Beyond Streptococcus mutans: clinical implications of the evolving dental caries aetiological paradigms and its associated microbiome

Longitudinal Microbiome Changes in Supragingival Biofilm Transcriptomes Induced by Orthodontics

INTRODUCTION

Common oral diseases are known to be associated with dysbiotic shifts in the supragingival microbiome, yet most oral microbiome associations with clinical end points emanate from cross-sectional studies. Orthodontic treatment is an elective procedure that can be exploited to prospectively examine clinically relevant longitudinal changes in the composition and function of the supragingival microbiome.

METHODS

A longitudinal cohort study was conducted among 24 adolescent orthodontic patients who underwent saliva and plaque sampling and clinical examinations at time points: before fixed appliance bonding and at 1, 6, and 12 wk thereafter. Clinical indices included bleeding on probing (BOP), mean gingival index (GI), probing depths (PDs), and plaque index (PI). To study the biologically (i.e., transcriptionally) active microbial communities, RNA was extracted from plaque and saliva for RNA sequencing and microbiome bioinformatics analysis. Longitudinal changes in microbiome beta diversity were examined using PERMANOVA tests, and the relative abundance of microbial taxa was measured using Kruskal-Wallis tests, Wilcoxon rank-sum tests, and negative binomial and zero-inflated mixed models.

RESULTS

Clinical measures of oral health deteriorated over time-the proportion of sites with GI and PI ≥1 increased by over 70% between prebonding and 12 wk postbonding while the proportion of sites with PD ≥4 mm increased 2.5-fold. Streptococcus sanguinis, a health-associated species that antagonizes cariogenic pathogens, showed a lasting decrease in relative abundance during orthodontic treatment. Contrarily, caries- and periodontal disease-associated taxa, including Selenomonas sputigena, Leptotrichia wadei, and Lachnoanaerobaculum saburreum, increased in abundance after bonding. Relative abundances of Stomatobaculum longum and Mogibacterium diversum in prebonding saliva predicted elevated BOP 12 wk postbonding, whereas Neisseria subflava was associated with lower BOP.

CONCLUSIONS

This study offers insights into longitudinal community and species-specific changes in the supragingival microbiome transcriptome during fixed orthodontic treatment, advancing our understanding of microbial dysbioses and identifying targets of future health-promoting clinical investigations.

KNOWLEDGE TRANSFER STATEMENT

Bonding braces was associated with subsequent changes in the oral microbiome characterized by increases in disease-associated species, decreases in health-associated species, and worsened clinical measures of oral health.

qPCR assay optimisation for a clinical study comparing oral health risk in Rett syndrome

PURPOSE

This study aimed to validate qPCR assays for specific microbiota, for use on dental plaque samples stored on Whatman FTA cards to compare relative oral health risk in Rett syndrome.

METHODS

Supragingival dental plaque samples were collected, using a sterile swab, (COPAN FLOQswab™) swabbed onto Whatman FTA™ cards. DNA extraction was performed using a modified Powersoil™ protocol. Where published assays were unsuitable, species-specific qPCR assays for caries-associated, gingivitis-associated and oral-health-associated bacteria were designed using multiple sequence alignment, Primer3Plus and PrimerQuest. Assays were run using absolute quantification. Limit of detection (LOD) and limit of quantification (LOQ) were calculated, and PCR products verified by Sanger sequencing.

RESULTS

Most assays allowed detection using real-time qPCR with high specificity on samples collected on FTA cards. Several assays showed low or even single gene copy numbers on the test samples.

CONCLUSION

Assays were optimised for detection and evaluation of oral health risk in dental plaque samples stored on FTA cards when cold storage is not feasible, except for F. nucleatum. Several assays showed gene copy numbers less than the LOQ or outside the range of the standard curve, so there is merit in optimising these assays using digital droplet PCR.

Pine-Oil-Derived Sodium Resinate Inhibits Growth and Acid Production of Streptococcus mutans In Vitro

S. mutans is a key pathogen in dental caries initiation and progression. It promotes oral biofilm dysbiosis and biofilm acidification. Sodium resinate is a salt of pine-oil-derived resin which has antimicrobial properties. Pine-oil-derived resin consists of terpenes, diterpenes, and abietic acids. The aim of this study was to determine the effects of pine (Pinus sylvestris) oil resinate (RS) on growth and acid production of cariogenic S. mutans strains in planktonic form and biofilm. The S. mutans type strain NCTC10449 and clinical isolate CI2366 were grown on 96-well plates for testing of RS effects on growth and biofilm formation, and on plates with integrated pH-sensitive optical ensors for real-time measurements of the effects of RS on bacterial acid production. We found that even short-time exposure to RS inhibits the growth and acid production of S. mutans in the planktonic phase and biofilms. In addition, RS was able to penetrate the biofilm matrix and reduce acid production inside S. mutans biofilm. RS thus shows potential as a novel antibacterial agent against cariogenic bacteria in biofilm.

Plaque Microbiome in Caries-Active and Caries-Free Teeth by Dentition

OBJECTIVE

Describe associations between dental caries and dental plaque microbiome, by dentition and family membership.

METHODS

This cross-sectional analysis included 584 participants in the Center for Oral Health Research in Appalachia Cohort 1 (COHRA1). We sequenced the 16S ribosomal RNA gene (V4 region) of frozen supragingival plaque, collected 10 y prior, from 185 caries-active (enamel and dentinal) and 565 caries-free (no lesions) teeth using the Illumina MiSeq platform. Sequences were filtered using the R DADA2 package and assigned taxonomy using the Human Oral Microbiome Database.

RESULTS

Microbiomes of caries-active and caries-free teeth were most similar in primary dentition and least similar in permanent dentition, but caries-active teeth were significantly less diverse than caries-free teeth in all dentition types. Streptococcus mutans had greater relative abundance in caries-active than caries-free teeth in all dentition types (P < 0.01), as did Veillonella dispar in primary and mixed dentition (P < 0.01). Fusobacterium sp. HMT 203 had significantly higher relative abundance in caries-free than caries-active teeth in all dentition types (P < 0.01). In a linear mixed model adjusted for confounders, the relative abundance of S. mutans was significantly greater in plaque from caries-active than caries-free teeth (P < 0.001), and the relative abundance of Fusobacterium sp. HMT 203 was significantly lower in plaque from caries-active than caries-free teeth (P < 0.001). Adding an effect for family improved model fit for Fusobacterium sp. HMT 203 but notS. mutans.

CONCLUSIONS

The diversity of supragingival plaque composition from caries-active and caries-free teeth changed with dentition, but S. mutans was positively and Fusobacterium sp. HMT 203 was negatively associated with caries regardless of dentition. There was a strong effect of family on the associations of Fusobacterium sp. HMT 203 with the caries-free state, but this was not true for S. mutans and the caries-active state.

KNOWLEDGE TRANSFER STATEMENT

Patients' and dentists' concerns about transmission of bacteria within families causing caries should be tempered by the evidence that some shared bacteria may contribute to good oral health.

Prevention of bacterial biofilm formation on orthodontic brackets by non-crosslinked chitosan coating

During orthodontic treatment, the patients are susceptible to dental caries as a result of the bacterial adhesion and biofilm formation around the orthodontic brackets. Prevention of the caries-related biofilm formation is of significance for maintaining both aesthetics and health of the teeth. Herein, the brackets were functionalized with antibacterial activity via coating a layer of non-crosslinked chitosan (CS). We firstly demonstrated the ability of free CS scaffolds (not coated on brackets) to inhibit the formation of Streptococcus mutans biofilms (inhibition rate 94.3 % for CS-0.3 mg) and to eradicate the mature biofilms (biofilm loss rate 99.8 % for CS-1.2 mg). Further, the inhibition of S. mutans biofilm formation on brackets by CS coating was investigated for the first time. As a result, the CS-coated brackets (Br-CS) kept the great biofilm inhibition capacity of free CS scaffolds. In detail, the Br-CS, prepared by immersing brackets in CS solutions (containing 1.0, 2.5, 5.0 and 10 mg/mL CS) and freeze-drying, showed the biofilm inhibition rate of 48.5 %, 88.6 %, 96.4 % and 99.6 %, respectively. In conclusion, coating orthodontic brackets with the non-crosslinked CS is a potential approach for inhibiting biofilm formation and protecting patients from dental caries.

The microbiome of African penguins (Spheniscus demersus) under managed care resembles that of wild marine mammals and birds

Animals under managed care in zoos and aquariums are ideal surrogate study subjects for endangered species that are difficult to obtain in the wild. We compared the fecal and oral microbiomes of healthy, managed African penguins (Spheniscus demersus) to those of other domestic and wild vertebrate hosts to determine how host identity, diet, and environment shape the penguin microbiome. The African penguin oral microbiome was more similar to that of piscivorous marine mammals, suggesting that diet and a marine environment together play a strong role in shaping the oral microbiome. Conversely, the penguin cloaca/fecal microbiome was more similar to that of other birds, suggesting that host phylogeny plays a significant role in shaping the gut microbiome. Although the penguins were born under managed care, they had a gut microbiome more similar to that of wild bird species compared to domesticated (factory-farmed) birds, suggesting that the managed care environment and diet resemble those experienced by wild birds. Finally, the microbiome composition at external body sites was broadly similar to that of the habitat, suggesting sharing of microbes between animals and their environment. Future studies should link these results to microbial functional capacity and host health, which will help inform conservation efforts.

Evaluation of the antibacterial activity of Enamelast® and Fluor defender® fluoride varnishes against Streptococcus mutans biofilm: an in vitro study in primary teeth

PURPOSE

The aim of the current work was to compare the antibacterial activity of Enamelast® and Fluor defender® fluoride varnish on biofilm generation by Streptococcus mutans on extracted primary teeth.

METHODS

Thirty-six primary molars were collected and sliced into seventy-two test model disks. All specimens were examined, and the cracked or broken ones were discarded. A total number of specimens (n = 54) were divided into two experimental analyses viz; biofilm formation (n = 27) and microscopic examination (n = 27). Specimens of each analysis were tested under different experimental conditions: a negative control group (n = 9), Fluor defender group (n = 9), and Enamelast group (n = 9). Following treatment, biofilms were generated by adherent Streptococcus mutans on the test model disks on three time intervals: 24 h (n = 3), 48 h (n = 3), and 72 h (n = 3) for each analysis. Then, for biofilm formation analysis, the biofilm was detected spectrophotometrically at 620 nm after being stained by crystal violet. For microscopical analysis, the surfaces of the test model disks were visualized by scanning electron microscopy (SEM), and each image was processed and analyzed using ImageJ software.

RESULTS

At 48 and 72 h, Enamelast® and Fluor defender®-treated group showed significantly (p < 0.001) slight adhered bacterial cells when compared with the negative control group as revealed by the absorbance and SEM. Compared with the Fluor defender®-treated group, the absorbance of the Enamelast®-treated group showed a significant (p < 0.001) increase by approximately 7- and 16.5-fold at 48 and 72 h, respectively. Similarly, SEM showed that the number of bacterial cells adhered to enamel surfaces in the Fluor defender®-treated group was significantly (p < 0.001) fewer than the Enamelast®-treated group by approximately 36.55% and 20.62% at 48 and 72 h after exposure, respectively.

CONCLUSION

We conclude that the anti-biofilm activity of Fluor defender® against Streptococcus mutans was significantly (p < 0.001) greater than Enamelast® fluoride varnish. The use of Fluor defender® is encouraged as a preventive measure in children with the high risk of developing dental caries.

Lactobacillus paracasei ET-22 Suppresses Dental Caries by Regulating Microbiota of Dental Plaques and Inhibiting Biofilm Formation

Dental caries is a common and multifactorial biofilm disease that is associated with dietary habits and microbiota. Among the various pathogens inducing caries, S. mutans is the most extensively studied. Promoting oral health with probiotics has gained considerable attention. Lactobacillus paracasei (L. paracasei) strains were reported to modulate the gut microbiota and enhance host resistance to disease. Our previous research has found that L. paracasei ET-22 (ET-22) could inhibit S. mutans biofilms in vitro. However, the preventive effect in vivo and functional mechanism of ET-22 on dental caries were unclear. In this study, the preventive effects of ET-22 on dental caries in mice were checked. Meanwhile, the functional mechanism of ET-22 was further investigated. Results showed that the supplementation of ET-22 in drinking water significantly improved the caries scoring of mice. The microbiota of dental plaques revealed that the live and heat-killed ET-22 similarly regulated the microbial structure in plaque biofilms. Functional prediction of PICRUSt showed that the addition of live and heat-killed ET-22 may inhibit biofilm formation. By the in vitro trials, the live and heat-killed ET-22 indeed inhibited the construction of S. mutans biofilms and EPS productions of biofilms. This evidence suggests that ET-22 can restrain dental caries by regulating the microbiota of dental plaques and inhibiting biofilm formation, which may be partly mediated by the body components of ET-22.

Multivariable Projections of Caries-Free Prevalence and the Associated Factors from 2019 to 2030 among Schoolchildren Aged 6, 12 and 16-Year-Old in Malaysia

This study identified caries-free associated factors and conducted multivariable projections of the caries-free prevalence until 2030 among six-, 12-, and 16-year-old schoolchildren in Malaysia. It was a secondary data analysis of caries-free prevalence and potential associated factors obtained from the Health Information Management System (HIMS), Department of Statistics Malaysia (DOSM), and Food Balance Sheets (FBS). Multiple linear regression and regression with ARMA errors were employed to determine the associated factors and predict the caries-free prevalence from 2019 or 2020 until 2030 for the six-, 12-, and 16-year-old groups, respectively. Gross Domestic Product (GDP) and household income, sugar consumption, and water fluoridation were significantly associated with caries-free status, with the most impactful in all age groups being water fluoridation. With the projected values of the associated factors, the caries-free prevalence in schoolchildren of all age groups in Malaysia is predicted to increase in the next decade. Similar to the past decade, the prevalence trend will remain the highest among the 12-year-olds and the lowest among six-year-olds. Caries-free prevalence was predicted to increase by 9.10%, 15.52%, and 15.10% in the six-, 12-, and 16-year-old groups, respectively. The prevalence multiplied the highest at four times greater than in the past ten years among 16-year-olds, compared with less than 2% in the six- and 12-year-old groups. In conclusion, by factoring in economic factors, sugar consumption, water fluoridation, and age groups, the caries-free prevalence of schoolchildren in Malaysia is projected to increase at different rates in the next decade until 2030. Thus, strategic oral health plans to recognise effective promotion programmes and strengthen others for each age group are crucial.

Saccharibacteria (TM7), but not other bacterial taxa, are associated with childhood caries regardless of age in a South China population

Background

Human microbiome dysbiosis is related to various human diseases, and identifying robust and consistent biomarkers that apply in different populations is a key challenge. This challenge arises when identifying key microbial markers of childhood caries.

Methods

We analyzed unstimulated saliva and supragingival plaque samples from children of different ages and sexes, performed 16S rRNA gene sequencing, and sought to identify whether consistent markers exist among subpopulations by using a multivariate linear regression model.

Results

We found that Acinetobacter and Clostridiales bacterial taxa were associated with caries in plaque and saliva, respectively, while Firmicutes and Clostridia were found in plaque isolated from children of different ages in preschool and school. These identified bacterial markers largely differ between different populations, leaving only Saccharibacteria as a significant caries-associated phylum in children. Saccharibacteria is a newly identified phylum, and our taxonomic assignment database could not be used to identify its specific genus.

Conclusion

Our data indicated that, in a South China population, oral microbial signatures for dental caries show age and sex differences, but Saccharibacteria might be a consistent signal and worth further investigation, considering the lack of research on this microbe.

Selenomonas sputigena acts as a pathobiont mediating spatial structure and biofilm virulence in early childhood caries

Streptococcus mutans has been implicated as the primary pathogen in childhood caries (tooth decay). While the role of polymicrobial communities is appreciated, it remains unclear whether other microorganisms are active contributors or interact with pathogens. Here, we integrate multi-omics of supragingival biofilm (dental plaque) from 416 preschool-age children (208 males and 208 females) in a discovery-validation pipeline to identify disease-relevant inter-species interactions. Sixteen taxa associate with childhood caries in metagenomics-metatranscriptomics analyses. Using multiscale/computational imaging and virulence assays, we examine biofilm formation dynamics, spatial arrangement, and metabolic activity of Selenomonas sputigena, Prevotella salivae and Leptotrichia wadei, either individually or with S. mutans. We show that S. sputigena, a flagellated anaerobe with previously unknown role in supragingival biofilm, becomes trapped in streptococcal exoglucans, loses motility but actively proliferates to build a honeycomb-like multicellular-superstructure encapsulating S. mutans, enhancing acidogenesis. Rodent model experiments reveal an unrecognized ability of S. sputigena to colonize supragingival tooth surfaces. While incapable of causing caries on its own, when co-infected with S. mutans, S. sputigena causes extensive tooth enamel lesions and exacerbates disease severity in vivo. In summary, we discover a pathobiont cooperating with a known pathogen to build a unique spatial structure and heighten biofilm virulence in a prevalent human disease.

Streptococcus salivarius as an Important Factor in Dental Biofilm Homeostasis: Influence on Streptococcus mutans and Aggregatibacter actinomycetemcomitans in Mixed Biofilm

A disturbed balance within the dental biofilm can result in the dominance of cariogenic and periodontopathogenic species and disease development. Due to the failure of pharmacological treatment of biofilm infection, a preventive approach to promoting healthy oral microbiota is necessary. This study analyzed the influence of Streptococcus salivarius K12 on the development of a multispecies biofilm composed of Streptococcus mutans, S. oralis and Aggregatibacter actinomycetemcomitans. Four different materials were used: hydroxyapatite, dentin and two dense polytetrafluoroethylene (d-PTFE) membranes. Total bacteria, individual species and their proportions in the mixed biofilm were quantified. A qualitative analysis of the mixed biofilm was performed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results showed that in the presence of S. salivarius K 12 in the initial stage of biofilm development, the proportion of S. mutans was reduced, which resulted in the inhibition of microcolony development and the complex three-dimensional structure of the biofilm. In the mature biofilm, a significantly lower proportion of the periodontopathogenic species A. actinomycetemcomitans was found in the salivarius biofilm. Our results show that S. salivarius K 12 can inhibit the growth of pathogens in the dental biofilm and help maintain the physiological balance in the oral microbiome.

Digital imaging and qPCR analysis and comparison of short-term plaque removal effects of tooth brushing

Purpose

Digital image technology and a real-time fluorescent quantitative polymerase chain reaction (RQ-PCR) were used to determine the changes in dental plaque caused by different toothbrushing tools.

Methods

A total of 120 subjects were selected and divided into four groups: a manual toothbrush group, a manual toothbrush combined with an oral irrigator group, an electric toothbrush combined with an oral irrigator group, and an electric toothbrush group. We compared the changes in plaque count, plaque area, and colony colonization of the four groups after different cleaning tools had been used for a period of time.

Results

Dental plaque count and plaque area decreased in all four groups. The decreases in plaque count and Streptococcus mutans in the electric toothbrush combined with an oral irrigator group were significantly higher than those in other groups.

Conclusion

Electric toothbrush combined with an oral irrigator shows a good result for plaque removal effect. Digital image analysis combined with biological methods can be used to evaluate dental plaque.

Antibacterial one-step self-etching dental adhesive with silver nanoparticles synthesized in situ

OBJECTIVES

The objective of this study is to value the long-term antibacterial capability and adhesive properties of one-step self-etching dental adhesive containing silver nanoparticles (AgNPs) synthesized in situ.

METHODS

One-step self-etching adhesives with various weight percentages of silver 2-ethylhezanoate (0%, 0.05%, 0.10%, and 0.20%) were obtained by in-situ synthesis; the sizes and distribution of the AgNPs in resin were observed. The antibacterial effects of dentin-resin specimens were assessed by various test methods after being aged for 1 week to 1 year. The microtensile bond strength (μTBS) and interfacial nanoleakage (NL) were evaluated using extracted human teeth after being aged for 1 day and 1 year.

RESULTS

Uniform distribution of AgNPs in resin was observed in all experimental groups, and the average size was 4.71 nm-4.81 nm. All groups containing AgNPs showed significant antibacterial differences from the control group (P<0.05) over the ageing of 1 year. Although the increase of concentration tended to improve antibacterial activity, significant differences were not observed between the 0.10% and 0.20% groups (P>0.05). No significant differences were observed between all experimental groups and the control group in μTBS testing and NL testing at 1-day and 1-year time points (P>0.05).

CONCLUSIONS

0.10% AgNPs synthesized in situ might be appropriate to impart a long-term antibacterial ability to the one-step self-etching adhesive, without affecting its adhesive performance.

CLINICAL SIGNIFICANCE

This study suggests that in-situ synthesis of AgNPs is an effective method to improve the antibacterial ability of dental adhesives with the potential to inhibit secondary caries.

Current Infections of the Orofacial Region: Treatment, Diagnosis, and Epidemiology

Undoubtedly, diagnosing and managing infections is one of the most challenging issues for orofacial clinicians. As a result of the diversity of symptoms, complicated behavior, and sometimes confusing nature of these conditions, it has become increasingly difficult to diagnose and treat them. It also highlights the need to gain a deeper insight into the orofacial microbiome as we try to improve our understanding of it. In addition to changes in patients' lifestyles, such as changes in diet, smoking habits, sexual practices, immunosuppressive conditions, and occupational exposures, there have been changes in patients' lifestyles that complicate the issue. Recent years have seen the development of new infection treatments due to the increased knowledge about the biology and physiology of infections. This review aimed to provide a comprehensive overview of the types of infections in the mouth, including the types that viruses, fungi, or bacteria may cause. It is important to note that we searched the published literature in the Scopus, Medline, Google Scholar, and Cochran databases from 2010 to 2021 using the following keywords: "Orofacial/Oral Infections," "Viral/Fungal/Bacterial Infections", "Oral Microbiota" And "Oral Microflora" without limiting our search to languages and study designs. According to the evidence, the most common infections in the clinic include herpes simplex virus, human papillomavirus, Candida albicans, Aspergillus, Actinomycosis, and Streptococcus mutans. The purpose of this study is to review the new findings on characteristics, epidemiology, risk factors, clinical manifestations, diagnosis, and new treatment for these types of infectious diseases.

In Vitro Study on Green Propolis as a Potential Ingredient of Oral Health Care Products

Propolis is increasingly being discussed as an alternative to commonly used antiseptics. This in vitro study focused on the ethanolic extract of green Brazilian propolis (EEPg) as an additive in an oral health care product. We investigated (i) a potential inflammation-modulation activity of EEPg when a periodontal or Candida biofilm was exposed to monocytic (MONO-MAC-6) cells, (ii) the adhesion of oral pathogens to gingival keratinocytes and (iii) the antimicrobial and antibiofilm effect of different toothpaste formulations. EEPg decreased the levels of interleukin (IL)-1β and increased IL-10 in MONO-MAC cells challenged with a periodontal biofilm. In contact with TIGK cells, EEPg reduced the numbers of adherent Porphyromonas gingivalis to 0.5% but did not affect the adhesion of Candida albicans. The frequent brushing of a cariogenic biofilm with a toothpaste supplemented with EEPg reduced the surface microhardness loss of enamel specimens. Mixing an experimental erythritol toothpaste with 25 and 50 mg/mL of EEPg confirmed the antibacterial activity of EEPg against oral bacteria and particularly inhibited periodontal biofilm formation. The suggested toothpaste formulations seem to have potential in the prevention of caries, gingivitis and periodontitis and should be evaluated in further in vitro research and in clinical trials.

Dvorak C, Den Besten P. Dental caries as a risk factor for bacterial blood stream infection (BSI) in children undergoing hematopoietic cell transplantation (HCT)

Background

Hematopoietic cell transplantation (HCT) is a potentially curative therapy for a wide range of pediatric malignant and nonmalignant diseases. However, complications, including blood stream infection (BSI) remain a major cause of morbidity and mortality. While certain bacteria that are abundant in the oral microbiome, such as S. mitis, can cause BSI, the role of the oral microbial community in the etiology of BSI is not well understood. The finding that the use of xylitol wipes, which specifically targets the cariogenic bacteria S. mutans is associated with reduced BSI in pediatric patients, lead us to investigate dental caries as a risk factor for BSI.

Methods

A total of 41 pediatric patients admitted for allogenic or autologous HCT, age 8 months to 25 years, were enrolled. Subjects with high dental caries risk were identified as those who had dental restorations completed within 2 months of admission for transplant, or who had untreated decay. Fisher's exact test was used to determine if there was a significant association between caries risk and BSI. Dental plaque and saliva were collected on a cotton swab from a subset of four high caries risk (HCR) and four low caries risk (LCR) children following pretransplant conditioning. 16SrRNA sequencing was used to compare the microbiome of HCR and LCR subjects and to identify microbes that were significantly different between the two groups.

Results

There was a statistically significant association between caries risk and BSI (p < 0.035) (Fisher's exact test). Multivariate logistic regression analysis showed children in the high dental caries risk group were 21 times more likely to have BSI, with no significant effect of age or mucositis severity. HCR subjects showed significantly reduced microbial alpha diversity as compared to LCR subjects. LEfse metagenomic analyses, showed the oral microbiome in HCR children enriched in order Lactobacillales. This order includes Streptococcus and Lactobacillus, both which contain bacteria primarily associated with dental caries.

Discussion

These findings support the possibility that the cariogenic microbiome can enhance the risk of BSI in pediatric populations. Future metagenomic analyses to measure microbial differences at, before, and after conditioning related to caries risk, may further unravel the complex relationship between the oral microbiome, and whether it affects health outcomes such as BSI.

Effect of strontium-doped bioactive glass-ceramic containing toothpaste on prevention of artificial dentine caries formation: an in vitro study

Backgroud

Root caries in aging population was prevalent worldwide. Due to the absence of enamel and specific structure of dentine, bacteria are able to penetrate further into dentine at an earlier stage of lesion development. The aim of this study was to investigate the effect of adding of a strontium-doped bioactive glass-ceramic (HX-BGC) to a fluoride-free toothpaste on prevention of formation of artificial dentine caries.

Methods

Thirty-six human tooth specimens were allocated to three groups (n = 12 per group). Group 1 treated with slurry containing a fluoride-free toothpaste and 5% HX-BGC, Group 2 was treated with fluoride-free toothpaste slurry, and Group 3 received deionized water as a negative control. The specimens were subjected to four cycles (15 h demineralization and 8 h remineralization for one cycle) of biochemical cycling. A mixed suspension of five bacteria species (Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Actinomyces naeslundii) were prepared in brain heart infusion broth with 5% sucrose and used as acidic challenge in biochemical cycling. Subsequently, surface morphology of the dentine lesion was assessed by scanning electron microscopy, while the lesion depths and mineral loss were assessed by micro-computed tomography.

Results

The mean lesion depths in dentine in Groups 1 to 3 were 87.79 ± 16.99 μm, 101.06 ± 10.04 μm and 113.60 ± 16.36 μm, respectively (p = 0.002). The mean amounts of mineral loss in Groups 1 to 3 were 0.82 ± 0.10 g/cm³, 0.89 ± 0.09 g/cm³ and 0.96 ± 0.11 g/cm³, respectively (p = 0.016). No obvious differences in the surface morphology were seen among the groups.

Conclusion

Addition of strontium-doped bioactive glass-ceramic to fluoride-free toothpaste has potential to reduce formation of dentine lesions.

Metabolic differences of the oral microbiome related to dental caries - A pilot study

OBJECTIVE

We aimed to investigate the composition and functions discrepancy of supragingival plaque associated with active deciduous teeth caries in mixed dentitions.

DESIGN

Thirty-three subjects with mixed dentition participated in this study. Children with deciduous teeth caries (dt ≥ 3) were recruited to the caries group, whereas children without deciduous teeth caries (dt = 0) were recruited to the caries-free group. Plaque were collected from deciduous teeth surface and permanent teeth surface respectively. A total of 66 samples of dental plaque were collected and conserved. Illumina 16S rRNA sequencing and diversity analysis were performed for microbiome. Untargeted liquid chromatograph-mass (LC-MS) and partial least squares discriminant analysis were performed for metabolome.

RESULTS

A dominant microbiome of 8 phyla and 22 genera were detected. The alpha diversity indices did not detect differences between the caries and caries-free groups (p > 0.05). Beta diversity analysis showed that the microbiota composition was similar between subgroups. Comparative analysis at genus level did not detect difference between caries and caries-free subgroups. The metabolomics analysis yielded 419 biochemical metabolites, 56 of which were related to caries status. Metabolites in glucose metabolism and byproducts of oxidative stress were identified as related to dental caries in mixed dentition. Dominant bacteria are positively correlated with metabolites, such as Streptococcus and organic acids.

CONCLUSIONS

The upgrade of glucose metabolism and oxidative stress was observed in caries status. Functions discrepancy of oral microbiome may be more pronounced than the composition of oral microbiome with active dental caries in mixed dentitions.

Comparison of the Effect of Diode Laser Irradiation and Fluoride Varnish on Salivary Streptococcus mutans Bacterial Colonies Counts: A Randomized Controlled Clinical Trial

Aim

The aim of this study was to assess antibacterial effects of diode laser irradiation and fluoride varnish on Streptococcus (S) mutans bacterial colonies counts in saliva.

Materials and Methods

This was a randomized controlled clinical trial research, in which 36 healthy caries-free schoolchildren aged 7-10 years referred to Birjand University dental school were selected randomly. None of the subjects had used any fluoride products before sampling. They divided into three groups: Group A: Diode laser irradiation, Group B: Fluoride varnish (FV) + diode laser irradiation, and Group C: FV. From each child, the baseline unstimulated saliva samples were obtained, transferred to the mitis salivarius agar (MSA) culture media and assessed for S. mutans colonies counts. The follow-up unstimulated saliva samples were collected one day after the treatments. Then the number of colony-forming units per milliliter were counted and analyzed statistically using Wilcoxon, Mann Whitney U and Kruskal-Wallis tests (p ≤ 0.05).

Results

No adverse events were reported. Salivary count of S. mutans significantly decreased in all groups. The highest and lowest number of the colonies of S. mutans in treated groups was observed in group I and group II, respectively. S. mutans was not completely eliminated by any of the treatments.

Conclusion

Considering the limitations of this study, antimicrobial efficacy of fluoride varnish + diode laser was higher than that of FV or diode laser alone. So this laser in combination with fluoride varnish may be useful in prevention of dental caries and antimicrobial treatment protocols.

Clinical trial registry

IRCTID: IRCT 201,706 181,7756N20

How to cite this article

Darmiani S, Yousefi M, Rad MS. Comparison of the Effect of Diode Laser Irradiation and Fluoride Varnish on Salivary Streptococcus mutans Bacterial Colonies Counts: A Randomized Controlled Clinical Trial. Int J Clin Pediatr Dent 2022;15(S-2):S239-S241.

Development and characterization of an oral microbiome transplant among Australians for the treatment of dental caries and periodontal disease: A study protocol

BACKGROUND

Oral microbiome transplantation (OMT) is a novel concept of introducing health-associated oral microbiota into the oral cavity of a diseased patient. The premise is to reverse the state of oral dysbiosis, and restore the ecological balance to maintain a stable homeostasis with the host immune system. This study will assess the effectiveness, feasibility, and safety of OMT using an interdisciplinary approach.

METHODS/DESIGN

To find donors suitable for microbial transplantation, supragingival plaque samples will be collected from 600 healthy participants. Each sample (200μL) will subsequently be examined in two ways: 1) 100μL of the sample will undergo high-throughput 16S rRNA gene amplicon sequencing and shotgun sequencing to identify the composition and characterisation of a healthy supragingival microbiome, 2) the remaining 100μL of the plaque sample will be mixed with 25% artificial saliva medium and inoculated into a specialised in-vitro flow cell model containing a hydroxyapatite disk. To obtain sufficient donor plaque, the samples would be grown for 14 days and further analysed microscopically and sequenced to examine and confirm the growth and survival of the microbiota. Samples with the healthiest microbiota would then be incorporated in a hydrogel delivery vehicle to enable transplantation of the donor oral microbiota. The third step would be to test the effectiveness of OMT in caries and periodontitis animal models for efficacy and safety for the treatment of oral diseases.

DISCUSSION

If OMTs are found to be successful, it can form a new treatment method for common oral diseases such as dental caries and periodontitis. OMTs may have the potential to modulate the oral microbiota and shift the ecological imbalances to a healthier state.

Microbial colonisation associated with conventional and self-ligating brackets: a systematic review

Background:

Decalcification and gingivitis caused by plaque accumulation around brackets are common iatrogenic effects of fixed appliances. The influence of conventional versus self-ligating bracket design on microbial colonisation is unknown.

Objective:

To assess the levels of microbial colonisation associated with conventional and self-ligating brackets.

Search sources:

Three databases were searched for publications from 2009 to 2021.

Data selection:

Randomised controlled trials comparing levels of microbial colonisation before and during treatment with conventional and self-ligating brackets were assessed independently and in duplicate.

Data extraction:

Data were extracted independently by two authors from the studies that fulfilled the inclusion criteria. Risk of bias assessments were made using the revised Cochrane risk of bias tool for randomized trials. The quality of the included studies was assessed using the Critical Appraisal Skills Programme Checklist.

Results:

A total of 11 randomised controlled trials were included in this systematic review. Six of the studies were found to be at low risk of bias and five presented with some concerns. The studies were considered moderate to high quality. Five trials reported no statistically significant difference in microbial colonisation between bracket types. The remaining studies showed mixed results, with some reporting increased colonisation of conventional brackets and others increased colonisation of self-ligating brackets. The heterogeneity of study methods and outcomes precluded meta-analysis.

Conclusion:

Of the 11 studies included in this systematic review, five found no differences in colonisation between conventional and self-ligating brackets. The remaining studies showed mixed results. The evidence is inconclusive regarding the association between bracket design and levels of microbial colonisation.

Photoinactivation of multispecies cariogenic biofilm mediated by aluminum phthalocyanine chloride encapsulated in chitosan nanoparticles

This study aimed to characterize the aluminum phthalocyanine chloride (AlClPc) encapsulated in chitosan nanoparticles (CN) and apply it in antimicrobial photodynamic therapy (aPDT) on multispecies biofilm composed of Streptococcus mutans, Lactobacillus casei, and Candida albicans to analyze the antimicrobial activity and lactate production after treatment. Biofilms were formed in 24-well polystyrene plates at 37 °C for 48 h under microaerophilia. The following groups were evaluated (n = 9): as a positive control, 0.12% chlorhexidine gluconate (CHX); phosphate-buffered saline (PBS) as a negative control; 2.5% CN as release vehicle control; the dark toxicity control of the formulations used (AlClPc and AlClPc + CN) was verified in the absence of light; for aPDT, after 30 min incubation time, the photosensitizers at a final concentration of 5.8 × 10^-3 mg/mL were photoirradiated for 1 min by visible light using a LED device (AlClPc + L and AlClPc + CN + L) with 660 nm at the energy density of 100 J/cm². An in vitro kit was used to measure lactate. The biofilm composition and morphology were observed by scanning electron microscopy (SEM). The antimicrobial activity was analyzed by quantifying colony forming units per mL (CFU/mL) of each microorganism. Bacterial load between groups was analyzed by ANOVA and Tukey HSD tests (α = 0.05). A lower lactate dosage was observed in the aPDT AlClPc + CN + L and CHX groups compared to the CN and AlClPc groups. The aPDT mediated by the nanoconjugate AlClPc + CN + L showed a significant reduction in the viability of S. mutans (3.18 log10 CFU/mL), L. casei (4.91 log10 CFU/mL), and C. albicans (2.09 log10 CFU/mL) compared to the negative control PBS (p < 0.05). aPDT using isolated AlClPc was similar to PBS to the three microorganisms (p > 0.05). The aPDT mediated by the nanoconjugate AlClPc + CN + L was efficient against the biofilm of S. mutans, L. casei, and C. albicans.

Intelligent pH-responsive dental sealants to prevent long-term microleakage

OBJECTIVES

Microleakage is a determinant factor of failures in sealant application. In this study, DMAEM (dodecylmethylaminoethyl methacrylate), a pH-responsive antibacterial agent, was incorporated into resin-based sealant for the first time. The objectives of this study were to: (1) investigate the long-term performance of DMAEM-modified sealants against oral microbial-aging; and (2) investigate the long-term preventive effect of DMAEM-modified sealants on microleakage.

METHODS

Depth-of-cure and cytotoxicity of DMAEM-modified sealants were measured. Then, an aging model using biofilm derived from the saliva of high caries experience children was conducted. After aging, microhardness and surface roughness were measured. Biofilm activity, lactic acid production and exopolysaccharide (EPS) production were measured. 16S rRNA gene sequencing were also performed. The effects of DMAEM on microleakage were tested using an in vitro microleakage assessment.

RESULTS

The addition of DMAEM with a mass fraction of 2.5-10% did not affect depth-of-cure values and cytotoxicity of sealants. Adding 2.5-10% DMAEM did not affect the surface roughness and microhardness after aging. Compared to control, adding 2.5-10% DMAEM reduced biofilm metabolic activity by more than 80%. The lactic acid production and EPS production were reduced by 50% in DMAEM groups. DMAEM-modified sealants maintained the microbial diversity of biofilm after aging, they also inhibited the growth of lactobacillus. The 5% and 10% DMAEM groups exhibited a significant reduction in microleakage compared to control.

SIGNIFICANCE

The long-term antibacterial activities against oral microbial-aging and the long-term microecosystem-regulating capabilities enabled DMAEM-modified sealant to prevent microleakage in sealant application and thus prevent dental caries.

Quantitative difference of oral pathogen between individuals with gastric cancer and individuals without cancer

The loss of teeth and lack of oral hygiene have been associated with the risk of developing gastric cancer (GC) in several populations evidenced in epidemiological studies. In this study, we quantitatively compared the proportion of oral pathogens in individuals with gastric cancer and individuals without cancer in a referral hospital in the city of Belém, Brazil. This study evaluated 192 patients with GC and 192 patients without cancer. Periodontal clinical examination was performed, and all individuals were submitted to the collection of salivary and dental biofilms. When comparing the median periodontal indexes in the gastric and cancer-free groups, it was statistically significant (p < 0.001) in the gastric cancer group compared to the probing depth of the periodontal pocket. Levels of bacterial DNA were observed in saliva and dental plaque, with a statistically significant difference (p < 0.001) between individuals with cancer and without neoplasia in all the bacteria surveyed. Significant relationships (p < 0.001) between biological agents and GC have been found in bacterial species that cause high rates of periodontal pathology and caries. The results suggest a different quantitative association in the presence of oral pathogens between individuals without cancer and patients with GC. As noted, it cannot be said that the bacteria present in the oral cavity increase the risk of gastric cancer or are aggravating factors of the disease. However, it is worth mentioning that, as it is part of the digestive system, the lack of care for the oral cavity can negatively affect the treatment of patients with gastric cancer.

Synergistic biocidal effects of metal oxide nanoparticles-assisted ultrasound irradiation: Antimicrobial sonodynamic therapy against Streptococcus mutans biofilms

BACKGROUND

Antimicrobial sonodynamic therapy (aSDT) is an adjunctive modality, which uses ultrasound irradiation to kill microbial cells by the activation of a sonosensitizer. The aim of this study was to evaluated the synergistic biocidal effects of zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO₂ NPs) as the metal oxide nanoparticles (MONPs)-assisted ultrasound irradiation against Streptococcus mutans biofilms.

MATERIALS AND METHODS

Following preparation and characterization of MONPs, cellular uptake and generation of intracellular reactive oxygen species (ROS) were assessed. After determination of the sub-significant reduction (SSR) doses of ZnO NPs, TiO₂ NPs, ZnO/TiO₂ NPs, and ultrasound intensity against S. mutans, anti-biofilm effects of aSDT were assessed using colorimetric assay, plate counting, and field emission scanning electron microscope (FESEM) analysis. Also, the metabolic activity of S. mutans and the expression levels of glucosyltransferase B (gtfB) as a main virulence factor of S. mutans were evaluated by XTT assay and quantitative real-time polymerase chain reaction following ZnO/TiO₂ NPs^SSR- mediated aSDT.

RESULTS

The finding of this study showed that an incubation time of 5 min was sufficient to achieve maximal uptake of MONPs. The ROS production following aSDT using ZnO NPs, TiO₂ NPs, and ZnO/TiO₂ NPs were ~ 4.1-, 5.6-, and 11.7-fold increase, respectively. The dose-dependent reduction in cell viability of S. mutans was revealed by increasing the concentrations of ZnO NPs, TiO₂ NPs, ZnO/TiO₂, as well as ultrasound intensities. According to the data, 1.5 µg/mL, 3.1 µg/mL, 25 µg/mL, and 0.75 W/cm² were considered as the SSR doses of ZnO/TiO₂ NPs, ZnO NPs, TiO₂ NPs, and ultrasound intensity, respectively (P>0.05). ZnO/TiO₂ NPs^SSR-mediated aSDT showed a significantly higher biofilm inhibitory activity than the other treatment groups (P<0.05). Based on the FE-SEM analysis, aSDT based on the ZnO/TiO₂ NPs^SSR had a strong anti-biofilm effect against preformed biofilms of S. mutans on the enamel slabs. Also, the metabolic activity of S. mutans and the expression levels of gtfB were significantly decreased to 85.5% and 12.3-fold, respectively following ZnO/TiO₂ NPs^SSR-mediated aSDT (P<0.05). No considerable difference was observed in anti-biofilm activity between ZnO/TiO₂ NPs^SSR- mediated aSDT and 0.2% CHX (P>0.05).

CONCLUSION

The results revealed anti-metabolic and anti-biofilm potential activities of ZnO/TiO₂ NPs-mediated aSDT against S. mutans with the highest cellular uptake and ROS generation.

A Novel Competence Pathway in the Oral Pathogen Streptococcus sobrinus

Streptococcus sobrinus is an etiologic cause of dental caries (tooth decay) in humans. Our knowledge of S. sobrinus is scant despite the organism's important role in oral health. It is widely believed that S. sobrinus lacks the natural competence pathways that are used by other streptococci to regulate growth, virulence, and quorum sensing. The lack of natural competence has also prevented genetic manipulation of S. sobrinus, limiting our knowledge of its pathogenicity. We discovered that most strains of S. sobrinus contain a new class of the ComRS competence system. Although S. sobrinus is typically placed among the mutans group streptococci, the S. sobrinus ComRS system is most similar to the competence pathways in the salivarius group. Unlike all other ComRS systems, the S. sobrinus pathway contains 2 copies of the transcriptional regulator ComR and has a peptide pheromone (XIP) that lacks any aromatic amino acids. Synthetic XIP enables transformation of S. sobrinus with plasmid or linear DNA, and we leverage this newfound genetic tractability to confirm that only 1 of the ComR homologs is required for induced competence while the other appears to suppress competence. Exogenous XIP increases the expression of bacteriocin gene clusters and produces an antimicrobial response that inhibits growth of S. mutans. We also identified 2 strains of S. sobrinus that appear to be "cheaters" by either not responding to or not producing XIP. We show how a recombination event in the nonresponsive strain could restore function of the ComRS pathway but delete the gene encoding XIP. Thus, the S. sobrinus ComRS pathway provides new tools for studying this pathogen and offers a lens into the evolution of ecological cheaters.

Obesity Drives an Oral Microbiota Signature of Female Patients with Periodontitis: A Pilot Study

The aim of this study was to analyze the link between oral microbiota and obesity in humans. We conducted a pilot study including 19 subjects with periodontitis divided into two groups: normo-weighted subjects (NWS) with a body mass index (BMI) between 20 and 25 (n = 9) and obese subjects (OS) with a BMI > 30 (n = 10). Obesity was associated with a poor oral health status characterized by an increased number of missing teeth and a higher score of periodontal-support loss associated with dysbiotic oral microbiota (39.45 ± 3.74 vs. 26.41 ± 11.21, p = 0.03 for the Chao 1 index). Oral microbiota taxonomic analysis showed that the abundance of the Capnocytophaga genus was higher (2.47% ± 3.02 vs. 0.27% ± 0.29, p = 0.04) in OS compared to NWS. Obese females (OF) were characterized by an increase in the Streptococcus genus (34.12% ± 14.29 vs. 10.55% ± 10.42, p = 0.05) compared to obese males (OM), where the Neisseria genus was increased (5.75% ± 5.03 vs. 58.05% ± 30.64, p = 0.008). These first data suggest that sex/gender is determinant in the link between oral dysbiotic microbiota and obesity in patients with periodontitis. Our results could lead to recommendations concerning therapeutic strategies for obese patients with periodontitis following the sex/gender.

Effectiveness of the use of xylitol chewing gum in prevention of dental caries: A systematic review

This systematic review of the literature assessed the effectiveness of using chewing gum containing only xylitol compared to prevention strategies or placebo in reducing the incidence of carious lesions in children using data obtained from randomized controlled trials. Electronic search was carried out in PubMed MEDLINE, Latin American and Caribbean Literature on the Health Science, Web of Science, Scopus, Science Direct, and Scientific Electronic Library Online through the period between 2000 and 2020. Included clinical studies were done in children when the xylitol was dispensed in gum and the preventive effect of xylitol on tooth decay was compared to other preventive strategies or control groups. The studies were evaluated for their quality to obtain the level of evidence. The preventive fraction of each study was extracted. Two hundred studies were found. After analyzing the inclusion and removal of duplicates, only five studies were analyzed for the quality of evidence. With the analysis through the Grading of Recommendations Assessment, Development, and Evaluation system, it was possible to verify the very low level of scientific evidence on the effectiveness of gums containing only xylitol for the prevention of caries in children. The preventive fraction obtained varied between - 0.31 and 0.57 depending on the compared prevention strategy. The conflicting results, limitations, and inconsistencies of the studies allow us to establish that there is insufficient evidence to support the use of gums containing only xylitol for the prevention of caries in children. Other properly designed clinical trials need to be carried out.

Detection of Inflammatory and Homeostasis Biomarkers after Selective Removal of Carious Dentin-An In Vivo Feasibility Study

Deep carious dentin lesions induce an immune reaction within the pulp-dentin complex, leading to the release of cytokines, which might be suitable biomarkers in pulp diagnostics. This in vivo feasibility study determines the concentration of different cytokines after selective removal of carious infected dentin (SCR). In our methodology, paired samples are obtained from 21 patients—each of them with two deep carious lesions at posterior teeth without clinical symptoms. After SCR, lesions are randomly assigned to treatment strategy: Group 1 (11 patients): Carious dentin is covered either with Biodentine^TM (n = 11) or gutta-percha (n = 11) before using the adhesive Optibond^TM FL. Group 2 (10 patients): The adhesives Clearfil^TM SE Protect Bond (n = 10) or Clearfil^TM SE Bond 2 (n = 10) are directly applied. Prepared cavities are rinsed with phosphate buffered saline containing 0.05% Tween 20 (10X) for five minutes immediately after SCR (visit 1) and eight weeks later (visit 2). Rinsing liquid is regained. Concentrations of IL-1β, IL-6, IL-10, C-reactive protein (CRP), TNF-α, IFN-γ, TIMP-1, -2, and MMP-7, -8, -9 are assessed by customized multiplex assays, evaluated with fluorescence analyzer. Non-parametric statistical analysis (Wilcoxon, Mann–Whitney U Test, p < 0.05) is performed (SPSS 25). Our results show that concentrations of CRP, IL-1β, IL-6, TIMP-1, -2, and MMPs were detectable. Median concentrations of CRP, IL-1β und IL-6 were significantly higher in visit 1 (304.9, 107.4, 3.8 pg/mL), compared to visit 2 (67.8, 2.3, 0.0 pg/mL; p_i < 0.001). The study revealed that the non-invasive determination of cytokines from prepared dental cavities is possible.

Fabrication of oral nanovesicle in-situ gel based on Epigallocatechin gallate phospholipid complex: Application in dental anti-caries

The conventional anti-caries agents exhibit many shortcomings such as poor stability, low efficacy or short residence time in the oral environment, it is urgent to develop efficacy treatments to prevent dental caries. As the most active polyphenols from tea, Epigallocatechin gallate (EGCG) shows remarkable anti-cariogenic bioactivity. However, the poor stability and low bioavailability of EGCG limit its potential application. This study aimed to fabricate nanovesicles in-situ gel based on EGCG phospholipid complex in order to increase its stability and efficacy. The formation of EGCG phospholipid complex was characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The ethanol injection method was used to prepare the EGCG-loaded nanovesicles, an optimal ratio of Poloxamer407 (P407) and Poloxamer188 (P188) as in-situ gel matrix was selected to fabricate oral nanovesicles in-situ gel. EGCG-loaded nanovesicle in-situ gel based on the phospholipid complex had uniform spherical shape without any agglomeration. The discrete nanoparticle with a size (131.44 ± 4.24 nm) and a negative zeta potential value at -30.7 ± 0.5 mV possessed good physical stability and high entrapment efficiency (83.66 ± 3.2%). The formulation exhibited a strong antibacterial activity on S. mutans, which could reduce acid production and tooth surface adhesion. In addition, EGCG formulation could inhibit the formation of glucan and biofilm from S. mutans by suppressing the activity of glycosyltransferase enzymes (GTF). In conclusion, the EGCG-loaded nanovesicle in-situ gel holds great promise as an efficient anti-cariogenic formulation for topical oral delivery.

Changes in the Microbiome of the Inner Surface of Clear Aligners After Different Usage Periods

Clear aligners are removable orthodontic appliances that cover the tooth surface. The microbial composition and pH of the inner surface of aligners directly affect the enamel health. In this study, eight subjects who used the same type of clear aligners were instructed to brush their teeth normally and to not clean their aligners until sampling. Saliva and the contents of the inner surface of the aligners (liquid and plaque) were collected at 0 h (T0), 4 h (T4), 8 h (T8), 12 h (T12), and 24 h (T24) after usage, and pH values and microbial compositions were measured. The microbial composition was analyzed with 16S rRNA gene sequencing, and changes were assessed based on operational taxonomic unit abundance. The pH, alpha diversity values, and abundance of specific microbes on the inner surface of the aligners gradually decreased from T0 to T24 (P < 0.05). An insignificant increase in microbial community beta diversity was observed from T0 to T24. Principal component analysis revealed that the microbial composition at T0 was different from at T12 and T24. The relative abundances of phylum Firmicutes (P < 0.01), orders Lactobacillales and Bacteroidales (P < 0.05), and genus Streptococcus and species Streptococcus infantis increased significantly, while those of genera Actinomyces and Rothia and species Rothia aeria decreased significantly at T24 (P < 0.05). These findings reveal that uncleaned aligners might lead to enamel damage, especially after continuous usage for 12 h. Thus, clear aligners should be cleaned after 12 h of usage or at least within 24 h of usage.

Keyes triad in type 2 diabetes mellitus: A microbiological study

Background:

With the increasing prevalence of type 2 diabetes mellitus (DM), there is a need to assess if the elevated salivary glucose levels provide an environment conducive to the growth of cariogenic microorganisms specifically Streptocooccus mutans and Lactobacillus acidophilus.

Materials and Methods:

Forty-five patients were divided into three groups consisting of patients with type 2 DM with caries, patients with type 2 DM without caries and age-matched healthy nondiabetic individuals (control). Saliva samples were subjected to semiautomatic salivary glucose estimation by the glucose oxidase-peroxidase method, using the Tulip glucose estimation kit. Swabs were immediately inoculated onto Mitis Salivarius Bacitracin agar and Man Rogosa Sharpe agar.

Results:

In Group A, statistically significant positive correlation was found between S. mutans and salivary glucose (r = 0.858) as well as L. acidophilus and salivary glucose (r = 0.853). In Group B, a statistically significant positive correlation was found only between S. mutans and salivary glucose (r = 0.705) and not between L. acidophilus and salivary glucose (r = 0.387). The control group did not show a statistically significant correlation.

Conclusion:

It is established that salivary glucose levels reflect the diabetic state of an individual. The salivary glucose level predicted a 1.7 times higher caries susceptibility in a diabetic, as shown by results in this study. Salivary glucose causes an increase in the cariogenic load in diabetic patients, thus warranting a modification of the Keyes triad.

Identifying risk factors of severe early childhood caries in infants from Bosnia and Herzegovina

OBJECTIVE

The aim of the study was to investigate risk factors for S-ECC among infants under 24 months of age living in Banja Luka, Bosnia and Herzegovina.

METHODS

A cross-sectional population-based study was carried out. Considering inclusion criteria, the total sample consisted of 192 examined infants under 24 months of age. Parents/caregivers were interviewed ahead of each dental examination of children. Following data collection, outcome measures were: the presence/absence of S-ECC (children with at least one active early carious lesion on the smooth surfaces of the maxillary anterior teeth/caries-free children) and the severity of dental caries (no caries, initial caries and cavitated caries lesion).

RESULTS

Overall results of the study indicated that 22.9% of infants had initial caries, while 12.0% (95% CI: 8.1-17.3) of infants had at least one cavitated carious lesion. Multivariate logistic regression analysis showed that the age of infants (p < 0.001) and family monthly income (p = 0.003) variables were statistically significant predictors for the development of caries.

CONCLUSIONS

This research found that the most important risk predictors for the development and severity (intensity) of S-ECC in infants under 24 months of age were low monthly income of parents and the infant's age.

Physicochemical Characteristics of Arginine Enriched NaF Varnish: An In Vitro Study

The in vitro study objectives were to investigate the effect of arginine (Arg) incorporation in a 5% sodium fluoride (NaF) varnish on its physical and chemical properties including F/Arg release. Six experimental formulations were prepared with L-arginine (L-Arg) and L-arginine monohydrochloride at 2%, 4%, and 8% w/v in a 5% NaF varnish, which served as a control. The varnishes were subjected to assessments for adhesion, viscosity, and NaF extraction. Molecular dynamics were simulated to identify post-dynamics total energy for NaF=Arg/Arg>NaF/Arg<NaF concentrations. The Arg/F varnish release profiles were determined in polyacrylic lactate buffer (pH-4.5; 7 days) and artificial saliva (pH-7; 1 h, 24 h, and 12 weeks). Incorporation of L-Arg in NaF varnish significantly influences physical properties ameliorating retention (p < 0.001). L-Arg in NaF varnish institutes the Arg-F complex. Molecular dynamics suggests that NaF>Arg concentration denotes the stabilized environment compared to NaF<Arg (p < 0.001). The 2% Arg-NaF exhibits periodic perennial Arg/F release and shows significantly higher integrated mean F release than NaF (p < 0.001). Incorporating 2% L-arginine in 5% NaF varnish improves its physical properties and renders a stable matrix with enduring higher F/Arg release than control.

Deep metagenomics examines the oral microbiome during dental caries, revealing novel taxa and co-occurrences with host molecules

Dental caries, the most common chronic infectious disease worldwide, has a complex etiology involving the interplay of microbial and host factors that are not completely understood. In this study, the oral microbiome and 38 host cytokines and chemokines were analyzed across 23 children with caries and 24 children with healthy dentition. De novo assembly of metagenomic sequencing obtained 527 metagenome-assembled genomes (MAGs), representing 150 bacterial species. Forty-two of these species had no genomes in public repositories, thereby representing novel taxa. These new genomes greatly expanded the known pangenomes of many oral clades, including the enigmatic Saccharibacteria clades G3 and G6, which had distinct functional repertoires compared to other oral Saccharibacteria. Saccharibacteria are understood to be obligate epibionts, which are dependent on host bacteria. These data suggest that the various Saccharibacteria clades may rely on their hosts for highly distinct metabolic requirements, which would have significant evolutionary and ecological implications. Across the study group, Rothia, Neisseria, and Haemophilus spp. were associated with good dental health, whereas Prevotella spp., Streptococcus mutans, and Human herpesvirus 4 (Epstein-Barr virus [EBV]) were more prevalent in children with caries. Finally, 10 of the host immunological markers were significantly elevated in the caries group, and co-occurrence analysis provided an atlas of potential relationships between microbes and host immunological molecules. Overall, this study illustrated the oral microbiome at an unprecedented resolution and contributed several leads for further study that will increase the understanding of caries pathogenesis and guide therapeutic development.

The oral microbiome and salivary proteins influence caries in children aged 6 to 8 years

BACKGROUND

Oral microbiome and salivary proteins play a critical role in the occurrence and development of caries. In this study, we used metagenomic and metaproteomic analyses to explore the microbiological and proteinic biomarkers and investigate the etiology of caries in 6-8 years old children. Our study aims to offer a better comprehension of these factors and the relationship with caries, and these findings might facilitate caries risk assessment and provide a basis for future prevention strategies.

METHODS

Children 6 to 8 years old living in rural isolated areas including 40 caries-active subjects and 40 caries-free subjects were recruited. Supragingival plaque and unstimulated saliva were collected for 16S rDNA pyrosequencing and isobaric tags for relative and absolute quantitation (iTRAQ) technique coupled with quantitative nano-flow liquid chromatography-tandem mass spectrometry (LC-MS/MS), respectively.

RESULTS

We found 6 phyla and 13 genera predominant in all the samples, and differences in relative abundances can be observed. The Alpha diversity analysis demonstrated that the richness and diversity of the bacterial communities were similar between children with caries-free and caries-active groups; LEfSe detected differences in the bacterial community including Dialister, Selenomonas, Actinomyces, and Mogibacterium in the caries-active group (P < 0.05) and Capnocytophaga, Fusobacterium, Desulfuromonadales, Haemophilus, and Porphyromonas in the caries-free group(P < 0.05). The core microbiome was defined as 18 predominant genera in children with caries. The results of the salivary proteome identified 9135 unique peptides and 1662 proteins group from 20 salivary samples. Two hundred fifty-eight proteins were differentially expressed between the caries-free and caries-active groups.

CONCLUSIONS

The diversity of the microbial community has little effect on caries but some bacteria with different relative abundance between the caries-active and caries-free group could be considered as potential biomarkers for children with caries. In addition, as a critical host factor of caries, the salivary proteins are different in caries-free and caries-active groups.

Minimum intervention dentistry in the US: an update from a cariology perspective

Despite evidence strongly supporting use of non-invasive or minimally invasive procedures in caries management, there is still a large gap between evidence-based recommendations and application of these concepts in practice, with the practice of dentistry still largely dominated by invasive procedures in the US. This paper describes efforts in education and clinical practice in the US in the last decade to promote evidence-based cariology strategies, which support a minimum intervention dentistry (MID) philosophy. These include, for example: a competency-based core cariology curriculum framework which has been developed and disseminated. National education accreditation standards supporting caries management are likely to soon be changed to support assessment of best evidence in cariology. There are several ongoing efforts by organised dentistry and other groups involving dental educators, researchers and clinical practitioners to promote cariology concepts in practice, such as the development of evidence-based clinical practice guidelines for caries management by the American Dental Association. Within each of these strategies there are challenges, but also opportunities to expand the implementation of MID in the US, which create optimism for future improvements over time.

Streptococcus mutans bystander-induced bioeffects following sonodynamic antimicrobial chemotherapy through sonocatalytic performance of Curcumin-Poly (Lactic-co-Glycolic Acid) on off-target cells

To assessed the Streptococcus mutans bystander-induced bioeffects following sonodynamic antimicrobial chemotherapy (SACT) by Curcumin-Poly (Lactic-co-Glycolic Acid) nanoparticles (Cur-PLGA-NPs). Cur-PLGA-NPs were synthesized and characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), and Attenuated Total Reflection Fourier Transform IR (ATR-FTIR) spectroscopy, as well as, determination of in vitro drug release. Following the successful synthesis and characterization of Cur-PLGA-NPs, the cell survival, intracellular ROS production, apoptotic effects, DNA fragmentation, and gene expression levels of pro-inflammatory cytokines were investigated on human gingival fibroblast (HGF) cells as off-target cells through S. mutans bystander-induced bioeffects following SACT (BCS^S). No significant cytotoxic and damage caused by the release of ROS from BCS^S were observed in HGF cells (P > 0.05). There was no DNA fragmentation and anti-proliferation effects on HGF cells. The expression levels of bFGF, TNF-α, and IL-8 genes were increased after exposure to BCS^S to 15.4-, 13.5-, and 8.7-fold, respectively (P < 0.05), while TGF-ß and IL-10 were downregulated to -4.1- and -6.8-fold, respectively (P < 0.05). It could be concluded that there were no bystander bioeffects of targeted sonocatalytic stress on off-target cells.

Conceptualization of dental caries by dental students is related to their preventive oral care routine

OBJECTIVE

Whether the understanding of dental caries influences how future dentists manage the disease themselves has not been previously studied. Thus, this study evaluated whether the conceptualization (understanding) of dental caries by dental students is related to their own preventive oral care routine.

METHODS

Dental students at a U.S. dental school (n = 517) were invited to voluntarily respond to an anonymous electronic survey in spring 2018. Demographic characteristics, caries conceptualization (CC), dental care habits, and self-caries risk determination were asked. Discursive responses to CC were analyzed by content analysis technique, and categories [c] were created. Chi-square and Fisher's exact tests were used for analysis.

RESULTS

Overall response rate was 54.5% (n = 282, 48.2% female). Three researchers independently analyzed discursive answers and classified them into 1 of 6 caries concept categories [c]: [c1] only signs of the disease (10.3%), [c2] bacterial disease-not specifying bacterial metabolism (38.3%), [c3] bacterial byproducts-not specifying substrate (13.8%), [c4] biological or multifactorial concept (24.8%), [c5] comprehensive multifactorial disease (8.2%), or [c6] other (4.6%). Only 33% completely defined dental caries according to the modern understanding of the disease (c4-c5). Statistical differences were found between: CC and diet modification, CC and rinsing after brushing, year of school (YS) and self-determined caries-risk, YS and brushing at school, and YS and rinsing after brushing (P < 0.05).

CONCLUSION

Our data suggest that the students' understanding of the disease can influence how they will manage the disease in terms of diet modification and behavior after brushing. Moreover, self-caries risk determination influenced students' brushing behavior.

Conjugate of chitosan nanoparticles with chloroaluminium phthalocyanine: Synthesis, characterization and photoinactivation of Streptococcus mutans biofilm

BACKGROUND

Antimicrobial photodynamic therapy (aPDT) using chloroaluminium phthalocyanine (ClAlPc) has high oxidative power allowing for the control of biofilms, especially when the photosensitizer is administered in an appropriate release vehicle. This study aimed to develop/characterize the ClAlPc encapsulated in chitosan nanoparticles (CSNPs), and evaluate its antimicrobial properties against S. mutans biofilms.

METHODS

CSNPs were prepared by ion gelation, and characterization studies included particle size, polydispersion index (IPd), zeta potential, accelerated stability, absorption spectrum and ClAlPc quantification. The S. mutans biofilms were formed in bovine dentin blocks at 37 °C for 48 h under microaerophilic conditions. 8 μM ClAlPc was combined with a diode laser (InGaAlP) at 660 nm and 100 J/cm². The aPDT toxicity was verified by dark phototoxicity. The antimicrobial activity was verified by CFU/mL and biofilm was analyzed by scanning electron microscopy (SEM). The number of viable bacteria was analyzed by ANOVA and Tukey HSD tests (α = 0.05).

RESULTS

The characterization revealed that the ClAlPc nanoparticles were found in nanometer-scale with adequate photophysical and photochemical properties. The aPDT mediated by ClAlPc + CSNPs nanoconjugate showed a significant reduction in the viability of S. mutans (1log10 CFU/mL) compared to the negative control (PBS, p < 0.05). The aPDT mediated by ClAlPc was similar to PBS (p > 0.05). SEM revealed change in biofilm morphology following the treatment of bacteria with aPDT ClAlPc + CSNPs. Cells were arranged as single or in shorted chains. Irregular shapes of S. mutans were found.

CONCLUSION

ClAlPc nanoparticles are considered stable and aPDT mediated by ClAlPc + CSNPs nanoconjugate was effective against S. mutans biofilm.

Short-term effects of fixed orthodontic appliance on concentrations of mutans streptococci and persister cells in adolescents

INTRODUCTION

Orthodontic patients are at an increased risk for developing caries. Dental caries is a biofilm-mediated disease, with mutans streptococci (MS) as the primary etiologic bacterial group. It has been suggested that persister cells (PCs), a subset of cells within the biofilm, contribute to the chronic infectious nature of dental caries. PC formation can be induced by environmental stressors such as orthodontic treatment. The aim of this study was to quantify MS, aerobic and facultative anaerobe bacterial PC proportions from plaque samples during the initial stage of orthodontic treatment. This study is the first to analyze the role of PCs in a population of patients highly susceptible to caries, that is, patients undergoing orthodontic treatment.

METHODS

Plaque samples were collected from 17 participants (11 males and 6 females; age range: 11-18 years) before and 1 month after insertion of fixed orthodontic appliances. Percentages of MS and PCs were determined with selective media and a classical persister microbial assay, respectively.

RESULTS

There was a statistically significant decrease in %MS (P = 0.039) but no statistically significant difference in %PCs (P = 0.939) after 1 month of orthodontic appliance placement.

CONCLUSION

Our study illustrated the technical feasibility of analysis of PCs in plaque samples of patients during orthodontic treatment and revealed that PC formation during orthodontic treatment is highly variable across individuals.

Effect of a bioactive cement on the microbial community in carious dentin after selective caries removal - An in-vivo study

OBJECTIVES

Selective caries removal in deep lesions means that soft carious affected dentin is left in the center of the cavity. Thus, using a tricalcium silicate cement Biodentine™ (Septodont, Paris) to seal the remaining soft dentin could have an antibacterial effect. This in-vivo study aimed to do quantitative and qualitative analyses on the bacterial composition within carious dentin before and after selective caries removal when applying Biodentine.

METHODS

Eleven patients with deep primary carious lesions at two posterior teeth without pulpal symptoms were included. Carious dentin was selectively removed and sampled with a sterile round bur (Komet No. 18) at baseline visit and eight weeks later. On the first visit, one lesion per patient, the remaining carious dentin was covered with Biodentine before adhesive restoration. Caries samples were investigated by microbial cultivation, molecular analysis and amplicon deep-sequencing of 16S rRNA genes. Bacterial DNA from intact cells was differentiated from cell-free DNA by DNase degradation prior to DNA isolation.

RESULTS

Reduction of cell-derived as well as cell-free bacterial DNA eight weeks after selective caries removal was significantly higher when Biodentine was applied. Lactobacillus was most abundant within the microbial community of deep carious dentin lesions at the first visit. After intervention with Biodentine application, Lactobacillus was diminished to a high degree. In general, the diversity in samples, as well as bacterial composition differed interindividually as well as intraindividually.

CONCLUSION AND CLINICAL SIGNIFICANCE

Despite the heterogenous and diversity of microbial composition in patients, Biodentine can have beneficial antibacterial effects when applied to residual carious dentin, offering an alternative and safe treatment option. The study is officially registered with German Clinical Trials Register (DRKS00011067).

How useful are current caries risk assessment tools in informing the oral health care decision-making process?

BACKGROUND

Caries risk assessment (CRA) tools could address oral health disparities and enhance the efficiency of the oral health care system. The authors aimed to explore the feasibility and limitations of using clinical CRA tools in informing oral health care policy-making processes.

METHODS

The authors used the National Health and Nutrition Examination Survey to construct 10 CRA models from a sample of clinical CRA tools identified from the literature. They used these models to estimate the proportion of publicly insured people aged 1 through 20 years categorized as at low, moderate, and high risk, and they projected their oral health care costs.

RESULTS

The authors found substantial variation among the selected models in assigning risk levels. The weighted average proportions (range) of people categorized as at low, moderate, and high risk were 25% (0%-66%), 14% (0%-50%), and 61% (11%-100%), respectively. Depending on the CRA model, the projected annual cost of covering this population ranged from $18 billion to $127 billion.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Developing a valid, evidence-based, accurate, and reliable population-based CRA model could address the variability among clinical CRA tools, improve estimates of dental disease burden, help design targeted oral public health programs, and enable comparative effectiveness analyses among oral health care interventions.

Precision Reengineering of the Oral Microbiome for Caries Management

Technological advancements have revolutionized our understanding of the complexity and importance of the human microbiome. This progress has also emphasized the need for precision therapeutics, as it has underscored the dilemmas, such as dysbiosis and increasing antibiotic resistance, associated with current, broad-spectrum treatment modalities. Dental caries remains the most common chronic disease worldwide, accompanied by a tremendous financial and social burden, despite widespread and efficacious fluoride and hygienic regimens. Over the past several decades, various precision approaches to combat dental caries, including vaccines, probiotics, and antimicrobial compounds, have been pursued. Despite the distinct overall conceptual strengths of each approach, for various reasons, there are currently no approved precision antibiotic therapeutics to prevent dental caries. Specifically targeted antimicrobial peptides (STAMPs) are synthetic molecules that combine the antibiotic moiety of a traditional antimicrobial peptide with a targeting domain to provide specificity against a particular organism. Conjoining the killing domain from the antimicrobial, novispirin G10, and a targeting domain derived from the Streptococcus mutans pheromone, CSP, the STAMP C16G2 was designed to provide targeted killing of S. mutans, widely considered the keystone species in dental caries pathogenesis. C16G2 was able to selectively eliminate S. mutans from complex ecosystems while leaving closely related, yet health-associated, oral species unharmed. This remodeling of the dental plaque community is expected to have significant advantages compared to conventional broad-spectrum mouthwashes, as the intact, surviving community is apt to prevent reinfection by pathogens. Following successful phase I clinical trials that evaluated the safety and basic microbiology of C16G2 treatments, the phase II trials of several C16G2 formulations are currently in progress. C16G2 represents an exciting advance in precision therapeutics, and the STAMP platform provides vast opportunities for both the development of additional therapeutics and the overall study of microbial ecology.

Novel Probiotic Mechanisms of the Oral Bacterium Streptococcus sp. A12 as Explored with Functional Genomics

Health-associated biofilms in the oral cavity are composed of a diverse group of microbial species that can foster an environment that is less favorable for the outgrowth of dental caries pathogens, like Streptococcus mutans A novel oral bacterium, designated Streptococcus A12, was previously isolated from supragingival dental plaque of a caries-free individual and was shown to interfere potently with the growth and virulence properties of S. mutans In this study, we applied functional genomics to begin to identify molecular mechanisms used by A12 to antagonize, and to resist the antagonistic factors of, S. mutans Using bioinformatics, genes that could encode factors that enhance the ability of A12 to compete with S. mutans were identified. Selected genes, designated potential competitive factors (pcf), were deleted. Certain mutant derivatives showed a reduced capacity to compete with S. mutans compared to that of the parental strain. The A12 pcfO mutant lost the ability to inhibit comX -inducing peptide (XIP) signaling by S. mutans, while mutants with changes in the pcfFEG locus were impaired in sensing of, and were more sensitive to, the lantibiotic nisin. Loss of PcfV, annotated as a colicin V biosynthetic protein, resulted in diminished antagonism of S. mutans Collectively, the data provide new insights into the complexities and variety of factors that affect biofilm ecology and virulence. Continued exploration of the genomic and physiological factors that distinguish commensals from truly beneficial members of the oral microbiota will lead to a better understanding of the microbiome and new approaches to promote oral health.IMPORTANCE Advances in defining the composition of health-associated biofilms have highlighted the important role of beneficial species in maintaining health. Comparatively little, however, has been done to address the genomic and physiological bases underlying the probiotic mechanisms of beneficial commensals. In this study, we explored the ability of a novel oral bacterial isolate, Streptococcus A12, to compete with the dental pathogen Streptococcus mutans using various gene products with diverse functions. A12 displayed enhanced competitiveness by (i) disrupting intercellular communication pathways of S. mutans, (ii) sensing and resisting antimicrobial peptides, and (iii) producing factors involved in the production of a putative antimicrobial compound. Research on the probiotic mechanisms employed by Streptococcus A12 is providing essential insights into how beneficial bacteria may help maintain oral health, which will aid in the development of biomarkers and therapeutics that can improve the practice of clinical dentistry.

Label-Free Electrochemical Detection of S. mutans Exploiting Commercially Fabricated Printed Circuit Board Sensing Electrodes

This paper reports for the first time printed-circuit-board (PCB)-based label-free electrochemical detection of bacteria. The demonstrated immunosensor was implemented on a PCB sensing platform which was designed and fabricated in a standard PCB manufacturing facility. Bacteria were directly captured on the PCB sensing surface using a specific, pre-immobilized antibody. Electrochemical impedance spectra (EIS) were recorded and used to extract the charge transfer resistance (R_ct) value for the different bacteria concentrations under investigation. As a proof-of-concept, Streptococcus mutans (S. mutans) bacteria were quantified in a phosphate buffered saline (PBS) buffer, achieving a limit of detection of 10³ CFU/mL. Therefore, the proposed biosensor is an attractive candidate for the development of a simple and robust point-of-care diagnostic platform for bacteria identification, exhibiting good sensitivity, high selectivity, and excellent reproducibility.

Amplicon-based microbiome study highlights the loss of diversity and the establishment of a set of species in patients with dentin caries

Objectives

To elicit patterns in pathogenic biofilm composition we characterized the oral microbiome present in patients with dentin caries in comparison to healthy subjects.

Methods

16S amplicon sequencing was used to analyse a total of 56 patients; 19 samples of carious dentin (pooled from at least three teeth) and 37 supragingival samples (pooled from three healthy tooth surfaces). Oral and periodontal status and socio-demographic parameters were recorded. Group assignment, smoking and further socio-demographic parameters were used as explanatory variables in the microbiome composition analysis.

Results

Overall, a total of 4,110,020 DNA high-quality sequences were yielded. Using a threshold of similarity >97% for assigning operational taxonomic units (OTU), a total of 1,537 OTUs were identified. PERMANOVA showed significant differences in microbiome composition between the groups caries/healthy (p = 0.001), smoking/non-smoking (p = 0.007) and fluoride intake during childhood yes/no (tablets p = 0.003, salt p = 0.023). The healthy microbiome had a significantly higher diversity (alpha diversity, p<0.001) and a lower dominance (Berger-Parker index, p<0.001). It was dominated by Fusobacteria. A linear discriminant analysis effect size (LEfSe) yielded a set of 39 OTUs being more abundant in carious dentin samples, including Atopobium spp. (14.9 log2FoldChange), Lactobacillus casei (11.6), Acinetobacter spp. (10.8), Lactobacillus gasseri (10.6), Parascardovia denticolens (10.5), Olsenella profusa (10.4), and others. Also Propionibacterium acidifaciens (7.2) and Streptococcus mutans (5.2) were overabundant in caries lesions.

Conclusions

The healthy microbiome was highly diverse. The advanced caries microbiome was dominated by a set of carious associated bacteria where S. mutans played only a minor role. Smoking and fluoride intake during childhood influenced the microbiome composition significantly.

Clinical significance

The presented investigation adds knowledge to the still not fully comprehended patterns of oral microbiomes in caries compared with oral health. By analysing the genetics of biofilm samples from oral health and severe tooth decay we found distinct discriminating species which could be targets for future therapeutic approaches.