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Oral microecological balance is closely associated with the development of dental caries. Oxidative stress is one of the important factors regulating the composition and structure of the oral microbial community. Streptococcus mutans is linked to the occurrence and development of dental caries. The ability of S. mutans to withstand oxidative stress affects its survival competitiveness in biofilms. The oxidative stress regulatory mechanisms of S. mutans include synthesis of reductase, regulation of metal ions uptake, regulator PerR, transcription regulator Spx, extracellular uptake of glutathione, and other related signal transduction systems. Here, we provide an overview of how S. mutans adapts to oxidative stress and its influence on oral microecology, which may offer novel options to investigate the cariogenic mechanisms of S. mutans in the oral microenvironment, and new targets for the ecological prevention and treatment of dental caries. [ABSTRACT FROM AUTHOR]

AbstractDental caries, as a biofilm-related disease, is closely linked to dysbiosis in microbial ecology within dental biofilms. Beyond its impact on oral health, bacteria within the oral cavity pose systemic health risks by potentially entering the bloodstream, thereby increasing susceptibility to bacterial endocarditis, among other related diseases. Streptococcus mutans, a principal cariogenic bacterium, possesses virulence factors crucial to the pathogenesis of dental caries. Its ability to adhere to tooth surfaces, produce glucans for biofilm formation, and metabolize sugars into lactic acid contributes to enamel demineralization and the initiation of carious lesions. Its aciduricity and ability to produce bacteriocins enable a competitive advantage, allowing it to thrive in acidic environments and dominate in changing oral microenvironments. In contrast, commensal streptococci, such as Streptococcus sanguinis, Streptococcus gordonii, and Streptococcus salivarius, act as primary colonizers and compete with S. mutans for adherence sites and nutrients during biofilm formation. This competition involves the production of alkali, peroxides, and antibacterial substances, thereby inhibiting S. mutans growth and maintaining microbial balance. This dynamic interaction influences the balance of oral microbiota, with disruptions leading to shifts in microbial composition that are marked by rapid increases in S. mutans abundance, contributing to the onset of dental caries. Thus, understanding the dynamic interactions between commensal and pathogenic bacteria in oral microecology is important for developing effective strategies to promote oral health and prevent dental caries. This review highlights the roles and competitive interactions of commensal bacteria and S. mutans in oral microecology, emphasizing the importance of maintaining oral microbial balance for health, and discusses the pathological implications of perturbations in this balance. [ABSTRACT FROM AUTHOR]

Caries is a chronic infectious disease that occurs in the hard tissues of teeth. The interaction of oral microorganisms, host, food and time leads to the occurrence and progression of caries. Free sugar is an important food factor in the occurrence of dental caries. This paper reviews the research progress on the relationship between free sugar and caries in recent years, providing a reference for further clarifying the mechanism of the occurrence and progression of caries caused by free sugar and exploring the methods of caries prevention. The cariogenic mechanism of free sugar is multifaceted. Free sugar can not only be used by oral microorganisms in dental plaque biofilms to produce acid and synthesize intracellular and extracellular polysaccharides but also cause an imbalance in oral microecology and enhance gene expression related to the cariogenic toxicity of oral microorganisms. Based on the correlation between free sugar and caries, it is important to limit the intake amount and frequency of free sugar to prevent caries. This can be achieved mainly by formulating public health policies for reducing sugar, creating a low-sugar family environment with good eating habits, using sugar substitutes and using fluoride. There are few studies on the relationship between free sugar and oral microecology. More research is needed to better understand the effect of free sugar on oral microecology and its mechanism and to validate the caries-preventing effect of various sugar reduction measures. We believe such studies would open up new avenues for the effective prevention of caries.

Esophageal squamous cell carcinoma (ESCC) is a malignant tumor of the digestive system in the esophageal squamous epithelium. Many studies have linked esophageal cancer (EC) to the imbalance of oral microecology. In this work, different machine learning (ML) models including Random Forest (RF), Gaussian mixture model (GMM), K-nearest neighbor (KNN), logistic regression (LR), support vector machine (SVM) and extreme gradient boosting (XGBoost) based on Genetic Algorithm (GA) optimization was developed to predict the relationship between salivary flora and ESCC by combining the relative abundance data of Bacteroides, Firmicutes, Proteobacteria, Fusobacteria and Actinobacteria in the saliva of patients with ESCC and healthy control. The results showed that the XGBoost model without parameter optimization performed best on the entire dataset for ESCC diagnosis by cross-validation (Accuracy = 73.50%). Accuracy and the other evaluation indicators, including Precision, Recall, F1-score and the area under curve (AUC) of the receiver operating characteristic (ROC), revealed XGBoost optimized by the GA (GA-XGBoost) achieved the best outcome on the testing set (Accuracy = 89.88%, Precision = 89.43%, Recall = 90.75%, F1-score = 90.09%, AUC = 0.97). The predictive ability of GA-XGBoost was validated in phylum-level salivary microbiota data from ESCC patients and controls in an external cohort. The results obtained in this validation (Accuracy = 70.60%, Precision = 46.00%, Recall = 90.55%, F1-score = 61.01%) illustrate the reliability of the predictive performance of the model. The feature importance rankings obtained by XGBoost indicate that Bacteroides and Actinobacteria are the two most important factors in predicting ESCC. Based on these results, GA-XGBoost can predict and diagnose ESCC according to the relative abundance of salivary flora, providing an effective tool for the non-invasive prediction of esophageal malignancies.

Objective To explore from the perspective of microorganisms the changes in plaque microbial community of children with severe early childhood caries (S-ECC) before and 3 months after dental treatment. Meanwhile to show the effect of treatment on the maintenance of long- term caries-free state. Methods S-ECC children completed dental treatment under general anesthesia. We collected plaque from caries-free dental surfaces before treatment (caries, C) and at the postoperative follow-up review time points of 7 days (C-7D), 1 month (C-1 M), and 3 months (C-3 M). We included caries-free children (caries free, CF) as the control group to analyze the dynamic modification process of the plaque microbial community in the short-term pre- and postdental treatment. Results Species clustering analysis showed that the compositions of the microbial communities of the S-ECC and CF groups were highly similar. The α diversity index was not statistically significant (P>0.05). From the analysis of the relative abundance, Leptotrichia spp. and Aggregatibacter spp. decreased after treatment compared with before treatment (P

The oral microecological balance is closely associated with the development of dental caries. Oxidative stress is one of the important factors regulating the composition and structure of the oral microbial community. Streptococcus mutans is closely related to the occurrence and development of dental caries. The ability of S. mutans to withstand oxidative stress affects its survival competitiveness in biofilms. The oxidative stress regulatory mechanisms of S. mutans include the synthesis of reductase, the regulation of iron and manganese uptake by metalloregulatory proteins, transcription regulator Spx, extracellular uptake of glutathione and other related signal transduction systems. The current research focuses on how S. mutans adapts to a complex external environment through an oxidative stress response and its influence on oral microecology. We can design targeted small molecular compounds for key signaling pathways to inhibit oxidative stress and weaken the virulence of S. mutans, which is important for oral microecological modulation and dental caries prevention and treatment.

Objectives: This study aimed to evaluate the effectiveness of urushiol as an additive to surface acid etchant on dentin structure, by assessing the biostability of dentin, and determine the bonding strengths of dentin and enamel to the composite in the complicated oral microecology.Methods: Etchants with different concentrations of urushiol (0.5, 1, or 3 wt%) were formulated and tested for their bonding performance. Demineralized dentin beams that were etched with experimental etchants were incubated in simulated body fluid solutions by evaluating the weight decrement after 1 month. The effects of urushiol on dentin and matrix metalloproteinases were confirmed by scanning electron microscopy (SEM). Moreover, the antibiotic actions of urushiol on the common cariogenic bacteria Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii as well as the biofilm were evaluated, and its effect on bacterial morphology was observed by scanning electron microscopy. Finally, enamel and dentin specimens were prepared from human molars to determine the depth of demineralization by the etchants and the relationship with the resin bond strengths to enamel and dentin (μTBS) and the morphology of the bonding interface.Results: Urushiol could interact with dentine and inhibit collagenase activity, resulting in biostable dentine. The application of the etchants containing 0.5, 1, or 3 wt% urushiol significantly improved the durability of the dentin bonding interface with its instinctive antibacterial property (p < 0.05).Conclusion: Urushiol not only improves dentin stability by interacting with collagen and inactivating MMP activity but also plays a role in the antibacterial effects in the complicated oral microecology. The effectiveness of urushiol etchant prolongs the longevity of bonded dental restorations without compromising clinical operation time.

The caries-preventive effect of topical fluoride application has been corroborated by a number of clinical studies. However, the effect of fluoride on oral microecology remains unclear. To monitor the effect of fluoride on dental plaque microecology and demineralization/remineralization balance of enamel initial caries. Three-year-old children were enrolled and treated with fluoride at baseline and 6 months. International Caries Detection and Assessment System II indices of 52 subjects were measured at baseline, 3, 6, and 12 months. Supragingival plaque samples of 12 subjects were collected at baseline, 3 and 14 days for 16S rRNA sequencing. Changes in microbial community structure were observed at 3 days after fluoridation. Significant changes in the relative abundance of microorganisms were observed after fluoride application, especially Capnocytophaga, unidentified Prevotellaceae and Rothia. Functional prediction revealed that cell movement, carbohydrate and energy metabolism were affected significantly after fluoride application. Fluoride significantly inhibited enamel demineralization and promoted remineralization of early demineralized caries enamel at 3 months. Fluoride application significantly inhibited the progression of enamel initial caries and reversed the demineralization process, possibly by disturbing dental plaque microecology and modulating the physicochemical action of demineralization/remineralization. This deepened our understanding of caries-preventive effects and mechanisms of fluoride. [ABSTRACT FROM AUTHOR]

Varieties of microorganisms reside in the oral cavity contributing to the occurrence and development of microbes associated with oral diseases; however, the distribution and in situ abundance in the biofilm are still unclear. In order to promote the understanding of the ecosystem of oral microbiota and the diagnosis of oral diseases, it is necessary to monitor and compare the oral microorganisms from different niches of the oral cavity in situ. The fluorescence in situ hybridization (FISH) has proven to be a powerful tool for representing the status of oral microorganisms in the oral cavity. FISH is one of the most routinely used cytochemical techniques for genetic detection, identification, and localization by a fluorescently labeled nucleic acid probe, which can hybridize with targeted nucleic acid sequences. It has the advantages of rapidity, safety, high sensitivity, and specificity. FISH allows the identification and quantification of different oral microorganisms simultaneously. It can also visualize microorganisms by combining with other molecular biology technologies to represent the distribution of each microbial community in the oral biofilm. In this review, we summarized and discussed the development of FISH technology and the application of FISH in oral disease diagnosis and oral ecosystem research, highlighted its advantages in oral microbiology, listed the existing problems, and provided suggestions for future development.. [ABSTRACT FROM AUTHOR]

Background: The caries-preventive effect of topical fluoride application has been corroborated by a number of clinical studies. However, the effect of fluoride on oral microecology remains unclear. Objective: To monitor the effect of fluoride on dental plaque microecology and demineralization/remineralization balance of enamel initial caries. Methods: Three-year-old children were enrolled and treated with fluoride at baseline and 6 months. International Caries Detection and Assessment System II indices of 52 subjects were measured at baseline, 3, 6, and 12 months. Supragingival plaque samples of 12 subjects were collected at baseline, 3 and 14 days for 16S rRNA sequencing. Results: Changes in microbial community structure were observed at 3 days after fluoridation. Significant changes in the relative abundance of microorganisms were observed after fluoride application, especially Capnocytophaga, unidentified Prevotellaceae and Rothia. Functional prediction revealed that cell movement, carbohydrate and energy metabolism were affected significantly after fluoride application. Fluoride significantly inhibited enamel demineralization and promoted remineralization of early demineralized caries enamel at 3 months. Conclusion: Fluoride application significantly inhibited the progression of enamel initial caries and reversed the demineralization process, possibly by disturbing dental plaque microecology and modulating the physicochemical action of demineralization/remineralization. This deepened our understanding of caries-preventive effects and mechanisms of fluoride. [ABSTRACT FROM AUTHOR]

Varieties of microorganisms reside in the oral cavity contributing to the occurrence and development of microbes associated with oral diseases; however, the distribution and in situ abundance in the biofilm are still unclear. In order to promote the understanding of the ecosystem of oral microbiota and the diagnosis of oral diseases, it is necessary to monitor and compare the oral microorganisms from different niches of the oral cavity in situ. The fluorescence in situ hybridization (FISH) has proven to be a powerful tool for representing the status of oral microorganisms in the oral cavity. FISH is one of the most routinely used cytochemical techniques for genetic detection, identification, and localization by a fluorescently labeled nucleic acid probe, which can hybridize with targeted nucleic acid sequences. It has the advantages of rapidity, safety, high sensitivity, and specificity. FISH allows the identification and quantification of different oral microorganisms simultaneously. It can also visualize microorganisms by combining with other molecular biology technologies to represent the distribution of each microbial community in the oral biofilm. In this review, we summarized and discussed the development of FISH technology and the application of FISH in oral disease diagnosis and oral ecosystem research, highlighted its advantages in oral microbiology, listed the existing problems, and provided suggestions for future development..

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Esophageal squamous cell carcinoma (ESCC) is a malignant tumor of the digestive system in the esophageal squamous epithelium. Many studies have linked esophageal cancer (EC) to the imbalance of oral microecology. In this work, different machine learning (ML) models including Random Forest (RF), Gaussian mixture model (GMM), K-nearest neighbor (KNN), logistic regression (LR), support vector machine (SVM) and extreme gradient boosting (XGBoost) based on Genetic Algorithm (GA) optimization was developed to predict the relationship between salivary flora and ESCC by combining the relative abundance data of Bacteroides , Firmicutes , Proteobacteria , Fusobacteria and Actinobacteria in the saliva of patients with ESCC and healthy control. The results showed that the XGBoost model without parameter optimization performed best on the entire dataset for ESCC diagnosis by cross-validation (Accuracy = 73.50%). Accuracy and the other evaluation indicators, including Precision, Recall, F1-score and the area under curve (AUC) of the receiver operating characteristic (ROC), revealed XGBoost optimized by the GA (GA-XGBoost) achieved the best outcome on the testing set (Accuracy = 89.88%, Precision = 89.43%, Recall = 90.75%, F1-score = 90.09%, AUC = 0.97). The predictive ability of GA-XGBoost was validated in phylum-level salivary microbiota data from ESCC patients and controls in an external cohort. The results obtained in this validation (Accuracy = 70.60%, Precision = 46.00%, Recall = 90.55%, F1-score = 61.01%) illustrate the reliability of the predictive performance of the model. The feature importance rankings obtained by XGBoost indicate that Bacteroides and Actinobacteria are the two most important factors in predicting ESCC. Based on these results, GA-XGBoost can predict and diagnose ESCC according to the relative abundance of salivary flora, providing an effective tool for the non-invasive prediction of esophageal malignancies.

Objective The aim of this article was to study the variation in oral microflora of the subgingival plaque during and after radiotherapy. Design During and after radiotherapy, microbial samples were collected at seven time points (early stage, medium stage, and later stage of radiotherapy, and 1 month, 3 months, 6 months, and 1 year after radiotherapy) in three subjects for a total of 21 samples. Polymerase chain reaction (PCR) amplification was carried out on the 16S rDNA hypervariable V1–V3 region, and then the PCR products were determined by high-throughput pyrosequencing. Results The rarefaction curve indicating the richness of the microflora demonstrated that the number of operational taxonomic units (OTUs) was in decline from the early stage of radiotherapy to the time point 1 month after radiotherapy and then trended upward. The Shannon diversity index declined during radiotherapy (ranging from 4.59 to 3.73), and generally rose after radiotherapy, with the lowest value of 3.5 (1 month after radiotherapy) and highest value of 4.75 (6 months after radiotherapy). A total of 120 genera were found; five genera ( Actinomyces , Veillonella , Prevotella , Streptococcus , Campylobacter ) were found in all subjects across all time points. Conclusion The richness and diversity of oral ecology decreased with increased radiation dose, and it was gradually restored with time. [ABSTRACT FROM AUTHOR]

PURPOSE: To evaluate the effect of beryllium (Be2* on chemical elements of cell membrane and H2O2 production of Streptococcus oralis (S.oralis), thus to explore the microbiologie mechanisms of periodontal diseases which may occur after prosthodontic treatment. METHODS: S.oralis was put into artificial saliva with different Be2* concentration (5 mg/L, 10 mg/L, 20 mg/L and 40 mg/L) and anaerobic cultured for 24 hours. The amount of chemical elements in the membrane of S.oralis were tested with X-ray energy dispersive spectroscopy, and the H2O2, produced by S. oralis was detected with ABTS-HRP. The data were analyzed with one-way ANOVA using SPSS 11.0 software package. RESULTS: The amount of calcium in the cell membrane of beryllium treated S. oralis decreased, while the amount of phosphorus increased. Natrium increased with the increase of Be2* in the euhure, but changed contrarily when S. oralis was treated with 20mg/L Be2*. H2O2 produced by S. oralis reduced when the concentration of Be2* was at 40mg/L (P<0.05). CONCLUSIONS: Beryllium affects the amount of chemical elements in cell membrane and H2O2 production of S. oralis, which may result in a disturbance in the microecologic balance of subgingival microbes after proshodontic treatments and eventually contribute to periodontal diseases. Supported by Science Project of Department of Education of Zhejiang Province (Y200804029) and Science Foundation of Wenzhou Science and Technology Bureau (201150088) . [ABSTRACT FROM AUTHOR]

Lactobacilli have been considered as major contributors to human dental caries for over a century. Recent in vitro model studies have shown that when compared to Streptococcus mutans, a keystone pathogen of human dental caries, the ability of lactobacilli to form biofilms is poor, although differences exist between the different major species. Further studies using molecular and bioinformatics approaches provide evidence that multiple mechanisms, including adhesin-receptor mediated physical contact with S. mutans , facilitate the adherence and establishment of lactobacilli on the tooth surface. There is also evidence that under conditions like continuous sugar consumption, weak acids and other antimicrobials such as bacteriocins from lactobacilli can become detrimental to the microbial community, especially those in the proximity. Details on the underlying mechanisms of how different Lactobacillus sp. establish and persist in the highly complex microbiota on the tooth surface await further investigation.

Objective: To investigate the effect of oral appliance treatment on oral micro ecological environment of patients with malocclusion. Methods: 48 patients with malocclusion, who accepted the oral appliance treatment in the department of stomatology in our hospital, were selected. Oral microorganism were collected and cultured before and 1, 3, 6 months after the orthodontic treatment respectively. The changes of oral micro ecological environment before and after orthodontic treatment were observed and compared. Results: ① One month after the orthodontic treatment, streptococcus mutans and lactic acid bacteria in mouth was higher than before, and the difference of the detection rate of streptococcus mutans was statistically significant(P<0.05). After 3,6 months, the detection rate of streptococcus mutans, and lactic acid bacteria in mouth increased obviously than before, and the difference was statistically significant(P<0.05 or P<0.01). ② One month after the orthodontic treatment, the detection rate of porphyromonas gingivalis, actinobacillus actinomycetemcomitans and nucleic acid bacillus in mouth was higher than before, and the difference of the detection rate of porphyromonas gingivalis, actinobacillus actinomycetemcomitans was statistically significant(P<0.05). After 3,6 months, the detection rate of porphyromonas gingivalis, actinobacillus actinomycetemcomitans and nucleic acid bacillus was increased obviously than before,and the difference was statistically significant(P<0.05 or P<0.01). Conclusions: The application of oral appliance will destroy the balance of oral micro ecological environment, affect the teeth and periodontal health, which should be paid attention to so as to adopt prevention and intervention early for the patients with malocclusion. [ABSTRACT FROM AUTHOR]

Objective: To investigate the relationship between the composition of salivary microecology and thyroid-stimulating hormone (TSH) levels in healthy adults., Methods: Healthy subjects were included in the high-TSH group ( n =22, 3.00-4.20 mIU/L) and the low-TSH group ( n =24, 0.60-1.80 mIU/L) according to their TSH level. Clinical and laboratory examinations were conducted to measure and analyze the relevant clinical and biochemical indicators. Saliva samples were collected in the two groups and microbial genetic profiles were acquired by 16S rDNA sequencing and bioinformatics analysis., Results: There was no significant difference in the relevant clinical and biochemical indicators between the high-TSH group and the low-TSH group ( P >0.05). Individuals with higher TSH levels had higher abundance and species diversity of salivary microbiome. Partial least squares discriminant analysis (PLS-DA) found that the microecology of the the high-TSH group and the low-TSH group (Adonis, P =0.0460) showed obvious differences in β diversity. Wilcoxon rank-sum test and LEFSe analysis showed significant difference in the abundance of Fusobacterium between the high-TSH group and the low-TSH group., Conclusion: Differences in the composition of microecology were observed in the saliva of healthy subjects with high TSH levels and those with low TSH levels, and the abundance of Fusobacterium showed the most significant difference between the high and low TSH groups., (Copyright© by Editorial Board of Journal of Sichuan University (Medical Sciences).)

Hydrogen peroxide, an important antimicrobial agent in oral cavity, plays a significant role in the balance of oral microecology. At the early stage of biofilm formation, about 80% of the detected initial colonizers belong to the genus Streptococcus. These oral streptococci use different oxidase to produce hydrogen peroxide. Recent studies showed that the produced hydrogen peroxide plays a critical role in modulating oral microecology. Hydrogen peroxide modulates biofilm development attributed to its growth inhibitory nature. Hydrogen peroxide production is closely associated with extracellular DNA(eDNA) release from microbe and the development of its competent cell which are critical for biofilm development and also serves as source for horizontal gene transfer. Microbe also can reduce the damage to themselves through several detoxification mechanisms. Moreover, hydrogen peroxide is also involved in the regulation of interactions between oral microorganisms and host. Taken together, hydrogen peroxide is an imperative ecological factor that contributes to the microbial equilibrium in the oral cavity. Here we will give a brief review of both the origin and the function in the oral microecology balance of hydrogen peroxide.