning on dentin tissue stabilization, bacterial adhesion, and stem cell toxicity. METHODS: Dentin beams (n = 204) from extracted human molars were demineralized in phosphoric acid and treated with TC (2.5, 5, and 7.5%), 50% ethanol-water mixture (vehicle control) or 2.5% glutaraldehyde (GA) (positive control) for 30 minutes. Demineralized but untreated specimens served as the negative control. After treatment, collagen crosslinking was characterized by measuring the elastic modulus (Er) and hardness (n = 5). Biodegradation resistance was examined by determining the loss of dry mass (n = 8), hydroxyproline release (n = 4) and scanning electron microscopy (n = 2), after exposure to bacterial collagenase. Inhibition of bacterial adhesion was investigated by colony counting assay (n = 12) and scanning electron microscopy (n = 2). Viability of stem cells of the apical papilla on TC-conditioned dentin was determined using the Cell Counting Kit-8 assay (n = 8). Data were statistically analyzed using one-way analysis of variance (ANOVA) test followed by Dunnett's multiple comparisons at a significance level of 5%. RESULTS: TC-conditioned dentin showed a concentration-dependent increase in Er and hardness. The Er and hardness of 5% and 7.5% TC-conditioned dentin were significantly greater than that of the negative control and vehicle control groups (P < .05). There was no significant difference in the biodegradation resistance between GA and 5% TC-conditioned dentin (P > .05). TC-conditioned dentin showed a well-preserved collagen fibril network with clear cross-banding, comparable to GA-conditioned dentin. All concentrations of TC inhibited bacterial adhesion on dentin, significantly greater than the negative control (P < .05). There was no reduction in viability of stem cells of the apical papilla viability on TC-conditioned dentin compared to the negative control (P > .05). CONCLUSIONS: TC conditioning stabilized the dentin and protected it from enzymatic degradation. TC prevented bacterial adhesion on the dentin but maintained stem cell viability.

Effect of cryotherapy duration on experimentally induced connective tissue inflammation in vivo.

Objectives: This study tested the hypothesis that cryotherapy duration influences lipopolysaccharide (LPS)-induced inflammation in a rat model. Materials and Methods: Six Wistar rats (Rattus norvegicus albinus) were used. Five sites were selected per animal and divided into 5 groups: a negative control group (NC), 2 positive control groups (PC1 and PC2), and 2 experimental groups (E1 and E2). Cryotherapy was applied for 1 minute (E1) or 5 minutes (E2). An acute inflammatory response was induced in the PC and E groups via subcutaneous administration of 0.5 mL/kg. In the PC2 group, a catheter was inserted without additional treatment. For the E1 and E2 groups, 2.5°C saline solution was administered through the implanted catheters for 1 and 5 minutes, respectively. The rats were sacrificed, and samples were obtained and processed for histological analysis, specifically examining the presence of polymorphonuclear neutrophils and hemorrhage. The χ2 test was used to compare the presence of acute inflammation across groups. Dependent variables were compared using the linear-by-linear association test. Results: Inflammation and hemorrhage varied significantly among the groups (p = 0.001). A significantly higher degree of acute inflammation was detected (p = 0.0002) in the PC and E1 samples than in the E2 group, in which cryotherapy was administered for 5 minutes. The PC and E1 groups also exhibited significantly greater numbers of neutrophils (p = 0.007), which were essentially absent in both the NC and E2 groups. Conclusions: Cryotherapy administration for 5 minutes reduced the acute inflammation associated with LPS and catheter implantation.

Effect of Dentine Conditioning with Silver Diamine Fluoride on Wettability of Root Canal Sealers.

OBJECTIVE: To test the null hypothesis that dentine treatment with silver diamine fluoride (SDF), a potent antimicrobial agent, following use of proteolytic and chelating agents does not influence the wettability of an epoxy resin (AH Plus, Dentsply Sirona, Charlotte, NC, USA) and a tricalcium silicate sealer (BioRoot RCS, Septodont, Saint-Maur-des-Fossés, France). METHODS: Seventy-two intraradicular dentine specimens were divided into six groups based on the final irrigation solutions used: 2.5% sodium hypochlorite (NaOCl) and 17% ethylenediaminetetraacetic acid (EDTA) (NaOCl-EDTA) (group 1); NaOCl-EDTA-NaOCl (group 2); NaOCl-EDTA followed by 3.8% SDF, NaOCl-EDTA-SDF (group 3); NaOCl-EDTA-NaOCl-SDF (group 4); SDF (group 5) and saline (group 6). After irrigation, the specimens were divided into subgroups according to the sealer used, AH Plus or BioRoot RCS. Contact angles were measured using a contact angle analyser. The data were analysed using an independent t test, one-way analysis of variance (ANOVA) and Tamhane T2 post hoc test, with the level of significance set at P < 0.05. RESULTS: In the epoxy resin sealer group, dentine surfaces treated with only SDF showed the lowest contact angle. This was significantly less than the groups in which NaOCl was used as the final irrigant (P < 0.05). In the tricalcium silicate-based sealer group, the groups treated with SDF showed significantly greater contact angles when compared to the control group (P < 0.05). CONCLUSION: It was concluded that SDF conditioning of dentine favours the wettability of epoxy resin sealer but is detrimental to the wettability of tricalcium silicate sealer.

Intracellular bacterial eradication using a novel peptide in vitro.

AIM: To determine the effect of a novel antimicrobial peptide (AMP; OP145) and cell-penetrating peptide (Octa-arginine/R8) conjugate on the killing of intracellular Enterococcus faecalis, compared to OP145 and an antibiotic combination recommended for regenerative endodontic procedures. METHODOLOGY: The biocompatible concentrations of OP145 and OP145-R8 were determined by assessing their cytotoxicity against human macrophages and red blood cells. Spatiotemporal internalization of the peptides into macrophages was investigated qualitatively and quantitatively by confocal laser scanning microscopy and flow cytometry respectively. Killing of extracellular and intracellular E. faecalis OG1RF by the peptides was determined by counting the colony-forming units (CFU). Intracellular antibacterial activity of the peptides was compared to a double antibiotic combination. Confocal microscopy was used to confirm the intracellular bacterial eradication. Significant differences between the different test groups were analysed using one-way analysis of variance. p < .05 was considered to be statistically significant. RESULTS: Peptides at a concentration of 7.5 µmol/L were chosen for subsequent experiments based on the results of the alamarBlue™ cell viability assay and haemolytic assay. OP145-R8 selectively internalized into lysosomal compartments and the cytosol of macrophages. Conjugation with R8 improved the internalization of OP145 into macrophages in a temporal manner (70.53% at 1 h to 77.13% at 2 h), while no temporal increase was observed for OP145 alone (60.53% at 1 h with no increase at 2 h). OP145-R8 demonstrated significantly greater extracellular and intracellular antibacterial activity compared to OP145 at all investigated time-points and concentrations (p < .05). OP145-R8 at 7.5 µmol/L eradicated intracellular E. faecalis after 2 h (3.5 log reduction compared to the control; p < .05), while the antibiotics could not reduce more than 0.5 log CFU compared to the control (p > .05). Confocal microscopy showed complete absence of E. faecalis within the OP145-R8 treated macrophages. CONCLUSIONS: The results of this study demonstrated that the conjugation of an AMP OP145 to a cell-penetrating peptide R8 eradicated extracellular and intracellular E. faecalis OG1RF without toxic effects on the host cells.

A laboratory investigation on the effect of biguanide- and pyridine-derived antiseptics on the adhesion of resin composites to dentin.

Optimal bonding of adhesive restorations to dentin is crucial to prevent microleakage and enhance the survival of root-filled teeth. The aim of this study was to investigate the effect of chlorhexidine (CHX), alexidine (ALX) and octenidine dihydrochloride (OCT) on the bond strength of resin composites to coronal dentin. Human coronal dentin specimens were treated with 2% CHX, 0.1% ALX, 0.1% OCT or saline then restored with traditional or bulk-fill resin composites. The adhesion strength between the resin and dentin was measured using the microtensile bond strength and failure mode was determined using a stereomicroscope. Treatment with ALX and OCT resulted in significantly greater µTBS compared with CHX and saline, irrespective of the resin composite used. Alexidine treatment predominantly resulted in mixed failure, while adhesive failures were frequently observed in CHX and saline-treated dentin. In conclusion, final irrigation with ALX or OCT improved the bonding of resin composites to dentin.

Accumulated Hard Tissue Debris and Root Canal Shaping Profiles Following Instrumentation with Gentlefile, One Curve, and Reciproc Blue.

INTRODUCTION: This laboratory study aimed to evaluate the accumulated hard tissue debris (AHTD) and shaping performance following root canal instrumentation with a novel stainless steel rotary system (Gentlefile; MedicNRG, Kibbutz Afikim, Israel) compared with two single-file nickel-titanium instruments of different kinematics through micro-computed tomography (micro-CT) analysis. METHODS: Thirty isthmus-containing mesial roots of human mandibular molars with a curvature of 15°-35° were scanned with micro-CT at an isotropic resolution of 12 µm and randomly assigned to three groups (n = 10) according to the instruments used for canal preparation: Gentlefile (GF; #23/.04), One Curve (OC; #25/.06; Micro-Mega, Besancon, France), and Reciproc Blue R25 (RB; #25/.08; VDW, Munich, Germany). The AHTD, unprepared canal surface area, volume changes, surface area changes, and transportation were evaluated by comparing preoperative and postoperative micro-CT images. In addition, the time required for canal preparation was recorded. Data were statistically analyzed using the one-way analysis of variance (ANOVA) test or the Kruskal-Wallis test at a significance level of 5%. RESULTS: No significant differences were observed in the percentage of AHTD or in the unprepared canal surface area between the three groups (P > .05). The RB group demonstrated a significantly greater percentage increase in volume and surface area than the GF group (P < .05). The GF and OC groups showed significantly less transportation at 3 mm from the apex than the RB group (P < .001). The OC group required significantly less time for instrumentation than the RB and GF groups (P < .05). CONCLUSIONS: Instrumentation with GF (#23/.04), OC, and RB yielded similar levels of AHTD and unprepared surface area in isthmus-containing curved canals. GF achieved this with less dentin removal and apical transportation, at the expense of a longer preparation time.

Revisiting ESKAPE Pathogens: virulence, resistance, and combating strategies focusing on quorum sensing.

The human-bacterial association is long-known and well-established in terms of both augmentations of human health and attenuation. However, the growing incidents of nosocomial infections caused by the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter sp.) call for a much deeper understanding of these organisms. Adopting a holistic approach that includes the science of infection and the recent advancements in preventing and treating infections is imperative in designing novel intervention strategies against ESKAPE pathogens. In this regard, this review captures the ingenious strategies commissioned by these master players, which are teamed up against the defenses of the human team, that are equally, if not more, versatile and potent through an analogy. We have taken a basketball match as our analogy, dividing the human and bacterial species into two teams playing with the ball of health. Through this analogy, we make the concept of infectious biology more accessible.

A heptadeca amino acid peptide subunit of cathelicidin LL-37 has previously unreported antifungal activity.

Yeasts such as Candida albicans, albeit being ubiquitous members of the skin, oral and vaginal microbiome, can cause superficial to life-threatening infections. Human cathelicidin LL-37-based peptides have antibacterial activity and yet, their antifungal activity remains to be thoroughly characterized. The aim of this study was to comprehensively investigate the activity of LL-37-based peptides against C. albicans. LL-37 and its derivatives were tested for their ability to kill C. albicans planktonic cells in the presence of various biological matrices (serum, plasma, saliva and urine), that have been reported to inactivate peptides. The antibiofilm activity, resistance development and biocompatibility were investigated for the lead peptide. GK-17, a 17 amino acid peptide, showed remarkable stability to fungal aspartyl proteases and rapidly killed planktonic C. albicans despite the presence of biological matrices. GK-17 also inhibited adhesion to biotic and abiotic substrates, inhibited biofilm formation and eradicated preformed biofilms in the presence of biological matrices. Compared to nystatin, GK-17 had a lower propensity to allow for resistance development by C. albicans. The peptide showed concentration-dependent biocompatibility to red blood cells, with only 30% hemolysis even at 4× the fungicidal concentration. Taken together, GK-17 is a novel antifungal peptide with promising effects against C. albicans.

Evaluation of machine-assisted irrigation on removal of intracanal biofilm and extrusion of sodium hypochlorite using a three-dimensionally printed root canal model.

PURPOSE: This study aimed to compare the biofilm removal and apical extrusion of sodium hypochlorite (NaOCl) following machine-assisted irrigation using a three-dimensionally (3D) printed dentin-insert model. METHODS: Multispecies biofilms were formed in a 3D-printed curved root canal model with dentin insert. The model was then placed in a container that was filled with 0.2% agarose gel containing 0.1% m-Cresol purple. Root canals were irrigated with 1% NaOCl using syringe irrigation, sonically agitated (EndoActivator or EDDY) or ultrasonically activated (Endosonic Blue) irrigation. Samples were photographed and the color-changed area was measured. Biofilm removal was assessed using colony-forming unit counting, confocal laser scanning microscopic analysis and scanning electron microscopic observations. The data were analyzed using one-way ANOVA, followed by Tukey test (P < 0.05). RESULTS: EDDY and Endosonic Blue demonstrated significantly greater reduction of biofilms compared to other groups. No significant differences were observed in the remaining biofilm volume in syringe irrigation and EndoActivator groups. Furthermore, EDDY and Endosonic Blue presented with numerous exposed dentinal tubules. EDDY showed significantly greater NaOCl extrusion compared to other groups. CONCLUSION: Ultrasonic activation with a small-sized nickel-titanium file irrigation system may be beneficial in intracanal biofilm removal avoiding extrusion of NaOCl beyond the root apex.

The presence of Enterococcus faecalis in saliva as a risk factor for endodontic infection.

Aim: The aim of the present study was to investigate and correlate the prevalence of Enterococcus faecalis in saliva and in root canals with different pulpal and periapical conditions. Methodology: Sixty-seven patients were divided into five groups based on pulpal and periapical tissue status: healthy vital teeth (HVT, n=7), healthy treated teeth without lesion (HTT, n=9), irreversible pulpitis (IP, n=13), necrosis (N, n=18), and post-treatment apical periodontitis (PTAP, n=20). Saliva, rubber dam, sterility control and pre-treatment root canal samples were collected and microbiologically processed by culture method. The phylogenetic relationship of E. faecalis isolates collected from root canals and saliva were investigated by whole genome sequencing. Fisher's exact test was used to correlate the presence of E. faecalis in root canals or saliva with clinical and/or radiographic findings. Linear/logistic regression analyses were performed to establish the relationship between the presence of E. faecalis in root canals, saliva, and the status of periapical tissues. Results: E. faecalis was found in 18 root canal and saliva samples. E. faecalis root canal isolates were recovered with the highest frequency from post-treatment apical periodontitis. The occurrence of E. faecalis in saliva was strongly associated with its detection in the root canals (P < 0.001). The pretreatment presence of E. faecalis in root canals was associated with significantly higher odds of having periapical lesions (OR=11.03; 95% CI, 1.27-95.70; p < 0.05). Saliva and root canal isolates from the same patient were highly correlated at the phylogenetic level (Jaccard index >0.95). Conclusion: This pilot study confirms the role of E. faecalis in developing peri-radicular lesions in secondary endodontic infections and suggests that saliva could be the main source of infection. Further studies are needed to investigate the exact origin of this bacteria and its true role in the pathogenesis of secondary/persistent endodontic infections.

A systematically biosynthetic investigation of lactic acid bacteria reveals diverse antagonistic bacteriocins that potentially shape the human microbiome.

BACKGROUND: Lactic acid bacteria (LAB) produce various bioactive secondary metabolites (SMs), which endow LAB with a protective role for the host. However, the biosynthetic potentials of LAB-derived SMs remain elusive, particularly in their diversity, abundance, and distribution in the human microbiome. Thus, it is still unknown to what extent LAB-derived SMs are involved in microbiome homeostasis. RESULTS: Here, we systematically investigate the biosynthetic potential of LAB from 31,977 LAB genomes, identifying 130,051 secondary metabolite biosynthetic gene clusters (BGCs) of 2,849 gene cluster families (GCFs). Most of these GCFs are species-specific or even strain-specific and uncharacterized yet. Analyzing 748 human-associated metagenomes, we gain an insight into the profile of LAB BGCs, which are highly diverse and niche-specific in the human microbiome. We discover that most LAB BGCs may encode bacteriocins with pervasive antagonistic activities predicted by machine learning models, potentially playing protective roles in the human microbiome. Class II bacteriocins, one of the most abundant and diverse LAB SMs, are particularly enriched and predominant in the vaginal microbiome. We utilized metagenomic and metatranscriptomic analyses to guide our discovery of functional class II bacteriocins. Our findings suggest that these antibacterial bacteriocins have the potential to regulate microbial communities in the vagina, thereby contributing to the maintenance of microbiome homeostasis. CONCLUSIONS: Our study systematically investigates LAB biosynthetic potential and their profiles in the human microbiome, linking them to the antagonistic contributions to microbiome homeostasis via omics analysis. These discoveries of the diverse and prevalent antagonistic SMs are expected to stimulate the mechanism study of LAB's protective roles for the microbiome and host, highlighting the potential of LAB and their bacteriocins as therapeutic alternatives. Video Abstract.

One-Pot Preparation of Cetylpyridinium Chloride-Containing Nanoparticles for Biofilm Eradication.

Quaternary ammonium compounds (QACs) have been widely used due to their excellent antimicrobial activity. However, using the technology where nanomaterials are employed as drug carriers to deliver QAC drugs has not been fully explored. In this study, mesoporous silica nanoparticles (MSNs) with short rod morphology were synthesized in a one-pot reaction using an antiseptic drug cetylpyridinium chloride (CPC). CPC-MSN were characterized via various methods and tested against three bacterial species (Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis), which are associated with oral infections, caries, and endodontic pathology. The nanoparticle delivery system used in this study prolonged the release of CPC. The manufactured CPC-MSN effectively killed the tested bacteria within the biofilm, and their size allowed them to penetrate into dentinal tubules. This CPC-MSN nanoparticle delivery system demonstrates potential for applications in dental materials.

Fracture Resistance of Endodontically Treated Maxillary Premolars with Non-carious Cervical Lesions Restored with Different Post Systems.

OBJECTIVE: To test the hypothesis that the (i) presence of non-carious cervical lesions (NCCLs) and (ii) type of post system have no effect on the fracture resistance and pattern in endodontically treated maxillary premolars. METHODS: Human maxillary first premolars (n=60) with two root canals were randomly allocated into four groups (n=15). Buccal wedge-shaped NCCLs were prepared in 45 teeth specimens. Following root canal treatment, the specimens were randomly divided into (i) composite resin core (CRC); (ii) NCCLs + composite resin core (NCCL+CRC); (iii) NCCLs+prefabricated fibre-reinforced composite post + composite resin core (NCCL+PFRC+CRC); (iv) NCCLs+custom fibre posts + composite resin core (NCCL+CFP+CRC). All specimens were subjected to thermocycling (5°C to 55°C/5000 cycles). The compressive load was applied non-axially to the palatal cusp with a universal testing machine at a crosshead speed of 0.5 mm/min at a 30° angle until fracture. Fracture patterns were examined using a loupe magnification (2.5×) under transillumination. Statistical analyses were performed using non-parametric tests and pairwise comparisons of the load-to-fracture among the groups. Chi-square test was used to analyse the fracture patterns (P=0.05). RESULTS: Fracture resistance of NCCL+PFRC+CRC was significantly higher than NCCL+CRC (P=0.011), while NCCL+CFP+CRC did not show any significant difference when compared to NCCL+CRC (P=0.089). No statistical difference was found between CRC, NCCL+PFRC+CRC and NCCL+CFP+CRC (P=1.000). The frequencies of favourable fracture patterns in descending orders were as follows: CRC (80%), NCCL+CFP+CRC (73%), NCCL+PFRC+CRC (60%), and NCCL+CRC (40%). Chi-square test did not show significant differences in fracture patterns among all groups (P=0.110). CONCLUSION: Restoration of the endodontically treated maxillary premolars with NCCLs, with or without post, resulted in similar fracture resistance as their counterparts without NCCLs. Placement of a prefabricated fibre-reinforced composite post exhibited greater fracture resistance to the maxillary premolars with restored NCCLs than those without a post. (EEJ-2022-06-077).