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    20 April 2021, Volume 29 Issue 4
    Expert Forum
    Etiology, pathogenesis, diagnosis and treatment of oral submucous fibrosis
    JIAN Xinchun,GAO Xing
    2021, 29(4):  217-225.  DOI: 10.12016/j.issn.2096-1456.2021.04.001
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    Oral submucous fibrosis (OSF) is a chronic disease that produces scars, tissue fibrosis, and precancerous lesions. Epidemiological studies have shown that chewing betel nut is the most significant risk factor for OSF. Many studies have also indicated that habits such as chewing and smoking tobacco and drinking alcohol increase the risk of OSF, which is widely recognized as an oral precancerous lesion or a potentially malignant oral disorder. Pathological characteristics include chronic inflammation, excessive collagen deposition in the connective tissues below the oral mucous epithelium and local inflammation in the lamina propria or deep connective tissues. OSF patients have a 7%~30% chance of developing oral cancer. Submucosal local injection of triamcinolone and tanshinone was mainly used for the treatment of oral submucosal fibrosis. This treatment improves mouth opening and alleviates the burning sensation in OSF, and the treatment efficacy was as high as 93%. The article will discuss the occurrence, development, diagnosis and treatment of oral submucous fibrosis for clinical management by the medical community.

    Basic Study
    A novel biomimetic micro/nano hierarchical interface of titanium enhances adhesion, proliferation and osteogenic differentiation of bone marrow mesenchymal cells
    WANG Min,JIANG Nan,ZHU Songsong
    2021, 29(4):  226-233.  DOI: 10.12016/j.issn.2096-1456.2021.04.002
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    Objective To design a novel biomimetic micro/nano hierarchical interface on endosseous titanium implants and investigate its effect on the biological activity of bone marrow mesenchymal cells. Methods Electrochemical anodization and spark plasma sintering were used to modify smooth titanium (untreated Ti group) with a microporous trabecular bone-like architecture (micro-Ti group) and TiO2 nanotube architecture (nano-TiO2 group). Additionally, electrochemical anodization was employed to prepare TiO2 nanotubes on microporous trabecular bone-like architectures, which formed a novel biomimetic hierarchical interface (micro/nano-TiO2 group). Four groups of titanium samples were characterized by field emission scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle (CA). Bone marrow mesenchymal cells (BMMCs) were seeded on four groups of titanium samples. Scanning electron microscopy (SEM) was employed to observe cell morphology. Cell proliferation was determined by MTT assay. The expression of focal adhesion proteins (F-actin; vinculin; osteocalcin, OCN; osteopontin, OPN) were observed under a confocal laser scanning microscope (CLSM). The mRNA expression levels of osteogenic factors (runt-related transcription factor 2, RUNX2; osteocalcin, OCN; osteopontin, OPN; collagen I, COL I) were assessed by qRT-PCR. Results The micro/nano- TiO2 group featured a hydrophilic surface (CA=9° ± 2.1°). The results of the MTT assay indicated that the relative cell proliferation rates for the nano- TiO2 and micro/nano-TiO2 samples were significantly increased compared with those for the untreated-Ti and micro-Ti samples (P<0.001) after 5-9 days. The ALP results indicated that the micro/nano-TiO2 sample gained the highest value at 14 days. After 72 h of incubation, the expression of osteocalcin (OCN) and osteopontin (OPN) on micro/nano-TiO2 was the strongest. After 24 h incubation, the expression of F-actin on micro/nano-TiO2 was the strongest. In comparison with untreated-Ti and micro-Ti samples,the mRNA expression levels of all the osteogenic factors (runt-related transcription factor 2, RUNX2; osteocalcin, OCN; osteopontin, OPN; Collagen I, COL I) were markedly increased on the nano-TiO2 and micro/nano-TiO2 samples, the mRNA expression levels of collagen I (COL I) were significantly different between the nano-TiO2 and micro/nano-TiO2 samples versus the untreated-Ti and micro-Ti samples (P<0.001). Conclusion The novel biomimetic micro/nano hierarchical interface has a positive effect on cell attachment, viability and osteogenic differentiation of bone marrow mesenchymal cells.

    Kaempferol promotes osteogenic differentiation of mouse bone marrow mesenchymal cells under tension stress via the mTORC1 signaling pathway
    CUI Linna,JIANG Xiaowen,HUANG Huaqing,CHEN Jinyong
    2021, 29(4):  234-240.  DOI: 10.12016/j.issn.2096-1456.2021.04.003
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    Objective To investigate the activation of the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway molecules during the process by which kaempferol (Kae) promotes osteogenic differentiation of mouse bone marrow mesenchymal cells (BMMCs) under cyclic and uniaxial tension. Methods BMMCs isolated and cultured in vitro were subjected to uniaxial dynamic tension with a 10% shape variable. The appropriate concentration of Kae was selected by cytotoxicity testing. The endogenous mTOR signal was inhibited by pp242. Four hours after traction, alkaline phosphatase (ALP) and osteocalcin (OCN) were detected by chemical colorimetry and ELISA, and the relative concentration of intracellular calcium was detected by flow cytometry. Phosphorylation of mTOR, 4E/BP1, and ribosomal protein S6 kinases (S6K), which are the main molecules of the endogenous mTORC1 signaling pathway, and expression of osteogenic transcription factors (Runx2 and Osterix) were detected by western blotting (WB), and mRNA expression levels of the above factors were detected by qRT-PCR. Results The cytotoxicity test showed that 10 μmol/L Kae had little inhibitory effect on cell proliferation but had the strongest osteogenic ability. Four hours after stretching, Kae effectively promoted the osteogenic differentiation of BMMCs. The expression of ALP was (153.04 ± 18.72) U/mg, the expression of OCN was (1.64 ± 0.25) U. The mRNA and protein levels of Runx2 and Osterix were upregulated, and the intracellular calcium content was decreased. The mRNA and protein phosphorylation of mTOR and S6K was upregulated, and the opposite effect was observed with 4E/BP1. After pp242 was added to inhibit mTOR signaling, mTOR and S6K mRNA and protein phosphorylation were downregulated, but 4E/BP1 mRNA and protein phosphorylation was upregulated. The osteogenic differentiation of BMMCs was also significantly inhibited, mRNA and protein expression of Runx2 and Osterix were significantly downregulated, ALP and OCN expression were downregulated, and intracellular calcium content was increased. Conclusion Kae promotes osteogenic differentiation of mouse BMMCs under uniaxial dynamic tension through the mTORC1 signaling pathway.

    Cinical Study
    Efficacy and safety of Bifidobacteria in preventing caries: a systematic review and meta-analysis
    HAO Siyuan,WANG Jiahe,ZHANG Xiaoqi,ZOU Jing,WANG Yan
    2021, 29(4):  241-248.  DOI: 10.12016/j.issn.2096-1456.2021.04.004
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    Objective To systematically evaluate the efficacy and safety of Bifidobacteria in preventing caries. Methods Databases including PubMed, Embase, The Cochrane Library, Web of Science, Scopus, Clinicaltrials. gov, CNKI, WanFang Data and VIP were electronically searched from inception to April 2020 to collect randomized controlled trials of Bifidobacterium for caries. Meta-analysis was performed using Revman 5.4 software. Results In total, 10 randomized controlled trials (RCT) of 518 patients, including 262 in the test group and 256 in the control group, were included. Meta-analysis results reveal no statistically significant differences in salivary Streptococcus mutans counts (SMD=-0.31, 95%CI -0.66 to 0.04, P=0.08) (RR=0.53, 95%CI 0.17 to 1.66, P=0.28) and salivary Lactobacilli counts (SMD=-0.07, 95%CI -0.39 to 0.26, P=0.69) (RR=0.87, 95%CI 0.59 to 1.29, P=0.50). No statistical differences in the counts of Streptococcus mutans and Lactobacillus counts were noted in dental plaque, and no statistical difference in the occurrence of caries in deciduous teeth. Three of the 10 RCTS included in this study did not report adverse events, 5 had no adverse reactions, and 2 reported gastrointestinal discomfort.Conclusion Current evidence suggests that Bifidobacteria do not effectively reduce Streptococcus mutans counts and Lactobacillus counts in saliva and dental plaque, or reduce the occurrence of caries in deciduous teeth. The safety of this treatment also requires further investigation.

    1 429 cases treated with nitrous oxide inhalation sedation in dental clinic: a retrospective study
    DENG Yujie,YANG Xiaobin,CHEN Hao,LAI Jinhuan,ZHOU Miao
    2021, 29(4):  249-253.  DOI: 10.12016/j.issn.2096-1456.2021.04.005
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    Objective The use and effect of nitrous oxide sedation techniques in oral clinics were analyzed retrospectively. Methods Patients who were treated with nitrous oxide inhalation sedation in the clinic of the Affiliated Stomatological Hospital of Guangzhou Medical University from January 1, 2016, to December 30, 2018, were examined. Age and gender of the patients, dental treatments involved, reasons for nitrous oxide inhalation, sedative effects and adverse reactions were compiled. Results A total of 1 429 cases were examined, comprising 587 males and 842 females, and the average age was 32.64±16.34 years old. Among the patients who underwent nitrous oxide inhalation sedation in the oral clinic, 79.98% needed tooth extraction, and 79.50% had a dental fear of procedures. The patients were divided into following 7 age groups: 5-15 years old, 16-25 years old, 26-35 years old, 36-45 years old, 46-55 years old, 56-65 years old and > 65 years old. The sedation satisfaction rate of the 5-15-year-old group was 45.71%, and the sedation satisfaction rate of the other 6 age groups was 90.83%- 96.20% (P < 0.001). The incidence of total adverse reactions was 5.39%; the incidence was higher in females than in males, and the incidence was higher in the 16-25 age group than in the other age groups (P < 0.05). The most frequent adverse reaction was vertigo (81.82%). Conclusion Among the four common oral outpatient treatment programs including the extraction of teeth, dental implants, pulp treatment and periodontal treatment, patients undergoing inhalation sedation of nitrous oxide in the dental extraction most. The most common reason for requiring sedation is dental fear, and the sedative effect of the 5-15-year-old group was significantly worse than that of the other age groups. The incidence of adverse reactions of nitrous oxide sedation was low and manageable.

    Comparison of diagnosing the relationship between the root of maxillary posterior tooth and maxillary sinus between panoramic radiography and cone beam computer tomography
    SHU Jingjing,ZENG Feiyue,ZHANG Yanan,XU Qimei,TANG Jialu,XU Bin,SONG Liang
    2021, 29(4):  254-259.  DOI: 10.12016/j.issn.2096-1456.2021.04.006
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    Objective To study the diagnostic accuracy and the distance between the root of maxillary posterior tooth and the maxillary sinus using panoramic radiography and cone beam computer tomography; to provide basic information for clinicians to treat diseases in the maxillary posterior region. Methods Eighty patients were included in this study. A total of 671 specimens were measured for the distance between the root tip and the maxillary sinus floor in both imaging modalities. Results The roots that did not contact the sinus floor or contacted but did not project into the sinus cavity showed an agreement of 82% and 70% when using panoramic radiography. Forty-eight percent of the roots that projected into the sinus cavity in panoramic radiography showed protrusion into the sinus with cone beam computer tomography (CBCT). For panoramic radiography and CBCT showing root projections into the sinus cavity, the average distances were 2.19 ± 1.82 mm and 1.47 ± 1.01 mm, respectively. There was a significant difference between the two values (P < 0.05). Conclusion Panoramic radiography is more accurate when roots of maxillary posterior teeth do not contact the sinus floor or contact it. However, it has a lower accuracy rate when the tooth roots protrude into the sinus.

    Review Articles
    Research progress on biomarkers related to radiotherapy and/or chemotherapy-induced oral mucositis
    LING Yunxiao,WANG Jiantao,WANG Yan
    2021, 29(4):  260-266.  DOI: 10.12016/j.issn.2096-1456.2021.04.007
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    Radiotherapy and/or chemotherapy-induced oral mucositis is a common oral complication in tumor patients undergoing radiotherapy and/or chemotherapy, which seriously compromises patients’ quality of life and even affects anti-tumor treatment. Biomarkers are signal indicators that appear at different biological levels before or during disease. A comprehensive understanding of the biomarkers associated with oral mucositis contributes to the early identification of high-risk patients with oral mucositis and aids in the screening of patients prone to develop severe oral mucositis, guiding the prevention and treatment of oral mucositis. This article reviews the existing biomarkers associated with oral mucositis. The literature review results showed that the biomarkers associated with oral mucositis included growth factors, inflammatory cytokines, genes, plasma antioxidants, and pro-apoptotic proteins/inhibitor of apoptosis proteins. These biomarkers can be used to predict the risk of oral mucositis or facilitate early discrimination of patients prone to exhibit severe radiotherapy and/or chemotherapy-induced oral mucositis. EGF, TNF-α, IL-6, IL-1β and CRP can be used to predict and evaluate the risk and development of oral mucositis, whereas genes such as excision repair cross complementing 1(ERCC1), X-ray repair cross complementing 1(XRCC1), methylenetetrahydrofolate reductase (MTHFR) and tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) have been focus of research in recent years. The genotypes and expression levels of some of these genes exhibit variable capacities to predict the risk and severity of oral mucositis. However, no biomarkers have been used in clinical practice, and more studies are needed in the future to verify the reliability and accuracy of these biomarkers, to provide a reference for the early accurate prevention and treatment of radiation and chemotherapy oral mucositis.

    Research progress on the relationship between the changes in microbial community composition of plaque and dental caries in children
    ZHOU Qingnan,SHANG Jiajian
    2021, 29(4):  267-272.  DOI: 10.12016/j.issn.2096-1456.2021.04.008
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    Among many factors affecting dental caries, bacteria are its initiating factor. From the perspective of ecological plaque hypothesis, the application of modern molecular biology methods enable scholars to deeply explore the relationship between the microbial population distribution, biodiversity, microbial community changes of dental plaque biofilm and the occurrence of dental caries in children. The decrease in microflora diversity is closely related to the occurrence of dental caries, which can be detected as early as 6 months before the occurrence of dental caries, providing an important basis for caries monitoring and caries risk assessment. Differential bacteria such as Lactobacillus and Veillonella may be used as biomarkers of caries in children to judge the risk of caries in children. However, current studies have shown that the dominant bacteria in the microbial community structure vary in different processes of caries occurrence and development, that the interaction between different flora is still not clear, and that the specific cariogenic mechanism of the oral plaque microbial community in the process of caries occurrence and development has not been clarified. Further research is still needed to explore the changes in plaque microbial diversity and composition during the development of dental caries and to screen specific dental caries biomarkers. This paper also summarizes the related research findings.

    Effect of mechanical stimulation on the differentiation of stem cells in periodontal bone tissue engineering
    LI Tianle,CHANG Xinnan,QIU Xutong,FU Di,ZHANG Tao
    2021, 29(4):  273-278.  DOI: 10.12016/j.issn.2096-1456.2021.04.009
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    Currently, cell transplantation in combination with scaffold materials are one of the main strategies in periodontal bone tissue engineering. In periodontal bone tissues, the stiffness and spatial structure of tissues such as alveolar bone and cementum differ, and the difference in mechanical properties of scaffolds also has disparate effects on the proliferation and differentiation of stem cells. Accumulating evidence shows that mechanical stimulating factors such as matrix stiffness and scaffold topography modulate biological behaviors of various seeding cells, including adipose-derived stem cells and periodontal ligament stem cells. A hard matrix can promote cytoskeletal stretching of stem cells, leading to nuclear translocation of Yes-associated protein (YAP) and promoting osteogenic differentiation by upregulating alkaline phosphatase (ALP) and osteocalcin (OCN) via the Wnt/β-catenin pathway. The topologic structure of scaffolds can affect cell adhesion and cytoskeletal remodeling, increase the hardness of cells and promote the osteogenic differentiation of stem cells. In this paper, the effects of mechanical stimulation on the differentiation of stem cells in periodontal bone tissue engineering are reviewed.

    Applications and prospects of 3D printing technology in pulp regeneration
    TAN Guozhong,JIANG Qianzhou
    2021, 29(4):  279-283.  DOI: 10.12016/j.issn.2096-1456.2021.04.010
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    In recent years, pulp regeneration has become a research hotspot in the field of stomatology. 3D printing can realize precise control of structure and shape of scaffolds, which provide basis for seed cell adhesion and growth factor release. The 3D printing "pulp complexes" constructed by 3D printing scaffolds for tissue engineering provides a new direction for pulp regeneration research. This paper reviews the applications of 3D printing technology in pulp regeneration. The results of literature review showed that the scaffold materials, seed cells and growth factors in the 3D printing "pulp complexes" all play an important role in the pulp regeneration research. Among them, the scaffold materials act as carriers to load seed cells and growth factors and provide a suitable microenvironment for them. The common seed cells such as dental pulp stem cells, stem cells from apical papilla and stem cells from the human pulp of exfoliated deciduous teeth can provide the cellular basis for pulp regeneration. Moreover, the introduction of growth factors can further support the differentiation of pulp tissue and the reconstruction of pulp vessels and promote pulp regeneration. At present, the 3D printing "pulp complexes" in the study of dental pulp regeneration has made some progress and can induce the formation of pulp-like tissues in the laboratory. However, preparing 3D-printing "pulp complex" with good biological activity, which integrates biomimetic blood vessels and nerves to supply oxygen and nutrients to the cells in the root canal, remains a huge challenge and still needs further exploration and research.

    Research progress on the application of antibacterial titanium alloys in stomatology
    FAN Dongyang,WANG Qiang,ZHOU Yijun,LI Siwen,FENG Xu,LIU Chunran,CUI Jiasen,SUN Hongchen
    2021, 29(4):  284-288.  DOI: 10.12016/j.issn.2096-1456.2021.04.011
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    Currently, titanium alloys are widely used in the field of stomatology; however, owing to long-term exposure to a complex microbial environment, dental plaques easily form on the surface of the materials, affecting the use efficiency and the service life of the materials. The antibacterial titanium alloy is a new kind of titanium alloy with antimicrobials added through surface modification or overall modification. Based on the location of antibacterial agents in titanium alloy materials, antibacterial titanium alloys can be divided into coating and alloy types. The antibacterial effect of coated antibacterial titanium alloy is good, but the disadvantage is that most of the coatings are not wear-resistant. The widely-used antibacterial agent of the alloy type is metal elements, which can be evenly distributed in the alloy, and the antibacterial properties are stable and long-lasting. Based on whether antibacterial agents can be released, antibacterial titanium alloys can be further divided into active antibacterial and passive antibacterial types. Active antibacterial type titanium alloys can release loaded antibacterial agents, and the antibacterial effect is more obvious, but the release duration of antibacterial agents is relatively short. Passive antibacterial titanium alloys exhibit an antibacterial effect by contact sterilization or inhibition of bacterial adhesion instead of releasing antibacterial agents. The antibacterial titanium alloy can inhibit the adhesion of bacteria on the surface of the material and prolong the service life of oral orthodontic appliances, implants and titanium plates. Moreover, the mechanical properties of the titanium alloy after antibacterial modification are not significantly affected, and the addition of antibacterial agents such as hydroxyapatite can increase the osteogenic function of the material. Therefore, the alloy has good application prospects in the fields of dental implant, orthodontic treatment and oral and maxillofacial surgery. However, most of the current studies on antibacterial titanium alloys are in vitro experiments, and their long-term clinical effects and antibacterial mechanisms are still unclear and need further study.