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INTRODUCTION Epidemiological studies have shown a close relationship between smoking and dental caries. Bacteria are one of the essential factors of caries formation. The imbalance of cariogenic bacteria and commensal bacteria in dental plaque results in higher production of acid that can corrode dental hard tissue. The aim of our review is to summarize the effect of smoking on caries-related bacteria. METHODS English articles available in Pubmed and ScienceDirect databases and published before December 2018 were searched. A variety of evidence was collected including not only the influence of cigarette products on bacteria strains in vitro but also their effect on bacterial composition in saliva and dental plaque in vivo . We particularly emphasize the mechanisms by which nicotine acts on oral bacteria. RESULTS The components of cigarettes promote the growth of cariogenic microorganisms. The mechanisms of how nicotine enhances Streptococcus mutans, Lactobacilli, Streptococcus gordonii, Actinomyces and Candida albicans are described separately in detail. The commensal bacteria, Streptococcus sanguinis , show less competitive capability in the presence of nicotine. Smoking influences saliva by lowering the buffer capability, altering its chemical agent and bacterial components, and therefore promotes the formation of a caries-susceptible environment. CONCLUSIONS Cigarette smoking and nicotine exposure promote the cariogenic activity of oral microorganisms and the formation of a caries-susceptible environment. This suggests that smokers should quit smoking, amongst other health reasons, also for their oral health.

Manipulation of biofilm formation in Shewanella is beneficial for application to industrial and environmental biotechnology. BpfA is an adhesin largely responsible for biofilm formation in many Shewanella species. However, the mechanism underlying BpfA production and the resulting biofilm remains vaguely understood. We previously described the finding that BpfA expression is enhanced by DosD, an oxygen-stimulated diguanylate cyclase, under aerobic growth. In the present work, we identify FlrA as a critical transcription regulator of the bpfA operon in Shewanella putrefaciens CN32 by transposon mutagenesis. FlrA acted as a repressor of the operon promoter by binding to two boxes overlapping the Ϫ10 and Ϫ35 sites recognized by 70 . DosD regulation of the expression of the bpfA operon was mediated by FlrA, and cyclic diguanylic acid (c-di-GMP) abolished FlrA binding to the operon promoter. We also demonstrate that FlhG, an accessory protein for flagellum synthesis, antagonized FlrA repression of the expression of the bpfA operon. Collectively, this work demonstrates that FlrA acts as a central mediator in the signaling pathway from c-di-GMP to BpfA-associated biofilm formation in S. putrefaciens CN32.IMPORTANCE Motility and biofilm are mutually exclusive lifestyles, shifts between which are under the strict regulation of bacteria attempting to adapt to the fluctuation of diverse environmental conditions. The FlrA protein in many bacteria is known to control motility as a master regulator of flagellum synthesis. This work elucidates its effect on biofilm formation by controlling the expression of the adhesin BpfA in S. putrefaciens CN32 in response to c-di-GMP. Therefore, FlrA plays a dual role in controlling motility and biofilm formation in S. putrefaciens CN32. The cooccurrence of flrA, bpfA, and the FlrA box in the promoter region of the bpfA operon in diverse Shewanella strains suggests that bpfA is a common mechanism that controls biofilm formation in this bacterial species.KEYWORDS FlrA, Shewanella, biofilm, cyclic di-GMP, transcriptional factor B iofilm formed by bacteria is a multicell architecture for adaptation to diverse niches (1). Shewanella can form biofilm on a variety of surfaces, such as ferric oxides, electrodes, stainless steel, and glass (2-4). This genus is also renowned for an extracellular respiration ability to reduce iron oxide, electrodes, and other extracellular electron acceptors, including heavy metal ions. Such an ability has diverse potential applications in bioengineering and bioremediation (5). Biofilm formation in Shewanella benefits close contact with solid electron acceptors, thereby accelerating iron oxide reduction and improving current output, as well as inducing spatially stratified metabolic responses during contaminant exposure (4, 6, 7). Biofilm formed by Shewanella prevents microbially induced corrosion of steel and cast iron pipes (8, 9). On the other hand, biofilm formation of Shewanella also causes problems in some circumstances. For

Background/Aims Indirect pulp capping, pulpotomy, and apexification are three common endodontic treatments for immature traumatized incisors. They all affect tooth root development to some extent. The aim of this retrospective study was to compare the influence of these treatments on root development of immature permanent incisors following dental trauma. Materials and Methods Twenty‐one indirect pulp capping, 48 pulpotomy, and 58 apexification cases with a mean age of 8.4 ± 1.0 years and median follow up of 12 months were included. NIH ImageJ with TurboReg plug‐in was used to correct angular differences between the pre‐operative and recall periapical radiographs, and to calculate variations of root length, dentin wall thickness, and apical closure. Kruskal‐Wallis ANOVA followed by pairwise comparisons was applied to compare the radiographic variations. The type of apical closure was assessed qualitatively and analyzed using Fisher's exact test. Results The apexification group had a lower trend toward apical closure than the other two groups (P < .05). It also showed thinner dentin wall thickness compared with the pulpotomy group (P = .001). There was no significant difference between pulpotomy and indirect pulp capping in the trend to apical closure (P > .05) or dentin wall thickness (P = .775). There was no significant difference in the variation of root length among the three groups (P = .06). There was a moderate correlation between the treatment and the type of apical closure (Cramer's V Coefficient = .375). Pulpotomy tended to form a normal apical constriction rather than a calcific barrier while apexification showed the opposite inclination. Indirect pulp capping had no specific inclination toward any type of apical closure. Conclusions Apexification resulted in an abnormal root development mostly by affecting the dentin wall thickness and apical closure. Pulpotomy was beneficial for normal root development of immature traumatized teeth.

Streptococcus mutans is one of the major pathogens of dental caries. Oxyresveratrol, a natural compound found in plants, exerts inhibitory effects on many bacterial species but its effect on S. mutans is unknown. The objective of this study was to clarify the antibacterial effect of oxyresveratrol on S. mutans, including effects on basic viability, acidogenicity, acidurity, and extracellular polysaccharide synthesis. The expression of nine genes that encode virulence and protective factors in S. mutans was measured by qRT‐PCR. Oxyresveratrol showed a dose‐dependent inhibitory effect on survival of S. mutans. At 250 μg ml−1, oxyresveratrol reduced the S. mutans survival rate, inhibited synthesis of water‐insoluble glucans, compromised biofilm formation, and significantly down‐regulated the expression of glucosyltransferase‐I (gtfB) and glucosyltransferase‐SI (gtfC). However, the enzymatic activity of lactate dehydrogenase protein was increased and the expression of lactate dehydrogenase (ldh) and ATP synthase subunit beta (atpD) genes were also up‐regulated. Besides, glucosyltransferase S (gtfD) up‐regulation indicated that water‐soluble glucan synthesis was promoted. The vicR, liaR, and comDE genes, which exert a self‐protective function in response to external stress, were also up‐regulated. In conclusion, oxyresveratrol inhibited the growth of S. mutans and also reduced biofilm formation, acid production, and synthesis of water‐insoluble glucans by this organism. In addition, oxyresveratrol also activated a series of S. mutans self‐protection mechanisms.

Epstein-barr virus (EBV) is a definite tumorigenic virus, which can form lifelong latency in the host, which is difficult to be recognized and completely eliminated by the immune system. It is closely related to the occurrence and development of nasopharyngeal cancer, gastric cancer and various types of lymphoma. At present, a total of 44 Epstein-barr virus-encoded microRNAs (EBV miRNAs) have been found. In response to the immune system of the body, EBV miRNAs can inhibit the expression and presentation of viral antigens, inhibit immune activation and immunotoxicity, assisting host cells to escape from immunity, and providing conditions for further immortalized tumorigenesis of the host cells.

Rebuilding mineralized tissues in skeletal and dental systems remains costly and challenging. Despite numerous demands and heavy clinical burden over the world, sources of autografts, allografts, and xenografts are far limited, along with massive risks including viral infections, ethic crisis, and so on. Per such dilemma, artificial scaffolds have emerged to provide efficient alternatives. To date, cell‐free biomimetic mineralization (BM) and cell‐dependent scaffolds have both demonstrated promising capabilities of regenerating mineralized tissues. However, BM and cell‐dependent scaffolds have distinctive mechanisms for mineral genesis, which makes them methodically, synthetically, and functionally disparate. Herein, these two strategies in regenerative dentistry and orthopedics are systematically summarized at the level of mechanisms. For BM, methodological and theoretical advances are focused upon; and meanwhile, for cell‐dependent scaffolds, it is demonstrated how scaffolds orchestrate osteogenic cell fate. The summary of the experimental advances and clinical progress will endow researchers with mechanistic understandings of artificial scaffolds in rebuilding hard tissues, by which better clinical choices and research directions may be approached.

The homeostatic imbalance in dental plaque associated with a sharp increase in the number of cariogenic bacteria such as Streptococcus mutans is critical for the occurrence and development of caries. Probiotic therapy can restore ecological balance by replacing cariogenic pathogens with probiotics.