Chinese Journal of Dental Research, 02/2020

Coronavirus disease 2019 has become a worldwide pandemic that is seriously jeopardising people's health. The National Health Commission and regional health administrations have issued regulations on the prevention and control of coronavirus disease 2019. Dentistry involves many invasive treatments, which differentiates it from other forms of medical practice. The following guidelines were produced by experts from the Stomatological Healthcare Service branch of the Chinese Stomatological Association to prevent the spread of coronavirus disease 2019 in dental clinics. The guidelines are in accordance with the relevant laws and documents from the health administration and range from technical guidelines to advice on how dental treatment should be conducted. Dental institutions can take these suggestions as a reference, based on the current local epidemic situation. It is anticipated that the guidelines will help dental institutions of different sizes to prevent the spread of the epidemic. Keywords: coronavirus disease 2019 (COVID-19), nosocomial infection prevention and control 

In December 2019, some new and unexplained cases of pneumonia were found in Wuhan, Hubei province, China, and were later named as coronavirus disease 2019 by the World Health Organisation. The number of cases increased rapidly, and the virus spread continuously. Tens of thousands of medical staff throughout the country have since rushed to Wuhan to provide intensive medical treatment. Due to high levels of stress and work intensity, insufficient sleep and a lack of access to water after entering the isolation ward, staff may suffer from oral mucosal ulcers and other oral mucosal diseases. Police officers, community workers, family members in quarantine and even patients with mild coronavirus 2019, as well as those who have previously had oral mucosal disease, have also reported experiencing discomfort as a result of stress-induced oral mucosal disorders, such as recurrent aphthous ulcers, chronic cheilitis and oral lichen planus. This article will offer some suggestions for the prevention, treatment and care of the above-mentioned oral mucosal diseases during the fight against coronavirus 2019, focusing on measures to deal with the oral mucosal damage caused in response to stress. Keywords: cheilitis, coronavirus disease 2019 (COVID-19), oral lichen planus, recurrent aphthous ulcers, stress response

A severe public health crisis has been declared worldwide since coronavirus disease 2019 (COVID-19) was classified as a pandemic of acute respiratory infectious disease by the World Health Organisation (WHO). China has taken strict measures to curb the spread of the disease to save lives, and has managed to control the outbreak. COVID-19 is mainly transmitted through respiratory droplets and close physical contact, so it is challenging to prevent nosocomial infection and possible spread during dental treatment. Since the initial phase of the COVID-19 outbreak, a disease prevention and control strategy based on the new concept of population risk classification and rational use of personal protective equipment has been implemented by the Peking University Hospital of Stomatology. Nosocomial infection prevention and control concepts and measures relating to dental diagnosis and treatment are critically checked in the hospital. Our experiences in handling this situation are shared here and may have wide-ranging implications for infection prevention and control (IPC) for COVID-19 in dental practices worldwide. Keywords: coronavirus disease 2019, dentistry, health care personnel, infection prevention and control, personal protective equipment, population risk classification

Clinical and epidemiological studies suggest that human-to-human transmission of coronavirus disease 2019 (COVID-19) most frequently occurs through virus-laden respiratory droplets discharged from infected individuals while coughing and sneezing. Aerosols can act as another potential transmission route. The World Health Organisation (WHO) has advised medical personnel to consider taking 'airborne precautions'. It is important to protect dentists and patients and reduce the amount of spatter produced during dental procedures. In order to prevent airborne transmission, dental offices should be sufficiently ventilated, with great emphasis placed upon removing bioaerosols. Keywords: aerosol, airborne transmission, disease prevention during dental care, SARS-CoV-2, ventilation

Objective: To understand the immune molecular landscapes of the two major costimulatory and coinhibitory pathways (B7 and TNFR families) in oral squamous cell carcinoma. Methods: The B7 family members (CD80, CD86, CD274, ICOSLG, CD276, VTCN1, NCR3LG1, HHLA2 and PDCD1LG2) and TNFR family members (TNFSF4, CD40, CD70, TNFSF9, TNFRSF14 and TNFSF18) were used to analyse the costimulatory and coinhibitory pathway alterations in oral squamous cell carcinoma. The online tools UCSC Xena and cBioPortal were used to derive oral squamous cell carcinoma patients' clinical parameters, mRNA levels, mutations, DNA copy number alterations and methylation levels. The correlations between mRNA levels and methylation levels were determined using Spearman's correlation analysis. A Kaplan-Meier survival analysis was performed to examine the relationships between mRNA expression levels and overall survival. Results: Compared with normal oral epithelial tissues, approximately 23.1% of patients showed upregulation of B7 expression and 15.3% showed upregulation of TNFR expression in oral squamous cell carcinoma, with CD274 (PD-L1) upregulation being the most common alteration. Mutations and copy number alterations were shown to have little effect on B7 and TNFR expression. The mRNA levels of B7 and TNFR genes were negatively correlated with their methylation levels. Furthermore, oral squamous cell carcinoma patients with high expression levels of CD274 showed poor overall survival, while those with high expression levels of CD276 or HHLA2 showed good clinical outcomes. Conclusion: This study elucidated the molecular landscapes of the B7 and TNFR genes in oral squamous cell carcinoma, which could provide a novel strategy for clinical therapy. Keywords: B7, genomic alteration, oral squamous cell carcinoma, survival, TNFR

Objective: To investigate and characterise the differences between the open chromatin regions of oral and epidermal keratinocytes. Methods: Human immortalised oral epithelial cell lines (HIOECs) were used as the standard model for oral keratinocytes, and primary normal human epidermal keratinocytes (NHEKs) were chosen as the model for epidermal keratinocytes. Assay for transposase accessible chromatin using sequencing (ATAC-seq) and H3K27ac chromatin immunoprecipitation sequencing (ChIP-seq) were used to evaluate the dynamic changes in open chromatin regions and active enhancers during oral keratinocyte differentiation. In silico prediction and dual-luciferase assays were used to evaluate the enriched motifs and maintain enhancer activity in specific enriched HIOECs. Integration and comparison of HIOEC ATAC-seq with NHEK ATAC-seq were used to identify oral keratinocyte–enriched open chromatin regions along with key motifs governing differential enhancer activity. The genomic regulatory elements and GWAS overlap algorithm was used to compare the annotation rate of HIOEC-overlapped craniofacial enhancers with other craniofacial enhancers for orofacial cleft–associated variants. Results: During the differentiation of HIOECs, 14933 open chromatin regions became more accessible. Grainyhead-like (GRHL) and Krüppel-like factor (KLF) motifs were overrepresented in maintaining HIOEC-specific activity. Compared with NHEKs, 16161 open chromatin regions were uniquely accessible in HIOECs. Within these regions, the C/EBP motif governed HIOEC-specific enhancer regulating SOX2 and PITX2, which enhanced oral keratinocyte wound healing. When intersected with human craniofacial super-enhancers, open chromatin regions in HIOECS can better annotate the common variants associated with orofacial cleft. Conclusion: The intrinsic differences between the open chromatin regions of human oral and epidermal keratinocytes are directly maintained by a set of transcription factors. Keywords: keratinocytes, open chromatin regions, transcription factors

Objective: To explore the self-assembly and gelation properties of synthetic peptides, and their efficacy on hydroxyapatite (HAP) nucleation and in situ remineralisation of initial caries lesions. Methods: Mass spectrometry and reversed-phase high performance liquid chromatography (RPHPLC) were used to confirm the successful synthesis of peptides. Their self-assembly properties and conformation stability were evaluated using circular dichroism (CD) spectroscopy and Fourier-transform infrared spectroscopy (FTIR). Cell Counting Kit-8 (CCK-8; Dojindo, Kumamoto, Japan) was used to evaluate their cytotoxicity. The efficacy of the peptides on HAP nucleation and in situ remineralisation of initial caries lesions was explored using FTIR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction and transverse microradiography analysis. Results: Two kinds of self-assembly β-sheet peptides named ID4 and ID8, respectively, were successfully synthesised with purities greater than 95%. Both were stable under neutral physiological conditions and had low cytotoxicity. ID4 and ID8 showed calcium responsive self-assembly properties and could self-assemble into nanofibres. Compared with ID4, ID8 resulted in the rapid formation of hydrogel with a lower concentration of calcium, and self-assembled ID8 hydrogel induced the formation of flower-like HAP and significantly promoted the remineralisation of initial enamel caries. Conclusion: ID8 could serve as the template to induce HAP nucleation and promote biomimetic remineralisation of initial caries lesions. These results underpin future research on peptide design, and ID8 may be a promising bioactive component for anti-caries applications. Keywords: β-sheet peptide, hydroxyapatite, initial caries lesions, remineralisation, self-assembly

Objective: To compare the biological characteristics of dental pulp stem cells (DPSCs) and inflamed dental pulp derived stem cells (I-DPSCs) in vitro and their regeneration potential in Beagle immature premolars. Methods: Pulpitis was induced in the premolars of one beagle dog by opening the pulp chamber for 2 weeks, and inflammation was histologically confirmed. DPSCs and I-DPSCs were isolated from normal and inflamed dental pulp, and cell morphology, expression of mesenchymal stem cell markers, clone formation ability, cell proliferation and osteogenic/odontogenic differentiation potential were compared. The dental pulp of 20 roots from 10 immature premolars was extracted and divided into two groups. DPSCs or I-DPSCs with scaffolds were transplanted into the root canals. The roots were extracted after 3 months, and pulp regeneration was evaluated by histological analysis. The data were statistically analysed using one-way ANOVA and a Student t test. Results: Histological analyses showed lymphocyte infiltration and elevated TNF-α expression, which confirmed the diagnosis of pulpitis. I-DPSCs showed similar morphology, marker gene expression and clone formation ability but greater proliferation ability and osteogenic/odontogenic differentiation potential. Pulp-like tissue formation and bone- and dentine-like tissue deposition were observed in both DPSC- and I-DPSC–transplanted roots. Conclusion: DPSCs derived from inflammatory dental pulp tissue have similar biological characteristics to those from normal dental pulp and could mediate pulp and dentine regeneration in immature premolars. Keywords: dental pulp stem cells, inflamed dental pulp, tissue regeneration

Three patients diagnosed with peri-implant disease after osseointegration exhibited soft tissue oedema and fistulae. Treatment options for controlling the fistulae were investigated. Free subepithelial connective tissue grafts (SCTGs) and microinvasive surgery were used to improve the soft tissue biotype of the patients with fistulae. After SCTG surgery, the fistulae disappeared. The clinical outcomes were stable and aesthetic outcomes were satisfactory after 3–5 years of follow-up. Based on this study, utilising SCTG to improve the tissue biotype may be an effective clinical approach for controlling fistulae occurring during peri-implant disease. Keywords: connective tissue, follow-up, microinvasive surgery, peri-implant disease, tissue biotype