Application of personalized templates in minimally invasive management of coronal dens invaginatus: a report of two cases.

BACKGROUND: Treating the coronal dens invaginatus (CDI) with pulp infection commonly involves the removal of invagination, which increases the risk of perforation and fracture, and compromises the tooth structure. Minimally invasive endodontic management of CDI is highly recommended. This report describes two cases of type II CDI with the application of personalized templates. CASE PRESENTATION: Two cases of type II CDI, affecting the main root canal in a maxillary canine and a lateral incisor, were diagnosed. A guided endodontics (GE) approach was applied. Cone-beam computed tomography and intraoral scans were imported and aligned in a virtual planning software to design debridement routes and templates. The MICRO principle (which involves the aspects of Mechanical (M) debridement, Irrigation (I), Access cavities (C), Rectilinear routes (R), and Obstruction (O)) was proposed for designing optimal debridement routes for future applications. The templates were innovatively personalized and designed to preserve the tooth structure maximally while effectively debriding the root canal. Root canal treatment with supplementary disinfection was then performed. The follow-up of the two patients revealed favorable clinical and radiographic outcomes. CONCLUSIONS: The GE approach could be a feasible method for preserving healthy dental structure while effectively debriding the root canal, thereby achieving successful and minimally invasive endodontic treatment for CDI.

Pudilan Keyanning mouthwash inhibits dextran-dependent aggregation and biofilm organization of Streptococcus mutans.

AIMS: This research aimed to investigate the inhibitory effects of Pudilan mouthwash (PDL) on Streptococcus mutans (S. mutans) biofilms and identify its chemical components. METHODS AND RESULTS: The impacts of 100% concentrated PDL on S. mutans biofilm were detected by colony-forming unit (CFU) assays, crystal violet staining, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and quantitative real-time PCR (qRT‒PCR). The biocompatibility with human gingival fibroblasts (HGFs) was evaluated by Cell-Counting-Kit-8 (CCK-8) assay. And chemical components were identified by UPLC-HRMS. PBS and 0.12% chlorhexidine were used as negative and positive controls, respectively. Results indicate early 8-h S. mutans biofilms are sensitive to PDL. Additionally, it leads to a decrease in bacterial activities and dextran-dependent aggregation in 24-h S. mutans biofilms. PDL significantly downregulates the gene expression of gtfB/C/D and smc. And 114 components are identified. CONCLUSIONS: PDL has an inhibitory effect on S. mutans and favorable biocompatibility. It has potential to be exploited as a novel anti-biofilm agent.

Sucrose selectively regulates Streptococcus mutans polysaccharide by GcrR.

Streptococcus mutans (S. mutans) is the principal etiological agent in cariogenesis because of its ability to metabolize sucrose into extracellular polysaccharides (EPS). The response regulators GcrR and VicR could regulate EPS metabolism, but with opposing regulatory functions. However, the cooperative interactions between gcrR and vicR regulating sucrose-selective EPS metabolism have not been fully elucidated. First, we constructed several dual-mutant strains (vicR + gcrR+, vicR and gcrR overexpression; vicR + gcrR-, vicR overexpression and gcrR deficient; ASvicRgcrR+, vicR low-expression and gcrR overexpression; ASvicRgcrR-, vicR low-expression and gcrR deficient) to clarify gtfB/gtfC expression levels were modulated by gcrR regardless of the vicR gene expression levels. Next, we found gcrR deletion mutant (SmugcrR) displayed obvious auto-aggregation and bacterial cells were densely packed in enriched EPS induced by sucrose. In the contrast, SmugcrR biofilm showed very little carbohydrate-dependent aggregation in the absence of sucrose. The presence of sucrose amplifies the negative regulation of gcrR acting as a 'switch-off'. After sucrose induction, dexA gene expression was significantly enhanced in gcrR overexpression mutant (SmugcrR+). Furthermore, GcrR was shown to directly bind to the promoter region of the dexA gene. Taken together, our results reveal that GcrR interacts with VicR to block EPS biosynthesis via polysaccharide digestion by DexA, and that this process is induced in a sucrose-selective manner. Hence, targeting GcrR is a potential strategy for the management of dental caries.

A Dentin Biomimetic Remineralization Material with an Ability to Stabilize Collagen.

The integrity of collagen matrix structure is a prerequisite for effectively inducing biomimetic remineralization. Repeated low pH stimulation activates matrix metalloproteinases (MMPs) in dental caries. Activated MMPs cause the breakdown of collagen fibrils. Collagen stabilization is a major obstacle to the clinical application of remineralization templates. Here, galardin-loaded poly(amido amine) (PAMAM)-NGV (PAMAM-NGV@galardin, PNG) is constructed to induce collagen stabilization and dentin biomimetic remineralization simultaneously, in order to combat early caries in dentin. PAMAM acts in the role of nucleation template for dentin remineralization, while galardin acts as the role of MMPs inhibitor. NGV peptides modified on the surface of dendrimer core can form small clusters with synergistic movement in short range, and those short-range clusters can form domain areas with different properties on the surface of PAMAM core and restrict the movement of collagen, favoring collagen crosslinking, which can be explained through the computational simulation analysis results. NGV peptides and galardin show a dual collagen-protective effect, laying the foundation for the dentin remineralization effect induced by PAMAM. PNG induces dentin remineralization in an environment with collagenase, meanwhile showsing anti-dentin caries efficacy in vivo. These findings indicate that PNG has great potential to combat early dentin caries for future clinical application.

Evaluation of the ability of adhesives with antibacterial and remineralization functions to prevent secondary caries in vivo.

OBJECTIVE: The bonding interface of dental filling therapy is the weak point in resisting secondary caries. Adhesives containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) have been demonstrated in vitro to prevent bacteria from producing acid and to promote tooth remineralization. The present study aimed to evaluate the efficacy of adhesive with NACP and DMAHDM to prevent secondary caries in vivo. MATERIALS AND METHODS: Artificial cavities were created on the first molar on both sides of the maxillary in a rat model. One side was treated with adhesive containing NACP + DMAHDM, while on the other side, a commercial adhesive served as control. After 24 days of cariogenic feeding, the degree of secondary caries was evaluated by micro-CT and a modified Keyes scoring method. Quantitative real-time PCR (qPCR) and colony-forming unit (CFU) counts were used to evaluate the antibacterial efficacy of the materials. Biocompatibility was also investigated. RESULTS: In the rat model, the adhesive with NACP + DMAHDM showed excellent biocompatibility and effectively decreased the amount of bacteria. The experimental group demonstrated excellent remineralization effectiveness, with a lower modified Keyes score and mineral loss of 34.16 ± 2.13 vol% µm, compared with 77.44 ± 7.22 vol% µm in the control group, according to micro-CT (P < 0.05), showing excellent capacity to inhibit secondary caries. CONCLUSIONS: The NACP-DMAHDM-containing adhesive exhibited good performance in preventing secondary caries in vivo. CLINICAL RELEVANCE: Adhesives containing NACP and DMAHDM have great potential for use in clinical dentistry to prevent secondary caries by inhibiting bacterial growth and promoting remineralization.

The rnc Gene Regulates the Microstructure of Exopolysaccharide in the Biofilm of Streptococcus mutans through the ß-Monosaccharides.

Streptococcus mutans is known as the crucial pathogen of human dental caries, owing to its contribution to the biofilm development via the capacity of synthesizing exopolysaccharide (EPS), which mainly compose of α-glycosidic bond and ß-glycosidic bond. ß-glycosidic bond is less flexible than α-glycosidic bond because of differences between their configurational properties. Previous studies have shown that the rnc gene is implicated in the EPS formation and the cariogenicity of S. mutans. However, the effects of rnc on the microstructure of EPS have been not well-understood yet. Here, we further investigated how the rnc gene worked to modulate microstructural properties of the extracellular polysaccharide of S. mutans using glycomics methods. The gas chromatography-mass spectrometer showed that the proportion of glucose was decreased in water-soluble EPS and galactose was absent in water-insoluble EPS from the S. mutans rnc-deficient strain (Smurnc), compared with the isogenic wild-type strain (UA159). The composition of functional groups and the displacement of hydrogen bond were analyzed by infrared radiation and 1H nuclear magnetic resonance, respectively. In addition, phenotypic modulation of the biofilm matrix was assessed by microscopy. We found that the EPS of UA159 and the rnc overexpression strain (Smurnc+) mainly consisted of ß-glycosidic bonds. Conversely, the EPS of Smurnc were made up of mostly α-glycosidic bonds, leading to the attenuation of biofilm biomass and bacterial adhesion. Furthermore, the existence of ß-glycosidic bond was verified by enzyme digestion. Collectively, the rnc gene modulates the conversion of ß-glycosidic bonds, which may play important roles in regulating the micromolecule structure of the EPS matrix, thus affecting the characteristics of S. mutans biofilm. These data illustrate that ß-glycosidic bonds mediated by rnc may be potential targets for the prevention and treatment of dental caries.

The impact of diabetes on periodontal diseases.

The susceptibility and severity of periodontal diseases is made more severe by diabetes, with the impact on the disease process inversely proportional to the level of glycemic control. Although type 1 diabetes mellitus and type 2 diabetes mellitus have different etiologies, and their impact on bone is not identical, they share many of the same complications. Studies in animals and humans agree that both forms of diabetes increase inflammatory events in periodontal tissue, impair new bone formation, and increase expression of RANKL in response to bacterial challenge. High levels of glucose, reactive oxygen species, and advanced glycation end-products are found in the periodontium of diabetic individuals and lead to increased activation of nuclear factor-kappa B and expression of inflammatory cytokines such as tumor necrosis factor and interleukin-1. Studies in animals, moreover, suggest that there are multiple cell types in periodontal tissues that are affected by diabetes, including leukocytes, vascular cells, mesenchymal stem cells, periodontal ligament fibroblasts, osteoblasts, and osteocytes. The etiology of periodontal disease involves the host response to bacterial challenge that is affected by diabetes, which increases the expression of RANKL and reduces coupled bone formation. In addition, the inflammatory response also modifies the oral microbiota to render it more pathogenic, as demonstrated by increased inflammation and bone loss in animals where bacteria are transferred from diabetic donors to germ-free hosts compared with transfer from normoglycemic donors. This approach has the advantage of not relying upon limited knowledge of the specific bacterial taxa to determine pathogenicity, and examines the overall impact of the microbiota rather than the presumed pathogenicity of a few bacterial groups. Thus, animal studies have provided new insights into pathogenic mechanisms that identify cause-and-effect relationships that are difficult to perform in human studies.

Brick tea consumption is a risk factor for dental caries and dental fluorosis among 12-year-old Tibetan children in Ganzi.

Brick tea contains high concentration of fluoride. The aim of the present work was to explore whether and how the brick tea is a risk factor for dental caries and dental fluorosis among Tibetan children in Ganzi. A cross-sectional study was conducted with 368 12-year-old Tibetan children in Ganzi. Dental caries was measured by DMFT index, and dental fluorosis severity was measured by Dean's Index. Community Fluorosis Index was used to estimate public health significance of dental fluorosis. Oral health-related behaviors and awareness, dietary habits and socioeconomic status were determined by a questionnaire. Bivariate and multivariate analyses were used to determine risk factors associated with dental caries and dental fluorosis. Dental caries prevalence was 37.50%, mean DMFT was 0.84 ± 1.53, while dental fluorosis prevalence was 62.23%. Community Fluorosis Index was 1.35, indicating a medium prevalent strength of dental fluorosis. Dental fluorosis was associated with mother's regular consumption of brick tea and residence altitude, and dental caries was associated with mother's regular consumption of brick tea. Mother's regular consumption of brick tea was a risk factor for both dental fluorosis and dental caries among children. Reducing mother's brick tea consumption during pregnancy and lactation may improve oral health status of their children.

Structural equation modelling for associated factors with dental caries among 3-5-year-old children: a cross-sectional study.

BACKGROUND: The aim of the current study was to explore the factors influencing dental caries among 3-5-year-old children in Sichuan Province and the interrelationship between these factors using structural equation modelling (SEM). METHODS: A cross-sectional study was conducted among 2746 3-5-year-old children in Sichuan Province. Examination of caries was conducted on all children and a questionnaire was answered by the children's caregiver. SEM alternative models were constructed to interpret the intricate relationships between socio-economic status (SES), caregiver's oral health knowledge, attitudes, children's oral health behaviours and children's dental caries. RESULT: The results showed that dental caries were significantly associated with dietary behaviours (ß = 0.11, SE = 0.03, P = 0.001, BC 95% CI =0.05/0.18) and SES (ß = - 0.17, SE = 0.03, P<0.001, BC 95% CI = -0.23/- 0.10) directly, While the indirect effect of SES on dmft is in an opposite direction (ß = 0.08, SE = 0.02, BC 95% CI = 0.04/0.12). CONCLUSION: We found that unhealthy dietary behaviours increased the prevalence of dental caries. However, oral health knowledge and attitude failed to affect dietary behaviour in this model. This result warns that oral health education should strengthen feeding-related knowledge. Meanwhile, it also reminds that it is easier known than done. Future oral health education should focus on exploring a more effective way for the public to turn knowledge into action.

The Regulator Gene rnc Is Closely Involved in Biofilm Formation in Streptococcus mutans.

Streptococcus mutans is an important factor in the etiology and pathogenesis of dental caries, largely owing to its ability to form a stable biofilm. Previous animal studies have indicated that rnc could decrease the amount of sulcal caries, and that the downregulation of cariogenicity might be due to its capacity to disrupt biofilm formation. However, the biofunctions by which rnc is involved in biofilm formation remain to be elucidated. In this study, we further investigate the role of rnc based on the study of mature biofilm. Scanning electron microscopy and the crystal violet assay were used to detect the biofilm forming ability. The production and distribution of exopolysaccharides within biofilm was analyzed by exopolysaccharide staining. Gel permeation chromatography was used to perform molecular weight assessment. Its adhesion force was measured by atomic force microscopy. The expression of biofilm formation-associated genes was analyzed at the mRNA level by qPCR. Here, we found that rnc could occur and function in biofilm formation by assembling well-structured, exopolysaccharide-encased, stable biofilms in S. mutans. The weakened biofilm forming ability of rnc-deficient strains was associated with the reduction of exopolysaccharide production and bacterial adhesion. Over all, these data illustrate an interesting situation in which an unappreciated regulatory gene acquired for virulence, rnc, most likely has been coopted as a potential regulator of biofilm formation in S. mutans. Further characterization of rnc may lead to the identification of a possible pathogenic biofilm-specific treatment for dental caries.

Effects of combined exogenous dextranase and sodium fluoride on Streptococcus mutans 25175 monospecies biofilms.

PURPOSE: To investigate the effects of exogenous dextranase and sodium fluoride on a S. mutans monospecies biofilm. METHODS: S. mutans 25175 was grown in tryptone soya broth medium, and biofilm was formed on glass slides with 1.0% sucrose. Exogenous dextranase and sodium fluoride were added alone or together. The biofilm morphology was analyzed by confocal laser scanning microscopy. The effects of the drug on the adhesion and exopolysaccharide production by the biofilms were evaluated by scintillation counting and the anthrone method, respectively. RESULTS: In this study, we found that the structure of initial biofilm and mature biofilm were partly altered by dextranase and high concentrations of sodium fluoride separately. However, dextranase combined with a low concentration of sodium fluoride could clearly destroy the typical tree-like structure of the biofilm, and led to less bacterial adhesion than when the dextranase or fluoride were used alone (P < 0.05). The amounts of soluble and insoluble exopolysaccharide were significantly reduced by combining dextranase with a low concentration of sodium fluoride, much more than when they were used alone (P < 0.05). These data indicate that dextranase and a low concentration of sodium fluoride may have synergistic effects against S. mutans biofilm and suggest the application of a low concentration of sodium fluoride in anticaries treatment.

A Chinese herb preparation, honokiol, inhibits Streptococcus mutans biofilm formation.

OBJECTIVE: This study aimed to investigate the antibiofilm and anticariogenic effects of honokiol, a traditional Chinese medicine, on the cariogenic bacterium Streptococcus mutans (S. mutans). DESIGN: The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of honokiol on S. mutans UA159 were measured. Then, S. mutans were treated with honokiol at concentrations of 1/2 MIC and 1/4 MIC. Extracellular polysaccharide (EPS) synthesis was assessed with confocal laser scanning microscopy (CLSM) and the anthrone-sulfuric method. Crystal violet staining and scanning electron microscopy (SEM) were used to demonstrate the characteristics and morphology of S. mutans biofilms. Colony-forming unit (CFU) assay was performed to observe the antibacterial effect of honokiol. Lactic acid production of 24-h biofilms was measured by the lactic acid assay. The expression level of caries-related genes (gtfB/C/D, comD/E and ldh) was identified by quantitative real-time PCR (qRTPCR) to explore the relevant mechanism. And the cytotoxic effect on human gingival fibroblasts (HGFs) was evaluated by the Cell Counting Kit-8 (CCK-8) assay. RESULTS: The MIC and MBC of honokiol on S. mutans were 30 µg/mL and 60 µg/mL, respectively. Honokiol inhibited biofilm formation, EPS synthesis and lactic acid production. It also decreased the expression of glucosyltransferases (Gtfs) and quorum sensing (QS) system encoding genes. Moreover, honokiol showed favorable biocompatibility with HGFs. CONCLUSIONS: Honokiol has an inhibitory effect on S. mutans and favorable biocompatibility, with application potential as a novel anticaries agent.

Spermine-starch nanoparticles with antisense vicR suppress Streptococcus mutans cariogenicity.

Dental caries of permanent teeth is a common public health concern and has the second-highest incidence among global diseases. The exopolysaccharides (EPS) synthesized by Streptococcus mutans (S. mutans) are the principal virulence factor for cariogenic etiology. We previously discovered that an endogenous antisense vicR RNA (ASvicR) could significantly inhibit EPS synthesis in S. mutans and reduce its cariogenicity. However, ASvicR cannot be directly applied in the oral environment. An appropriate vector is of great need to protect ASvicR from being degraded by nucleases for effective gene delivery to S. mutans. Functionally modified starches shed light on this field because of their excellent biocompatibility and biodegradability. In this study, a biocompatible and biodegradable spermine-starch nanocomposite (SSN) was constructed for ASvicR delivery. Starch was cationically functionalized by grafting endogenous spermine to closely bind with the recombinant ASvicR plasmid. The SSN not only protected the recombinant ASvicR plasmid from DNase I but also achieved highly efficient gene transformation to S. mutans via the hydrolysis of α-amylase in the saliva. In addition, SSN-ASvicR was shown to endow ASvicR with an increasing transformation efficiency approximately four times that of the naked ASvicR plasmid, as well as allowing for targeting specificity to the transcription of the vicR gene and the suppression of biofilm organization via EPS digestion. In particular, SSN-ASvicR nanoparticles exhibited excellent biological safety and maintained oral microbiota homeostasis in vivo. The SSN can be prepared in a ready-to-use formulation for targeting cariogenic bacteria, thus demonstrating important prospects in the prevention of dental caries.

An engineered dual-functional peptide with high affinity to demineralized dentin enhanced remineralization efficacy in vitro and in vivo.

Dental caries continues to be a major global public health problem. Remineralization of demineralized dentin is regarded as one of the hotspots in the current study in the treatment of dental caries. However, traditional remineralization agents, which usually lack the ability to bind to demineralized dentin collagen, are easily removed by the fluids in the oral cavity, thus decreasing the remineralization efficacy. Non-collagenous proteins (NCPs) have significant effects on the biomineralization of dentin due to their dual high binding capacity to the collagen fibers and minerals. But NCPs are hard to extract, store and use directly. Inspired by the biological behavior of NCPs, in this study, we selected two functional sequences of NCPs to develop a novel and engineered dual-functional peptide (which is referred to as CYP) with collagen-binding and mineral-absorbing capability. The binding ability of CYP to collagen fibers and demineralized dentin was investigated, and the results suggested that CYP was endowed with good binding capacity to demineralized dentin, which could resist the washing of the fluid. In addition, we confirmed that CYP exerted formidable remineralization effects in collagen fibers and demineralized dentin following an in vitro remineralization regimen. Furthermore, the dual functions of CYP with good biocompatibility can simultaneously bind collagen and induce nanocrystal precipitation, thereby significantly absorbing calcium and phosphorus ions to form regenerated minerals for reversing the tooth decay process in the rat caries model. Overall, the dual functional peptide CYP fabricated in this study provides an ideal and smart strategy for dentin remineralization and the treatment of caries.

Drug delivery systems for oral disease applications.

There are many restrictions on topical medications for the oral cavity. Various factors affect the topical application of drugs in the oral cavity, an open and complex environment. The complex physical and chemical environment of the oral cavity, such as saliva and food, will influence the effect of free drugs. Therefore, drug delivery systems have served as supporting structures or as carriers loading active ingredients, such as antimicrobial agents and growth factors (GFs), to promote antibacterial properties, tissue regeneration, and engineering for drug diffusion. These drug delivery systems are considered in the prevention and treatment of dental caries, periodontal disease, periapical disease, the delivery of anesthetic drugs, etc. These carrier materials are designed in different ways for clinical application, including nanoparticles, hydrogels, nanofibers, films, and scaffolds. This review aimed to summarize the advantages and disadvantages of different carrier materials. We discuss synthesis methods and their application scope to provide new perspectives for the development and preparation of more favorable and effective local oral drug delivery systems.

Science Popularization Education regarding Oral Health-General Health for Nonmedical Undergraduates Applying a SPOC Teaching Model.

Objective: To see how effective a blended teaching model based on a small private online course (SPOC) is in a science popularization education course on oral health-general health (OHGH). Methods: The SPOC blended teaching model was created using an elective classroom course "Oral Prophylaxis and Hygiene" in conjunction with an online learning course called "Preventive Dentistry" from the China University massive open online course (MOOC) for the science popularization education on OHGH. Students' evaluations and teaching efficacy of this science popularization education course were tested using pre- and postcourse questionnaires. Results: In all, 105 valid questionnaires were returned. Before the course, 95.2% of the students expressed an interest in learning more knowledge on oral disease and OHGH. When compared to those of the precourse, students' knowledge of oral diseases and OHGH was significantly higher (P < 0.0001) and the associated practice after science popularization education was much increased (P < 0.0001 or P = 0.0005), except for root canal therapy (P = 0.3886). The scores of students on the scientific popularization task also improved when compared to those of the previous classroom-only teaching (P < 0.0001). In the postcourse questionnaire, students rated the SPOC teaching mode significantly higher than both online learning and classroom teaching alone (P < 0.0001; P = 0.0117); the SPOC blended teaching was judged as more suitable for science popularization education (P < 0.0001). Conclusion: The application of the SPOC teaching mode for the science popularization education course on OHGH to nonmedical undergraduates has better teaching outcomes and is more likely to be accepted by college students.

Dual-functional adhesive containing amorphous calcium phosphate nanoparticles and dimethylaminohexadecyl methacrylate promoted enamel remineralization in a biofilm-challenged environment.

OBJECTIVE: The cariogenic biofilm on enamel, restoration, and bonding interface is closely related to dental caries and composite restoration failure. Enamel remineralization at adhesive interface is conducive to protecting bonding interface and inhibiting secondary caries. This study intended to assess the remineralization efficiency of adhesive with dimethylaminohexadecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on initial caries lesion of biofilm-coated enamel. METHODS: Artificial initial carious lesion was created via 72-hour immersion in demineralization solution and cariogenic biofilm was formed after 24-hour culture of Streptococcus mutans (S. mutans). Specimens were then divided into 4 groups: enamel control, enamel treated with NACP, DMAHDM and NACP+DMAHDM respectively. Samples next underwent 7-day cycling, 4 h in BHIS (brain heart infusion broth containing 1 % sucrose) and 20 h in AS (artificial saliva) per day. The pH of BHIS was tested daily. So did the concentration of calcium and phosphate in BHIS and AS. Live/dead staining, colony-forming unit (CFU) count, and lactic acid production of biofilms were measured 7 days later. The enamel remineralization efficiency was evaluated by microhardness testing and transverse microradiography (TMR) quantitatively. RESULTS: Enamel of NACP+DMAHDM group demonstrated excellent remineralization effectiveness. And the NACP+DMAHDM adhesive released a great number of Ca2+ and PO43- ions, increased pH to 5.81 via acid neutralization, decreased production of lactic acid, and reduced CFU count of S. mutans (P < 0.05). SIGNIFICANCE: The NACP+DMAHDM adhesive would be applicable to preventing secondary caries, strengthening enamel-adhesive interface, and extending the lifespan of composite restoration.

Derivation of a Risk Score for High Caries Risk in 3- to 5-year-old Children in Sichuan Province.

PURPOSE: To explore potential caries risk indicators in 3- to 5-year-old children, and develop a simple risk-score model to screen the children at high risk of caries with decayed, filled, and missing teeth (dmft) > 2. MATERIALS AND METHODS: A cross-sectional study involving 2746 children 3 to 5 years of age was conducted in Sichuan province. Children were examined for dmft index, and sociodemographic and behavioural factors were acquried through a questionnaire completed by their caregivers. A prediction model was developed by backward multivariate logistic regression, and its overfitting degree was examined with 5-fold cross-validation. A simple risk-score model was derived to screen the children with dmft > 2 at high risk of caries with the ß regression coefficient obtained from the multivariate regression model. RESULTS: A child's oral health status was identified as the highest risk indicator with a ß regression coefficient of 1.093. The mean area under curve (AUC) from the 5-fold cross-validation was 0.7408 (95% CI: 72.21%, 75.95%), with a bias of only ca 1%. This result allowed us to eliminate substantial overfitting of the prediction model. The AUC of the risk scoring system was 0.7455 (95% CI: 72.70%, 76.40%), which indicated good screenability. CONCLUSIONS: This risk score model has the advantages of simplicity, low cost and relatively high accuracy, and is suitable for use in developing countries, especially for primary screening for high risk of caries. It shows that certain child behaviours and parental attitude play an important role in dental caries among preschool children.

The vicK gene of Streptococcus mutans mediates its cariogenicity via exopolysaccharides metabolism.

Streptococcus mutans (S. mutans) is generally regarded as a major contributor to dental caries because of its ability to synthesize extracellular polysaccharides (EPS) that aid in the formation of plaque biofilm. The VicRKX system of S. mutans plays an important role in biofilm formation. The aim of this study was to investigate the effects of vicK gene on specific characteristics of EPS in S. mutans biofilm. We constructed single-species biofilms formed by different mutants of vicK gene. Production and distribution of EPS were detected through atomic force microscopy, scanning electron microscopy and confocal laser scanning microscopy. Microcosmic structures of EPS were analyzed by gel permeation chromatography and gas chromatography-mass spectrometry. Cariogenicity of the vicK mutant was assessed in a specific pathogen-free rat model. Transcriptional levels of cariogenicity-associated genes were confirmed by quantitative real-time polymerase chain reaction. The results showed that deletion of vicK gene suppressed biofilm formation as well as EPS production, and EPS were synthesized mostly around the cells. Molecular weight and monosaccharide components underwent evident alterations. Biofilms formed in vivo were sparse and contributed a decreased degree of caries. Moreover, expressional levels of genes related to EPS synthesis were down-regulated, except for gtfB. Our report demonstrates that vicK gene enhances biofilm formation and subsequent caries development. And this may due to its regulations on EPS metabolism, like synthesis or microcosmic features of EPS. This study suggests that vicK gene and EPS can be considered as promising targets to modulate dental caries.

Regulating Oral Biofilm from Cariogenic State to Non-Cariogenic State via Novel Combination of Bioactive Therapeutic Composite and Gene-Knockout.

The objectives were to investigate a novel combination of gene-knockout with antimicrobial dimethylaminohexadecyl methacrylate (DMAHDM) composite in regulating oral biofilm from a cariogenic state toward a non-cariogenic state. A tri-species biofilm model included cariogenic Streptococcus mutans (S. mutans), and non-cariogenic Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii). Biofilm colony-forming-units (CFUs), lactic acid and polysaccharide production were measured. TaqMan real-time-polymerase-chain reaction was used to determine the percentage of each species in biofilm. The rnc gene-knockout for S. mutans with DMAHDM composite reduced biofilm CFU by five logs, compared to control (p < 0.05). Using parent S. mutans, an overwhelming S. mutans percentage of 68.99% and 69.00% existed in biofilms on commercial composite and 0% DMAHDM composite, respectively. In sharp contrast, with a combination of S. mutans rnc knockout and DMAHDM composite, the cariogenic S. mutans percentage in biofilm was reduced to only 6.33%. Meanwhile, the non-cariogenic S. sanguinis + S. gordonii percentage was increased to 93.67%. Therefore, combining rnc-knockout with bioactive and therapeutic dental composite achieved the greatest reduction in S. mutans, and the greatest increase in non-cariogenic species, thereby yielding the least lactic acid-production. This novel method is promising to obtain wide applications to regulate biofilms and inhibit dental caries.