Epigenetic regulation mechanism: roles in enamel formation and developmental defects of enamel / 中华口腔医学杂志

Enamel formation is a series of complex physiological processes, which are regulated by critical genes spatially and temporally. These processes involve multiple developmental stages covering ages and are prone to suffer signal interference or gene mutations, ultimately leading to developmental defects of enamel (DDE). Epigenetic modifications have important regulatory roles in gene expression during enarnel development. New technologies including high-throughput sequencing, chromatin immunoprecipitation sequencing (ChIP-seq), and DNA methylation chip are emerging in recent years, making it possible to establish genome-wide epigenetic modification profiles during developmental processes. The regulatory role of epigenetic modification with spatio-temporal pattern, such as DNA methylation, histone modification and non-coding RNA, has significantly expanded our understanding of the regulatory network of enamel formation, providing a new theoretical basis of clinical management and intervention strategy for DDE. The present review briefly describes the enamel formation process of human beings' teeth as well as rodent incisors and summarizes the dynamic characteristics of epigenetic modification during enamel formation. The functions of epigenetic modification in enamel formation and DDE are also emphatically discussed.

Effects of prenatal nicotine exposure on enamel formation of offspring mice / 中华口腔医学杂志

Objective: To investigate the effects of nicotine on the morphology, structure of offspring's dental germ, enamel organ and other dental tissues and the further potential epigenetic mechanisms by establishing prenatal nicotine exposure mouse model. Methods: Ten C57BL/6 pregnant mice were randomly divided into control group (physiological saline subcutaneous injection) and prenatal nicotine exposure (PNE) group (nicotine subcutaneous injection) by using a random number table. Postnatal day 0 (P0), postnatal day 14 (P14) and postnatal day 25 (P25) offspring mice were collected for subsequent experiments. The offspring mice were divided into offspring control group and offspring PNE group according to the maternal group respectively. Weights of P0 and P25 offspring mice were recorded. Micro-CT, scanning electron microscope (SEM) and Vickers hardness test were performed to analyze the related parameters of hard tissues including alveolar bones and mandibular incisors. Total RNAs were extracted from mandible tissues and the third generation of dental epithelial stem cells (DESC) in P25 mice. The relative expression levels of osteogenic and ameloblastic differentiation related genes were measured by real-time quantitative PCR (RT-qPCR). Immunohistochemical stainings of paraffin sections were then performed to observe the distribution and expression level of proliferating cell nuclear antigen (Pcna), amelogenin (Amelx), histone H3 trimethylated at lysine 27 (H3K27me3) and enhancer of zeste homolog 2 (Ezh2). Cell counting kit-8 (CCK-8) assays were used to detect the cell viabilities of DESCs after administrations of different concentrations of nicotine (0.01, 0.1, 1 mmol/L) and GSK126 (an inhibitor of histone methyltransferase Ezh2). Results: Compared with the control group, pregnant mice in PNE group were more likely to have adverse pregnancy outcomes, such as significantly lower offspring body weight [P0: offspring control (1.20±0.04) g, offspring PNE (0.99±0.02) g, P<0.001; P25: offspring control (15.26±1.70) g, offspring PNE (9.65±1.32) g, P<0.001] and increased stillbirths rate [offspring control (0), offspring PNE (46.40±9.30) %, P<0.001]. At P14 and P25, the distance parameters between the enamel mineralized deposits of mandibular incisors and the mesial surface of the first molar in offspring PNE group [P14: (-1 349±45) μm; P25: (-1 192±147) μm] was significantly decreased compared with the control group [P14: (-506±380) μm, P25: (504±198) μm] (P<0.05, P<0.001). The enamel column and enamel column stroma of incisors in offspring PNE group were blurred, arranged loosely and disorderly than those in the control group, while the microhardness of incisor enamel in offspring PNE group [(245.7±18.4) MPa] was significantly lower compared to the control group [(371.9±28.7) MPa] (P<0.001). HE staining showed disordered pre-ameloblast (Pre-Am) arrangement and delayed mineralization deposition point in offspring PNE group compared with the control group, while the length of transit-amplifying cell (TA) and Pre-Am region were prolonged as well. Immunohistochemical staining results displayed that the overall Pcna (P<0.05), H3K27me3 (P<0.01), Ezh2 (P<0.01) expression of labial cervical loop (LaCL) in PNE group were increased, while the positive signal of Amelx in ameloblast cytoplasm was impaired. In vitro, the addition of 1 mmol/L nicotine could significantly upregulate the expression level of Pcna (P<0.01) and downregulate the expression levels of B lymphoma Mo-MLV insertion region 1 (P<0.05), leucine rich repeats and immunoglobulin like domains 1 (P<0.05), Amelx (P<0.01). In addition, 1 mmol/L nicotine could also significantly enhance the proliferation activity of DESCs (P<0.001). Addition of 10 μmol/L GSK126, could rescue the proliferation activation effect of 1 mmol/L nicotine on DESCs. Conclusions: PNE may delay the process of enamel formation and lineage differentiation, leading to the abnormal proliferation of DESCs and changes of epigenetic modification state in H3K27me3, which affect the development of enamel in offspring mice,suggesting PNE might be one of risk environmental factor for tooth development.

Analysis on SARS‑CoV‑2 contamination in the environment exposure to the SARS‑CoV‑2 cases in Huangpu District of Shanghai in 2022 / 中国热带医学

@#Abstract: Objective　To analyze the detection of SARS‑CoV‑2 in household environment and public place environment of Huangpu District, and describe the feature of SARS‑CoV‑2 contamination in the environment exposure to the infected cases, so as to support the control strategies such as disinfection and health communication. Methods　The results of RT-PCR test for the environmental samples exposure to the cases infected by SARS‑CoV‑2 during February 1 to March 31 2022 in Huangpu District of Shanghai were collected as the research data. Pearson χ2 was used to test the significance of the differences between positive rates of SARS‑CoV‑2 contamination. Results　From February 1 to March 31, household environment samples had a higher positive rate (6.47%, 234/3 618) of SARS‑CoV‑2 contamination while the public place samples had a lower one (1.22%, 47/3 582) in Huangpu District of Shanghai (χ2=141.908, P<0.01). Among the household buildings, the lane houses of old style representing poorer living condition had the highest positive rates (8.31%, 96/1 155) of SARS‑CoV‑2 contamination while the apartments representing better living condition had the lowest (3.59%, 22/612) (F=5.25，P<0.05). Among the samples from household environment, samples regarding sewerage had the highest positive rates (13.30%,58/436) of SARS‑CoV‑2 contamination, while samples regarding the tool of cooking and sweeping had the lowest (3.10%,17/548) (F=9.84，P<0.01). Among the samples from public place environment, samples regarding entertainment tools had the highest positive rates (13.33%, 2/15) of SARS‑CoV‑2 contamination, while samples regarding the tool of cooking and sweeping had the lowest (0.62%, 4/646) (F=4.22，P<0.01). Conclusion　In the environment exposure to the SARS‑CoV‑2 infected cases, the disinfection, ventilation and cleaning should be intensified strictly. SARS‑CoV‑2's surviving in sewage environment should be evaluation dynamically. More health communication should be pushed to people of poorer living condition.

Pharmacokinetics and drug safety of oral infectious disease during pregnancy / 华西口腔医学杂志

Pregnancy is a time of particular vulnerability in terms of physiologic changes resulting in higher risk of oral infectious diseases. There is emerging evidence showing that irrational dental treatment and drug therapy are associated with adverse pregnancy outcomes, including infant malformation or spontaneous abortion. This article reviews the pharmacokinetics of medications in pregnant women and the fetus and introduces a guideline for drug therapy and common dental drugs used during pregnancy.

Indirect pulp therapy for deciduous teeth with deep caries lesions / 华西口腔医学杂志

Deciduous teeth are the first dentition of humans and play an important role in children's physical and mental development. Dental caries are one of the most common oral diseases in children. According to the data of the World Health Organization, 60%-90% of school children worldwide develop dental caries. In China, dental caries of primary teeth feature high incidence and low rate of visits. Without timely treatment, the deep caries lesions of primary teeth can lead to teeth defect, pulpitis, apical periodontitis, and maxillofacial space infection. Moreover, the premature loss of deciduous teeth can cause malocclusion and eruption disorder of subsequent permanent teeth. These conditions all cause considerable effects on children's oral health and physical and mental development. Performing active and effective measures to treat deciduous teeth with deep caries lesions is important to maintain the integrity and normal physiological function of dentition and facilitate normal eruption of permanent teeth. The current situation of indirect pulp therapy in China was studied in this paper. Basic concepts, including indirect pulp capping, interim therapeutic restoration, partial caries removal, stepwise caries removal, and atraumatic restorative therapy, have been defined by consulting domestic and foreign literature. A theoretical basis for improving the clinical pathway of deciduous teeth with deep caries lesions is provided by explaining the technical connotation and therapeutic importance of indirect pulp therapy in primary teeth.

Bivalent histone modifications during tooth development / 国际口腔科学杂志·英文版

Histone methylation is one of the most widely studied post-transcriptional modifications. It is thought to be an important epigenetic event that is closely associated with cell fate determination and differentiation. To explore the spatiotemporal expression of histone H3 lysine 4 trimethylation (H3K4me3) and histone H3 lysine 27 trimethylation (H3K27me3) epigenetic marks and methylation or demethylation transferases in tooth organ development, we measured the expression of SET7, EZH2, KDM5B and JMJD3 via immunohistochemistry and quantitative polymerase chain reaction (qPCR) analysis in the first molar of BALB/c mice embryos at E13.5, E15.5, E17.5, P0 and P3, respectively. We also measured the expression of H3K4me3 and H3K27me3 with immunofluorescence staining. During murine tooth germ development, methylation or demethylation transferases were expressed in a spatial-temporal manner. The bivalent modification characterized by H3K4me3 and H3K27me3 can be found during the tooth germ development, as shown by immunofluorescence. The expression of SET7, EZH2 as methylation transferases and KDM5B and JMJD3 as demethylation transferases indicated accordingly with the expression of H3K4me3 and H3K27me3 respectively to some extent. The bivalent histone may play a critical role in tooth organ development via the regulation of cell differentiation.

The similarity between human embryonic stem cell-derived epithelial cells and ameloblast-lineage cells / 国际口腔科学杂志·英文版

This study aimed to compare epithelial cells derived from human embryonic stem cells (hESCs) to human ameloblast-lineage cells (ALCs), as a way to determine their potential use as a cell source for ameloblast regeneration. Induced by various concentrations of bone morphogenetic protein 4 (BMP4), retinoic acid (RA) and lithium chloride (LiCl) for 7 days, hESCs adopted cobble-stone epithelial phenotype (hESC-derived epithelial cells (ES-ECs)) and expressed cytokeratin 14. Compared with ALCs and oral epithelial cells (OE), ES-ECs expressed amelogenesis-associated genes similar to ALCs. ES-ECs were compared with human fetal skin epithelium, human fetal oral buccal mucosal epithelial cells and human ALCs for their expression pattern of cytokeratins as well. ALCs had relatively high expression levels of cytokeratin 76, which was also found to be upregulated in ES-ECs. Based on the present study, with the similarity of gene expression with ALCs, ES-ECs are a promising potential cell source for regeneration, which are not available in erupted human teeth for regeneration of enamel.

Translational dental medicine / 华西口腔医学杂志

Over the last decade, as tremendous innovations have been achieved in scientific technology, translational medicine has come into the focus of academic medicine, and significant intellectual and financial efforts have been made to initiate a multitude of bench-to-bedside projects. The concept of translational medicine is described as the transfer of new understandings of disease mechanisms gained in the laboratory into the development of new methods for diagnosis, therapy, and prevention and their first testing in humans, meanwhile, translational medicine also is described as a patient-oriented population research and the translation of results from clinical studies into everyday clinical practice and health decision making. Translational medicine is a hot spot in recent academic field, and it is crucial for improving the living standard of population and renewing the research idea and technology. It has, however, significant obstacles during the approach of translational medicine. We here review the background, concept, current situation of translational dental medicine, key components and obstacles of translational medicine.

Morphology and developmental groove of maxillary permanent central incisors in Sichuan people / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the morphology of maxillary permanent central incisors of people in Sichuan so as to provide some guidance for emulational restoration of fixed prosthesis.</p><p><b>METHODS</b>Fifty-eight extracted maxillary permanent central incisors were selected from people in Sichuan. All of the teeth involved in this study were selected according to certain criterions. The length and width of the anatomical crowns, the length and the width of the developmental grooves and the angles formed by the two sides of the developmental grooves were measured.</p><p><b>RESULTS</b>The average length and width of anatomical crowns in Sichuan people were (11.9 +/- 1.3) mm and (8.7 +/- 0.8) mm respectively. And the average length and width of the developmental grooves were (5.7 +/- 0.9) mm and (2.1 +/- 0.5) mm respectively. There were no statistical differences between the length of the mesial and distal developmental grooves and so were the width. The ratio of the length of crowns to that of the developmental grooves was 2.1, while for the width, it was 4.2. The angles of the mesial and distal developmental grooves formed by its two sides were 23 degrees +/- 4.7 degrees and 23 degrees +/- 5.7 degrees respectively.</p><p><b>CONCLUSION</b>The average length and width of maxillary permanent incisors were close to Wang's report, which means the length and width of the maxillary permanent incisors of people in Sichuan were quite close to those of Chinese people. The ratio of the length of anatomical dental crowns to that of the developmental grooves was steady, and so was the ratio of the width of them. The angles of the developmental grooves were quite steady too. These may help us in making fixed prosthesis.</p>

Investigation of influence on apical sealability generated by root canal sealer placement / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the influence of sealer placement on apical sealability in root canal treatment.</p><p><b>METHODS</b>100 extracted single root canal teeth were selected. All canals were prepared by manual Protaper instrument in a step-back way. The samples were divided into 5 groups randomly. A group: 30 samples, sealer placement by chief gutta percha; B group: 30 samples, sealer placement by K file; C group: 30 samples, sealer placement by spreader; D group: 5 samples, a positive control; E group: 5 samples, a negative control. There were 2 subsets in each experimental group which were obturated by lateral gutta percha with or without sealer. Glucose oxidase method was used to measure the apical leakage at the 1st 2nd, 4th, 7th, 10th, 15th, 20th, 25th, 30th day of the experiment.</p><p><b>RESULTS</b>Apical sealability varied with different sealer placement methods (F=4.832, P=0.001). Sealer placement by chief gutta percha (A group) had the best instant apical sealability. However, lateral gutta percha with or without sealer didn't affect the apical sealibility.</p><p><b>CONCLUSION</b>Placing the same kind sealer in different ways can affect the apical sealability. There were no significant differences of the apical leakage no matter the lateral gutta percha with or without sealer. In order to get better instant apical sealability and simplify the clinic operation, placing the sealer with a chief gutta percha while the lateral gutta percha without sealer is recommended.</p>