Oral microbial communities in 5-year-old children with versus without dental caries.

BACKGROUND: Caries in young children has received more and more attention. The study of the oral microbiota may help to understand the polymicrobial etiology of dental caries. OBJECTIVES: To investigate the diversity and structure of microbial communities in saliva samples from 5-year-old children with versus without dental caries. METHODS: A total of 36 saliva samples were collected from 18 children with high caries (HB group) and from 18 children without caries (NB group). Then, 16S rDNA was amplified from bacterial samples using polymerase chain reaction, and high-throughput sequencing was performed using Illumina Novaseq platforms. RESULTS: Sequences were clustered into operational taxonomic units (OTUs), which were distributed among 16 phyla, 26 classes, 56 orders, 93 families, 173 genera, and 218 species. Firmicutes, Bacteroides, Proteobacteria, Actinobacteria, Fusobacteria, Patescibacteria, Epsilonbacteraeota, Cyanobacteria, Acidobacteria and Spirochaetes were basically the same in different groups, but their relative abundances were different. The core microbiome was defined as the species from 218 shared microbial taxa. The alpha diversity test showed that there were no significant differences in microbial abundance and diversity between the high caries and no caries groups. The results from principal coordinate analysis (PCoA) and hierarchical clustering showed that the two groups had similar microorganisms. The biomarkers of different groups were defined by LEfSe analysis to identify potential caries-related and health-related bacteria. Co-occurrence network analysis of dominant genera showed that oral microbial communities in the no caries group were more complex and aggregated than those in the high caries group. Finally, the PICRUSt algorithm was used to predict the function of the microbial communities from saliva samples. The obtained results showed that mineral absorption was greater in the no caries group than in the high caries group. BugBase was used to determine phenotypes present in microbial community samples. The obtained results showed that Streptococcus was greater in the high caries group than in the no caries group. CONCLUSION: Findings of this study provide a comprehensive understanding of the microbiological etiology of dental caries in 5-year-old children and are expected to provide new methods for its prevention and treatment.

LIPUS inhibited the expression of inflammatory factors and promoted the osteogenic differentiation capacity of hPDLCs by inhibiting the NF-κB signaling pathway.

BACKGROUND AND OBJECTIVES: As a chronic infectious disease, periodontitis could lead to tooth and bone loss. Low-intensity pulsed ultrasound (LIPUS) is a safe, noninvasive treatment method to effectively inhibit inflammation and promote bone differentiation. However, the application of LIPUS in curing periodontitis is still rare. Our study aimed to explore the ability of LIPUS to inhibit inflammatory factors and promote the osteogenic differentiation capacity of human periodontal ligament cells (hPDLCs), and its underlying mechanism. MATERIAL AND METHODS: Human periodontal ligament cells were obtained and cultured from the premolar tissue samples for experiments. First, hPDLCs were treated for 24 hours using lipopolysaccharide (LPS) and then exposed to LIPUS (10 mW/cm2 , 30 mW/cm2 , 60 mW/cm2 , and 90 mW/cm2 ) to determine the appropriate intensity to inhibit expression of the inflammatory factors interleukin-6 (IL-6) and interleukin-8 (IL-8) expression. The expression of IL-6 and IL-8 was detected by real-time PCR and enzyme-linked immunosorbent assay. The safety of the most appropriate intensity of LIPUS was tested by a cell counting kit 8 test and an apoptosis assay. Then, LPS-induced hPDLCs were treated in osteogenic medium for 7-21 days with or without LIPUS (90 mW/cm2 , 30 min/d) stimulation. The osteogenic genes RUNX2, OPN, OSX, and OCN were measured by real-time PCR. Additionally, osteogenic differentiation capacity was determined using alkaline phosphatase (ALP) staining, ALP activity analysis, and Alizarin red staining. The activity of the nuclear factor-kappa B (NF-κB) signaling pathway was determined by western blotting, real-time PCR, immunofluorescence, and pathway blockade assays. RESULTS: Lipopolysaccharide significantly upregulated the production and gene expression of IL-6 and IL-8, while LIPUS stimulation significantly inhibited IL-6 and IL-8 expression in an intensity-dependent manner. LIPUS (90 mW/cm2 ) was chosen as the most appropriate intensity, and there was no detrimental influence on cell proliferation and status with or without osteogenic medium. In addition, consecutive stimulation with LIPUS (90 mW/cm2 ) for 30 min/d for 7 days could also inhibit IL-6 and IL-8 gene expression, upregulate the expression of the osteogenesis-related genes RUNX2, OPN, OSX, and OCN, and promote osteogenic differentiation capacity in osteogenic medium in inflamed hPDLCs. The NF-κB signaling pathway was inhibited with LIPUS (90 mW/cm2 ) via inhibition of the phosphorylation of IκBα and the translocation of p65 into the nucleus in inflamed hPDLCs. Additional investigations of the NF-κB inhibitor, BAY 11-7082, revealed that LIPUS (90 mW/cm2 ) acted similarly to BAY 11-7802 to inhibit the NF-κB signaling pathway and increase osteogenesis-related genes and promote the osteogenic differentiation capacity of inflamed hPDLCs. CONCLUSION: Low-intensity pulsed ultrasound (90 mW/cm2 ) stimulation could be a safe method to inhibit IL-6 and IL-8 in hPDLCs by inhibiting the NF-κB signaling pathway. The effect of LIPUS (90 mW/cm2 ) and BAY 11-7082 on LPS-induced inflammation demonstrated that both of these agents were capable of promoting osteogenesis-related gene expression and osteogenic differentiation in hPDLCs, suggesting that the effect of LIPUS on the promotion of osteogenic activity could be mediated in part through its ability to inhibit the NF-κB signal pathway. Hence, LIPUS could be a potential therapeutic method to cure periodontitis.

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.

Untargeted metabolomics of saliva in pregnant women with and without gestational diabetes mellitus and healthy non-pregnant women.

Objective: The aim of this study was to compare the differences in salivary metabolites between pregnant women with gestational diabetes mellitus (GDM), healthy pregnant women (HPW), and healthy non-pregnant women (HNPW), and analyze the possible associations between the identified metabolites and gingivitis. Method: The study included women with GDM (n = 9, mean age 28.9 ± 3.6 years, mean gestational age 30.1 ± 3.2 weeks), HPW (n = 9, mean age 27.9 ± 3.0 years, mean gestational age 28.6 ± 4.7 weeks), and HNPW (n = 9, mean age 27.7 ± 2.1 years). Saliva samples were collected from all participants and were analyzed with LC-MS/MS-based untargeted metabolomic analysis. Metabolite extraction, qualitative and semi-quantitative analysis, and bioinformatics analysis were performed to identify the differential metabolites and metabolic pathways between groups. The identified differential metabolites were further analyzed in an attempt to explore their possible associations with periodontal health and provide evidence for the prevention and treatment of periodontal inflammation during pregnancy. Results: In positive ion mode, a total of 2,529 molecular features were detected in all samples, 166 differential metabolites were identified between the GDM and HPW groups (89 upregulated and 77 downregulated), 823 differential metabolites were identified between the GDM and HNPW groups (402 upregulated and 421 downregulated), and 647 differential metabolites were identified between the HPW and HNPW groups (351 upregulated and 296 downregulated). In negative ion mode, 983 metabolites were detected in all samples, 49 differential metabolites were identified between the GDM and HPW groups (29 upregulated and 20 downregulated), 341 differential metabolites were identified between the GDM and HNPW groups (167 upregulated and 174 downregulated), and 245 differential metabolites were identified between the HPW and HNPW groups (112 upregulated and 133 downregulated). A total of nine differential metabolites with high confidence levels were identified in both the positive and negative ion modes, namely, L-isoleucine, D-glucose 6-phosphate, docosahexaenoic acid, arachidonic acid, adenosine, adenosine-monophosphate, adenosine 5'-monophosphate, xanthine, and hypoxanthine. Among all pathways enriched by the upregulated differential metabolites, the largest number of pathways were enriched by four differential metabolites, adenosine, adenosine 5'-monophosphate, D-glucose 6-phosphate, and adenosine-monophosphate, and among all pathways enriched by the downregulated differential metabolites, the largest number of pathways were enriched by three differential metabolites, L-isoleucine, xanthine, and arachidonic acid. Conclusion: Untargeted metabolomic analysis of saliva samples from pregnant women with GDM, HPW, and HNPW identified nine differential metabolites with high confidence. The results are similar to findings from previous metabolomics studies of serum and urine samples, which offer the possibility of using saliva for regular noninvasive testing in the population of pregnant women with and without GDM. Meanwhile, the associations between these identified differential metabolites and gingivitis need to be further validated by subsequent studies.

Effects of topical fluoride application on oral microbiota in young children with severe dental caries.

While the effect of fluoride on severe early childhood caries (S-ECC) is clear, knowledge of how it influences the oral microbiota and the consequential effects on oral health is limited. In this cohort study, we investigated the changes introduced in the oral ecosystem before and after using fluoride varnish in 54- to 66-month-old individuals (n=90: 18 children were sampled at 5 different time points). 16S rDNA was amplified from bacterial samples using polymerase chain reaction, and high-throughput sequencing was performed using Illumina MiSeq platforms. Many pronounced microbial changes were related to the effects of fluoride varnishing. The health-associated Bacteroides and Uncultured_bacterium_f_Enterobacteriaceae were enriched in the saliva microbiome following treatment with fluoride varnishing. Co-occurrence network analysis of the dominant genera showed that different groups clearly showed different bacterial correlations. The PICRUSt algorithm was used to predict the function of the microbial communities from saliva samples. The results showed that starch and sucrose metabolism was greater after fluoride use. BugBase was used to determine phenotypes present in microbial community samples. The results showed that Haemophilus and Neisseria (phylum Proteobacteria) was greater before fluoride use. We conclude that the changes in oral microbiology play a role in fluoride prevention of S-ECC.

Untargeted metabolomics of saliva in caries-active and caries-free children in the mixed dentition.

Objective: To compare the differences in salivary metabolites between caries-active and caries-free children in the mixed dentition, and explore their correlation with caries status. Methods: The study involved 20 children (aged 8-9 years) in the mixed dentition, including 10 caries-active (aged 8.6 ± 0.49years) and 10 caries-free children(aged 8.5 ± 0.5years), with a male/female ratio of 1:1. The saliva samples were collected from all children. Metabolite extraction, LC-MS/MS-based untargeted metabolomics, qualitative and semi-quantitative analysis and bioinformatics analysis were performed to identify differential metabolites between the two sample groups. The differential metabolites identified were further analyzed in an attempt to find their correlations with caries status. Results: In the positive ion mode, a total of 1606 molecular features were detected in the samples of the two groups, 189 of which were differential metabolites when comparing the caries-active group with the caries-free group, including 104 up-regulated and 85 down-regulated metabolites. In the negative ion mode, a total of 532 molecular features were detected in the samples of two groups, 70 of which were differential metabolites when comparing the caries-active group with the caries-free group, including 37 up-regulated and 33 down-regulated metabolites. In the positive ion mode, two of the top 5 up-regulated differential metabolites were found in and annotated to specific metabolic pathways, whereas in the negative ion mode, only one of the top 5 up-regulated differential metabolites was found in and annotated to specific metabolic pathways. In both the positive and negative ion modes, the top 5 down-regulated differential metabolites were both annotated to the metabolic pathways. KEGG pathway enrichment analysis of differential metabolites showed that histamine and arachidonic acid identified in the positive ion mode, as well as succinate and L-histidine identified in the negative ion mode were enriched in the top 3 significantly altered pathways. Conclusion: The enriched differential metabolites including histamine, L-histidine and succinate were correlated with the presence of dental caries, but their role in the caries process needs to be further investigated.

[Application of metronidazole combined with minocycline in reducing infection after dental implant in patients with localized periodontitis].

PURPOSE: To explore the value of metronidazole combined with minocycline in reducing infection after dental implant in patients with localized periodontitis. METHODS: A total of 120 patients with localized periodontitis who underwent dental implantation in the Department of Stomatological, Shanghai Pudong New Area People's Hospital from August 2021 to September 2022 were selected. According to the way of postoperative infection prevention, the patients were divided into control group and experimental group, with 60 patients in each group. The control group was orally given roxithromycin capsules, and the experimental group was locally coated with minocycline hydrochloride ointment and metronidazole gel. The incidence of postoperative infection and complications was compared between the two groups. The modified gingival creval bleeding index (mSBI), periodontal probing depth (PD) and modified plaque index (mPLI) of the patients were examined by periodontal probe. Serum C-reactive protein (CRP) level was determined by immunoturbidimetry and tumor necrosis factor-α(TNF-α) and interleukin-6(IL-6) level was determined by ELISA. SPSS 25.0 software package was used for statistical analysis of the data. RESULTS: Good healing rate of the experimental group was 91.67% higher than that of the control group 73.33%, postoperative infection rate was 8.33% and complication rate was 6.67% in the experimental group, significantly lower than that of the control group (26.67% and 20.00%), respectively (P＜0.05). After treatment, the level of CRP, TNF-α and IL-6 in the experimental group were significantly lower than those in the control group (P＜0.05). At 3 and 6 months after treatment, mSBI, mPLI and PD in the experimental group were significantly lower than those in the control group(P＜0.05). CONCLUSIONS: The administration of minocycline hydrochloride and metronidazole in patients with localized periodontitis undergoing implantation can reduce oral inflammatory response, reduce postoperative infection and other complications, and improve periodontal health.

Perceived impact of the COVID-19 pandemic on infection containment training and mental state of dental residents in China: A longitudinal study.

Background: COVID-19 has presented a challenge for dental settings and dental schools: how to continue providing dental care and maintain education during the pandemic while remaining healthy. We highlight the necessity of infection containment control training for dental residents and rethink the tasks of safeguarding trainees' health and cultivating their abilities to deal with public health crises in the future. This paper may also serve as a health policy reference for policy makers. Objective: The study aimed to compare the formats, frequency, contents, emphasis, and test scores of infection containment control training pre- and post-pandemic. Besides, after the COVID-19 outbreak, we assessed the increased anxiety level, communication difficulties, and confidence of dental residents impacted by the pandemic. Methods: A total of 251 dental residents in Stomatological Hospital of Chongqing Medical University were recruited to complete a questionnaire of their routine involvement in infection control training before and after the COVID-19 outbreak. A self-designed 10-point Likert scale was used to assess the increased anxiety level, communication difficulties, and confidence in facing with the future public health crisis impacted by the pandemic. Results: After the outbreak, although more trainees chose online assessment than offline assessment, most of them (74.90%) still preferred in-person training rather than online training. Contents that trainees had been focusing on were affected by the COVID-19 outbreak. Thereafter, they were more inclined to learn crisis management. Over half of the participants (56.17%) participated in training more frequently after the outbreak. However, postgraduate students participated in training less frequently than others after the outbreak (p < 0.01). First-year trainees accounted for the majority in the population who emphasized considerably on infection control training and whose test scores had increased after the outbreak. In addition, the percentage of women scoring increasingly in post-pandemic assessment was significantly higher than that of men. In this study, the average increased anxiety level caused by COVID-19 was 5.51 ± 2.984, which was positively related to communication difficulties with patients caused by the pandemic. The trainees whose homes were located in Hubei Province showed higher increased anxiety levels (8.29 ± 2.93) impacted by the pandemic than the trainees from other provinces (p < 0.05). However, the former's confidence in coping with future public health crises was not significantly different from that of others (p > 0.05). Conclusions: Owing to the impact of COVID-19, the contents that the trainees focused on, frequency, emphasis, and test scores of infection containment control training were changed. Some recommendations have been provided for policy makers to attach importance to crisis-based training to cultivate dental residents in the post-pandemic era.

[Effect of oral implant restoration on dentition defect patients and its impact on TNF-α and IL-6 levels in gingival crevicular fluid].

PURPOSE: To investigate the clinical effects of oral implant restoration in patients with dentition defects and the its impact on tumor necrosis factor-α(TNF-α) and interleukin-6(IL-6) levels in gingival crevicular fluid. METHODS: Eighty-four patients with dentition defects from May 2017 to August 1919 in People's Hospital of Shanghai Pudong District were enrolled and randomly divided into control group (n=42) and experimental group (n=42). Patients in the control group were repaired by routine methods,while those in the experimental group were treated with oral implant restoration. The effect of restoration was evaluated 6 months after treatment. The levels of TNF-α, IL-6 in the gingival crevicular fluid and dental function were compared between the 2 groups. The data were analyzed using SPSS 18.0 software package. RESULTS: The levels of TNF-α and IL-6 in the experimental group and the control group after treatment were significantly higher than those before treatment (P<0.05). The levels of TNF-α and IL-6 in the experimental group were significantly lower than those in the control group 6 months after treatment (P<0.05). The scores of dental function in the experimental group and the control group were significantly higher than those before treatment (P<0.05). The scores of retention, speech, chewing and aesthetics of the experimental group 6 months after treatment were significantly higher than the control group (P<0.05). The incidence of infection, pricking, post and core loosing and teeth missing in the experimental group was significantly lower than that of the control group (P<0.05). CONCLUSIONS: In the treatment of patients with dentition defects, implant restoration has little effect on the levels of TNF-α and IL-6 in gingival crevicular fluid, which is helpful to improve dental function and reduce the incidence of postoperative complications. Therefore, it is worthwhile to be popularized in clinical application.

Low-intensity pulsed ultrasound promotes tissue regeneration in rat dental follicle cells in a porous ceramic scaffold.

The aim of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the osteogenic differentiation of dental follicle cells (DFCs) in vitro and on the regenerative effects of DFC-OsteoBoneTM complexes in vivo. DFCs were isolated and characterized. In the in vitro study, DFCs were cultured in an osteogenic medium in the presence or absence of LIPUS. The expression levels of ALP, Runx2, OSX, and COL-I mRNA were analyzed using real-time polymerase chain reaction (RT-PCR) on day 7. Alizarin red staining was performed on day 21. The state of the growth of the DFCs that were seeded on the scaffold at 3, 5, 7, and 9 days was detected by using a scanning electron microscope. In our in vivo study, 9 healthy nude mice randomly underwent subcutaneous transplantation surgery in one of three groups: group A, empty scaffold; group B, DFCs + scaffold; and group C, DFCs + scaffold + LIPUS. After 8 weeks of implantation, a histological analysis was performed by HE and Mason staining. Our results indicate that LIPUS promotes the osteogenic differentiation of DFCs by increasing the expression of the ALP, Runx2, OSX, and COL-I genes and the formation of mineralized nodules. The cells can adhere and grow on the scaffolds and grow best at 9 days. The HE and Mason staining results showed that more cells, fibrous tissue and blood vessels could be observed in the DFCs + scaffold + LIPUS group than in the other groups. LIPUS could promote the osteogenic differentiation of DFCs in vitro and promote tissue regeneration in a DFCs-scaffold complex in vivo. Further studies should be conducted to explore the underlying mechanisms of LIPUS.

[Orthodontic intrusion of the first and second mandibular molars with a vacuum-formed removable appliance: a case report].

This case report focused on a patient with supraeruption of the first and second mandibular molars as a result of loss of the first and second maxillary molars for a long time. We adopted a combination of a vacuum-formed removable appliance and elastics to intrude the first and second mandibular molars by using a continuous, light force to acquire sufficient restoration space for maxillary molars. Thus, the dental-implant treatment was successful, and a good and stable occlusal relationship was established.

Prevascularized bladder acellular matrix hydrogel/silk fibroin composite scaffolds promote the regeneration of urethra in a rabbit model.

OBJECTIVE: To evaluate the effects of urethral regeneration with prevascularized bladder acellular matrix hydrogel (BAMH)/silk fibroin (SF) composite scaffolds in a rabbit model. MATERIALS AND METHODS: BAMH/SF and collagen Type I hydrogel/SF (CH/SF) scaffolds were prepared and the structure of the scaffolds was assessed using scanning electron microscopy. BAMH/SF, CH/SF and SF scaffolds were incubated in the omentum of male rabbits for two weeks and then harvested for repairing autologous urethral defects. Histological analysis of the incubated scaffolds was performed to evaluate the neovascularization capacity, and the outcomes of urethroplasty were evaluated at one and three months post-operatively. RESULTS: The composited scaffolds were composed of a highly porous BAMH or CH buttressed by compact SF outer layer. The histological analysis of the incubated BAMH/SF revealed a signifcant increase of the neovascularization among three groups after a two-week incubation. At three months, the urethra maintained wide caliber in the BAMH/SF group. Strictures were found in the CH/SF and SF groups. Histologically, at one month, intact and multilayer epithelium occurred in the BAMH/SF group, and one layer epithelium was found in the CH/SF and SF groups. However, there was similar epithelial regeneration in BAMH/SF and CH/SF groups at three months (p > 0.05). Comparisons of smooth muscle content and vessel density among the SF, CH/SF and BAMH/SF revealed a significant increase at each time point (p < 0.05). CONCLUSION: Our results demonstrate that incubated BAMH/SF promote neovascularization, and prevascularized BAMH/SF promote the regeneration of the urethral epithelium and smooth muscle, which indicates its potential for urethral reconstruction.

Characterization of bladder acellular matrix hydrogel with inherent bioactive factors.

Bladder acellular matrix (BAM) hydrogel may have great potential in tissue engineering due to outstanding biocompatibility and the presence of inherent bioactive factors in BAM. In this study, we prepared the BAM hydrogel by the method of enzymatic solubilization with pepsin and characterize the microrheological properties of the BAM precursor solution. The structures of the BAM hydrogel were characterized by scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Furthermore, the growth factors including vascular endothelial growth factor (VEGF), platelet-derived growth factor B (PDGF-BB), keratinocyte growth factor (KGF) were quantified by ELISA. The biological performances of the hydrogels were evaluated by cultivating porcine iliac endothelial cells (PIECs) in vitro. Lyophilized BAM showed porous structure with pore diameter ranging from 50 to 100µm. BAM 4-G hydrogel (4mg/mL) with a short gelation time of 3.95±0.07min presents better thermal stability than BAM 6-G hydrogel (6mg/mL). Growth factors in the BAM hydrogel maintain valuable biological activity even after digestion process. The BAM hydrogel supported the adhesion and growth of PIECs well and has great potential for further tissue engineering.

Low-intensity pulsed ultrasound promotes tissue regeneration in rat dental follicle cells in a porous ceramic scaffold

Abstract The aim of this study was to investigate the effects of low-intensity pulsed ultrasound (LIPUS) on the osteogenic differentiation of dental follicle cells (DFCs) in vitro and on the regenerative effects of DFC-OsteoBoneTM complexes in vivo. DFCs were isolated and characterized. In the in vitro study, DFCs were cultured in an osteogenic medium in the presence or absence of LIPUS. The expression levels of ALP, Runx2, OSX, and COL-I mRNA were analyzed using real-time polymerase chain reaction (RT-PCR) on day 7. Alizarin red staining was performed on day 21. The state of the growth of the DFCs that were seeded on the scaffold at 3, 5, 7, and 9 days was detected by using a scanning electron microscope. In our in vivo study, 9 healthy nude mice randomly underwent subcutaneous transplantation surgery in one of three groups: group A, empty scaffold; group B, DFCs + scaffold; and group C, DFCs + scaffold + LIPUS. After 8 weeks of implantation, a histological analysis was performed by HE and Mason staining. Our results indicate that LIPUS promotes the osteogenic differentiation of DFCs by increasing the expression of the ALP, Runx2, OSX, and COL-I genes and the formation of mineralized nodules. The cells can adhere and grow on the scaffolds and grow best at 9 days. The HE and Mason staining results showed that more cells, fibrous tissue and blood vessels could be observed in the DFCs + scaffold + LIPUS group than in the other groups. LIPUS could promote the osteogenic differentiation of DFCs in vitro and promote tissue regeneration in a DFCs-scaffold complex in vivo. Further studies should be conducted to explore the underlying mechanisms of LIPUS.

Rapid synthesis of cellulose esters by transesterification of cellulose with vinyl esters under the catalysis of NaOH or KOH in DMSO.

Traditionally, a long reaction time was required in the synthesis of cellulose esters (CEs). In this work, dimethyl sulfoxide (DMSO)/aqueous NaOH or KOH was introduced as an efficient reaction system for rapidly synthesizing CEs by transesterification. Surprisingly, cellulose could react with vinyl acetate, vinyl propionate, and vinyl butyrate and synthesized cellulose acetate, cellulose propionate, and cellulose butyrate with a high degree of substitution (2.14-2.34) in 5 min, which was in sharp contrast to hours of existing methods. The effects of solvents, catalysts, and esterifying agents on the synthesis of CEs were comparatively investigated to better understand this method. The structure and thermal properties of obtained CEs were characterized by Fourier transform infrared (FTIR) and (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopies and differential scanning calorimetry. Results from these spectra confirmed the successful synthesis of these CEs. Furthermore, these CEs showed similar thermal properties compared to products obtained from other methods.

[Study on exopolysaccharides produced by planktonic and attached Streptococcus sobrinus].

PURPOSE: To elucidate the amount of exopolysaccharides produced by Streptococcus sobrinus when cultivated at different conditions. METHODS: S. sobrinus was grown in TS broth and was allowed to attach to the cover glass surface to form bioflims. The anthrone method was applied to measure the amounts of soluble and insoluble exopolysaccharides produced by attached S. sobrinus and planktonic ones when cultivated at different time and in different concentrations of sucrose. The data were analyzed using SPSS 10.0 software package, Dunnett's t test was used to compare the difference between the two groups. RESULTS: Attached bacteria synthesized more insoluble polysaccharide than planktonic ones at every sucrose concentration (P<0.05), but almost the same production of soluble polysaccharide (P>0.05). CONCLUSION: The ability of S. sobrinus to synthesize insoluble polysaccharide was enhanced in the adherent phase, which may clarify why bacteria in biofilms are highly cariogenic.