[Effect of bleaching combined with Er:YAG or Nd:YAG laser on shear bond strength and microleakage of resin restoration].

PURPOSE: To evaluate the effects of bleaching combined with Er:YAG laser or Nd:YAG laser on bond strength and microleakage of resin fillings on enamel surface. METHODS: Sixty-four pieces of enamel specimens prepared from isolated teeth were randomly divided into 4 groups(n=16): control group, simple bleaching group, bleaching combined with Er: YAG laser group and bleaching combined with Nd:YAG laser group. Then the shear bond strength and the depth of microleakage were tested, and the fracture mode of the specimen was observed under microscope. SPSS 26.0 software package was used for statistical analysis. RESULTS: After bleaching simply, the bond strength of the restoration was significantly decreased, and the marginal microleakage was significantly increased(P＜0.05). There was no significant difference in shear bond strength and microleakage depth between the group bleaching combined with Er: YAG laser and control group(P＞0.05). The shear bond strength after bleaching combined with Nd:YAG laser was significantly reduced (P＜0.05), but there was no significant difference in the depth of microleakage compared with unbleached microleakage(P＞0.05). Bonding interface fracture was the main fracture mode for all groups. CONCLUSIONS: Compared to traditional bleaching, bleaching combined with laser has certain clinical advantages due to its less influence on bond strength and microleakage of resin fillings.

Mapping the human oral and gut fungal microbiota in patients with metabolic dysfunction-associated fatty liver disease.

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a phenotype of liver diseases associated with metabolic syndrome. The pathogenesis MAFLD remains unclear. The liver maintains is located near the intestine and is physiologically interdependent with the intestine via metabolic exchange and microbial transmission, underpinning the recently proposed "oral-gut-liver axis" concept. However, little is known about the roles of commensal fungi in the disease development. This study aimed to characterize the alterations of oral and gut mycobiota and their roles in MAFLD. Twenty-one MAFLD participants and 20 healthy controls were enrolled. Metagenomics analyses of saliva, supragingival plaques, and feces revealed significant alterations in the gut fungal composition of MAFLD patients. Although no statistical difference was evident in the oral mycobiome diversity within MAFLD and healthy group, significantly decreased diversities were observed in fecal samples of MAFLD patients. The relative abundance of one salivary species, five supragingival species, and seven fecal species was significantly altered in MAFLD patients. Twenty-two salivary, 23 supragingival, and 22 fecal species were associated with clinical parameters. Concerning the different functions of fungal species, pathways involved in metabolic pathways, biosynthesis of secondary metabolites, microbial metabolism in diverse environments, and carbon metabolism were abundant both in the oral and gut mycobiomes. Moreover, different fungal contributions in core functions were observed between MAFLD patients and the healthy controls, especially in the supragingival plaque and fecal samples. Finally, correlation analysis between oral/gut mycobiome and clinical parameters identified correlations of certain fungal species in both oral and gut niches. Particularly, Mucor ambiguus, which was abundant both in saliva and feces, was positively correlated with body mass index, total cholesterol, low-density lipoprotein, alanine aminotransferase, and aspartate aminotransferase, providing evidence of a possible "oral-gut-liver" axis. The findings illustrate the potential correlation between core mycobiome and the development of MAFLD and could propose potential therapeutic strategies.

Prevalence of taste and smell dysfunction in mild and asymptomatic COVID-19 patients during Omicron prevalent period in Shanghai, China: a cross-sectional survey study.

OBJECTIVES: COVID-19, which is caused by SARS-CoV-2, is a severe threat to human health and the economy globally. This study aimed to investigate the prevalence of taste and/or smell dysfunction and associated risk factors in mild and asymptomatic patients with Omicron infection in Shanghai, China.DesignThis was a questionnaire-based cross-sectional study. SETTING: COVID-19 patients at the makeshift hospital in the Shanghai World Expo Exhibition and Convention Centre were recruited from March to April 2022. PARTICIPANTS: In total, 686 COVID-19-infected patients who were defined as mild or asymptomatic cases according to the diagnostic criteria of New Coronavirus Pneumonia Prevention and Control Programme ninth edition (National Health Commission of China, 2022) were enrolled. MEASURES: Data to investigate taste and smell loss and to characterise other symptoms were collected by the modified Chemotherapy-induced Taste Alteration Scale and Sino-Nasal Outcome Test-22 questionnaires. The risk factors for the severity of taste/smell dysfunction were analysed by binary logistic regression models. RESULTS: 379 males (379/686, 55.2%) and 307 females (307/686, 44.8%) completed the questionnaires to record recent changes in taste and smell ability. A total of 302 patients (44%) had chemosensory dysfunction with Omicron infection, of which 22.7% (156/686) suffered from both taste and smell dysfunction. In addition, cough (60.2%), expectoration (40.5%), fever (33.2%) and sore throat (32.5%) were common symptoms during Omicron infection. The quality-of-life-related indicators were negatively associated with participants' self-reported taste and smell dysfunction. CONCLUSIONS: The prevalence of taste or/and smell dysfunction in patients with Omicron infections was 44%. Individuals with chemosensory dysfunction had significantly higher rates of various upper respiratory influenza-like symptoms, xerostomia and bad breath. Moreover, smell dysfunction was a risk factor for the prevalence of taste dysfunction in patients with Omicron infection. TRIAL REGISTRATION NUMBER: ChiCTR 2200059097.

Osteomodulin protects dental pulp stem cells from cisplatin-induced apoptosis in vitro.

Human dental pulp stem cells (hDPSCs) are considered promising multipotent cell sources for tissue regeneration. Regulation of apoptosis and maintaining the cell homeostasis is a critical point for the application of hDPSCs. Osteomodulin (OMD), a member of the small leucine-rich proteoglycan family, was proved an important regulatory protein of hDPSCs in our previous research. Thus, the role of OMD in the apoptosis of hDPSCs was explored in this study. The expression of OMD following apoptotic induction was investigated and then the hDPSCs stably overexpressing or knocking down OMD were established by lentiviral transfection. The proportion of apoptotic cells and apoptosis-relative genes and proteins were examined with flow cytometry, Hoechst staining, Caspase 3 activity assay, qRT-PCR and western blotting. RNA-Seq analysis was used to explore possible biological function and mechanism. Results showed that the expression of OMD decreased following the apoptotic induction. Overexpression of OMD enhanced the viability of hDPSCs, decreased the activity of Caspase-3 and protected hDPSCs from apoptosis. Knockdown of OMD showed the opposite results. Mechanistically, OMD may act as a negative modulator of apoptosis via activation of the Akt/Glycogen synthase kinase 3ß (GSK-3ß)/ß-Catenin signaling pathway and more functional and mechanistic possibilities were revealed with RNA-Seq analysis. The present study provided evidence of OMD as a negative regulator of apoptosis in hDPSCs. Akt/GSK-3ß/ß-Catenin signaling pathway was involved in this process and more possible mechanism detected needed further exploration. This anti-apoptotic function of OMD provided a promising application prospect for hDPSCs in tissue regeneration.

The role of ZBTB16 in odontogenic differentiation of dental pulp stem cells.

OBJECTIVE: Odontogenic differentiation of dental pulp stem cells (DPSCs) is highly controlled by the activation of several transcription factors. The zinc finger and BTB domain-containing 16 (ZBTB16) gene encodes a BTB/POZ domain and zinc finger containing transcription factors and is involved in several biological processes, but little is known about its role in odontogenic differentiation. The main goal of the current study was to determine the role of ZBTB16 in odontogenic differentiation of DPSCs. DESIGN: ZBTB16, runt-related transcription factor 2 (RUNX2), and osterix (OSX) were silenced via small-hairpin RNA (shRNA) lentivirus. The odontoblastic differentiation of DPSCs was detected by alkaline phosphatase (ALP) staining, activity measurement, and alizarin red S staining in vitro. The gene and protein expression levels were assessed by RT-qPCR and western blotting. Further, an ectopic implantation experiment was performed to explore the role of ZBTB16 in mineralization regulation in vivo followed by histological examination. RESULTS: The silencing of ZBTB16 attenuated ALP activity and mineralized nodules formation by DPSCs. In addition, knockdown of ZBTB16 impaired the expression of markers involved in odontogenic differentiation, including dentin sialophosphoprotein, dentin matrix acidic phosphoprotein 1, and collagen 1 in vitro and vivo. Silencing the OSX gene suppressed ZBTB16 expression and, in turn, OSX expression decreased after ZBTB16 knockdown. However, shRUNX2 did not suppress ZBTB16 expression and shZBTB16 did not affect RUNX2 expression. CONCLUSIONS: ZBTB16 may play an important role in modulating the odontoblastic differentiation of DPSCs and act as a regulator of OSX in a possible feed-back cycle independent of RUNX2.

[Correlation analysis of supragingival microbiome and host blood lipid levels].

PURPOSE: To analyze the correlation between microbiome of supragingival plaque and host blood lipid levels. METHODS: Samples of supragingival plaques from 68 volunteers aged 45-60 years were collected. The total DNA was extracted, and 16S rDNA V3-V4 regions were amplified via PCR. The amplified products were sequenced by Illumina MiSeq PE300. After that, OTU clustering and species annotation were carried out. Then, the correlation of annotated species (genus level) and host blood lipid level were calculated with Spearman correlation analysis. SPSS 16.0 software package was used for statistical analysis. RESULTS: The average number of sequences obtained from the supragingival plaque samples was 41 929, and the number of OTUs obtained by clustering was 1 037. A total of 25 phyla, 45 classes, 92 orders, 155 families and 330 genera were annotated. Species heat maps showed a high degree of consistency in the species composition abundance of 68 samples. Spearman correlation analysis showed that among the supragingival microorganisms, Alloprevotella spp., Dialister spp., Peptostreptococcus spp. and Prevotella 7 spp., were negatively correlated with the host serum total cholesterol/low density lipoprotein cholesterol level. Neisseria spp. was positively correlated with host serum high-density lipoprotein cholesterol, but negatively correlated with Prevotella 2 spp.. CONCLUSIONS: The compositional structure of the supragingival microbiome is relatively stable and has a correlation with the host blood lipid levels. Profiles of supragingival microbiome can be promising biomarkers of the lipid metabolism of the host.

Comparative transcriptomics analysis of Streptococcus mutans with disruption of LuxS/AI-2 quorum sensing and recovery of methyl cycle.

OBJECTIVE: The LuxS/AI-2 quorum sensing (QS) system has critical roles in Streptococcus mutans cariogenicity. Whereas the molecular and cellular mechanisms of the LuxS/AI-2 QS system are not thoroughly understood. Given that LuxS has roles in QS and methyl cycle, its mutation can cause QS deficiency and methyl cycle disruption. The aim of this study was to investigate effects of the LuxS/AI-2 QS system on gene expression in Streptococcus mutans when methyl cycle was recovered with exogenous sahH gene. METHODS: Our previous study introduced the exogenous sahH gene from Pseudomonas aeruginosa into an S. mutans luxS-null strain to restore the disrupted methyl cycle, and this produced the solely the LuxS/AI-2 QS system deficient strain. Here, we analyzed the transcriptomics of this strain to get insights into the molecular mechanisms of the LuxS/AI-2 QS system applying RNA-seq. RESULTS: With recovery of methyl cycle, 84 genes didn't change in expression trends in S. mutans luxS-null strain. These genes mainly encode the ABC transporters, sugar transporter EII and enzymes of carbohydrate metabolism, and are rich in the Phosphotransferase system, Fructose and mannose metabolism, Amino sugar and nucleotide sugar metabolism, Galactose metabolism, Glycolysis/Gluconeogenesis, RNA degradation, Lysine biosynthesis, and Glycine, serine and threonine metabolism. CONCLUSIONS: The LuxS/AI-2 QS system may mainly affect ABC transporters and carbohydrate transport, transformation and metabolism via EII subunits and enzymes to influence virulence-associated traits without effects of methyl cycle inStreptococcus mutans.

Presence of voids after three obturation techniques in band-shaped isthmuses: a micro-computed tomography study.

BACKGROUND: The objective of the present micro-computed tomography (micro-CT) study was to assess the presence of voids in band-shaped isthmuses obturated using three different filling techniques. METHODS: Twenty-four artificial molar teeth with a band-shaped isthmus were allocated to three groups (n = 8) for obturation, according to the filling technique: single-cone (SC), continuous wave of condensation (CWC) or lateral condensation (LC). Obturation was performed with gutta-percha (GP) cones and iRoot SP (Innovative Bioceramix, Vancouver, Canada). Post-filling micro-CT scanning was performed. The percentage of filling materials and void volumes were calculated in the isthmus areas and data were analyzed using one-way ANOVA and Tukey tests. RESULTS: The mean percentage of void volumes and corresponding filling percentages in the isthmus areas after obturation in the SC groups was 22.98 % ± 1.19 %, 77.02 % ± 1.19 %; in the CWC groups 10.46 % ± 2.28 %, 89.54 % ± 2.28 %; and in the LC groups was 13.14 % ± 1.85 %, 86.86 % ± 1.85 %, respectively. CONCLUSIONS: In band-shaped isthmus area, the obturation quality of CWC was superior to SC and LC techniques.

Association Between Serum Thyroid-Stimulating Hormone Levels and Salivary Microbiome Shifts.

High serum thyroid-stimulating hormone (TSH) levels are linked to many metabolic disorders, but the effects of TSH levels on the oral microbiota are still largely unknown. This study aimed to explore the association between the salivary microbiome in adults and serum TSH levels. Saliva and fasting blood samples were obtained from a health census conducted in Southeast China. All participants were divided according to serum TSH levels. The microbial genetic profiles and changes were acquired by 16S rDNA sequencing and bioinformatics analysis. Relevant anthropometric and biochemical measurements such as insulin resistance, blood lipids, and body composition were evaluated with laboratory tests and physical examinations. The salivary microbiome in individuals with higher TSH level showed significantly higher taxa diversity. Principal coordinates analysis and partial least squares discriminant analysis showed distinct clustering in the Abnormal and Normal Groups (Adonis, P=0.0320). Granulicatella was identified as a discriminative genus for comparison of the two groups. Fasting serum insulin, Homeostatic Model Assessment for Insulin Resistance, and hemoglobin A1 were elevated in the Abnormal Group (P<0.05), showing the presence of insulin resistance in individuals with abnormal higher serum TSH levels. Distance-based redundancy analysis revealed the association of this distinctive difference with salivary microbiome. In conclusion, shifts in microbial profile were observed in the saliva of individuals with different serum TSH levels, and insulin resistance may play an important role in the biochemical and microbial alteration.

Effects of Bleaching Associated with Er:YAG and Nd:YAG Laser on Enamel Structure and Bacterial Biofilm Formation.

OBJECTIVE: To compare the effects of bleaching associated with Er:YAG and Nd:YAG laser on enamel structure and mixed biofilm formation on teeth surfaces. MATERIALS AND METHODS: Sixty-eight enamel samples were randomly divided into four groups (n = 17), control, Opalescence Boost only, Opalescence Boost plus Er: YAG laser, and Opalescence Boost plus Nd:YAG laser. The structure was observed using SEM after bleaching. Subsequently, the treated enamel samples were also cultured in suspensions of Streptococcus mutans, Streptococcus sanguis, Actinomyces viscosus, and Fusobacterium nucleatum (Fn) for 24 and 48 h. Biofilm formation was quantified by crystal violet staining, and the structure was visualized by confocal laser scanning microscopy. The data were analyzed using the Kruskal-Wallis method. RESULTS: The enamel structure significantly changed after bleaching. There was no obvious difference in the biofilm formation after 24 h; however, after 48 hours, the amount of biofilm increased significantly. Remarkably, the amount was significantly higher on enamel bleached only, however, there was no significant difference between samples bleached with Er:YAG or Nd:YAG laser compared to the control. CONCLUSIONS: Bleaching only appeared to markedly promote biofilm formation after 48 h, and the biofilms on samples bleached with Er:YAG or Nd:YAG laser did not change significantly, showing that bleaching with Er:YAG or Nd:YAG laser can be safely applied in clinical practice.

Extracellular vesicles derived from human dental pulp stem cells promote osteogenesis of adipose-derived stem cells via the MAPK pathway.

Recent studies have shown that co-culture systems play an important role in bone tissue engineering. In this study, human dental pulp stem cells (hDPSCs) were co-cultured with human adipose-derived stem cells (hADSCs), and osteoblastic phenotypes were found to be enhanced in co-cultures compared with monocultures of hDPSCs or hADSCs. Furthermore, GW4869, an inhibitor of extracellular vesicle (EV) formation, suppressed the mineralization of co-cultured cells. Studies indicate that the therapeutic potential of DPSCs is realized through paracrine action, in which EVs play an important role. To study their role, we successfully obtained and identified hDPSC-derived extracellular vesicles (hDPSC-EVs), and further investigated their effects on hADSCs and the underlying mechanism. hADSCs were stimulated with hDPSC-EVs, which were found to promote the migration and mineralization of hADSCs. Moreover, hDPSC-EVs promoted osteogenic differentiation by enhancing the phosphorylation of ERK 1/2 and JNK in hADSCs. To investigate the specific proteins in EVs that might play a role in hADSC osteogenic differentiation, we performed proteomic analysis of hDPSC-EVs. We determined the top 30 enriched pathways, which notably included the insulin signaling pathway. The number of genes enriched in the insulin signaling pathway was the largest, in addition to the "protein processing in endoplasmic reticulum" term. The MAPK cascade is a typical downstream pathway mediating insulin signaling. To further study the effects of hDPSC-EVs on maxillofacial bone regeneration, we used hDPSC-EVs as a cell-free biomaterial in a model of mandibular defects in rats. To assess the therapeutic potential of EVs, we analyzed their proteome. Animal experiments demonstrated that hDPSC-EVs promoted the regeneration of bone defects. Overall, these results highlight the potential of hDPSC-EVs to induce lineage specific differentiation of hADSCs. The results also indicated the importance of considering hDPSC-EVs as biomimetic materials for clinical translation of treatments for oral maxillofacial defects.

Recombinant bacteriophage T4 Rnl1 impacts Streptococcus mutans biofilm formation.

Bacteriophage T4 RNA ligase 1 (T4 Rnl1) can be stably expressed in many bacteria and has been reported to affect the bioactivity of the host bacteria. Recently, we constructed bacteriophage T4 Rnl1 expressing system in Streptococcus mutans, a crucial biofilm-forming and dental caries-causing oral pathogen. Here, we characterized the function of recombinant bacteriophage T4 Rnl1 in biofilm formation of S. mutans. The T4 Rnl1 mutant exhibited similar growth phenotype but resulted in a significant reduction of biofilm biomass compared to wild type strain and empty plasmid carrying strain. The abnormal biofilm of the T4 Rnl1 mutant harbored loose bacterial clusters with defective production and distribution of exopolysaccharides. Moreover, the expression of several biofilm formation-associated genes was dysregulated at mRNA level in the T4 Rnl1 mutant. These results reveal that the bacteriophage T4 Rnl1 exert antibiofilm activities against the cariogenic bacterium S. mutans, which impacts the spatial organization of the exopolysaccharides and further impairs the three-dimensional biofilm architecture. These findings implicate that manipulation of bacteriophage T4 Rnl1, a biological tool used for RNA ligation, will provide a promising approach to cariogenic biofilm control.

Shifts in the Bacterial Community of Supragingival Plaque Associated With Metabolic-Associated Fatty Liver Disease.

Metabolic-associated fatty liver disease (MAFLD), also known as the hepatic manifestation of metabolic disorders, has become one of the most common chronic liver diseases worldwide. The associations between some oral resident microbes and MAFLD have been described. However, changes to the oral microbial community in patients with MAFLD remain unknown. In this study, variations to the supragingival microbiota of MAFLD patients were identified. The microbial genetic profile of supragingival plaque samples from 24 MAFLD patients and 22 healthy participants were analyzed by 16S rDNA sequencing and bioinformatics analysis. Clinical variables, including indicators of insulin resistance, obesity, blood lipids, and hepatocellular damage, were evaluated with laboratory tests and physical examinations. The results showed that the diversity of the supragingival microbiota in MAFLD patients was significantly higher than that in healthy individuals. Weighted UniFrac principal coordinates analysis and partial least squares discriminant analysis showed that the samples from the MAFLD and control groups formed separate clusters (Adonis, P = 0.0120). There were 27 taxa with differential distributions (linear discriminant analysis, LDA>2.0) between two groups, among which Actinomyces spp. and Prevotella 2 spp. were over-represented in the MAFLD group with highest LDA score, while Neisseria spp. and Bergeyella spp. were more abundant in the control group. Co-occurrence networks of the top 50 abundant genera in the two groups suggested that the inter-genera relationships were also altered in the supragingival plaque of MAFLD patients. In addition, in genus level, as risk factors for the development of MAFLD, insulin resistance was positively correlated with the abundances of Granulicatella, Veillonella, Streptococcus, and Scardovia, while obesity was positively correlated to the abundances of Streptococcus, Oslenella, Scardovia, and Selenomonas. Metagenomic predictions based on Phylogenetic Investigation of Communities by Reconstruction of Unobserved States revealed that pathways related to sugar (mainly free sugar) metabolism were enriched in the supragingival plaque of the MAFLD group. In conclusion, as compared to healthy individuals, component and interactional dysbioses were observed in the supragingival microbiota of the MAFLD group.

Comparative characterization of mesenchymal stem cells from human dental pulp and adipose tissue for bone regeneration potential.

Bone tissue engineering is an area of regenerative medicine that attempts to repair bone defects. Seed cells such as dental pulp stem cells (DPSCs) and adipose tissue-derived stem cells (ADSCs) are two of the most well-characterized cells for bone regeneration because their use involves few ethical constraints and they have the ability to differentiate into multiple cell types, secreting growth factors and depositing mineral. However, bone regeneration ability of these cells remains unclear. This study aimed to compare the bone formation capacity of DPSCs and ADSCs in vitro and in vivo. Studies revealed that DPSCs had enhanced colony-forming ability, higher proliferative ability, stronger migration ability and higher expression of angiogenesis-related genes. They also secreted more vascular endothelial growth factor compared to ADSCs. In contrast, ADSCs grew more slowly compared to DPSCs but exhibited greater osteogenic differentiation potential, higher expression of osteoblast marker genes, and greater mineral deposition. Furthermore, after DPSCs and ADSCs were implanted into a mandibular defect of a rat for 6 weeks, ADSCs showed visible bone tissue as early as week 1 and promoted faster and greater bone regeneration compared to the DPSC group. These results suggest that ADSCs might be more useful than DPSCs for bone regeneration.

The role of osteomodulin on osteo/odontogenic differentiation in human dental pulp stem cells.

BACKGROUND: Extracellular matrix secretion and odontoblastic differentiation in human dental pulp stem cells (hDPSCs) are the cellular bases for reparative dentinogenesis. Osteomodulin (OMD) is a member of the small leucine-rich proteoglycan family distributed in the extracellular matrix but little is known about its role in osteo/odontogenic differentiation. The objective of this study was to investigate the role of OMD during osteo/odontoblastic differentiation of hDPSCs. METHODS: hDPSCs were selected using immune-magnetic beads and their capability of multi-differentiation was identified. OMD knockdown was achieved using short hairpin RNA (shRNA) lentivirus and was confirmed by western blot. Gene expression was measured by real-time qPCR and osteo/odontoblastic differentiation of hDPSCs was determined by alizarin red S staining. RESULTS: Compared with uninduced cells, the transcription of OMD was up-regulated by 35-fold at the late stage of osteo/odontogenic differentiation. shRNA-mediated gene silencing of OMD decreased the expression of odontoblastic genes, such as alkaline phosphatase (ALP), dentin matrix acidic phosphoprotein 1 (DMP1) and dentin sialophosphoprotein (DSPP). Besides, knockdown of OMD attenuated the mineralized nodules formation induced by osteo/odontogenic medium. CONCLUSIONS: These results implied that OMD may play a pivotal role in modulating the osteo/odontoblastic differentiation of hDPSCs.

A cone-beam computed tomography study of the mesial cervical concavity of maxillary first premolars.

OBJECTIVE: To investigate the mesial cervical concavity of maxillary first premolars and its relationship with root and canal configuration using cone-beam computed tomography (CBCT). DESIGN: Images of maxillary first premolars (n = 1056) were collected from patients (n = 601) who had undergonein vivo CBCT scanning. The root and canal number and morphology were evaluated. The following measurements of the mesial cervical concavity of the maxillary first premolars were evaluated in section images: dentine thickness (in concavity at the cemento-enamel junction), concavity angle, depression depth (distance from mesial dentinal surface at concavity to mesial proximity), concavity position (distance from mesial dentinal wall at invagination to the top of the mesial marginal ridge). The reliability of the data was analyzed with an unpaired Student's t test and Fisher's exact test. RESULTS: The percentages of maxillary first premolars with one root, two, and three roots were 55.5%, 43.7%, and 0.8% respectively. Mesial cervical concavity was recorded in 64.5% of single-root maxillary premolars. The prevalence of two-root maxillary first premolars with mesial cervical concavity was 73.8%. The means of the aforementioned four measurements were 1.705, 147.9, 1.640, and 5.247 mm. The values of dentine thickness (mm), depression depth (mm), and concavity position (mm) of the mesial cervical concavity were largest in two-root maxillary first premolars. The smallest concavity angle of the mesial cervical concavity was found in three-root maxillary first premolars. CONCLUSIONS: There is a high prevalence of mesial cervical concavity among maxillary first premolars. The mesial root concavity is more prevalent in single-rooted maxillary first premolars when there are two canals present, and its prevalence and degree of concavity increase with the number of roots.

The Impairment of Methyl Metabolism From luxS Mutation of Streptococcus mutans.

The luxS gene is present in a wide range of bacteria and is involved in many cellular processes. LuxS mutation can cause autoinducer(AI)-2 deficiency and methyl metabolism disorder. The objective of this study was to demonstrate that, in addition to AI-2-mediated quorum sensing (QS), methyl metabolism plays an important role in LuxS regulation in Streptococcus mutans. The sahH gene from Pseudomonas aeruginosa was amplified and introduced into the S. mutans luxS-null strain to complement the methyl metabolism disruption in a defective QS phenotype. The intracellular activated methyl cycle (AMC) metabolites [S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), homocysteine (HCY), and methionine] were quantified in wild-type S. mutans and its three derivatives to determine the metabolic effects of disrupting the AMC. Biofilm mass and structure, acid tolerance, acid production, exopolysaccharide synthesis of multispecies biofilms and the transcriptional level of related genes were determined. The results indicated that SAH and SAM were relatively higher in S. mutans luxS-null strain and S. mutans luxS null strain with plasmid pIB169 when cultured overnight, and HCY was significantly higher in S. mutans UA159. Consistent with the transcriptional profile, luxS deletion-mediated impairment of biofilm formation and acid tolerance was restored to wild-type levels using transgenic SahH. These results also suggest that methionine methyl metabolism contributes to LuxS regulation in S. mutans to a significant degree.

Ecological Shifts of Supragingival Microbiota in Association with Pregnancy.

Pregnancy is a physiological process with pronounced hormonal fluctuations in females, and relatively little is known regarding how pregnancy influences the ecological shifts of supragingival microbiota. In this study, supragingival plaques and salivary hormones were collected from 11 pregnant women during pregnancy (P1, ≤14 weeks; P2, 20-25 weeks; P3, 33-37 weeks) and the postpartum period (P4, 6 weeks after childbirth). Seven non-pregnant volunteers were sampled at the same time intervals. The microbial genetic repertoire was obtained by 16S rDNA sequencing. Our results indicated that the Shannon diversity in P3 was significantly higher than in the non-pregnant group. The principal coordinates analysis showed distinct clustering according to gestational status, and the partial least squares discriminant analysis identified 33 genera that may contribute to this difference. There were differentially distributed genera, among which Neisseria, Porphyromonas, and Treponema were over-represented in the pregnant group, while Streptococcus and Veillonella were more abundant in the non-pregnant group. In addition, 53 operational taxonomic units were observed to have positive correlations with sex hormones in a redundancy analysis, with Prevotella spp. and Treponema spp. being most abundant. The ecological events suggest that pregnancy has a role in shaping an at-risk-for-harm microbiota and provide a basis for etiological studies of pregnancy-associated oral dysbiosis.

Nardosinone Suppresses RANKL-Induced Osteoclastogenesis and Attenuates Lipopolysaccharide-Induced Alveolar Bone Resorption.

Periodontitis is a chronic inflammatory disease that damages the integrity of the tooth-supporting tissues, known as the periodontium, and comprising the gingiva, periodontal ligament and alveolar bone. In this study, the effects of nardosinone (Nd) on bone were tested in a model of lipopolysaccharide (LPS)-induced alveolar bone loss, and the associated mechanisms were elucidated. Nd effectively suppressed LPS-induced alveolar bone loss and reduced osteoclast (OC) numbers in vivo. Nd suppressed receptor activator of nuclear factor-κB ligand (RANKL)-mediated OC differentiation, bone resorption, and F-actin ring formation in a dose-dependent manner. Further investigation revealed that Nd suppressed osteoclastogenesis by suppressing the ERK and JNK signaling pathways, scavenging reactive oxygen species, and suppressing the activation of PLCγ2 that consequently affects the expression and/or activity of the OC-specific transcription factors, c-Fos and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1). In addition, Nd significantly reduced the expression of OC-specific markers in mouse bone marrow-derived pre-OCs, including c-Fos, cathepsin K (Ctsk), VATPase d2, and Nfatc1. Collectively, these findings suggest that Nd has beneficial effects on bone, and the suppression of OC number implies that the effect is exerted directly on osteoclastogenesis.

Gold nanoparticles promote osteogenic differentiation of human periodontal ligament stem cells via the p38 MAPK signaling pathway.

Gold nanoparticles (AuNPs) are a promising material for use in regenerative medicine due to their biocompatibility and easy functionalization with biomolecules including growth factors, DNA and peptides. In the present study, transmission electron microscopy indicated that the AuNPs were monodisperse and spherical in shape, with an estimated average diameter of 13 nm. And the cellular effects of AuNPs on the osteogenic differentiation of human periodontal ligament stem cells (hPDLSCs) and the associated signaling pathways in cell differentiation were investigated based on histochemical analysis of alkaline phosphatase activity and mineralization, quantitative polymerase chain reaction, and western blotting. The results indicated that AuNPs enhanced the differentiation of hPDLSCs into osteoblasts, increasing their osteogenic transcriptional profile including alkaline phosphatase, osterix, collagen type I and runt­related transcription factor 2 (RUNX2) and activating the p38 mitogen­activated protein kinase (MAPK) signaling pathway. Furthermore, AuNPs increased the protein level of RUNX2, which is crucial for osteogenic differentiation. These results suggested that AuNPs stimulate the osteogenesis of hPDLSCs partially via activation of the p38 MAPK signaling pathway.