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Objectives: Dental caries result from a microbial imbalance in the oral cavity. Probiotics ecologically modulate the oral microflora to prevent caries. This study evaluated the anti-cariogenic effects of two Lacticaseibacillus rhamnosus strains in vitro and in vivo to provide a more theoretical basis for its clinical applications in caries prevention., Methods: In the study, cariogenic biofilms were grown with L. rhamnosus (LGG) or L. rhamnosus ATCC 7469 and analyzed. Quantitative real-time PCR (qPCR), Scanning Electron Microscope (SEM), and Confocal laser scanning microscope (CLSM) were used to detect the changes in the composition and architectures; cariogenic activity was measured by the lactic acid production and Transverse Microradiography (TMR). The effects of LGG on the 12 Sprague-Dawley rat caries model were assessed using Keyes scores and micro-CT analysis. Oral microbiome changes were evaluated through 16S rRNA gene high-throughput sequencing., Results: L. rhamnosus can reduce cariogenic bacteria in biofilm by 14.7 % to 48.9 %, with LGG exhibiting more potent inhibitory effects. Both strains of L. rhamnosus can adhere to the surface of biofilms, reduce the extracellular polysaccharides (EPS) matrix, and loosen the biofilm structure. L. rhamnosus inhibited cariogenic activity by reducing the lactic acid production in biofilms. The bovine enamel blocks presented lower mineral loss values and lesion depth values in the group Core+L.rh and Core+LGG. LGG-ingested rats had significantly lower levels of moderate dentin lesions and higher mineral density than the control group. The 16 s rRNA gene sequencing revealed that LGG regulated the beta diversity of the oral microbial community in the rat dental caries model., Conclusions: This study revealed the promising potential of L. rhamnosus, especially the LGG strain, in the ecological prevention of dental caries., Clinical Significance: Probiotics may provide a strategy for preventing caries by regulating the oral microecological balance. The study revealed the promising anti-caries potential of the LGG probiotic strain in vivo and in vitro. It is expected that LGG could be used as an oral probiotic for the clinical prevention and treatment of caries., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Radiation caries is one of the most common complications of head and neck radiotherapy. A shift in the oral microbiota is the main factor of radiation caries. A new form of biosafe radiation, heavy ion radiation, is increasingly being applied in clinical treatment due to its superior depth-dose distribution and biological effects. However, how heavy ion radiation directly impacts the oral microbiota and the progress of radiation caries are unknown. Here, unstimulated saliva samples from both healthy and caries volunteers and caries-related bacteria were directly exposed to therapeutic doses of heavy ion radiation to determine the effects of radiation on oral microbiota composition and bacterial cariogenicity. Heavy ion radiation significantly decreased the richness and diversity of oral microbiota from both healthy and caries volunteers, and a higher percentage of Streptococcus was detected in radiation groups. In addition, heavy ion radiation significantly enhanced the cariogenicity of saliva-derived biofilms, including the ratios of the genus Streptococcus and biofilm formation. In the Streptococcus mutans-Streptococcus sanguinis dual-species biofilms, heavy ion radiation increased the ratio of S. mutans. Next, S. mutans was directly exposed to heavy ions, and the radiation significantly upregulated the gtfC and gtfD cariogenic virulence genes to enhance the biofilm formation and exopolysaccharides synthesis of S. mutans. Our study demonstrated, for the first time, that direct exposure to heavy ion radiation can disrupt the oral microbial diversity and balance of dual-species biofilms by increasing the virulence of S. mutans, increasing its cariogenicity, indicating a potential correlation between heavy ions and radiation caries. IMPORTANCE The oral microbiome is crucial to understanding the pathogenesis of radiation caries. Although heavy ion radiation has been used to treat head and neck cancers in some proton therapy centers, its correlation with dental caries, especially its direct effects on the oral microbiome and cariogenic pathogens, has not been reported previously. Here, we showed that the heavy ion radiation directly shifted the oral microbiota from a balanced state to a caries-associated state by increasing the cariogenic virulence of S. mutans. Our study highlighted the direct effect of heavy ion radiation on oral microbiota and the cariogenicity of oral microbes for the first time., Competing Interests: The authors declare no conflict of interest.

Antibiotic tolerance within a biofilm community presents a serious public health challenge. Here, we report the identification of a 2-aminoimidazole derivative that inhibits biofilm formation by two pathogenic Gram-positive bacteria, Streptococcus mutans and Staphylococcus aureus. In S. mutans, the compound binds to VicR, a key response regulator, at the N-terminal receiver domain, and concurrently inhibits expression of vicR and VicR-regulated genes, including the genes that encode the key biofilm matrix producing enzymes, Gtfs. The compound inhibits S. aureus biofilm formation via binding to a Staphylococcal VicR homolog. In addition, the inhibitor effectively attenuates S. mutans virulence in a rat model of dental caries. As the compound targets bacterial biofilms and virulence through a conserved transcriptional factor, it represents a promising new class of anti-infective agents that can be explored to prevent or treat a host of bacterial infections. IMPORTANCE Antibiotic resistance is a major public health issue due to the growing lack of effective anti-infective therapeutics. New alternatives to treat and prevent biofilm-driven microbial infections, which exhibit high tolerance to clinically available antibiotics, are urgently needed. We report the identification of a small molecule that inhibits biofilm formation by two important pathogenic Gram-positive bacteria, Streptococcus mutans and Staphylococcus aureus. The small molecule selectively targets a transcriptional regulator leading to attenuation of a biofilm regulatory cascade and concurrent reduction of bacterial virulence in vivo . As the regulator is highly conserved, the finding has broad implication for the development of antivirulence therapeutics that selectively target biofilms., Competing Interests: The authors declare no conflict of interest.

Previous research indicated that there is an aggregate of microorganism in oral cavity which takes part in promoting the occurrence of dental caries, but few studies on anticaries materials for these 'core microbiome' were developed. And We've found that DMAEM monomer has an obvious inhibitory effect on the growth of Streptococcus mutans and saliva biofilm, but the effect of that on the "core microbiome" of caries need further research. Thus, the objectives of this study were to explore the effect of DMAEM monomer on the core microbiota of dental caries, and to further study its anticaries effect. The changes of microbial structure and metabolic activity of the core microbiota biofilm were detected through measuring lactic acid yield, viable bacteria counts and demineralization depth, et al., and the anticaries potential in vivo of DMAEM monomer was evaluated by rat caries model. Meanwhile, high-throughput sequencing was used to analyze the microbial diversity change of saliva samples of rats. The results showed that DMAEM monomer could inhibit the growth of the core microbiota biofilm, decrease the metabolic activity and the acid production, as well as reduce the ability of demineralization under acidic conditions. Moreover, the degree of caries in the DMAEM group was significantly reduced, and the diversity and the evenness of oral microecology in the rats were statistically higher. In summary, DMAEM monomer could respond to acidic environment, significantly inhibit the cariogenic ability of the 'core microbiome' of caries, and help to maintain the microecological balance of oral cavity., (Copyright © 2023 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Taste receptors, originally identified in taste buds, function as the periphery receptors for taste stimuli and play an important role in food choice. Cohort studies have revealed that single nucleotide polymorphisms of taste receptors such as T1R1, T1R2, T2R38 are associated with susceptibility to oral diseases like dental caries. Recent studies have demonstrated the wide expression of taste receptors in various tissues, including intestinal epithelia, respiratory tract, and gingiva, with an emerging role of participating in the interaction between mucosa surface and microorganisms via monitoring a wide range of metabolites. On the one hand, individuals with different oral microbiomes exhibited varied taste sensitivity, suggesting a potential impact of the oral microbiota composition on taste receptor function. On the other hand, animal studies and in vitro studies have uncovered that a variety of oral cells expressing taste receptors such as gingival solitary chemosensory cells, gingival epithelial cells (GECs), and gingival fibroblasts can detect bacterial signals through bitter taste receptors to trigger host innate immune responses, thus regulating oral microbial homeostasis. This review focuses on how taste receptors, particularly bitter and sweet taste receptors, mediate the oral microbiota-host interaction as well as impact the occurrence and development of oral diseases. Further studies delineating the role of taste receptors in mediating oral microbiota-host interaction will advance our knowledge in oral ecological homeostasis establishment, providing a novel paradigm and treatment target for the better management of dental infectious diseases., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Dong, Liu, Zhu, Zhou, Tizzano, Peng, Zhou, Xu and Zheng.)

Oral bacteria directly affect the disease status of dental caries and periodontal diseases. The dynamic oral microbiota cooperates with the host to reflect the information and status of immunity and metabolism through two-way communication along the oral cavity and the systemic organs. The oral cavity is one of the most important interaction windows between the human body and the environment. The microenvironment at different sites in the oral cavity has different microbial compositions and is regulated by complex signaling, hosts, and external environmental factors. These processes may affect or reflect human health because certain health states seem to be related to the composition of oral bacteria, and the destruction of the microbial community is related to systemic diseases. In this review, we discussed emerging and exciting evidence of complex and important connections between the oral microbes and multiple human systemic diseases, and the possible contribution of the oral microorganisms to systemic diseases. This review aims to enhance the interest to oral microbes on the whole human body, and also improve clinician's understanding of the role of oral microbes in systemic diseases. Microbial research in dentistry potentially enhances our knowledge of the pathogenic mechanisms of oral diseases, and at the same time, continuous advances in this frontier field may lead to a tangible impact on human health., (© 2022. The Author(s).)

Nonnutritive sweeteners (NNSs) are sugar substitutes widely used to reduce the negative health effects of excessive sugar consumption. Dental caries, one of the most prevalent chronic diseases globally, results from a pathogenic biofilm with microecological imbalance and frequent exposure to sugars. Some research has shown that certain NNSs possess less cariogenic potential than sucrose, indicating their putative effect on oral microbiome. To uncover the alterations of acidogenic pathogens and alkali-generating commensals, as well as the biofilm cariogenic potential under the influence of NNSs, we selected four common NNSs (acesulfame-K, aspartame, saccharin, and sucralose) and established single-, dual-, and multispecies in vitro culture model to assess their effects on Streptococcus mutans ( S. mutans ) and/or Streptococcus sanguinis ( S. sanguinis ) compared to sucrose with the same sweetness. The results showed that NNSs significantly suppressed the planktonic growth, acid production, and biofilm formation of S. mutans or S. sanguinis compared with sucrose in single-species cultures. Additionally, decreased S. mutans / S. sanguinis ratio, less EPS generation, and higher pH value were observed in dual-species and saliva-derived multispecies biofilms with supplementary NNSs. Collectively, this study demonstrates that NNSs inhibit the cariogenic potential of biofilms by maintaining microbial equilibrium, thus having a promising prospect as anticaries agents., Competing Interests: The authors declare no conflict of interest., (Copyright © 2021 Jianhui Zhu et al.)

Candida albicans has been detected in root carious lesions. The current study aimed to explore the action of this fungal species on the microbial ecology and the pathogenesis of root caries. Here, by analyzing C. albicans in supragingival dental plaque collected from root carious lesions and sound root surfaces of root-caries subjects as well as caries-free individuals, we observed significantly increased colonization of C. albicans in root carious lesions. Further in vitro and animal studies showed that C. albicans colonization increased the cariogenicity of oral biofilm by altering its microbial ecology, leading to a polymicrobial biofilm with enhanced acidogenicity, and consequently exacerbated tooth demineralization and carious lesion severity. More importantly, we demonstrated that the cariogenicity-promoting activity of C. albicans was dependent on PHR2. Deletion of PHR2 restored microbial equilibrium and led to a less cariogenic biofilm as demonstrated by in vitro artificial caries model or in vivo root-caries rat model. Our data indicate the critical role of C. albicans infection in the occurrence of root caries. PHR2 is the major factor that determines the ecological impact and caries-promoting activity of C. albicans in a mixed microbial consortium.

Objective: Recurrent caries is a primary reason for restoration failure caused by biofilm acids. The objectives of this study were to: (1) develop a novel multifunctional composite with antibacterial function and calcium (Ca) and phosphate (P) ion release, and (2) investigate the effects on enamel demineralization and hardness at the margins under biofilms., Methods: Dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) were incorporated into composite. Four groups were tested: (1) Commercial control (Heliomolar), (2) Experimental control (0% DMAHDM + 0% NACP), (3) antibacterial group (3% DMAHDM + 0% NACP), (D) antibacterial and remineralizing group (3% DMAHDM + 30% NACP). Mechanical properties and Ca and P ion release were measured. Colony-forming units (CFU), lactic acid and polysaccharide of Streptococcus mutans (S. mutans) biofilms were evaluated. Demineralization of bovine enamel with restorations was induced via S. mutans, and enamel hardness was measured. Data were analyzed via one-way and two-way analyses of variance and Tukey's multiple comparison tests., Results: Adding DMAHDM and NACP into composite did not compromise the mechanical properties (P > 0.05). Ca and P ion release of 3% DMAHDM + 30% NACP was increased at cariogenic low pH. Biofilm lactic acid and polysaccharides were greatly decreased via DMAHDM, and CFU was reduced by 4 logs (P < 0.05). Under biofilm acids, enamel hardness at the margins was decreased to about 0.5 GPa for control; it was about 1 GPa for antibacterial group, and 1.3 GPa for antibacterial and remineralizing group (P < 0.05)., Conclusions: The novel 3% DMAHDM + 30% NACP composite had strong antibacterial effects. It substantially reduced enamel demineralization adjacent to restorations under biofilm acid attacks, yielding enamel hardness that was 2-fold greater than that of control composites. The novel multifunctional composite is promising to inhibit recurrent caries., (Copyright © 2020 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Veillonella species, known as the early colonizer of oral biofilm, are prevalent in oral microbiota. Seven Veillonella species have been isolated from oral cavity. Their distribution varies not only with different people but also with different sites in the oral cavity. Oral Veillonella are associated with oral diseases. They contribute to the adhesion of Streptococcus mutans and consume the lactate generated by streptococci. Veillonella species play an important role in the occurrence and development of periodontal diseases by providing adhesion sites for Porphyromonas gingivalis and boosting immune responses. The production of lipopolysaccharide and H2S is related to other oral diseases, such as pulpitis, periapical periodontitis, and halitosis. Several studies have been conducted on the relationship between Veillonella and oral diseases and the interaction between Veillonella and other pathological microorganisms, but limited knowledge is available at the molecular level. This article reviews the research progress in the relationship between Veillonella and oral infectious diseases, such as dental caries and periodontal diseases.

S-glutathionylation is an important post-translational modification (PTM) process that targets protein cysteine thiols by the addition of glutathione (GSH). This modification can prevent proteolysis caused by the excessive oxidation of protein cysteine residues under oxidative or nitrosative stress conditions. Recent studies have suggested that protein S-glutathionylation plays an essential role in the control of cell-signaling pathways by affecting the protein function in bacteria and even humans. In this study, we investigated the effects of S-glutathionylation on physiological regulation within Streptococcus mutans, the primary etiological agent of human dental caries. To determine the S-glutathionylated proteins in bacteria, the Cys reactive isobaric reagent iodoacetyl Tandem Mass Tag (iodoTMT) was used to label the S-glutathionylated Cys site, and an anti-TMT antibody-conjugated resin was used to enrich the modified peptides. Proteome profiling identified a total of 357 glutathionylated cysteine residues on 239 proteins. Functional enrichment analysis indicated that these S-glutathionylated proteins were involved in diverse important biological processes, such as pyruvate metabolism and glycolysis. Furthermore, we studied a thioredoxin-like protein (Tlp) to explore the effect of S-glutathionylation on interspecies competition between oral streptococcal biofilms. Through site mutagenesis, it was proved that glutathionylation on Cys41 residue of Tlp is crucial to protect S. mutans from oxidative stress and compete with S. sanguinis and S. gordonii. An addition rat caries model showed that the loss of S-glutathionylation attenuated the cariogenicity of S. mutans. Taken together, our study provides an insight into the S-glutathionylation of bacterial proteins and the regulation of oxidative stress resistance and interspecies competition., Competing Interests: The authors have declared that no competing interests exist.

Objectives: Resin infiltrant is used in early enamel caries. However, commercial resin infiltrant lacks persistent antibacterial activity. Dimethylaminododecyl methacrylate (DMADDM) was added to resin infiltrant to give it sustainable antibacterial properties and inhibit demineralization., Methods: After the application of resin infiltrant to bovine enamel, cytotoxicity, surface roughness, and aesthetics were assessed. A multi-species biofilm was incubated on the enamel disk before and one month after microbial-aging. After a 48-h anaerobic incubation, biomass accumulation, metabolic activity, and lactic acid were analyzed using a crystal violet assay, an MTT (3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and a lactic acid assay. Biofilm structure and composition were determined by live/dead staining, exopolysaccharide (EPS) staining, scanning electron microscopy (SEM), and quantitative polymerase chain reaction (qPCR). The depth and content of demineralization were tested by transverse microradiography (TMR)., Results: Incorporating DMADDM did not increase the cytotoxicity or change the physical properties when the mass fraction of the DMADDM was 2.5-10 %. The modification decreased the amount of bacterial biofilm, metabolic activity, lactic acid production, EPS, and the proportion of Streptococcus mutans in the biofilms. It also provided anti-demineralization effects. The surface roughness and antibacterial ability were not changed after one month of microbial-aging., Conclusion: The incorporation of DMADDM improved the antibacterial and anti-demineralization effects of the material. It demonstrated a sustained antibacterial effect., Clinical Significance: The antibacterial modification might be a potential choice for future clinical applications to inhibit early enamel caries., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Sucrose has long been regarded as the most cariogenic carbohydrate. However, why sucrose causes severer dental caries than other sugars is largely unknown. Considering that caries is a polymicrobial infection resulting from dysbiosis of oral biofilms, we hypothesized that sucrose can introduce a microbiota imbalance favoring caries to a greater degree than other sugars. To test this hypothesis, an in vitro saliva-derived multispecies biofilm model was established, and by comparing caries lesions on enamel blocks cocultured with biofilms treated with sucrose, glucose and lactose, we confirmed that this model can reproduce the in vivo finding that sucrose has the strongest cariogenic potential. In parallel, compared to a control treatment, sucrose treatment led to significant changes within the microbial structure and assembly of oral microflora, while no significant difference was detected between the lactose/glucose treatment group and the control. Specifically, sucrose supplementation disrupted the homeostasis between acid-producing and alkali-producing bacteria. Consistent with microbial dysbiosis, we observed the most significant disequilibrium between acid and alkali metabolism in sucrose-treated biofilms. Taken together, our data indicate that the cariogenicity of sugars is closely related to their ability to regulate the oral microecology. These findings advance our understanding of caries etiology from an ecological perspective.

Dental caries is the most common oral disease. The bacteriological aetiology of dental caries promotes the use of antibiotics or antimicrobial agents to prevent this type of oral infectious disease. Antibiotics have been developed for more than 80 years since Fleming discovered penicillin in 1928, and systemic antibiotics have been used to treat dental caries for a long time. However, new types of antimicrobial agents have been developed to fight against dental caries. The purpose of this review is to focus on the application of systemic antibiotics and other antimicrobial agents with respect to their clinical use to date, including the history of their development, and their side effects, uses, structure types, and molecular mechanisms to promote a better understanding of the importance of microbial interactions in dental plaque and combinational treatments., Competing Interests: The authors confirm that this article content has no conflicts of interest., (Copyright © 2020 Wei Qiu et al.)

Bacterial cell division is initiated by tubulin homologue FtsZ that assembles into a ring structure at mid-cell to facilitate cytokinesis. EzrA has been identified to be implicated in FtsZ-ring dynamics and cell wall biosynthesis during cell division of Bacillus subtilis and Staphylococcus aureus, the model rod and cocci. However, its role in pathogenic streptococci remains largely unknown. Here, the role of EzrA was investigated in Streptococcus mutans, the primary etiological agent of human dental caries, by constructing an ezrA in-frame deletion mutant. Our data showed that the ezrA mutant was slow-growing with a shortened length and extended width round cell shape compared to the wild type, indicating a delay in cell division with abnormalities of peptidoglycan biosynthesis. Additionally, FtsZ irregularly localized in dividing ezrA mutant cells forming angled division planes, potentially contributing to an aberrant cell shape. Furthermore, investigation using single-species cariogenic biofilm model revealed that deletion of ezrA resulted in defective biofilm formation with less extracellular polysaccharides and altered three-dimensional biofilm architecture. Unexpectedly, in a dual-species ecological model, the ezrA mutant exhibited substantially lower tolerance for H 2 O 2 and reduced competitiveness against one commensal species, Streptococcus sanguinis. Taken together, these results demonstrate that EzrA plays a key role in regulating cell division and maintaining a normal morphology in S. mutans and is required for its robust biofilm formation/interspecies competition. Therefore, EzrA protein represents a potential therapeutic target in the development of drugs controlling dental caries and other biofilm-related diseases., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Biofilm control is a critical approach to the better management of dental caries. Antimicrobial small molecules have shown their potential in the disruption of oral biofilm and control of dental caries. The objectives of this study were to examine the antimicrobial activity and cytotoxicity of a newly designed small-molecule compound, ZY354. ZY354 was synthesized, and its cytotoxicity was evaluated in human oral keratinocytes (HOK), human gingival epithelial cells (HGE), and macrophages (RAW) by CCK-8 assays. Minimal inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), minimum biofilm inhibition concentrations (MBICs), and minimum biofilm reduction concentrations (MBRCs) of ZY354 against common oral streptococci (i.e., Streptococcus mutans , Streptococcus gordonii , and Streptococcus sanguinis ) were determined by microdilution method. The exopolysaccharide (EPS)/bacterium ratio and the dead/live bacterium ratio in the ZY354-treated multispecies biofilms were determined by confocal laser scanning microscopy, and the microbial composition was visualized and quantified by fluorescent in situ hybridization and quantitative PCR (qPCR). The demineralizing activity of ZY354-treated biofilms was evaluated by transverse microradiography. The results showed that ZY354 exhibited low cytotoxicity in HOK, HGE, and RAW cells and exhibited potent antimicrobial activity against common oral streptococci. The EPS and the abundance of S. mutans were significantly reduced after ZY354 treatment, along with an increased dead/live microbial ratio in multispecies biofilms compared to the level with the nontreated control. The ZY354-treated multispecies biofilms exhibited reduced demineralizing activity at the biofilm/enamel interface. In conclusion, the small-molecule compound ZY354 exhibits low cytotoxicity and remarkable antimicrobial activity against oral streptococci, and it may have a great potential in anticaries clinical applications., (Copyright © 2019 American Society for Microbiology.)

The human microbiome project promoted further understanding on human oral microbes. Besides oral diseases such as dental caries, periodontal disease, and oral cancer, oral microbes are closely associated with systematic diseases. They have a close connection with digestive system diseases and even contribute to the origination and progression of colorectal cancer. By reviewing recent studies involving oral microbe-related digestive systemic diseases, we aim to propose the considerable role of oral microbes in relation to digestive systemic diseases and the way of oral microbes to multiple organs of digestive system.

Oral microbiome is potentially correlated with many diseases, such as dental caries, periodontitis, oral cancer and some systemic diseases. Twin model, as an effective method for studying human microbiota, is widely used in research of relationship between oral microbiota and dental caries. However, there were few researches focusing on caries discordant twins. In this study, in vitro assays were conducted combined with 16S rRNA sequencing analysis on oral microbiota sampled from twins who presented discordant caries experience and mice model was developed as well. Results showed that oral microbiota from caries-active twin possessed higher metabolic activity and produced more lactic production. 16S rRNA sequencing analysis showed that more than 80% of family taxa could be transferred into gnotobiotic-mice. Key caries-associated genera were significantly different between twins and the same difference in genus level could be found in mice as well (p < 0.05). This study suggested that oral microbiota of twins could be distinguished from each other despite the similarities in genetic make-up, living environment, and lifestyle. The difference in microbiota was applied to develop a mice model which may facilitate the investigation of core microbiota of dental caries.

Objectives: A new quaternary ammonium monomer (QAM), triethylaminododecyl acrylate (TEADDA) was synthesized, in which the position of the functional groups was different from that of dimethylaminododecyl methacrylate (DMADDM). The objectives were to: (1) investigate the effect of the changed position of the functional groups on the mechanical properties, anti-biofilm activity and biocompatibility of adhesive resin, and (2) study the anti-bacterial mechanism of QAM to improve the performance of the adhesive system modified by QAM., Methods: TEADDA and DMADDM were added into adhesives. Microtensile bond strength and surface charge density were measured. Multi-species biofilms were incubated on specimens for 16h, 48h and 72h and analyzed via MTT assay, lactic acid measurement and confocal laser scanning microscopy. The ratio of different species of bacteria was measured by real-time polymerase chain reaction. Cytotoxicity and biocompatibility were analyzed by eluents cytotoxicity test and histological images of H&E staining via an animal study in rats., Results: The mass fraction of TEDDA allowed to be added into adhesive was higher than that of DMADDM. However, even 10% TEADDA did not yield a strong anti-biofilm effect on biofilm growth, lactic acid production and bacteria compositions. TEADDA added into adhesives showed better mechanical properties but weaker anti-bacterial effect. There was no significant difference on cytotoxicity and biocompatibility between DMADDM and TEADDA., Significance: The study could be helpful for the investigation of the anti-caries mechanism of QAMs, the design of new QAMs and the improvement of the anti-caries activity of the modified dental materials., (Copyright © 2017 The Academy of Dental Materials. All rights reserved.)

We investigated the anticaries properties of an adhesive containing dimethylaminododecyl methacrylate (DMADDM) in vivo via a secondary caries animal model. Cavities were prepared in the maxillary first molars of Wistar rats. DMADDM-containing adhesives were applied on one side and commercial adhesives on the opposite side as a control. After a 3-week feeding period to induce secondary caries, the molars were harvested for the evaluation of the secondary caries. Lesion depth (LD) and mineral loss (ML) were measured via a micro-CT method, and a modified Keyes scoring method yielded scores for the caries lesions. Statistical analysis was divided into 2 parts: a correlation analysis between 2 evaluations with one-way ANOVA and a least-significant differences (LSD) test, and an evaluation of anticaries adhesives with a paired samples t test. The results showed that: (1) secondary caries was successfully produced in rats; (2) there was a correlation between the modified Keyes scoring method and micro-CT in the evaluation of the secondary caries; (3) the adhesive containing DMADDM significantly reduced both LD and ML (according to micro-CT), and also lowered the scores (based on the modified Keyes scoring method). This suggests that the novel DMADDM adhesive could perform an anticaries function in vivo via the secondary caries animal model which was also developed and testified in research. Secondary caries is one of the major reasons leading to the failure of caries restoration treatment. As a solution, anticaries adhesives perform well in biofilm inhibition in vitro. However, the lack of secondary caries animal models limits the evaluation of anticaries adhesives in vivo., (© 2017 The Author(s) Published by S. Karger AG, Basel.)

The phenotypic traits of Streptococcus mutans , such as fluoride tolerance, are usually associated with genotypic alterations. The aim of this study was to identify adaptive mutations of S. mutans to gradient fluoride concentrations and possible relationships between the mutations and fluoride tolerance. We identified a highly resistant S. mutans strain (FR1000) with a novel single nucleotide polymorphism (SNP, −36G→T) in the promoter region of F0F1-ATPase gene cluster (SMU_1527-SMU_1534) resistant to 1,000 ppm fluoride using the whole-genome Illumina PE250 sequencing. Thus, a −36G→T F0F1-ATPase promoter mutation from the parental strain S. mutans UA159 was constructed and named UA159-T. qRT-PCR showed that the F0F1-ATPase gene expression of both FR1000 and UA159-T was up-regulated, and fluoride tolerance of UA159-T was significantly improved. Complementation of Dicyclohexylcarbodiimide (DCCD), a specific inhibitor of F0F1-ATPase, increased fluoride susceptibility of FR1000 and UA159-T. Intracellular fluoride concentrations of fluoride tolerance strains were higher compared to UA159 strain as demonstrated by 18F analysis. Further validation with rat caries models showed that UA159-T caused more severe caries lesions under fluoride exposure compared with its parental UA159 strain. Overall, the identified −36G→T mutation in the promoter region of F0F1-ATPase gene drastically contributed to the fluoride tolerance and enhanced cariogenicity of S. mutans. These findings provided new insights into the mechanism of microbial fluoride tolerance, and suggested F0F1-ATPase as a potential target for suppressing fluoride resistant strains. [ABSTRACT FROM AUTHOR]

Background: The side effects of present antimicrobials like chlorhexidine (CHX) and the emergence of drug resistance necessitate the development of alternative agents to control dental caries. Aim: This study developed a novel small molecule, namely II-6s, and investigated its antimicrobial activities against common oral streptococci associated with dental caries. Methods: The susceptibility of streptococci to II-6s was evaluated by the microdilution method, time-kill assay and scanning electron microscopy. The exopolysaccharides, dead/live bacteria and bacterial composition of the II-6s-treated Streptococcus mutans/Streptococcus gordonii/Streptococcus sanguinis 3-species biofilms were analyzed by confocal laser scanning microscopy, fluorescent in situ hybridization and quantitative PCR. The anti-demineralization effect and cytotoxicity of II-6s were evaluated by transverse microradiography and CCK-8 assay, respectively. Repeated exposure of S. mutans to II-6s was performed to assess if II-6s could induce drug resistance. Results: II-6s exhibited antimicrobial activity similar to CHX against S. mutans, S. gordonii and S. sanguinis and significantly inhibited exopolysaccharides production, live bacteria and the demineralizing capability of the 3-species streptococcal biofilms. Besides, II-6s showed reduced cytotoxicity relative to CHX and did not induce drug resistance in S. mutans after 15 passages. Conclusion: - II-6s may serve as a promising part of a successful caries management plan. [ABSTRACT FROM AUTHOR]

A previous longitudinal study about using microbiome as a caries indicator has successfully predicted early childhood caries (ECC) in healthy individuals, but there is no evidence to verify the composition of core microbiota and its pathogenicity in vitro and in vivo. Biofilm acidogenicity, S. mutans count, and biofilm composition were estimated by pH evaluation, colony-forming unit, and quantitative PCR, respectively. Extracellular polysaccharide production and enamel demineralization were observed by confocal laser scanning microscopy (CLSM) and transverse microradiography (TMR), respectively. A rat caries model was established for dental caries formation in vivo, and caries lesions were quantified by Keyes Scoring. We put forward that microbiota including Veillonella parvula, Fusobacterium nucleatum, Prevotella denticola, and Leptotrichia wadei served as the predictors for ECC may be the core microbiota in ECC. This study found that the core microbiota of ECC produced limited acid, but promoted growth and acidogenic ability of S. mutans. Besides, core microbiota could help to promote the development of biofilms. Moreover, the core microbiota enhanced the enamel demineralization in vitro and increased cariogenic potential in vivo. These results proved that core microbiota could promote the development of dental caries and plays an important role in the development of ECC. [ABSTRACT FROM AUTHOR]

Objectives. Disruption of microbial biofilms is an effective way to control dental caries. Drug resistance and side effects of the existing antimicrobials necessitate the development of novel antibacterial agents. The current study was aimed at investigating the antibacterial activities of the repurposed natural compound napabucasin against oral streptococci. Methods. The minimum inhibitory concentration, minimum bactericidal concentration, minimum biofilm inhibition concentration, and minimum biofilm reduction concentration of Streptococcus mutans, Streptococcus gordonii, and Streptococcus sanguinis were examined by a microdilution method. Cytotoxicity of napabucasin against human oral keratinocytes, human gingival epithelia, and macrophage RAW264.7 was evaluated by CCK8 assays. The dead/live bacterium and exopolysaccharide in the napabucasin-treated multispecies biofilms were evaluated by confocal laser scanning microscopy. Microbial composition within the napabucasin-treated biofilms was further visualized by fluorescent in situ hybridization and qPCR. And the cariogenicity of napabucasin-treated biofilms was evaluated by transverse microradiography. Results. Napabucasin exhibited good antimicrobial activity against oral streptococcal planktonic cultures and biofilms but with lessened cytotoxicity as compared to chlorhexidine. Napabucasin reduced the cariogenic S. mutans and increased the proportion of the commensal S. gordonii in the multispecies biofilms. More importantly, napabucasin significantly reduced the demineralization capability of biofilms on tooth enamels. Conclusion. Napabucasin shows lessened cytotoxicity and comparable antimicrobial effects to chlorhexidine. Repurposing napabucasin may represent a promising adjuvant for the management of dental caries. [ABSTRACT FROM AUTHOR]

Dental caries is a common disease on a global scale. Resin composites are the most popular materials to restore caries by bonding to tooth tissues via adhesives. However, multiple factors, such as microleakage and recurrent caries, impair the durability of resinous restorations. Various innovative methods have been applied to develop adhesives with particular functions to tackle these problems, such as incorporating matrix metalloproteinase inhibitors, antibacterial or remineralizing agents into bonding systems, as well as improving the mechanical/chemical properties of adhesives, even combining these methods. This review will sum up the latest achievements in this field. [ABSTRACT FROM AUTHOR]

Oral biofilms attach onto both teeth surfaces and dental material surfaces in oral cavities. In the meantime, oral biofilms are not only the pathogenesis of dental caries and periodontitis, but also secondary caries and peri-implantitis, which would lead to the failure of clinical treatments. The material surfaces exposed to oral conditions can influence pellicle coating, initial bacterial adhesion, and biofilm formation, due to their specific physical and chemical characteristics. To define the effect of physical and chemical characteristics of dental prosthesis and restorative material on oral biofilms, we discuss resin-based composites, glass ionomer cements, amalgams, dental alloys, ceramic, and dental implant material surface properties. In conclusion, each particular chemical composition (organic matrix, inorganic filler, fluoride, and various metallic ions) can enhance or inhibit biofilm formation. Irregular topography and rough surfaces provide favorable interface for bacterial colonization, protecting bacteria against shear forces during their initial reversible binding and biofilm formation. Moreover, the surface free energy, hydrophobicity, and surface-coating techniques, also have a significant influence on oral biofilms. However, controversies still exist in the current research for the different methods and models applied. In addition, more in situ studies are needed to clarify the role and mechanism of each surface parameter on oral biofilm development. [ABSTRACT FROM AUTHOR]

Agglomeration is a common problem facing the preparation and application of nanomaterials, and whether nano-hydroxyapatite (nano HA) can modulate oral microecology left to be unclear. In this study, nano HA was disaggregated by sodium hexametaphosphate (SHMP) and ultrasonic cavitation to observe whether agglomeration would affect its effect on oral bacterial biofilm. Dynamic light scattering (DLS) and scanning electronic microscope (SEM) were used to observe the treatment solutions. Single-species biofilms and multi-species biofilms were treated with 10% nano HA, 10% disaggregated nano HA, 10% micro hydroxyapatite (micro HA) and deionized water (DDW) for 30 min and analyzed via MTT assay, lactic acid measurement, SEM and confocal laser scanning microscope (CLSM). Real-time polymerase chain reaction was performed to analyze the biofilm composition. Ultrasonic cavitation combined with SHMP could significantly reduce the degree of agglomeration of nano HA. Disaggregated nano HA could inhibit bacterial growth and reduce the ability of bacterial biofilm to produce lactic acid and extracellular polysaccharides. There was no significant difference on composition of multi-species biofilms between nano HA and disaggregated nano HA. The disaggregated nano-hydroxyapatite could inhibit the metabolism and acid production of oral bacterial biofilm, but did not significantly affect the composition of multi-species biofilms. [ABSTRACT FROM AUTHOR]

Streptococcus mutans is the primary etiological agent of human dental caries. Its major virulence factors, glucosyltransferases (Gtfs), utilize sucrose to synthesize extracellular polysaccharides (EPS), leading to the formation of dental plaque biofilm. The current study was designed to develop a novel self-targeting gene editing technology that targeted gtfs to inhibit biofilms formation. The CRISPR-Cas system (ie, clustered regularly interspaced short palindromic repeat, with CRISPR-associated proteins) provides sequence-specific protection against foreign genetic materials in archaea and bacteria, and has been widely developed for genomic engineering. The first aim of this study was to test whether components of the CRISPR-Cas9 system from S mutans UA159 is necessary to defend against foreign DNA. The data showed that a suitable PAM site, tracrRNA, Cas9, and RNase III are indispensable elements to perform normal function of S mutans CRISPR-Cas9 system. Based on these results, we designed self-targeting CRISPR arrays (containing spacer sequences identifying with gtfB) and cloned them onto plasmids. Afterward, we transformed the plasmids and editing templates into UA159 (self-targeting) to acquire desired mutants. Our data showed that this technology performed well and was able to successfully edit gtfB or gtfBgtfC genes. This resulted in high reduction in EPS synthesis and was able to breakdown biofilm formation, which is also a promising tool for dental clinics in order to prevent the formation of S mutans biofilms in the future. [ABSTRACT FROM AUTHOR]

• V. parvula didn't affect pH dynamics of S. mutans. • V. parvula promoted biofilms growth and EPS synthesis of S. mutans. • V. parvula is not, as previously thought, protective and associated with caries health. • V. parvula might participate in caries development through interactions with S. mutans. The aim of this study was to observe the effect of V. parvula on the physiological activity of S. mutans and elucidate the role of V. parvula on dental caries. We constructed dual-species biofilms formed by V. parvula and S. mutans , and measured the pH dynamics, biofilm growth, Extracellular Polysaccharide (EPS) synthesis, and expression of S. mutans EPS synthesis-associated genes affected by V. parvula. pH dynamics were not altered when V. parvula and S. mutans were co-cultured during a 120 -h test period. However, S. mutans cell number and EPS synthesis in dual-species biofilms were found to be significantly higher than in single-species biofilms. Moreover, expression levels of genes encoding glucosyltransferases (gtfs), gtfB and gtfC specifically, were up-regulated when S. mutans was co-cultured with V. parvula. Our findings indicate that V. parvula is not, as previously thought, protective and associated with caries health. On the contrary, V. parvula might participate in caries development through interactions with S. mutans. This study suggests that V. parvula may have an impact on the pathogenesis of dental caries. [ABSTRACT FROM AUTHOR]