Cultivable anaerobic microbiota of severe early childhood caries

Differences in Sweet Taste Perception and Its Association with the Streptococcus mutans Cariogenic Profile in Preschool Children with Caries

The aim of the study was to verify the hypothesis about differences in sweet taste perception in the group of preschool children with and without caries, and to determine its relationship with cariogenic microbiota and the frequency of sweets consumption in children. The study group included of 63 children aged 2–6 years: 32 with caries and 31 without caries. The study consisted of collecting questionnaire data and assessment of dental status using the decayed, missing, filled in primary teeth index (dmft) and the International Caries Detection and Assessment System (ICDAS II). The evaluation of sweet taste perception was carried out using a specific method that simultaneously assessed the level of taste preferences and the sensitivity threshold for a given taste. The microbiological analysis consisted of the assessment of the quantitative and qualitative compositions of the oral microbiota of the examined children. The sweet taste perception of children with caries was characterized by a lower susceptibility to sucrose (the preferred sucrose solution concentration was >4 g/L) compared to children without caries (in the range ≤ 4 g/L, p = 0.0015, chi-square test). A similar relationship was also observed for frequent snacking between meals (p = 0.0038, chi-square test). The analysis of studied variables showed the existence of a strong positive correlation between the perception of sweet taste and the occurrence and intensity of the cariogenic process (p = 0.007 for dmft; and p = 0.012 for ICDAS II), as well as the frequency of consuming sweets (p ≤ 0.001 for frequent and repeated consumption of sweets during the day, Spearman test) in children with caries. Additionally, children with an elevated sucrose taste threshold were more than 10-times more likely to develop S. mutans presence (OR = 10.21; 95% CI 3.11–33.44). The results of this study suggest the future use of taste preferences in children as a diagnostic tool for the early detection of increased susceptibility to caries through microbial dysbiosis towards specific species of microorganisms.

In vitro Synergy of Polyphenolic Extracts From Honey, Myrtle and Pomegranate Against Oral Pathogens, S. mutans and R. dentocariosa

The increasing incidence rate of oral diseases, the wide spread of antimicrobial resistance, and the adverse effects of conventional antibiotics mean alternative prevention and treatment options are needed to counteract oral pathogens. In this regard, our study aims to evaluate the antibacterial activity of polyphenolic extracts prepared from acacia honey, myrtle leaves, and pomegranate peel against cariogenic bacteria, such as Streptococcus mutans and Rothia dentocariosa. The chemical-physical parameters of acacia honey and the RP-HPLC polyphenolic profile of pomegranate peel extract have been previously described in our studies, while the characterization of myrtle extract, performed by HPLC analysis, is reported here. All the extracts were used singly and in binary combinations to highlight any synergistic effects. Moreover, the extracts were tested in association with amoxicillin to evaluate their ability to reduce the effective dose of this drug in vitro. The values of minimal inhibitory concentrations and minimal bactericidal concentrations have been used to quantitatively measure the antibacterial activity of the single extracts, while the fractional inhibitory concentration index has been considered as predictor of in vitro anticariogenic synergistic effects. Finally, a time-kill curve method allowed for the evaluation of the bactericidal efficacy of the combined extracts. The microbiological tests suggest that acacia honey, myrtle, and pomegranate extracts are able to inhibit the cariogenic bacteria, also with synergistic effects. This study provides useful and encouraging results for the use of natural extract combinations alone or in association with antibiotics (adjuvant therapy) as a valid alternative for the prevention and treatment of oral infectious diseases.

Gene expression profile of Scardovia spp. in the metatranscriptome of root caries

A few investigations of caries biofilms have identified Scardovia spp.; however, little is known about its involvement in caries pathogenesis. The purpose of this study was to assess the gene expression profile of Scardovia spp. in root caries, and compare it with other microorganisms. Clinical samples from active root caries lesions were collected. Microbial mRNA was isolated and cDNA sequenced. The function and composition of the Scardovia were investigated using two methods: a) de novo assembly of the read data and mapping to contigs, and b) reads mapping to reference genomes. Pearson correlation was performed (p < 0.05). Proportion of Scardovia inopinata and Scardovia wiggsiae sequences ranged from 0-6% in the root caries metatranscriptome. There was a positive correlation between the transcriptome of Lactobacillus spp. and Scardovia spp. (r = 0.70; p = 0.03), as well as with other Bifidobacteriaceae (r = 0.91; p = 0.0006). Genes that code for fructose 6-phosphate phosphoketolase (the key enzyme for "Bifid shunt"), as well as ABC transporters and glycosyl-hydrolases were highly expressed. In conclusion, "Bifid shunt" and starch metabolism are involved in carbohydrate metabolism of S. inopinata and S. wiggsiae in root caries. There is a positive correlation between the metabolism abundance of Lactobacillus spp., Bifidobacteriaceae members, and Scardovia in root caries.

Characterization of Scardovia wiggsiae Biofilm by Original Scanning Electron Microscopy Protocol

Early childhood caries (ECC) is a severe manifestation of carious pathology with rapid and disruptive progression. The ECC microbiota includes a wide variety of bacterial species, among which is an anaerobic newly named species, Scardovia wiggsiae, a previously unidentified Bifidobacterium. Our aim was to provide the first ultrastructural characterization of S. wiggsiae and its biofilm by scanning electron microscopy (SEM) using a protocol that faithfully preserved the biofilm architecture and allowed an investigation at very high magnifications (order of nanometers) and with the appropriate resolution. To accomplish this task, we analyzed Streptococcus mutans’ biofilm by conventional SEM and VP-SEM protocols, in addition, we developed an original procedure, named OsO₄-RR-TA-IL, which avoids dehydration, drying and sputter coating. This innovative protocol allowed high-resolution and high-magnification imaging (from 10000× to 35000×) in high-vacuum and high-voltage conditions. After comparing three methods, we chose OsO₄-RR-TA-IL to investigate S. wiggsiae. It appeared as a fusiform elongated bacterium, without surface specialization, arranged in clusters and submerged in a rich biofilm matrix, which showed a well-developed micro-canalicular system. Our results provide the basis for the development of innovative strategies to quantify the effects of different treatments, in order to establish the best option to counteract ECC in pediatric patients.

Characteristics of oral methicillin-resistant Staphylococcus epidermidis isolated from dental plaque

The oral microbial community is widely regarded as a latent reservoir of antibiotic resistance genes. This study assessed the molecular epidemiology, susceptibility profile, and resistance mechanisms of 35 methicillin-resistant Staphylococcus epidermidis (MRSE) strains isolated from the dental plaque of a healthy human population. Broth microdilution minimum inhibitory concentrations (MICs) revealed that all the isolates were nonsusceptible to oxacillin and penicillin G. Most of them were also resistant to trimethoprim (65.7%) and erythromycin (54.3%). The resistance to multiple antibiotics was found to be largely due to the acquisition of plasmid-borne genes. The mecA and dfrA genes were found in all the isolates, mostly dfrG (80%), aacA-aphD (20%), aadD (28.6%), aphA3 (22.9%), msrA (5.7%), and the ermC gene (14.3%). Classical mutational mechanisms found in these isolates were mainly efflux pumps such as qacA (31.4%), qacC (25.7%), tetK (17.1%), and norA (8.6%). Multilocus sequence type analysis revealed that sequence type 59 (ST59) strains comprised 71.43% of the typed isolates, and the eBURST algorithm clustered STs into the clonal complex 2-II(CC2-II). The staphyloccoccal cassette chromosome mec (SCCmec) type results showed that 25 (71.43%) were assigned to type IV. Moreover, 88.66% of the isolates were found to harbor six or more biofilm-associated genes. The aap, atlE, embp, sdrF, and IS256 genes were detected in all 35 isolates. This research demonstrates that biofilm-positive multiple-antibiotic-resistant ST59-SCCmec IV S. epidermidis strains exist in the dental plaque of healthy people and may be a potential risk for the transmission of antibiotic resistance.

Exploration of singular and synergistic effect of xylitol and erythritol on causative agents of dental caries

Non-cariogenic sweet substances, like sugar alcohols, are used to decrease the risk of caries by reducing the growth of dental plaque. The aim of our study was to reveal the impact of xylitol and erythritol on the growth and biofilm formation of cariogenic bacteria including as a novelty, set of clinical mutans streptococci and Scardovia wiggsiae and to assess the possible synergistic influence of these polyols. We found both xylitol and erythritol to express high growth inhibition effect on cariogenic bacteria. In synergistic effect experiments, 10% polyol combination with excess of erythritol was found to be more effective against growth of Streptococcus mutans and the combination with excess of xylitol more effective against growth of Streptococcus sobrinus and S. wiggsiae. In biofilm inhibition experiments, solutions of 10% polyols in different combinations and 15% single polyols were equally effective against mutans streptococci. At the same time, higher biofilm formation of S. wiggsiae compared to experiments without polyols was detected in different polyol concentrations for up to 34%. In conclusion, both erythritol and xylitol as well as their combinations inhibit the growth of different cariogenic bacteria. Biofilm formation of mutans streptococci is also strongly inhibited. When applying polyols in caries prophylaxis, it is relevant to consider that the profile of pathogens in a particular patient may influence the effect of polyols used.

Oral Lactobacilli Related to Caries Status of Children with Primary Dentition

Oral lactobacilli are members of a group of bacteria implicated in caries progression, although information regarding their transmission, colonization, and caries-associated species is not well established. This study isolated oral lactobacilli from a group of children with primary dentition for determination of Lactobacillus prevalence, detection of Streptococcus mutans, a major pathogen of caries initiation, and dental caries status of the children. Species of Lactobacillus isolates were determined from examination of 16S rDNA sequences. Subsequently, the most prevalent species was evaluated for involvement in caries status, and binding ability to type I collagen of all Lactobacillus isolates was determined in association with caries status. Multilocus sequence typing (MLST) of eleven loci was carried out to study strains of the predominant Lactobacillus sp. The detection of oral lactobacilli together with S. mutans was significantly associated with the highest dental caries indices, but there was no involvement of collagen-binding properties of Lactobacillus isolates in caries status. Lactobacillus fermentum was the most prevalent, and its presence was related to high scores of caries indices. MLST analysis of L. fermentum population could not specify a particular clone associated with caries status, but revealed sharing of identical L. fermentum strains among children in the same classrooms. Taken together, the data contributed useful information on the role of oral lactobacilli, in particular L. fermentum in dental caries.

Streptococcus mutans, sugar consumption, and oral hygiene: Which one has more effect on decayed, missing, and filled teeth (DMFT) score in Iranian adults?

BACKGROUND

Streptococcus mutans as an acid-generator of biofilm, sugar as a caries-conducive environment, and oral hygiene have been implicated as major etiological agents in dental caries. This study was designed to assess the association and impact of S. mutans, sugar consumption, and tooth brushing on decayed, missing, and filled teeth (DMFT) score in Iranian 20-30-year-old individuals and compare the effect of the three mentioned factors to find the most effective one.

MATERIALS AND METHODS

In this cross-sectional study, 459 adults completed a Sugar Frequency Questionnaire and were examined for dental caries using DMFT index, sugar consumption level, and tooth brushing frequency per day. Saliva and plaque samples were collected, and the target population without Streptococcus sobrinus in their microbial oral community was selected using polymerase chain reaction technique. Data were analyzed by one-way analysis of variance and multiple linear regression tests (α = 0.05).

RESULTS

Nearly 77.1% of the study population were harboring S. mutans. Mean DMFT of the population was 6.62. Mean comparison analysis showed that there is a strong relationship between S. mutans existence in mouth flora and DMFT scores (P < 0.0001). Multiple linear regression test showed higher percentage of S. mutans contribution (28.2%) in DMFT score changes than sugar consumption (3.6%) and tooth brushing (0.7%).

CONCLUSION

This study provides a recent report from S. mutans frequency and DMFT score in Iranian adult population. It is also the first study that shows significantly higher impact of S. mutans in microbial population of mouth microflora on caries development than sugar consumption and oral hygiene. Accordingly, S. mutans screening program should be more highlighted in preventive strategies.

Development of Streptococcus mutans biofilm in the presence of human colostrum and 3'-sialyllactose

Aim: To evaluate the initial adhesion and formation of Streptococcus mutans biofilm in vitro in the presence of saliva, human colostrum and 3'-sialyllactose. Methods: Human colostrum and salivas were collected from 30 mothers and newborn postpartum. Eighteen hours culture of S. mutans was treated with colostrum or 3'-sialyllactose in three different moments: before, during, and after 24 h from the microbial inoculation. Salivas were also tested in conjunction with colostrum. The assays were realized in sterile 96-well flat-bottom microtiter plates for 24 h. The biofilms were fixed, washed, stained with crystal violet, and extracted. Absorbance was measured to evaluate biofilm growth mass. Results: Colostrum applied after and during the inoculation decreased biofilm formation when compared with the control (p < .05). The presence of saliva increased the biofilm biomass (p < .05). The application of 3'-sialyllactose reduced biofilm formation independently of moments of application (p < .05). Conclusion: Saliva contributed to the proliferation of biofilm and colostrum did not prevent the initial adhesion, but interfered in the accumulation and development of microorganisms in biofilms. 3'-sialyllactose significantly decreased biofilm formation. This information expands the importance of colostrum as a potent oral antimicrobial biofluid.

Spatial Design of Polymicrobial Oral Biofilm in Its Native Disease State

Biofilms are structured microbial communities adhered to surfaces that cause many human infections. The study of oral biofilms has revealed complex composition, spatial organization, and phenotypic/genotypic diversity of the resident microbiota at the various sites in the mouth. Yet, knowledge about the spatial arrangement, positioning, and function of the polymicrobial community across the intact biofilm architecture remains sparse. Using multiple length scale imaging and computational analysis, we discovered unique spatial designs comprising mixed interbacterial species and interkingdom communities within intact biofilms formed on teeth of toddlers with caries. Intriguing structural patterns ranging from intermixed communities with extensive coaggregation (including bacterial-fungal clustering) to spatially segregated species forming a multilayered architecture were found. Among them, a distinctive 3-dimensional structure exhibited densely clustered cariogenic pathogens that were surrounded by outer layers of mixed bacterial communities in juxtaposition, forming a highly ordered spatial organization. These findings are particularly relevant as we approach the postmicrobiome era whereby studying the spatial structure of the pathogen and commensal microbiota may be important for understanding the microbiome function at the infection site to coordinate the disease process in situ.

The Role of Bacterial Biofilms in Dental Caries and Periodontal and Peri-implant Diseases: A Historical Perspective

Over the last hundred years, groundbreaking research in oral microbiology has provided a broad and deep understanding about the oral microbiome, its interactions with our body, and how the community can affect our health, be protective, or lead to the development of dental diseases. During this exciting journey, hypotheses were proposed, and concepts were established, discarded, and later revisited from updated perspectives. Dental plaque, previously considered a polymicrobial community of unspecific pathogenicity, is recognized as microbial biofilms with healthy, cariogenic, or periodontopathogenic profiles, resulting from specific ecologic determinants and host factors. The "one pathogen, one disease" paradigm of oral infections has been replaced by a holistic concept of a microbial community as the entity of pathogenicity. Cutting-edge technology can now explore large microbial communities related to different clinical conditions, which has led to finding several novel disease-associated species and potential pathobionts and pathobiomes. This vast amount of data generated over time has widened our view of the etiology of caries and periodontal and peri-implant diseases and has promoted updated strategies to treat and prevent the oral diseases.

Exploring the Maternal and Infant Oral Microbiomes: A Pilot Study

Setting the stage for good oral health early in life is critical to long-term oral and overall health. This exploratory study aimed to characterize and compare maternal and newborn oral microbiota among mother-infant pairs. Oral samples were collected from 34 pregnant African American women and their infants at 1 to 3 months of age. Extracted 16SrRNA genes were matched to the Human Oral Microbiome Database. Alpha and beta diversity differed significantly between overall maternal and infant microbiomes. Maternal or infant alpha diversity, however, was not differentiated by maternal gingival status. Several demographic and behavioral variables were associated with, but not predictive of, maternal oral microbiome alpha diversity. There was no association, however, among birth mode, feeding mode, and the infant oral microbiome. Megasphaera micronuciformis was the only periodontal pathogen detected among the infants. Notably, maternal gingival status was not associated with the presence/absence of most periodontal pathogens. This study provides an initial description of the maternal and infant oral microbiomes, laying the groundwork for future studies. The perinatal period presents an important opportunity where perinatal nurses and providers can provide oral assessment, education, and referral to quality dental care.

Temporal development of the oral microbiome and prediction of early childhood caries

Human microbiomes are predicted to assemble in a reproducible and ordered manner yet there is limited knowledge on the development of the complex bacterial communities that constitute the oral microbiome. The oral microbiome plays major roles in many oral diseases including early childhood caries (ECC), which afflicts up to 70% of children in some countries. Saliva contains oral bacteria that are indicative of the whole oral microbiome and may have the ability to reflect the dysbiosis in supragingival plaque communities that initiates the clinical manifestations of ECC. The aim of this study was to determine the assembly of the oral microbiome during the first four years of life and compare it with the clinical development of ECC. The oral microbiomes of 134 children enrolled in a birth cohort study were determined at six ages between two months and four years-of-age and their mother's oral microbiome was determined at a single time point. We identified and quantified 356 operational taxonomic units (OTUs) of bacteria in saliva by sequencing the V4 region of the bacterial 16S RNA genes. Bacterial alpha diversity increased from a mean of 31 OTUs in the saliva of infants at 1.9 months-of-age to 84 OTUs at 39 months-of-age. The oral microbiome showed a distinct shift in composition as the children matured. The microbiome data were compared with the clinical development of ECC in the cohort at 39, 48, and 60 months-of-age as determined by ICDAS-II assessment. Streptococcus mutans was the most discriminatory oral bacterial species between health and current disease, with an increased abundance in disease. Overall our study demonstrates an ordered temporal development of the oral microbiome, describes a limited core oral microbiome and indicates that saliva testing of infants may help predict ECC risk.

Clinical Trials with Herbal Products for the Prevention of Dental Caries and Their Quality: A Scoping Study

It is currently recognized that an injudicious strategy about caries in the last decades has been not only focusing of research mostly in children, but also the narrow focusing on fluoride, because despite sufficient availability of fluoride in water and oral healthcare products, caries levels escalate steadily as people get older and caries remain a main public health issue to be settled. In the last two decades the scientific community intensified efforts of exploring other products for caries prevention, herbal products being one of these approaches. Preliminary evidence indicated that clinical trials for caries prevention with herbal products are heterogeneous in design, quality and products evaluated, we therefore performed a scoping review intended to explore the main characteristics of such clinical trials. From an initial collection of 1986 unique papers from different literature databases, 56 articles satisfied the inclusion and exclusion criteria. The species investigated, dosage forms, study designs, duration of intervention, controls, endpoints, quality of reporting, and risk of bias are discussed. Of the trials reviewed here, 85.71% reported positive results but given the methodological flaws and biases affecting them, it is difficult to conclude on the efficacy of those products based on the studies published thus far.

Effect of CPP-ACP on Streptococcus mutans in saliva of high caries-risk preschool children: a randomized clinical trial

PURPOSE

The aim of this study was to assess the efficacy of CPP-ACP in reducing salivary S. mutans levels and compare its effect as a dentifrice to use of a fluoride dentifrice alone, or with the sequential use of a combination of both agents (fluoride, then CPP-ACP) in three groups of preschool children over a 6-month period.

METHODS

This was a double-blinded clinical trial, the sample (n = 127, age 4.6 ± 0.47 years), with high caries risk, was randomized into three groups which applied different agents twice daily; fluoride toothpaste (500 ppm, n = 50), CPP-ACP (10% w/v, n = 38), and combination group (n = 39) applied fluoride, then CPP-ACP. S. mutans salivary levels were measured by GC Saliva-Check Mutans^™.

RESULTS

Within groups, a significant decrease in S. mutans-positive children (SMPC) occurred in fluoride and combination groups at 3-months, (P < 0.05), and in all groups at 6-months, (P < 0.05). The highest reduction in SMPC occurred in the CPP-ACP group, however, there were no significant differences in SMPC between groups at all study intervals, (P > 0.05).

CONCLUSION

Although all agents were effective, CPP-ACP showed the highest reduction in SMPC over 6-months.

Streptococcus mutans isolated from children with severe-early childhood caries form higher levels of persisters

OBJECTIVES

Dental caries is the most common chronic infectious disease in children. Streptococcus mutans, the main cariogenic bacterial species, produces persisters, nongrowing dormant variants of regular cells associated with chronicity of diseases. We hypothesized that the recurrent nature of caries, particularly within populations with high-caries risk, is due partly to specific phenotypic features of S. mutans such as its ability to form persisters. We aimed to investigate the genotypic and phenotypic differences between the S. mutans from children with severe early-childhood caries (S-ECC) and those without caries.

METHODS

S. mutans from plaque samples of caries-free (CF) and S-ECC children were tested for their ability to adapt to a lethal pH in an acid tolerance response assay. The persister levels of S. mutans isolates was quantified in both groups.

RESULTS

S. mutanswas identified in all 23 S-ECC but only 6 of the 21 CF subjects. In most subjects, only one dominant S. mutans genotype was detected. No statistically significant differences in the mean survival percentage of S. mutans were observed between the two groups at a lethal pH of 3.5. However, the dominant genotype within a particular S-ECC subject exhibited a higher percentage of cell survival compared to those in the CF group. In S-ECC patients, S. mutans isolates displayed a ∼15-fold higher persistence phenotype than S. mutans isolates from CF patients.

CONCLUSIONS

The ability of S. mutans to produce high levels of persisters may contribute to part of an individual's ability to control caries disease activity and recurrent lesions.

Quantitative assessment of Scardovia wiggsiae from dental plaque samples of children suffering from severe early childhood caries and caries free children

Scardovia wiggsiae has recently been identified as a potential pathogen associated with dental caries. The aim of the present study was to detect and quantify S. wiggsiae from dental plaque samples of children suffering from severe early childhood caries and children who were caries free by employing a real time DNA polymerase chain reaction (Real-time PCR) method. Dental plaque samples were collected from children suffering from severe early childhood caries (S-ECC) (n = 30) and caries free children (CF) (n = 30) reporting to the out-patient clinics of the department of paediatric and preventive dentistry. Plaque samples from each group were subjected to real-time PCR, post DNA extraction. Both the groups showed the presence of the organism S. wiggsiae, however there was a significant difference in its quantification between groups, with the median number being 1.49 × 10⁸ cells per ml in caries free samples compared to 1.40 × 10⁹ cells per ml in S-ECC samples. S. wiggsiae were isolated from nearly all samples of children, both caries free and those suffering from S-ECC. However, their numbers differ drastically in both groups with the scales tipping towards the S-ECC group, proving their association with the disease process in a significant manner. The present study shows significant association of S. wiggsiae in severe early childhood caries.

Illumina-based sequencing analysis of pathogenic microorganisms in dental caries patients of different Chinese ethnic groups

Objective

To analyze the pathogenic community diversity of dental caries patients from Tu, Hui, Tibetan, and Han Chinese ethnic groups.

Methods

Forty saliva samples were collected from the following patients with dental caries: Tu from Huzhu County (n = 10), Hui from Ping’an County (n = 10), Han from Xining city (n = 10), and Tibetan from Yushu (n = 10). High-throughput sequencing of bacterial 16S rRNA genes (V3-V4) was performed using the Illumina MiSeq sequencing platform.

Results

Based on 97% similarity clustering, operational taxonomic units of Tu, Hui, Tibetan, and Han ethnic groups were 181, 210, 38, and 67, respectively. In Tu patients, 11 phyla, 19 classes, and 89 genera were identified, compared with 13 phyla, 21 classes, and 113 genera in Hui patients, two phyla, four classes, and 21 genera in Tibetan patients, five phyla, nine classes, and 34 genera in Han patients, and four phyla, five classes, and 12 genera from the control group. The main pathogens of dental caries included Veillonella, Aggregatibacter, Leptotrichia, Bacteroides, Granulicatella, Streptococcus, and Prevotella.

Conclusion

The pathogenic microorganisms of dental caries differ greatly among Tu, Hui, Tibetan, and Han ethnic groups. These findings provide a theoretical basis for the effective prevention and treatment of dental caries in different Chinese populations.

The Oral Bacterial Microbiome of Interdental Surfaces in Adolescents According to Carious Risk

Adolescence is closely associated with a high risk of caries. The identification of specific bacteria in an oral microniche, the interdental space of the molars, according to carious risk can facilitate the prediction of future caries and the anticipation of the progression or stabilization of caries in adolescents. A cross-sectional clinical study according to the bacteriological criteria of interdental healthy adolescents and carious risk factors-low and high-using a real-time polymerase chain reaction technique was conducted. The presence of 26 oral pathogens from the interdental microbiota of 50 adolescents aged 15 to 17 years were qualitatively and quantitatively analyzed. Bacteria known to be cariogenic (Bifidobacterium dentium, Lactobacillus spp., Rothia dentocariosa, Streptococcus cristatus, Streptococcus mutans, Streptococcus salivarius, Streptococcus sobrinus, and Streptococcus wiggsiae) did not present differences in abundance according to carious risk. Periodontal bacteria from the red complex are positively correlated with carious risk. However, only 3 bacteria-S. sobrinus, E corrodens and T. forsythia-presented a significant increase in the highest group. Estimating the risk of caries associated with bacterial factors in interdental sites of molars in adolescents contributes to the better definition of carious risk status, periodicity and intensity of diagnostic, prevention and restorative services.

Amino Sugars Modify Antagonistic Interactions between Commensal Oral Streptococci and Streptococcus mutans

N-Acetylglucosamine (GlcNAc) and glucosamine (GlcN) enhance the competitiveness of the laboratory strain DL1 of Streptococcus gordonii against the caries pathogen Streptococcus mutans Here, we examine how amino sugars affect the interaction of five low-passage-number clinical isolates of abundant commensal streptococci with S. mutans by utilizing a dual-species biofilm model. Compared to that for glucose, growth on GlcN or GlcNAc significantly reduced the viability of S. mutans in cocultures with most commensals, shifting the proportions of species. Consistent with these results, production of H₂O₂ was increased in most commensals when growing on amino sugars, and inhibition of S. mutans by Streptococcus cristatus, Streptococcus oralis, or S. gordonii was enhanced by amino sugars on agar plates. All commensals except S. oralis had higher arginine deiminase activities when grown on GlcN and, in some cases, GlcNAc. In ex vivo biofilms formed using pooled cell-containing saliva (CCS), the proportions of S. mutans were drastically diminished when GlcNAc was the primary carbohydrate. Increased production of H₂O₂ could account in large part for the inhibitory effects of CCS biofilms. Surprisingly, amino sugars appeared to improve mutacin production by S. mutans on agar plates, suggesting that the commensals have mechanisms to actively subvert antagonism by S. mutans in cocultures. Collectively, these findings demonstrate that amino sugars can enhance the beneficial properties of low-passage-number commensal oral streptococci and highlight their potential for moderating the cariogenicity of oral biofilms.IMPORTANCE Dental caries is driven by dysbiosis of oral biofilms in which dominance by acid-producing and acid-tolerant bacteria results in loss of tooth mineral. Our previous work demonstrated the beneficial effects of amino sugars GlcNAc and GlcN in promoting the antagonistic properties of a health-associated oral bacterium, Streptococcus gordonii, in competition with the major caries pathogen Streptococcus mutans Here, we investigated 5 low-passage-number clinical isolates of the most common streptococcal species to establish how amino sugars may influence the ecology and virulence of oral biofilms. Using multiple in vitro models, including a human saliva-derived microcosm biofilm, experiments showed significant enhancement by at least one amino sugar in the ability of most of these bacteria to suppress the caries pathogen. Therefore, our findings demonstrated the mechanism of action by which amino sugars may affect human oral biofilms to promote health.

The oral microbiota - a mechanistic role for systemic diseases

Human oral microbiota is the ecological community of commensal, symbiotic, and pathogenic microorganisms found in the oral cavity. Oral microbiota generally exists in the form of a biofilm and plays a crucial role in maintaining oral homeostasis, protecting the oral cavity and preventing disease development. Human oral microbiota has recently become a new focus research for promoting the progress of disease diagnosis, assisting disease treatment, and developing personalised medicines. In this review, the scientific evidence supporting the association that endogenous and exogenous factors (diet, smoking, drinking, socioeconomic status, antibiotics use and pregnancy) modulate oral microbiota. It provides insights into the mechanistic role in which oral microbiota may influence systemic diseases, and summarises the challenges of clinical diagnosis and treatment based on the microbial community information. It provides information for noninvasive diagnosis and helps develop a new paradigm of personalised medicine. All these benefit human health in the post-metagenomics era.

Analysis of oral bacterial communities: comparison of HOMINGS with a tree-based approach implemented in QIIME

Background: Molecular taxonomic assignments in oral microbial communities have been made using probe-matching approaches, but never compared to those obtained by more readily accepted tree-based approaches. Objective:  To compare community composition profiles obtained from a probe-matching approach (HOMINGS) to those from a closed-ended tree-based approach (QIIME using the eHOMD database). Design:  HOMINGS and QIIME were used for parallel analysis of ten mock community samples, and of 119 supragingival plaque samples from ecologically unique sites (sound tooth surfaces in healthy subjects, sound tooth surfaces in patients with primary Sjögren’s Syndrome, and carious lesions in Sjögren’s Syndrome patients). Linear discriminant analysis Effective Size (LEfSe) was used to identify discriminating taxa among the natural plaque samples. Results: Community composition profiles of all samples were congruent between the two analysis aproaches. Alpha and beta diversity of the natural plaque communities were likewise similar. Communities from pSS patients and those from individuals with normal salivary flow differed in alpha and beta diversity. Both classification approaches yielded differences in composition predicted for samples from these subject cohorts, and discriminating taxa were similar between approaches. Conclusions: A direct comparison demonstrates that HOMINGS is largely equivalent to the tree-based approach as implemented here.

Caries-associated oral microbiome in head and neck cancer radiation patients: a longitudinal study

Head and neck cancer (HNC) therapy often leads to caries development. Our goal was to characterize the oral microbiome of HNC patients who underwent radiation therapy (RT) at baseline (T0), and 6 (T6) and 18 (T18) months post-RT, and to determine if there was a relationship with increased caries. HOMINGS was used to determine the relative abundance (RA) of >600 bacterial species in oral samples of 31 HNC patients. The DMFS score was used to define patient groups with tooth decay increase (DMFS[+]) or no increase (DMFS[-]).A change in microbiome beta-diversity was observed at T6 and T18. The Streptococcus mutans RA increased at T6 in both DMFS[+] and DMFS[-] groups. The RA of Prevotella melaninogenica, the species often associated with caries in young children, decreased at T6 in the DMFS[-] group. The RA of the health-associated species, Abiotrophia defective, decreased in the DMFS[+] group. The oral microbiome underwent significant changes in radiation-treated HNC patients, whether they developed caries or not. Caries rates were not associated with a difference in salivary flow reduction between DMFS[+] andDMFS[-] groups. Patients who develop caries might be more susceptible to certain species associated with oral disease or have fewer potentially protective oral species.

Comparison of the salivary and dentinal microbiome of children with severe-early childhood caries to the salivary microbiome of caries-free children

BACKGROUND

The main objectives of this study were to describe and compare the microbiota of 1) deep dentinal lesions of deciduous teeth of children affected with severe early childhood caries (S-ECC) and 2) the unstimulated saliva of these children and 3) the unstimulated saliva of caries-free children, and to compare microbiota compositional differences and diversity of taxa in these sampled sites.

METHODS

Children with S-ECC and without S-ECC were recruited. The saliva of all children with and without S-ECC was sampled along with the deep dentinal microbiota from children affected by S-ECC. The salivary microbiota of children affected by S-ECC (n = 68) was compared to that of caries-free children (n = 70), by Illumina MiSeq sequencing of 16S rRNA amplicons. Finally, the caries microbiota of deep dentinal lesions of those children with S-ECC was investigated.

RESULTS

Using two beta diversity metrics (Bray Curtis dissimilarity and UniFrac distance), the caries microbiota was found to be distinct from that of either of the saliva groups (caries-free & caries-active) when bacterial abundance was taken into account. However, when the comparison was made by measuring only presence and absence of bacterial taxa, all three microbiota types separated. While the alpha diversity of the caries microbiota was lowest, the diversity difference between the caries samples and saliva samples was statistically significant (p < 0.001). The major phyla of the caries active dentinal microbiota were Firmicutes (median abundance value 33.5%) and Bacteroidetes (23.2%), with Neisseria (10.3%) being the most abundant genus, followed by Prevotella (10%). The caries-active salivary microbiota was dominated by Proteobacteria (median abundance value 38.2%) and Bacteroidetes (27.8%) with the most abundant genus being Neisseria (16.3%), followed by Porphyromonas (9.5%). Caries microbiota samples were characterized by high relative abundance of Streptococcus mutans, Prevotella spp., Bifidobacterium and Scardovia spp.

CONCLUSIONS

Distinct differences between the caries microbiota and saliva microbiota were identified, with separation of both salivary groups (caries-active and caries-free) whereby rare taxa were highlighted. While the caries microbiota was less diverse than the salivary microbiota, the presence of these rare taxa could be the difference between health and disease in these children.

Novel Approaches to the Control of Oral Microbial Biofilms

Effective management of biofilm-related oral infectious diseases is a global challenge. Oral biofilm presents increased resistance to antimicrobial agents and elevated virulence compared with planktonic bacteria. Antimicrobial agents, such as chlorhexidine, have proven effective in the disruption/inhibition of oral biofilm. However, the challenge of precisely and continuously eliminating the specific pathogens without disturbing the microbial ecology still exists, which is a major factor in determining the virulence of a multispecies microbial consortium and the consequent development of oral infectious diseases. Therefore, several novel approaches are being developed to inhibit biofilm virulence without necessarily inducing microbial dysbiosis of the oral cavity. Nanoparticles, such as pH-responsive enzyme-mimic nanoparticles, have been developed to specifically target the acidic niches within the oral biofilm where tooth demineralization readily occurs, in effect controlling dental caries. Quaternary ammonium salts (QAS) such as dimethylaminododecyl methacrylate (DMADDM), when incorporated into dental adhesives or resin composite, have also shown excellent and durable antimicrobial activity and thus could effectively inhibit the occurrence of secondary caries. In addition, custom-designed small molecules, natural products and their derivatives, as well as basic amino acids such as arginine, have demonstrated ecological effects by modulating the virulence of the oral biofilm without universally killing the commensal bacteria, indicating a promising approach to the management of oral infectious diseases such as dental caries and periodontal diseases. This article aims to introduce these novel approaches that have shown potential in the control of oral biofilm. These methods may be utilized in the near future to effectively promote the clinical management of oral infectious diseases and thus benefit oral health.

Rebalancing the Caries Microbiome Dysbiosis: Targeted Treatment and Sugar Alcohols

Dental caries is a disease that results from microbiome dysbiosis with the involvement of multiple cariogenic species, including mutans streptococci (MS), lactobacilli, Scardovia wiggsiae, and several Actinomyces species that have the cariogenic traits of acid production and acid tolerance. Sugar consumption also plays an important role interacting with microbiome dysbiosis, determining the fate of caries development. In addition, the MS transmission that encompasses multiple sources can have long-term impacts on the oral microbiome and caries development in children. Intervention in MS transmission in early childhood may promote effective long-term caries prevention. Anticaries regimens aimed against the above mechanisms will be important for successful caries management. Xylitol and erythritol may serve as good components of anticaries regimens as oral microbiome modifiers, sugar substitutes, and agents to prevent MS transmission in early childhood with both oral and systemic benefits. Further studies are needed to elucidate the mechanism of the anticaries effects of xylitol and erythritol with consideration of their impacts on the microbiome and bacterial virulence, in addition to cariogenic bacteria levels as well as their benefits for overall health. On the other hand, the anticaries agent C16G2, specifically targeting Streptococcus mutans, the most common cariogenic bacterial species, has shown good safety for short-term oral topical use and promising effects in reducing S. mutans in vitro and in vivo with the promotion of oral commensal bacteria. Future study on its anticaries effect will need to include its long-term impact on the oral microbiome and effects on other important cariogenic bacteria.

The Caries Microbiome: Implications for Reversing Dysbiosis

The oral microbiome plays a critical role in maintaining oral health. Frequent dietary carbohydrate intake can lead to dysbiosis of the microbial community from overproduction of acid with selection for increases in acidogenic, acid-tolerant bacteria. Knowledge of the caries-associated microbiome is key in planning approaches to reverse the dysbiosis to achieve health. For risk assessment and treatment studies, it would be valuable to establish whether microbial monitoring requires assay of multiple species or whether selected key species would suffice. Early investigations of the oral microbiota relied on culture-based methods to determine the major bacteria in health and disease. Microbial monitoring using gene probes facilitated study of larger populations. DNA probe methods confirmed and expanded the importance of transmission of bacteria from mother to infant and association of preselected species, including mutans streptococci and lactobacilli with caries in larger populations. 16S ribosomal RNA (rRNA) probes confirmed the wide diversity of species in oral and caries microbiomes. Open-ended techniques provide tools for discovery of new species, particularly when strain/clone identification includes gene sequence data. Anaerobic culture highlighted the caries association of Actinomyces and related species. Scardovia wiggsiae, in the Actinomyces/Bifidobacterium family, and several Actinomyces species have the cariogenic traits of acid production and acid tolerance. Next-generation sequencing combined with polymerase chain reaction methods revealed a strong association with mutans streptococci in a high caries population with poor oral hygiene and limited access to care. A population with a lower caries experience generally had lower or no Streptococcus mutans detection but harbored other acidogenic taxa in the microbiome. Study of the microbiome suggests a role for the assay of selected putative cariogenic species in more aggressive diseases. For many populations with caries progression, however, assay of multiple species will likely be warranted to determine the caries profile of the population and/or individuals under study.

Supragingival Plaque Microbiome Ecology and Functional Potential in the Context of Health and Disease

Oral health has substantial economic importance, with over $100 billion spent on dental care in the United States annually. The microbiome plays a critical role in oral health, yet remains poorly classified. To address the question of how microbial diversity and function in the oral cavities of children relate to caries diagnosis, we surveyed the supragingival plaque biofilm microbiome in 44 juvenile twin pairs. Using shotgun sequencing, we constructed a genome encyclopedia describing the core supragingival plaque microbiome. This unveiled several new previously uncharacterized but ubiquitous microbial lineages in the oral microbiome. Caries is a microbial community metabolic disorder that cannot be described by a single etiology, and our results provide the information needed for next-generation diagnostic tools and therapeutics for caries.

To address the question of how microbial diversity and function in the oral cavities of children relates to caries diagnosis, we surveyed the supragingival plaque biofilm microbiome in 44 juvenile twin pairs. Using shotgun sequencing, we constructed a genome encyclopedia describing the core supragingival plaque microbiome. Caries phenotypes contained statistically significant enrichments in specific genome abundances and distinct community composition profiles, including strain-level changes. Metabolic pathways that are statistically associated with caries include several sugar-associated phosphotransferase systems, antimicrobial resistance, and metal transport. Numerous closely related previously uncharacterized microbes had substantial variation in central metabolism, including the loss of biosynthetic pathways resulting in auxotrophy, changing the ecological role. We also describe the first complete Gracilibacteria genomes from the human microbiome. Caries is a microbial community metabolic disorder that cannot be described by a single etiology, and our results provide the information needed for next-generation diagnostic tools and therapeutics for caries.

Glass ionomer cements with milled, dry chlorhexidine hexametaphosphate filler particles to provide long-term antimicrobial properties with recharge capacity

OBJECTIVE

Glass ionomer cements (GICs) are a versatile material, offering the opportunity for ion exchange with the oral environment. The aim of this study was to develop a GIC that delivers a controlled, rechargeable dose of chlorhexidine (CHX) over an extended period without compromising mechanical properties.

METHODS

GICs were supplemented with finely milled particles of chlorhexidine hexametaphosphate (CHX-HMP). CHX release into artificial saliva was measured over 660 days, and recharge with CHX and CHX-HMP was investigated. Mechanical properties were investigated, and an agar diffusion test was carried out to assess antimicrobial properties using Streptococcus mutans and Scardovia wiggsiae.

RESULTS

Dose-dependent CHX release was observed, and this was ongoing at 660 days. Compared with related studies of GICs containing CHX-HMP, the fine, dry particles resulted in fewer adverse effects on mechanical properties, including tensile, compressive and biaxial flexural strength, with 1% CHX-HMP GICs indistinguishable from control specimens. The GICs could be recharged with CHX using both a conventional CHX digluconate solution comparable to commercial mouthrinses, and a suspension of CHX-HMP of equivalent concentration. Recharging with CHX digluconate increased subsequent CHX release by 50% compared with no recharge, and recharging with CHX-HMP increased subsequent CHX release by 100% compared with no recharge. The GICs inhibited growth of St. mutans and Sc. wiggsiae in a simple agar diffusion model.

SIGNIFICANCE

These materials, which provide sustained CHX release over clinically relevant timescales, may find application as a restorative material intended to inhibit secondary caries as well as in temporary restorations and fissure sealants.

In-vivo shift of the microbiota in oral biofilm in response to frequent sucrose consumption

Caries is associated with shifts of microbiota in dental biofilms and primarily driven by frequent sucrose consumption. Data on environmentally induced in vivo microbiota shifts are scarce therefore we investigated the influence of frequent sucrose consumption on the oral biofilm. Splint systems containing enamel slabs were worn for 3 × 7 days with 7-day intervals to obtain oral biofilm samples. After a three-month dietary change of sucking 10 g of sucrose per day in addition to the regular diet, biofilm was obtained again at the end of the second phase. The microbiota was analysed using Illumina MiSeq amplicon sequencing (v1-v2 region). In addition, roughness of the enamel surface was measured with laser scanning microscopy. The sucrose phase resulted in significant differences in beta-diversity and significantly decreased species richness. It was marked by a significant increase in abundance of streptococci, specifically Streptococcus gordonii, Streptococcus parasanguinis and Streptococcus sanguinis. Enamel surface roughness began to increase, reflecting initial impairment of dental enamel surface. The results showed that frequent sucrose consumption provoked compositional changes in the microbiota, leading to an increase of non-mutans streptococci, hence supporting the extended ecological plaque hypothesis and emphasizing the synergy of multiple bacterial species in the development of caries.

Cariogenic microbiome and microbiota of the early primary dentition: A contemporary overview

Recent advances in the field of molecular microbiology provide an unprecedented opportunity to decipher the vast diversity of the oral microbiome in health and disease. Here, we provide a contemporary overview of the oral microbiome and the microbiota of early childhood caries (ECC) with particular reference to newer analytical techniques. A MEDLINE search revealed a total of 20 metagenomic studies describing cariogenic microbiomes of ECC, 10 of which also detailed the healthy microbiomes. In addition, seven studies on site-specific microbiomes, focusing on acidogenic and aciduric microbiota of deep-dentinal lesions, were also reviewed. These studies evaluated plaque and saliva of children aged 1.5-11 years, in cohorts of 12-485 individuals. These studies reveal a very rich and diverse microbial communities, with hundreds of different phylotypes and microbial species, including novel species and phyla such as Scardovia wiggsiae, Slackia exigua, Granulicatella elegans, Firmicutes in the plaque biofilms of children with ECC. On the contrary, bacteria such as Streptococcus cristatus, S. gordonii, S. sanguinis, Corynebacterium matruchotii, and Neisseria flavescens were common in plaque biofilm of noncarious, healthy, tooth surfaces in subjects with caries. The review illustrates the immense complexity and the diversity of the human oral microbiota of the cariogenic plaque microbiome in ECC, and the daunting prospect of its demystification.

Role of microbial biofilms in the maintenance of oral health and in the development of dental caries and periodontal diseases. Consensus report of group 1 of the Joint EFP/ORCA workshop on the boundaries between caries and periodontal disease

BACKGROUND AND AIMS

The scope of this working group was to review (1) ecological interactions at the dental biofilm in health and disease, (2) the role of microbial communities in the pathogenesis of periodontitis and caries, and (3) the innate host response in caries and periodontal diseases.

RESULTS AND CONCLUSIONS

A health-associated biofilm includes genera such as Neisseria, Streptococcus, Actinomyces, Veillonella and Granulicatella. Microorganisms associated with both caries and periodontal diseases are metabolically highly specialized and organized as multispecies microbial biofilms. Progression of these diseases involves multiple microbial interactions driven by different stressors. In caries, the exposure of dental biofilms to dietary sugars and their fermentation to organic acids results in increasing proportions of acidogenic and aciduric species. In gingivitis, plaque accumulation at the gingival margin leads to inflammation and increasing proportions of proteolytic and often obligately anaerobic species. The natural mucosal barriers and saliva are the main innate defence mechanisms against soft tissue bacterial invasion. Similarly, enamel and dentin are important hard tissue barriers to the caries process. Given that the present state of knowledge suggests that the aetiologies of caries and periodontal diseases are mutually independent, the elements of innate immunity that appear to contribute to resistance to both are somewhat coincidental.

Oral microbiome development during childhood: an ecological succession influenced by postnatal factors and associated with tooth decay

Information on how the oral microbiome develops during early childhood and how external factors influence this ecological process is scarce. We used high-throughput sequencing to characterize bacterial composition in saliva samples collected at 3, 6, 12, 24 months and 7 years of age in 90 longitudinally followed children, for whom clinical, dietary and health data were collected. Bacterial composition patterns changed through time, starting with "early colonizers", including Streptococcus and Veillonella; other bacterial genera such as Neisseria settled after 1 or 2 years of age. Dental caries development was associated with diverging microbial composition through time. Streptococcus cristatus appeared to be associated with increased risk of developing tooth decay and its role as potential biomarker of the disease should be studied with species-specific probes. Infants born by C-section had initially skewed bacterial content compared with vaginally delivered infants, but this was recovered with age. Shorter breastfeeding habits and antibiotic treatment during the first 2 years of age were associated with a distinct bacterial composition at later age. The findings presented describe oral microbiota development as an ecological succession where altered colonization pattern during the first year of life may have long-term consequences for child´s oral and systemic health.

Functional profiles of coronal and dentin caries in children

Background: Dental caries results from a dysbiosis of tooth-associated biofilms and frequently extends through enamel into dentin which has a different structure and composition.

Objective: To evaluate the metatranscriptome of caries to determine the metabolic potential of caries communities compared with health.

Design: Samples from children, caries-free (CF: n = 4) or with coronal (CC: n = 5) or dentin (DC: n = 5) caries were examined for gene expression potential. Functional profiling was performed using HUMAnN2 (HMP Unified Metabolic Analysis Network).

Results: There was increased gene expression diversity in DC compared with CC and CF. Genes in CF included alcohol dehydrogenase from Neisseria sicca, methylenetetrahydrofolate reductase from Streptococcus sanguinis and choline kinase from streptococci. Genes in CC mapped mainly to Streptococcus mutans. Arginine deiminase in DC mapped to S. sanguinis and Actinomyces naeslundii. Glycerol kinase genes mapped to S. sanguinis in all groups whereas glycerol kinase in DC were from Rothia, Prevotella and streptococci. Uracil-DNA glycosylase in DC mapped to Prevotella denticola and Actinomyces. Repressor LexA in DC mapped to Scardovia wiggsiae, Dialister invisus and Veillonella parvula.

Conclusions: Functional profiling revealed enzyme activities in both caries and caries-free communities and clarified marked differences between coronal and dentin caries in bacterial composition and potential gene expression.

pH-Sensitive Compounds for Selective Inhibition of Acid-Producing Bacteria

Stimuli-responsive compounds that provide on-site, controlled antimicrobial activity promise an effective approach to prevent infections, reducing the need for systemic antibiotics. We present a novel pH-sensitive quaternary pyridinium salt (QPS), whose antibacterial activity is boosted by low pH and controlled by adjusting the pH between 4 and 8. Particularly, this compound selectively inhibits growth of acid-producing bacteria within a multispecies community. The successful antibacterial action of this QPS maintains the environmental pH above 5.5, a threshold pH, below which demineralization/erosion takes place. The design, synthesis, and characterization of this QPS and its short-chain analogue are discussed. In addition, their pH-sensitive physicochemical properties in aqueous and organic solutions are evaluated by UV-vis spectroscopy, dynamic light scattering, and NMR spectroscopy. Furthermore, the mechanism of action reveals a switchable assembly that is triggered by acid-base interaction and formed by tightly stacked π-conjugated systems and base moieties. Finally, a model is proposed to recognize the correlated but different mechanisms of pH sensitivity and acid-induced, pH-controlled antibacterial efficacy. We anticipate that successful application of these QPSs and their derivatives will provide protections against infection and erosion through targeted treatments to acid-producing bacteria and modulation of environmental pH.

The Impact of Maltitol-Sweetened Chewing Gum on the Dental Plaque Biofilm Microbiota Composition

Background: The oral cavity harbors a complex microbial ecosystem, intimately related to oral health and disease. The use of polyol-sweetened gum is believed to benefit oral health through stimulation of salivary flow and impacting oral pathogenic bacteria. Maltitol is often used as sweetener in food products. This study aimed to establish the in vivo effects of frequent consumption of maltitol-sweetened chewing gum on the dental plaque microbiota in healthy volunteers and to establish the cellular and molecular effects by in vitro cultivation and transcriptional analysis.

Results: An intervention study was performed in 153 volunteers, randomly assigned to three groups (www.trialregister.nl; NTR4165). One group was requested to use maltitol gum five times daily, one group used gum-base, and the third group did not use chewing gum. At day 0 and day 28, 24 h-accumulated supragingival plaque was collected at the lingual sites of the lower jaw and the buccal sites of the upper jaw and analyzed by 16S ribosomal rRNA gene sequencing. At day 42, 2 weeks after completion of the study, lower-jaw samples were collected and analyzed. The upper buccal plaque microbiota composition had lower bacterial levels and higher relative abundances of (facultative) aerobic species compared to the lower lingual sites. There was no difference in bacterial community structure between any of the three study groups (PERMANOVA). Significant lower abundance of several bacterial phylotypes was found in maltitol gum group compared to the gum-base group, including Actinomyces massiliensis HOT 852 and Lautropia mirabilis HOT 022. Cultivation studies confirmed growth inhibition of A. massiliensis and A. johnsonii by maltitol at levels of 1% and higher. Transcriptome analysis of A. massiliensis revealed that exposure to maltitol resulted in changes in the expression of genes linked to osmoregulation, biofilm formation, and central carbon metabolism.

Conclusion: The results showed that chewing itself only marginally impacted the plaque microbiota composition. Use of maltitol-sweetened gum lowered abundance of several bacterial species. Importantly, the species impacted play a key role in the early formation of dental biofilms. Further studies are required to establish if frequent use of maltitol gum impacts early dental-plaque biofilm development.

Potential Uses of Arginine in Dentistry

Carious lesions develop in tooth surfaces where there is an imbalance of the processes of acid and alkali production by supragingival biofilms. Since low pH is the main driving factor in the development of carious lesions, most efforts to identify an effective anticaries therapy have focused on targeting the acid-producing bacteria and their mechanisms of acid production. An expanding area of oral microbiology has now been devoted to explore microbial metabolic activities that help to neutralize biofilm pH and thus inhibit the caries process. Arginine metabolism via the arginine deiminase pathway (ADS) produces alkali in the form of ammonia that counteracts the effects of biofilm acidification from bacterial glycolysis. ADS also functions as an adaptive strategy used by certain bacteria to thrive in oral biofilms. Substantial evidence accumulated from laboratory and clinical observations supports the hypotheses that measurements of arginine metabolism via ADS may serve as an important caries risk assessment criterion and that providing arginine regularly to supragingival biofilms can be an effective therapy for caries intervention. This article reviews the potential of arginine-based therapies such as the use of arginine as prebiotic, ADS+ strains as probiotics, and oral care formulations containing arginine for prevention and management of dental caries.

Mutans Streptococci and Dental Caries: A New Statistical Modeling Approach

Survival analyses have been used to overcome some of the limitations encountered with other statistical analyses. Although extended Cox hazard modeling with time-dependent variables has been utilized in several medical studies, it has never been utilized in assessing the complex relationship between mutans streptococci (MS) acquisition (time-dependent covariate) and time to having dental caries (outcome). This study involved secondary analyses of data from a prospective study conducted at the University of Alabama at Birmingham. Low socioeconomic status, African-American preschool children from Perry County, AL, USA (n = 95) had dental examinations at age 1 year and annually thereafter until age 6 years by three calibrated dentists. Salivary MS tests were done at ages 1, 1.5, 2, 2.5, 3, and 4 years. The patterns of and relationship between initial MS detection (time-dependent covariate) and dental caries experience occurrence were assessed, using extended Cox hazard modeling. The median time without MS acquisition (50% of the children not having positive MS test) was 2 years. Approximately 79% of the children had positive salivary MS tests by the age of 4 years. The median caries experience survival (50% of the children not having dental caries) was 4 years. During the follow-up period, 65 of the children (68.4%) had their initial primary caries experience. Results of the extended Cox hazard modeling showed a significant overall/global relationship between initial caries experience event at any given time during the follow-up period and having a positive salivary MS test at any time during the follow-up period (hazard ratio = 2.25, 95% CI 1.06-4.75). In conclusion, the extended Cox modeling was used for the first time and its results showed a significant global/overall relationship between MS acquisition and dental caries. Further research using causal mediation analysis with survival data is necessary, where the mediator "presence of MS" is treated as a time-dependent variable.

Gene encoding the CTP synthetase as an appropriate molecular tool for identification and phylogenetic study of the family Bifidobacteriaceae

An alternative molecular marker with respect to the 16S rRNA gene demonstrating better identification and phylogenetic parameters has not been designed for the whole Bifidobacteriaceae family, which includes the genus Bifidobacterium and scardovial genera. Therefore, the aim of the study was to find such a gene in available genomic sequences, suggest appropriate means and conditions for asmplification and sequencing of the desired region of the selected gene in various strains of the bacterial family and verify the importance in classification and phylogeny. Specific primers flanking the variable region (~800 pb) within the pyrG gene encoding the CTP synthetase were designed by means of gene sequences retrieved from the genomes of strains belonging to the family Bifidobacteriaceae. The functionality and specificity of the primers were subsequently tested on the wild (7) and type strains of bifidobacteria (36) and scardovia (7). Comparative and phylogenetic studies based on obtained sequences revealed actual significance in classification and phylogeny of the Bifidobacteriaceae family. Gene statistics (percentages of mean sequence similarities and identical sites, mean number of nucleotide differences, P- and K-distances) and phylogenetic analyses (congruence between tree topologies, percentages of bootstrap values >50 and 70%) indicate that the pyrG gene represents an alternative identification and phylogenetic marker exhibiting higher discriminatory power among strains, (sub)species, and genera than the 16S rRNA gene. Sequences of the particular gene fragment, simply achieved through specific primers, enable more precisely to classify and evaluate phylogeny of the family Bifidobacteriaceae including, with some exceptions, health-promoting probiotic bacteria.

A Comparative Evaluation of Bifidobacteria Levels in Early Childhood Caries and Severe Early Childhood Caries

Background:

Bifidobacteria levels in saliva were found to be significantly correlated in adults with dental caries but less information available in the literature regarding its role in children.

Aim:

The aim is to compare the salivary levels of Bifidobacteria in children who are caries free with that of early childhood caries (ECC) and severe ECC (S-ECC).

Materials and Methods:

Saliva was collected using the tongue-loop method from a total of 60 children between the age group of 3–5 years and they were further divided into 3 groups. In addition, the age and gender of the children, sugar amount in diet, sugar frequency in diet, were recorded.

Results:

Bifidobacteria was isolated from all the three groups, but more were from S-ECC, followed by ECC and very few cases of caries-free children and was found to statistically significant (P < 0.001). Salivary levels of Bifidobacteria were significantly correlated with amount of sugar in the diet and frequency of sugar consumption.

Conclusions:

Salivary levels of Bifidobacteria were significantly associated with S-ECC and ECC, followed by caries free group. In future, it can be used as a salivary marker for caries risk assesment.

Genotypic characterization and comparison of Streptococcus mutans in American Indian and Southeast Iowa children

Early childhood caries is a complex health care issue that has a multifactorial etiology. One aspect of this etiology is the colonization and propagation of acidogenic bacteria at an early age. There have been several bacterial species associated with caries but 1 common species is Streptococcus mutans. Here, we describe genotypic diversity and commonality of Streptococcus mutans recovered from children representing 2 groups with similar socioeconomic demographics: a Northern Plains American Indian Tribe and a Southeast Iowa population. Forty 36‐month‐old American Indian children were selected from a cohort of 239 mothers and children, and forty 2‐ to 5‐year‐old children from Southeast Iowa were selected to compare the genotypic profiles of Streptococcus mutans recovered from each child's plaque. S. mutans isolates were selected from whole mouth plaque samples; DNA was extracted and amplified via AP‐PCR to show specific genotype patterns. These patterns were compared with GelComparIIv6.5 gel analysis software. We found 18 distinct genotypes from 524 isolates; 13 of which were common between the 2 communities. Five genotypes were unique to only the American Indian children while the Southeast Iowa children harbored no unique genotypes. Although the American Indian children had some genotypes that were not present in the Southeast Iowa children, these were not widely distributed among the community. Furthermore, the levels of genotypic diversity and commonality were similar between the 2 populations. This study sets the groundwork for a comprehensive comparison of genotypes and caries among larger subsections of both populations.

Differences in carbon source usage by dental plaque in children with and without early childhood caries

Early childhood caries (ECC) is a considerable pediatric and public health problem worldwide. Preceding studies have focused primarily on bacterial diversity at the taxonomic level. Although these studies have provided significant information regarding the connection between dental caries and oral microbiomes, further comprehension of this microbial community’s ecological relevance is limited. This study identified the carbon source metabolic differences in dental plaque between children with and without ECC. We compared the microbial community functional diversity in 18 caries-free subjects with 18 severe ECC patients based on sole carbon source usage using a Biolog assay. The anaerobic microbial community in the ECC patients displayed greater metabolic activity than that of the control group. Specific carbon source metabolism differed significantly between the two groups. Subjects from the two groups were well distinguished by cluster and principal component analyses based on discriminative carbon sources. Our results implied that the microbial functional diversity between the ECC patients and healthy subjects differed significantly. In addition, the Biolog assay furthered our understanding of oral microbiomes as a composite of functional abilities, thus enabling us to identify the ecologically relevant functional differences among oral microbial communities.