Objective　To study the stress distribution of cylindrical implants and conical implants at different implant depths in jaw by using three-dimensional finite element method. Methods With Astra Tech Osseo SpeedTM5.0sTX as reference, Solidworks software was used to simulate and establish the bone models of cylindrical implant and conical implants, abutments and crowns, respectively. The bone models were imported into abaques finite element software, and the force of 45 °180N was obliquely loaded on the crown. The Von-mises stress distribution of cylindrical implants and conical implants at different planting depths was analyzed. Results Under 45 °180N load, the maximum stress of cylindrical implants and conical implant appeared at the junction between implant and abutment. With the increase of implant depth in alveolar bone, the stress distribution range of both implants increased, and under the same load, the distribution of stress in conical implant was smaller than that in cylindrical implant. Conclusion Considering the shape and depth of implant, the stress of conical implant is smaller than that of column implant, so too deep planting should be avoided when implanting.

Objective　To explore the roles of YAP1-FOS in promoting the process of cell proliferation, migration and EMT in oral squamous cell carcinoma (OSCC). Methods　The YAP1 expression and subcellular localization in the OSCC cancer tissue and the surrounding normal tissue were detected by tissue immunofluorescence assay. The effect of YAP1 on cell proliferation in OSCC cells was tested by cell clonogenic assay. The effect of YAP1 on cell migration in OSCC cells was detected by cell scratch assay. The effects of YAP1 on the marker gene protein expression and changes in marker gene transcription level of EMT related molecule were respectively detected by Western blot and RT-PCR. The process in which YAP1 and FOS interacted with each other to control the conversion process of EMT through mutual regulation of downstream genes was detected by CoIP and immunoblot. Results　The immunofluorescence assay results showed that the YAP1 expression increased in OSCC cancer tissue and transferred from cytoplasm to cell nucleus. Clonogenic assay results showed that the clone number increased significantly after over-expression of YAP1 (P < 0.01). The scratch assay results showed that the wound distance significantly decreased after over-expression of YAP1(P < 0.01). Western blot and RT-PCR showed that the expression levels of the key gene of epithelial cells E-cadherin were downregulated (P < 0.01), while the expression levels of the key genes of mesenchymal cells, β-catenin, Vimentin and N-cadherin, were upregulated significantly after YAP1 over-. CoIP and immunoblot results showed that YAP1 interacted with FOS, then the ability of YAP1 promoting cell proliferation significantly weakened afte the depression of FOS expression, meanwhile the marker expression of EMT related molecule was significant down-regulated(P < 0.01). Conclusion　YAP1 combined with FOS genes promotes the cell proliferation, migration and EMT transcription in human OSCC, which provides a theoretical basis for the occurrence and development of human OSCC. YAP1-FOS may become the new drug target of human oral cancers.

Objective To study the effect of Porphyromonas gingivalis infection on rheumatoid arthritis in mice model. Methods The mice were divided into rheumatoid arthritis (CIA) group and periodontitis combined with rheumatoid arthritis (CIA+Pg) group. Periodontitis models were constructed by oral inoculation of Porphyromonas gingivalis, and the rheumatoid arthritis model was induced by bovine II collagen. To determine the effect of Porphyrinomonas gingivalis infection on the severity of rheumatoid arthritis, the severity of rheumatoid arthritis was assessed by rheumatoid arthritis score. The level of rheumatoid factor in plasma was detected by enzyme linked immunoassay kit. Results The onset of rheumatoid arthritis in the CIA+Pg group were significantly shorter than those of the CIA group, and the symptoms were more serious. The inflammatory factors related to rheumatoid arthritis such as TNF-α, IL-1, IL-6 and IL-17 were also significantly higher in CIA+Pg group. Conclusion The infection of Porphyromonas gingivalis can promote the occurrence of rheumatoid arthritis and aggravate the symptoms of it.

Objective　To evaluate the biosafety of four different disinfectants applied to microbial contamination control in DUWLs. Methods The cytotoxicity of four different disinfectants (hydrogen peroxide nano silver ion, sodium hypochlorite, hydrogen peroxide, chlorhexidine) on human oral mucosal epithelial cells under different concentrations in vitro and the biosafety of different disinfectants were studied and compared by CCK-8. Results The four disinfectants all produced cytotoxicity after being treated with human oral epithelial mucosal cells for a certain period of time under the common disinfection concentration. However, the toxicity grades of 0.2% hydrogen peroxide nano silver ion and 0.2% chlorhexidine were medium toxicity (Grade 2), the toxicity grades of 5.25% sodium hypochlorite and 3% hydrogen peroxide were severe toxicity (Grade 4). Conclusion The cytotoxicity of different disinfectants in vitro is different. Hydrogen peroxide nano silver ion and chlorhexidine are less toxic to cells than the sodium hypochlorite and hydrogen peroxide under the common concentration of water pollution control in dental unit waterlines and are relatively safe.

Aim:The purpose of this study was to assess the efficacy of desocclusol, eucalyptol and d-limonene on removal of gutta-percha, their effect on microhardness of dentin, and the antibacterial properties against Enterococcus faecalis (E. faecalis) during root canal retreatment. Methods: Forty single-canal roots, obturated with gutta-percha, were prepared and randomly devided into 4 groups(n=10). Group that free of any solvent was control group.Three of experimental groups were exposed to desocclusol, eucalyptol and d-limonene respectively during endodontic retreatment. Efficacy of each solvent was assessed by comparation of duration time, amount of apical extrusion and residual debris in the root canals. Vickers microhardness of each sample was recorded. Antibacterial activity on E. faecalis was also observed. The data were subjected to repeated statistical analysis. Results: All three organic solvents were found to be effective in the removal of root canal filling material compared with control group(P<0.05). D-limonene was more effective in significantly increasing the microhardness of dentin compared with desocclusol, which decreased the microhardness of root canal dentin(P<0.05). In the meantime, d-limonene had a stronger antibacterial activity than eucalyptol, while desocclusol had no obvious bacterial inhibition. Conclusion: These three organic solvents are all effective in removing gutta-percha in endodontic retreatment. D-limonene can increase the microhardness of dentin and has a stronger inhibitory effects on E.faecalis than desocclusol and eucalyptol.

Objective: To provide a procedure of tooth extraction for patients underwent radiotherapy and chemotherapy treatment. Methods: Seventeen patients who had received radiotherapy and chemotherapy were routinely examined bofore tooth extraction and treated with preoperative oral cleaning and prophylactic antibiotics. Minimally invasive tooth extraction with analgesia was ensured and blood pressure, heart rate and electrocardiogram were mornitored and recorded. Postoperative follow up was routinely carried out.Results: According to the preoperative examination results, the tooth extraction contraindications were excluded. The heart rate, blood pressure and electrocardiogram of the patients did not change significantly during the treatment period; the patients recovered well after surgery. Conclusion: Patients with stable condition after chemoradiotherapy can achieve safe tooth extraction if follow a certain treatment procedure.

Objective　To investigate the characteristics of maxillary sinus mucositis adjacent to teeth with apical periodontitis (AP) and evaluate its resolution after endodontic treatment with cone beam computed tomography(CBCT). Methods 25 maxillary sinuses in patients who had AP associated with maxillary posterior teeth were scanned with CBCT. When mucositis was found, its resolution was evaluated with CBCT imaging 3 months after endodontic treatment, and periapical healing was assessed by the periapical index(PAI) after 6 months. Results Excluding 2 sinusitis, mucositis was found in 14 of 23 sinuses (61％). Three months after therapy, mucositis was fully resolved in 5 of 14 patients (35.7％), partially resolved in 6 of 14 patients(42.9％), unchanged in 3 patients(21.4％). Six months after treatment, a total of 3 of 14 teeth (21.4％) were healed, 4 of 14 teeth(28.6％) were healing, 7 of 14 teeth(50％) had persistent AP. Conclusions Endodontic treatment is an effective therapy for posterior teeth associated with AP which can easily trigger maxillary sinus mucositis. CBCT can accurately assess the resolution of maxillary sinus mucositis before and after endodontic treatment, which has important clinical reference value.

Objective　To investigate the role of participatory treatment in dental treatment of preschool children. Methods 90 children aged 3 to 6, who first visited our stomatological clinic from June 2017 to June 2018 and needed to be re-visited, were selected. According to the random number method, they were divided into experimental group and control group, 45 cases in each group. The control group was given routine intervention, and the experimental group was given participatory treatment besides routine intervention at each visit. Children’s fear survey schedule-dental subscale (CFSS-DS), the Frankl behavior rating scale (Frankl), the Houpt behavior rating scale (Houpt) were used to evaluate the degree of dental fear, treatment compliance and treatment completion of the two groups after the first visit and the second visit, and their statistical differences were compared. Results The rate of re-visit in the experimental group was 93.33%, higher than that in the control group (77.78%), and the difference was statistically significant (?2=4.406, P<0.05). The CFSS-DS scores of the experimental group were lower than those in the control group, and the Frankl compliance and Houpt effect were better than those of the control group. There were significant differences between the two groups in the three scales(P all<0.05). Compared with the first visit, the CFSS-DS score of the experimental group was lower and Frankl treatment compliance was better, and the differences were statistically significant (P all< 0.05), but there was no significant difference in the results of the Houpt scale (P>0.05). Conclusion Participatory treatment in dental treatment of preschool children can alleviate the degree of dental fear, improve the treatment rate and compliance.

The root canal system of the maxillary first molar is complicated. The incidence of second distobuccal canal（DB2）in the maxillary first molar is low. This article reported a clinical case of maxillary first molar with a DB2 canal which acquired successful root canal treatment. Additionally, the paper discussed the root canal anatomy of the maxillary first molar, the characteristics of the missing canal and how to improve the ability of locating additional root canals.

The lack of alveolar bone volume after tooth loss has always been one of the most knotty problems in dental implantation. After a long period of exploration and research, a series of classical efficient surgical methods such as autogenous bone grafting and guided bone regeneration (GBR) have emerged, which to some extent well solved this problem. GBR technology has been favored by both dentists and patients for its advantages of good predictability of osteogenesis, low long-term bone resorption rate, easy filling and shaping, no second surgical area and fewer complications. However, with the progress of science and technology, platelet concentrate has come to the fore as a new technology. With a lot of unique advantages, platelet concentrate has proven its value in tissue augmentation in dental implant field, and even challenges the classical GBR technology. This article will focus on reviewing the advantages of platelet concentrate in dental implantation, especially in tissue augmentation.

The prevalence rate of cleft lip and palate in our country is high and most of the cleft lip and palate patients develop alveolar cleft at the same time. There is much literature indicating that alveolar bone level of the teeth near the cleft is low and orthodontic treatment before the alveolar bone grafting can aggravate the existing low alveolar bone level. So it is important to understand the morphology of the alveolar bone near the cleft and to limit the movement of the teeth in the pre-operation orthodontic treatment. Cone-beam computed tomography （CBCT） shows great accuracy and reproducibility in the quantitative research of alveolar bone, which have great advantage over the traditional two-dimensional periapical film. The present review focuses on the morphology of alveolar bone near the cleft.

Scaffolds for dental pulp regeneration have been gradually developed and become research hotspots in recent years. Hydrogel, with toughness, rheology, good bio-compatibility and biodegradability, was more and more widely used in dental pulp regeneration. Hydrogel plays an important role in control of stem cell fate, control of growth factor release and delivery of anti-inflammation and anti-bacteria drugs. In this article we reviewed the research progress on hydrogel in dental pulp regeneration.

Abstract：　Oral squamous cell carcinoma (OSCC) is one of the most usual oral epithelial malignant tumors.Its etiology is commonly concerned as interactions of genetic, environmental, infection and other multi-factors.Human papillomavirus has been identified as one of the risk factors for the occurrence of OSCC, while some other scholars believe that Epstein-Barr virus, herpes simplex virus type I, human cytomegalovirus,human herpes virus-6,hepatitis C virus and other viruses can also cause oral cancer, but these views are still controversial. This article reviews the literature in recent years to reveal the etiological role of viral infections in OSCC and provide ideas for future research.

Aquaporin 5 (AQP5) is a protein that can specifically transport water across membranes. It can significantly increase cell membrane water permeability, participate in water secretion and absorption, and maintain water balance inside and outside the cells. It plays a key role in human external secretion function. Recent studies have found that salivary gland secretion is inseparably related with the expression and localization of AQP5. AQP5 is clinically used as a target for the treatment of salivary gland secretion disorders, which has achieved considerable therapeutic effects. This article reviews the structure and function of AQP5 as well as its role in salivary gland secretion and clinical application.

Lingual orthodontics is applied widely in the clinical treatment with the patients’ increased demand for invisibility. The biomechanical characteristic of lingual orthodontics is very different from conventional labial orthodontics, especially in the effect of orthodontic force and the control of anchorage. This review discussed the biomechanical characteristic of lingual orthodontics and the clinical related implications.

Skeletal class II malocclusion characterized by mandibular retrognathism, is a common kind of orthodontic issues. Functional appliances can be used in growing adolescents, aimed to advance the growth of mandible, improve overjet and facial soft tissue profile. This article describes the research methods, dentoalveolar effects, skeletal effects and soft tissue profile effects of class II functional appliances.