Objective To explore the expression and significance of Dickkopf-1 (Dkk-1) and cell lymphoma/leukemia-2 (Bcl-2) protein in sinonasal squamoucell carcinoma(SNSCC) .MethodThe immunohistochemical SP method and Western blomethod were adopted to determine the expression of Dkk-1 and Bcl-2 in 30 specimenof SNSC(SNSCgroup) ,38 specimenof sinonasal inverted papillomas(SNIP group) and 20 specimenof middle turbinate mucosa(control group) .ResultThe expression of DKK-1 protein in the SNSCgroup wasignificantly down-regulated compared with the SNIP group and the control group ,while the expression of Bcl-2 protein in the SNSCgroup wasignificantly up-regulated compared with the SNIP group and the control group;in the SNSCgroup ,the positive rateof DKK-1 protein and Bcl-2 protein in the high and middle differentiation group and the low differentiation group were 100 .00% ,68 .75% ,33 .33% and 50 .00% ,62 .50% ,100 .00% respectively ,the differencewere statistically significan(P＜0 .05) .Conclusion Dkk-1 protein may play an importanpromoting role in the developmenand pro-gression procesof SNSC,the expression of Dkk-1 protein hanegative correlation with the expression of Bcl-2 protein in SNSC,which may become new targespoof SNSCgene therapy .

Objective To study the tooth and periodontal stress distribution and tooth displacement after apical root resection, so as to provide data support for clinicians to perform apical root surgery and improve the cure rate of apical root surgery. Methods Three-dimensional (3D) finite element model of normal maxillary central incisor with its periodontal tissues was established based on Micro CT image data. Then periapical periodontitis and apical root resection surgery were simulated. The model of periapical periodontitis and maxillary central incisor with different apical root resection length (3, 4, 5, 6, 7, 8 mm) and their supporting tissues were established. With the occlusal force applied, the biomechanical behavior of postoperative healing teeth was studied by 3D finite element analysis. The optimal apical resection length was obtained by comparing biomechanical effects of surgical restoration. Results The completely healed model reduced the stress (by 26.8%) and displacement (by 7.3%) compared with the apical periodontitis model. With the increase of apical root resection length, the stress of the teeth neck and periodontal ligament increased by 11.14% and 29.27%, respectively, when the root resection was 8 mm. The stress of the alveolar bone increased by 83.11%. The stress of new apical root at the section increased on the whole compared with the same part of normal tooth. The displacement of the tooth along the long axis also increased. The displacement significantly increased by 18.39% when the resection length was over 5 mm. Conclusions Apical root resection significantly improves the biomechanical properties of refractory apical periodontitis tooth. The recommended resection length was 3-5 mm and the crown-to-root ratio (CRR) should be larger than 0.84.

Objective:To assess the influence of a virtual simulation-based training system for composite resin filling on the knowledge acquisition, skill development, and overall learning experience of undergraduate stomatology students.Methods:Forty-one undergraduate students of grade 2019 majoring in stomatology were divided into two groups for preclinical training before their internships: the experimental group used a virtual training system for composite resin filling, while the control group watched instructional videos of the procedure. The two groups were compared for their first performance in composite resin filling during the internships and teaching feedback. The t-test and chi-square test were conducted for data analysis using SPSS 20.0. Results:After repeatedly using the virtual training system for composite resin filling, the students in the experimental group were able to master the key operational points of the procedure, all achieving high scores (an average of 91.77 points) with an average time of 10.39 minutes. During the internship phase, the experimental group and control group showed significant differences in the accuracy rates of instrument selection (85.71% vs. 40.00%), adhesive applying (76.19% vs. 45.00%), and layered filling (100.00% vs. 75.00%; all P<0.05). All the students unanimously recognized the value of the virtual simulation system and expressed their willingness to use it for preclinical training before internships. Nineteen students (90.48%) were satisfied with the learning experience with the virtual simulation training system. Conclusions:The virtual simulation training system for composite resin filling can improve students' understanding and proficiency levels of the technique before clinical internships, facilitating a smoother transition to the internship phase.

Objective : To compare the removal efficiency and the amounts of apically extruded debris using Twisted File (TF), Twisted File Adaptive (TFA), ProTaper, and ProTaper Next combined with ultrasonic irrigation and to provide an experimental basis for the selection of root canal instrumentation in the clinic. Methods: Forty mandibular premolars were randomly divided into 4 groups (n=10 teeth per group). The canals were cut using a Twisted File, Twisted File Adaptive, ProTaper, or ProTaper Next nickel-titanium instrument. The canals were irrigated with ultrasonic irrigation. The apically extruded debris were collected in preweighted Eppendorf tubes. The amount of dental tissue removed and extruded debris were assessed with an electronic balance. Results : The amount of tooth tissue removed in groups A, B, C and D was 20.5 ± 2.0 mg, 17.8 ± 4.2 mg, 20.8 ± 3.9 mg and 16.5 ± 2.2 mg, respectively. Combined with ultrasonic irrigation, the Twisted File and ProTaper had a better removal efficiency than the ProTaper Next(P < 0.05). There was no significant difference in the amount of extruded debris (χ2=4.057, P=0.255) among four groups. Conclusion The Twisted File and ProTaper had a better removal efficiency than the ProTaper Next combined with ultrasonic irrigation. There was no significant difference in the amount of extruded debris using four Nickel-titanium instruments combined with ultrasonic irrigation.