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Table of Content
10 April 2018, Volume 36 Issue 2
  • Orginal Article
    The applications of periodontal gingival surgery. Ⅱ: alternative materials
    Mao Erjia
    West China Journal of Stomatology. 2018, 36(2):  117-122.  doi:10.7518/hxkq.2018.02.001
    Abstract ( 1266 )   HTML ( 58 )   PDF(pc) (4913KB) ( 1581 )   Save
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    The main purposes of periodontal graft surgery include achieving root coverage, improving the clinical attach-ment level and keratinized tissue, and advancing the procedure of periodontal plastic surgery. Autogenous graft, such as sube-pithelial connective tissue graft-based procedure, provide the best outcomes for mean and complete root coverage, as well as increase in keratinized tissue. However, a disadvantage of the procedure is in the location of the operation itself: the additional surgical site (palate). Therefore, clinicians are always looking for graft substitutes. This article will discuss the evidence sup-porting the use of 1) acellular dermal matrix (ADM); 2) xenogeneic collagen matrix (XCM); 3) recombinant human platelet-derived growth factor (rhPDGF); 4) enamel matrix derivative (EMD); 5) guided tissue regeneration (GTR); 6) living cellularconstruct (LCC), all of which are used in conjunction with coronally advanced flaps as alternatives to autogenous donor tissue. The decision tree for treatments of Miller recession-type defects are also discussed.

    Protective effects of hydrogen-rich medium on lipopolysaccharides-induced injury in human periodontal ligament cells
    Min Zhou, Zuolin. Wang
    West China Journal of Stomatology. 2018, 36(2):  123-127.  doi:10.7518/hxkq.2018.02.002
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    Objective In this study, lipopolysaccharides (LPS) was used to damage human periodontal ligament cells (hPDLCs) and consequently investigate the protective effects of hydrogen on reducing oxidative stress and cell apoptosis rate. Methods hPDLCs were isolated, and then cultured with normal medium+1 μg·mL-1 LPS or with hydrogen-rich medium+1 μg·mL-1 LPS. Cell proliferation activity was assessed using a cell counting kit-8 (CCK-8), and lactic dehydrogenase (LDH) release was also detected. The activities of superoxide dismutase (SOD) and catalase (CAT), and the level of malonaldehyde (MDA) in supernatants were also measured. Cell apoptosis was detected by flow cytometry at 24 h after LPS stimulation. Results CCK-8 results showed that hydrogen could significantly improve hPDLCs growth and decrease cell apoptosis under LPS stimulation (P<0.05). However, no significant difference in LDH release was found between the two groups. The CAT levels significantly increased at 6 and 12 h in the hydrogen-rich medium as compared with the normal medium group (P<0.05, P<0.01, respectively). However, SOD levels were not significant different at each time point. At 6 h after LPS stimulation, the MDA levels in the cell supernatant of hydrogen-rich medium group were significantly reduced as compared with those in the normal medium group (P<0.05). Conclusion The hydrogen-rich medium can effectively improve hPDLCs proliferation activity and antioxidant capacity and reduce apoptosis and oxidative stress under LPS stimulation.

    Local injection of exogenous nerve growth factor improves early bone maturation of implants
    Yang Yao, Yu Du, Xia Gu, Mengkai Guang, Bo Huang, Ping. Gong
    West China Journal of Stomatology. 2018, 36(2):  128-132.  doi:10.7518/hxkq.2018.02.003
    Abstract ( 664 )   HTML ( 14 )   PDF(pc) (4155KB) ( 385 )   Save
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    Objective To investigate the effects of nerve growth factor (NGF) in the osteogenic action of implants and the maturation and reconstruction changes in bone tissues in the early stage of osseointegration. Methods The mouse implant model was established by placing titanium in the femoral head of the mouse and locally injecting NGF in the implant zone. On 1, 2 and 4 weeks after operation, stain samples were collected from animals using hematoxylin-eosin (HE) staining and Masson staining. The effect of NGF on the bone maturation was compared at different time points of early stage osseointe-gration. Results The results of HE and Masson staining indicated that the local injection of external NGF can up-regulate bone mass, amount of bone trabecula, and bone maturity in the mouse model. The mature bone rate in treatment group of 1 week and 4 weeks after operation were significantly higher than those in the control group (P<0.05). Conclusion NGF can shorten the period of bone maturation.

    Effects of protein kinase C and motigen-activated protein kinase kinase/extracellular regulated protein kinases signaling pathway on mRNA level of inducible nitric oxide synthase in Tca8113 cells
    Xuefeng Gao, Haibin Jiao, Changcheng Ye, Yingqun. Liu
    West China Journal of Stomatology. 2018, 36(2):  133-139.  doi:10.7518/hxkq.2018.02.004
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    Objective To explore the regulatory mechanism of inducible nitric oxide synthase (NOS-2) expression related to proliferation of Tca8113 cells. Methods RNAi mediated by short hairpin RNAs was utilized to knock down NOS-2, protein kinase C (PKC)-α, PKC-β and PKC-δ. Griess Reagent played a significant role on the detection of NO product after NOS-2 silence. The cell proliferation was determined by CCK8 method. Quantitative real-time polymerase chain reaction (q-PCR) was recruited to check the mRNA level of NOS-2, PKC-α, PKC-β and PKC-δ after treated by a variety of ways. Eventually, the measure of phosphorylation of extracellular regulated protein kinases (ERK)1/2 was performed by Western blotting in PMA-treated Tca8113 cells. Results The cell viability of Tca8113 decreased obviously after transfected with NOS-2 siRNA (P<0.01). PKC reduced the expression level of NOS-2 mRNA (P<0.05). PKC-α, PKC-β and PKC-δ worked together to regulate the level of NOS-2 mRNA (P<0.01). Motigen-activated protein kinase kinase (MEK)/ERK signaling pathway regulated the level of NOS-2 mRNA negatively (P<0.05). PKC down regulated the level of NOS-2 mRNA through MEK/ERK signaling pathway (P<0.05). Conclusion PKC regulates the mRNA level of NOS-2 related to proliferation through MEK/ERK signaling pathway in Tca8113 cells..

    Effects of inhibitory concentration minocycline on the proliferation, differentiation, and mineralization of osteoblasts
    Huaying Shao, Yigong Zhang, Xue Yang, Qiongyue Zhang, Xiaohong Wu
    West China Journal of Stomatology. 2018, 36(2):  140-145.  doi:10.7518/hxkq.2018.02.005
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    Objective To study the effect of the inhibitory concentration minocycline on the proliferation, differentiation, and expression of Runt-related transcription factor 2 (Runx2), alkaline phosphatase (ALP) and osteopontin (OPN) mRNA of osteoblasts. Methods Primary osteoblasts were cultured in osteogenic induction medium containing 0, 0.1, 0.5, 1, 10 μg·mL-1 minocycline. Cell counting kit-8 was used to observe cell proliferation. ALP activity assay, alizarin red S staining, and real-time quantitative polymerase chain reaction (PCR) were used to determine cell differentiation and mineralization. Results The groups with 0.1, 0.5, 1 μg·mL-1 minocycline promoted cell proliferation. The mRNA expression levels of ALP and Runx2 were up-regulated. Osteoblast-mediated mineralization was increased. The group with 1 μg·mL-1 showed maximal promotion effect (P<0.05). When the concentration increased to 10 μg·mL-1, the promoting effect began to decline, and the ALP activity and OPN expression were significantly inhibited (P<0.01). Conclusion Appropriate concentration of minocycline can promote osteoblasts proliferation, up-regulate the expression levels of Runx2, ALP and OPN, and increase the differen-tiation and mineralization of osteoblasts.

    Outcome and influential factors of speech therapy delivered to cleft patients with post-operative velopharyngeal com-petence
    Chunli Guo, Heng Yin, Jingtao Li, Chenghao Li, Yang Li, Bing Shi, Qian. Zheng
    West China Journal of Stomatology. 2018, 36(2):  146-149.  doi:10.7518/hxkq.2018.02.006
    Abstract ( 831 )   HTML ( 20 )   PDF(pc) (1068KB) ( 624 )   Save
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    Objective To analyze the training technique, intervention timing, and other related factors involved in the speech therapy delivered to cleft patients with velopharyngeal competence after surgery. Methods A retrospective study was conducted on 32 patients who received phonology-articulation speech therapies during 2012 to 2013 in Dept. of Cleft Lip and Palate, West China Hospital of Stomatology, Sichuan University. All patients achieved normal speech one year after therapy. Information collected included the types and number of consonant articulation error, the overall period of training, the interval between surgery and speech training, and the age during speech training. Statistical analyses were performed in SPSS 16.0. Results Ten patients received less than five sessions of training, seventeen received six to ten sessions, and five received eleven to twenty sessions. The number of sessions was positively correlated with the number of errors (rs=0.394, P=0.026). On the average, each additional error cost another 0.570 session for correction (confidence interval: 0.137-1.004). Moreover, the number of sessions was negatively correlated with age (P=0.055). Patients between 5 to 10 years old took significantly lesser sessions than those above 10 years. No correlation was found between the number of sessions and the interval between surgeries and trainings. Conclusion Appropriate speech therapy efficiently rehabilitate the speech condition of cleft patients with velopharyngeal sufficiency after surgery. The number of errors is directly proportional to the number of sessions needed. Patients above 10 years require more sessions than those less than 10 years.

    Salivary microbial communities associated with severe early childhood caries
    Tongzheng Sun, Fei Teng, Songbo Jia, Yongping Tang, Ming Jiang, Shi Huang, Xiao Yuan, Xiaolan Li, Fang Yang
    West China Journal of Stomatology. 2018, 36(2):  150-155.  doi:10.7518/hxkq.2018.02.007
    Abstract ( 1189 )   HTML ( 37 )   PDF(pc) (2612KB) ( 945 )   Save
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    Objective To compare the salivary microbial profiles of healthy subjects and those with severe early childhood caries (S-ECC) by using high-throughput sequencing. Methods Salivary samples were obtained from children with S-ECC (group C, n=24) and healthy children (group H,n=24). Total metagenomic DNA was extracted, and DNA amplicons of the V1-V3 hypervariable region of the 16S rRNA gene were generated and subjected to 454 sequencing. The characteristics of oral microbial communities from the two groups were compared based on microbial diversity and taxonomy assignment. Results First, the microbial richness was significantly higher in group C than group H (P<0.05). Second, the microbial com-munity structure was significantly different for the groups H and C (P<0.01). In addition, caries microbiota was significantly conserved in group C (P<0.001). High expression of suspected cariogenic microorganisms in group C (P<0.1) and health related microorganisms in group H (P<0.1) were identified. Finally, models of caries risk assessment were proposed to distin-guish caries from healthy subjects with over 70% accuracy.Conclusion Salivary microbiota and certain taxa, such as caries-associated taxa (Prevotella), may be useful to screen/assess the children’s risk of developing caries.

    Fabrication and accuracy research on 3D printing dental model based on cone beam computed tomography digital modeling
    Huirong Zhang, Lefeng Yin, Yanli Liu, Liyi Yan, Ning Wang, Gang Liu, Xiaoli An, Bin Liu
    West China Journal of Stomatology. 2018, 36(2):  156-161.  doi:10.7518/hxkq.2018.02.008
    Abstract ( 1530 )   HTML ( 34 )   PDF(pc) (2534KB) ( 1273 )   Save
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    Objective The aim of this study is to build a digital dental model with cone beam computed tomography (CBCT), to fabricate a virtual model via 3D printing, and to determine the accuracy of 3D printing dental model by comparing the result with a traditional dental cast. MethodsCBCT of orthodontic patients was obtained to build a digital dental model by using Mimics 10.01 and Geomagic studio software. The 3D virtual models were fabricated via fused deposition modeling technique (FDM). The 3D virtual models were compared with the traditional cast models by using a Vernier caliper. The measurements used for comparison included the width of each tooth, the length and width of the maxillary and mandibular arches, and the length of the posterior dental crest. Results 3D printing models had higher accuracy compared with the tradi-tional cast models. The results of the paired t-test of all data showed that no statistically significant difference was observed between the two groups (P>0.05). Conclusion Dental digital models built with CBCT realize the digital storage of patients’ dental condition. The virtual dental model fabricated via 3D printing avoids traditional impression and simplifies the clinical examination process. The 3D printing dental models produced via FDM show a high degree of accuracy. Thus, these models are appropriate for clinical practice.

    Improved temporary and treatment partial denture in the rehabilitation of patients with temporomandibular joint disorder syndrome
    Hao Zhang, Siwen Li, Jiahuan Fu, Shishi Li, Yanhong Wang, Xiudi Shi, Lu Bai, Hongmei. Ma
    West China Journal of Stomatology. 2018, 36(2):  162-166.  doi:10.7518/hxkq.2018.02.009
    Abstract ( 1239 )   HTML ( 25 )   PDF(pc) (3043KB) ( 945 )   Save
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    Objective This study aims to study the effect of the improved partial denture treatment in the rehabilitation of patients with temporomandibular joint disorders (TMD). Methods Twenty middle-aged and old patients suffering from osteoarthrosis were treated with the improved partial denture treatment. These patients were followed up during the partial denture treatment and after the rehabilitation. Both the clinical symptoms and Fricton’s craniomandibular index were used to evaluate the clinical effects. Data were analyzed using SPSS17.0. Results The effective rate reached 100% when the patients wore partial dentures for 1 month. All of the 20 patients were comfortable with temporomandibular joint, and they expressed ultimate satisfaction with the denture. The Fricton indexes of 20 patients decreased significantly after the treatment (P<0.05). Conclusion Partial denture treatment is an ideal method in rehabilitation for patients with TMD (osteoarthrosis) and dentition defect.

    Time lapse between endodontic and periodontal treatments of combined periodontal-endodontic lesion: a systematic review
    Yue Jin, Bin Chen, Yanhong Ni, Fuhua. Yan
    West China Journal of Stomatology. 2018, 36(2):  167-173.  doi:10.7518/hxkq.2018.02.010
    Abstract ( 998 )   HTML ( 33 )   PDF(pc) (1080KB) ( 1132 )   Save
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    Objective This study aims to evaluate the time lapse between the endodontic and periodontal treatments of the combined periodontal-endodontic lesion to guide the clinical treatment. Methods A systemic literature search was performed in articles published from 1980 to March 2017 using the electronic databases, including PubMed, EMbase, Cochrane, Web of Science, CNKI, CBM, and Wanfang Databases. Results After screening, two randomized controlled trials, two prospective case series studies, and eight case reports were ultimately included. All clinical studies and case reports were treated with root canal therapy and periodontal nonsurgical or periodontal surgical treatment, with root canal therapy as the initial treatment step. Changes in the periodontal probing depth and attachment loss were reported in all clinical studies and case reports. Conclusion An observational period between the endodontic and periodontal nonsurgical treatments may not be required. However, given that the quality of several included studies was limited, and the number of randomized controlled trials was small, a large number of randomized controlled trials are needed to verify this result.

    Effects of recasting in vacuum with argon on the chemical composition of ceramic alloys
    Yinghui Wang, Fenfang Qiu, Weiqing Wu, Hui Cheng
    West China Journal of Stomatology. 2018, 36(2):  174-177.  doi:10.7518/hxkq.2018.02.011
    Abstract ( 441 )   HTML ( 4 )   PDF(pc) (965KB) ( 340 )   Save
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    Objective This study aimed to determine the effect of recasting in vacuum with argon on the chemical compo-sition of cobalt-chromium (Co-Cr), commercially pure titanium (cpTi), palladium-based (Pd-based), and aurum-platinum (Au-Pt) ceramic alloys. Methods Without adding new alloys, Co-Cr, cpTi, Pd-based, and Au-Pt ceramic alloys were recast one to three times under the condition of vacuum compressive casting with argon. Before recasting, four previously cast ceramic alloys were treated with the corresponding method. After polishing, the chemical composition of the four ceramic alloys recasted one to three times were determined by energy-dispersive spectrometry. Results No significant difference was observed in the chemical composition of the four ceramic alloys recast 1-3 times (P>0.05).Conclusion Under the condition of vacuum with argon, the recasting had no obvious influence on the chemical composition of Co-Cr, cpTi, Pd-based, and Au-Pt ceramic alloys.

    Effects of copper content on the antibacterial performance and corrosion resistance of CoCrMoCu alloy
    Zhun Yin, Yibin Ren, Desong Zhan
    West China Journal of Stomatology. 2018, 36(2):  178-183.  doi:10.7518/hxkq.2018.02.012
    Abstract ( 563 )   HTML ( 9 )   PDF(pc) (1705KB) ( 525 )   Save
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    Objective This study aimed to determine the effects of copper content on the corrosion resistance of CoCrMoCu alloy and its in vitro antibacterial performance Methods CoCrMoCu specimens with different Cu contents (2%, 3%, 5%, and 7%) were prepared by vacuum melting method. CoCrMo without Cu served as control. The corrosion resistance of the specimens was measured by electrochemistry. The antibacterial effects of the specimens on Staphylococcus aureus and Esche-richia coli were analyzed by coating-film method. Results Compared with CoCrMo without Cu, the addition of 2%-5% Cu to CoCrMo improved the pitting and uniform corrosion of CoCrMo alloy and decreased the corrosion current density. The antibacterial performance of CoCrMoCu alloy increased with increased Cu content. The antibacterial rate of alloy was 99% when Cu content exceeded 5%. Conclusion Cu addition had a statistically significant influence on the corrosion resistance and antibacterial performance of CoCrMoCu. CoCrMoCu has better corrosion resistance and antibacterial performance when Cu content is 5%.

    Effects of tumor necrosis factor-α on osteogenic differentiation and Notch signaling pathway in human periodontal ligament stem cells
    Yu Ma, Shuhui Li, Xinxin Ding, Peiling. Wu
    West China Journal of Stomatology. 2018, 36(2):  184-189.  doi:10.7518/hxkq.2018.02.013
    Abstract ( 585 )   HTML ( 6 )   PDF(pc) (2283KB) ( 516 )   Save
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    Objective To evaluate the effects of tumor necrosis factor-α (TNF-α) on osteogenic differentiation and Notch signaling pathway of periodontal ligament stem cells (PDLSCs) and to investigate the regulatory role of Notch signaling path-way on the osteogenic differentiation of PDLSCs under the influence of TNF-α. Methods PDLSCs were obtained through enzyme digestion and tissue block method. The expression levels of stem cell surface markers CD105, CD90, CD146, CD45, and CD31 were detected by fluorescence activated cell sorter (FACS). PDLSCs were divided into experimental (10 ng·mL-1 TNF-α) and control groups (0 ng·mL-1 TNF-α). The proliferation ability of PDLSCs was detected using cell counting kit-8 (CCK-8). The effect of TNF-α on the osteogenic ability of PDLSCs were tested by measuring alkaline phosphatase (ALP) activity and conducting alizarin red staining and quantitative real-time polymerase chain reaction (PCR). We tested Notch signal pathway receptors Notch1, Notch2, ligand JAG1, JGA2, and downstream gene Hes-1. Changes in DLL1 expression were detected by quantitative real-time PCR. ResultsFACS profiling showed that PDLSCs were strongly positive for CD105, CD90, and CD146 but negative for CD45 and CD31. CCK-8 results showed that TNF-α could promote the proli-feration of PDLSCs (P<0.05). ALP activity in the experi-mental group was lower than that in the control group (P<0.05). Alizarin red staining showed that the experimental group had decreased mineralized nodules as compared with the control group. Quantitative real-time PCR results showed that the mRNA expression of osteogenic marker genes cementum attachment protein (CAP), osteopontin (OPN), and Runt-related transcription factor 2 (Runx2) significantly decreased in the experimental group as compared with those in the control group (P<0.05). The expression levels of Notch1, Notch2, JAG1, JGA2 and Hes-1 were significantly decreased (P<0.05), whereas those of Notch3 and DLL1 were increased in Notch signaling pathway-related molecules (P<0.05). Conclusion TNF-α can promote PDLSCs proliferation and inhibit bone differentiation and Notch signaling pathway expression, indicating that the Notch signaling pathway regulates PDLSCs osteogenic differentiation.

    Effect of bone morphogenetic protein-4 overexpression on the biological activity of mouse induced pluripotent stem cells
    Jin Qiu, Huiyu Zhang, Li Liu, Yinghui Tan
    West China Journal of Stomatology. 2018, 36(2):  190-193.  doi:10.7518/hxkq.2018.02.014
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    Objective This study aimed to construct the expression of bone morphogenetic protein-4 (BMP4) lentiviral vector gene and explore its influence on the biological activity of mouse induced pluripotent stem (iPS) cells. Methods iPS cell lines stably overexpressing BMP4 were constructed by lentivirus transfection (BMP4-overexpressing group). Cells without transfection served as the blank group, and cells with only vector transfection served as the empty-vector group. Cell prolifera-tion was detected by CCK8, and the expression levels of ameloblastin (AMBN), cytokeratin (CK) 14, dentin sialophospho-protein (DSPP), bone sialoprotein (BSP), and Runx2 mRNA were detected by quantitative polymerase chain reaction. Alkaline phosphatase (ALP) activity was used to detect the degree of cell differentiation. Results Compared with blank and empty-vector groups, proliferation activity and ALP activity of BMP4-overexpressing group obvious increased (P<0.05), BMP4, AMBN, CK14, DSPP, BSP, Runx2 mRNA expression also increased (P<0.05). Conclusion BMP4 can significantly promote the odontogenic differentiation of iPS.

    Prevalence survey of dental trauma to immature permanent teeth in Xi’an schoolchildren
    Xiaomin Wang, Xuelong Su, Hong Wang, Fei Liu, Yaping Zhao, Qingyu. Guo
    West China Journal of Stomatology. 2018, 36(2):  194-198.  doi:10.7518/hxkq.2018.02.015
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    Objective The prevalence rate, distribution, and reasons of immature permanent-tooth trauma in Xi’an were investigated and described, and a scientific basis was provided for the decision-making of health-administration departments. Methods Through cluster and simple random sampling survey, 4 013 pupils in schools from nine districts and four counties in Xi’an were sampled. All pupils and their parents were requested to complete a questionnaire. Oral examinations were con-ducted for children who had immature permanent teeth trauma. The number of trauma teeth and teeth were recorded. Survey data were analyzed statistically. Results The prevalence rate of immature permanent dental trauma was 10.5% in Xi’an. No significant differences were observed between districts and counties (P>0.05). The peak age of permanent dental trauma was at 7-9 years old, and the most was at 8 years old (31.5%). The first reason of trauma was falling down (50.9%), and the second reason was crash (36.0%). The most common trauma teeth were maxillary incisors (75.4%). Conclusion The prevalence rate of immature permanent teeth trauma in Xi’an was in the middle of all international levels. Children, who are vulnerable to dental trauma at their age, should be provided with appropriate prevention measures to reduce the incidence of dental trauma.

    Investigation on level and influencing factors of first aid knowledge among dentists in Sichuan province
    Yu Qiu, Yuanyuan Li, Tianguo Li, Yige Chen, Jingjun Kong, Jian. Pan
    West China Journal of Stomatology. 2018, 36(2):  199-203.  doi:10.7518/hxkq.2018.02.016
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    Objective The study aims to investigate the cognition degree and influencing factors of first aid knowledge among dentists in Sichuan province, and to provide suggestions for the training of oral clinician. Methods A questionnaire was designed for this study. It included the basic situation of population, first aid knowledge level, emergency situation often encountered in stomatology clinic, first aid training situation, learning approach and attitude of first aid knowledge, etc. This questionnaire was used to investigate the dentists of medical institutions in various cities in Sichuan province. The survey results was statistical analyzed. Results There were 245 valid questionnaires. 1) The level of first aid knowledge of dentists was generally lower in Sichuan province. Work department and other departments work experience were the influencing factors of knowledge level of first aid knowledge among dentists. 2) 87.3% of dentists believed that it was very necessary to master the knowledge of first aid, but in the event of an emergency situation, 73.5% of dentists only can find other doctors to guide themselves to help. 3) The most common way to learn first aid knowledge was through work experience and medical school’s first aid course. Conclusion Dentists should strengthen the learning and training to improve the first aid skill.

    Advances in the molecular mechanisms of perineural invasion in salivary adenoid cystic carcinoma
    Mei Zhang, Xinhua Liang, Yaling Tang
    West China Journal of Stomatology. 2018, 36(2):  204-211.  doi:10.7518/hxkq.2018.02.017
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    Salivary adenoid cystic carcinoma is a very common malignant neoplasm in the salivary glands. One of the most important features of salivary cystic carcinoma is perineural invasion, which renders its complete removal is very difficult through clinical surgery. Consequently, tumor recurrence occurs easily after clinical surgery. Therefore, the molecular mecha-nisms of perineural invasion in salivary adenoid cystic carcinoma are necessary to explore. These mechanisms are reviewed in this paper.

    Methods of removing failed implants
    Wanrong Wang, Xiaofeng Chang, Longlong He
    West China Journal of Stomatology. 2018, 36(2):  212-214.  doi:10.7518/hxkq.2018.02.018
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    Implant restoration has become one of the most regular methods of restoring dentition defect or edentulous. Implant placement and osseointegration are partly unreserved (fracture, implant is not in the correct three-dimensional position and cannot be repaired, peri-implantitis-affected nonmobile implants) need to be removed. This article reviews the different methods of removing implants and discusses the limitations of each method, as well as the complications that may occur during the procedure.

    Current situation of clinical research on impacted premolars
    Ranran Liu, Jun. Tian
    West China Journal of Stomatology. 2018, 36(2):  215-219.  doi:10.7518/hxkq.2018.02.019
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    Teeth impaction is a common developmental malformation in oral diseases. Impacted teeth are usually the canines, third molar, central incisors, premolars, and second molars. The prevalence of impaction of maxillary canines and mandibular wisdom teeth is higher than that of other teeth. Most recent studies have focused on the canines and third molars, but research on impacted premolars is limited. In clinical practice, the majority of orthodontic patients require premolar extrac-tion. Thus, impacted premolars play important roles in orthodontic design and prognosis. This article provides an overview of recent research on impacted premolars and summarizes epidemiological features, localizations, and treatments, with the aim of guiding practitioners on orthodontic design and therapy.

    Advances in surgical techniques of periodontal corticotomy
    Siyu Wang, Zhendong Wang, Bin. Yan
    West China Journal of Stomatology. 2018, 36(2):  220-225.  doi:10.7518/hxkq.2018.02.020
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    The number of adults seeking orthodontic treatment is increasing. Shortening the course of orthodontic treatment has become a research hotspot in recent years. Methods of accelerating tooth movement have been reported. Theoretical and clinical studies have confirmed that periodontal corticotomy is effective in accelerating tooth movement and increasing osteo-genic potential. Many surgical techniques of periodontal corticotomy have been developed. This review summarizes the history of periodontal corticotomy and the development of the surgical techniques in recent years, thereby providing references for the clinical application of corticotomy.

    Orthodontic intrusion of the first and second mandibular molars with a vacuum-formed removable appliance: a case report
    Qing Liu, Xinqi Huang, Dan Jiang, Haojun Chi, Lingjie Wang, Wentian Sun, Jun Liu
    West China Journal of Stomatology. 2018, 36(2):  226-228.  doi:10.7518/hxkq.2018.02.021
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    This case report focused on a patient with supraeruption of the first and second mandibular molars as a result of loss of the first and second maxillary molars for a long time. We adopted a combination of a vacuum-formed removable appliance and elastics to intrude the first and second mandibular molars by using a continuous, light force to acquire sufficient restoration space for maxillary molars. Thus, the dental-implant treatment was successful, and a good and stable occlusal relationship was established.

    Maxillary first premolar with four canals: a case report
    Yang Meng, Degang. Sun
    West China Journal of Stomatology. 2018, 36(2):  229-231.  doi:10.7518/hxkq.2018.02.022
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    This article presented a case of discovering and diagnosing three roots with four canals of the maxillary first premolar. We found and located the extra root canal by clinical diagnosis, careful observation during the operation, and mul-tiangle X-ray. We further confirmed the existence of the three roots with four canals with the help of cone-beam computed tomography. Finally, we verified the success of the high-quality root-canal therapy through root optical microscopy.