BACKGROUND:Based on variational principle and weighting technology of three-dimensional finite element method, human teeth with a complex morphology can be modeled, which helps to understand the stress distribution of dental hard tissue and prosthesis during the dynamic repair process. OBJECTIVE:To comprehensively analyze the three-dimensional finite element studies concerning biomechanics of dental prostheses, focusing on the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. METHODS:A computer-based search of PubMed (1993-04/2012-09), China Academic Journal Network Publishing Database (2001-2008), and VIP (2001-2008) was performed by the first author to retrieve articles concerning the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. The keywords were“porcelain-fused-to-metal, finite element method, stress analysis, root canal”in English and Chinese. Articles with repetitive contents or meta-analysis were ruled out. Then 40 articles were suitable for further analysis.RESULTS AND CONCLUSION:Finite element method has important significance to establish high-fidelity and high-accuracy models in oral medicine, thereby providing effective biomechanical information for the root canal treatment and post-treatment repair. Scholars continue to explore the stress distribution of dental prostheses during chewing. This review summarizes the stress changes of post and core crowns, supporting reference for further research. Three-dimensional finite element method can be used to build nonlinear three-dimensional finite element models with anisotropic biomechanical characteristics, and can gradual yimprove the transition from static analysis to a dynamic analysis, truly achieving accurate simulation of oral biology and dental morphology as wel as chewing function of the teeth.

Objective:To investigate the differences in ametropia among school-age children and between Han and Uygur ethnic groups in the main urban area of Kashgar, and to understand the epidemiological characteristics of myopia among children in Kashgar.Methods:A cross-sectional study was conducted.Random stratified sampling method was used to select the first to third grade students from 6 primary schools in the main urban areas of Kashgar, Xinjiang, from April to June 2018.Visual acuity was examined by the international standard visual acuity chart and refraction was detected by the automatic computer refractometer without cycloplegia.The subjects were classified into low vision (uncorrected visual acuity<0.8 in either eye), hyperopia≥2.00 D, myopia≥-1.00 D, astigmatism≥1.00 D and anisometropia≥1.00 D according to examination results.The percentage of different refraction states and percentage of different ethnic groups among myopic students in the three grades were analyzed.The study protocol was approved by an Ethics Committee of The First People's Hospital in Kashgar ([2021] QSY No.81).Results:A total of 6 108 students were enrolled, among which, there were 3 119 males and 2 989 females, 3 395 Uygur and 2 713 Han people, 2 016 first grade, 2 155 second grade and 1 937 third grade students.The detection rate of low vision was 13.5% (825/6 108) in the whole, 21.5% (584/2 713) in the Han people and 7.1% (241/3 395) in the Uygur people, 8.8% (176/2 016) in the first grade, 11.8% (254/2 155) in the second grade and 20.4% (395/1 937) in the third grade.The detection rate of myopia was 9.9% (606/6 108) in the whole, 17.6% (477/2 713) in the Han people and 3.8% (129/3 395) in the Uygur people, 4.4% (89/2 016) in the first grade, 8.1% (174/2 155) in the second grade and 17.7% (343/1 937) in the third grade.There were significant differences in percentage of low vision, myopia, astigmatism and anisometropia among different grades and between the two nationalities (all at P<0.001), and no significant difference in the percentage of hyperopia was found (P>0.05).Conclusions:The percentage of visual abnormalities and myopia in the first to third grade children in Kashgar is lower than the national average, but the percentage is gradually increasing with age.The percentage of visual abnormalities and myopia among Han pupils is close to the national average, and far higher than that of Uygur pupils.

Objective: To observe the analgesic and anti-inflammatory effect of mandelic acid. Methods: Fifty Kunming mice were randomly divided into 5 groups:the blank control group (0. 1 ml/10 g), mandelic acid high (300 mg·kg-1), medium (200 mg ·kg-1 ) and low (140 mg·kg-1 ) dose groups, and the positive control ( aspirin) group, ig, qd. The analgesic effect of mandelic acid was observed by writhing test and hot plate method in mice. The ear swelling model caused by dimethyl benzene in mice was a-dopted to observe the analgesic effect. Results:Mandelic acid in each dose group could make the number of writhing in mice signifi-cantly reduced and pain threshold extended, and when compared with the blank control group, the difference was statistically significant (P<0. 01). The writhing times of mice mandelic acid high dose group was fewer than that of the positive control group, and there was no statistically significant between the groups (P>0. 05). In low and medium dose group, the writhing times of mice were more than those of the positive control group, and there was a significant difference between the low dose group and the positive control group( P<0. 05). The pain threshold of the mice in each mandelic acid dose group was higher than that of the positive control group, the pain threshold increased significantly in the high dose group before and after the administration, and the difference was statistically signifi-cant when compared with the positive control group (P<0. 05). The effect of mandelic acid on the ear swelling of mice was not signifi-cant, and when compared with the blank control group, the difference was not significant (P>0. 05). Conclusion:Mandelic acid has significant analgesic effect, while anti-inflammatory effect is not obvious.

Objective To investigate pathogenic genes related to the phenotype of fetus with severely short limbs in the first and second trimester by whole exome sequencing (WES). Methods Thirteen fetuses with severely short limbs detected by ultrasonography in the first and second trimester admitted in Chinese PLA General Hospital from September 2016 to June 2018 were collected. All cases were performed induced abortion, 6 of which were carried out karyotype analysis of amniotic fluid at the same time. WES and copy number variations (CNV) were performed on specimens from fetal tissues after labor induction. The suspected pathogenic mutations were validated by Sanger sequencing reactions. Results No abnormal karyotypes or pathological CNV were found. In 10 fetuses, pathogenic or possibly pathogenic mutations were detected in the following genes: COL2A1, FGFR3, COL1A1, COL1A2, DYNC2LI1 and TRIP11, all of which were essential to skeletal development. The diagnostic yield of WES in the fetuses with severe short limbs was 10/13. Conclusions In the first and second trimester, most of the fetuses with extremely short limbs suffer from monogenic diseases. WES is likely to be a valuable diagnostic testing option for the fetuses with severe short limbs.

Objective:To investigate the status quo of multi-level pre-job training for clinical nursing teachers and analyze their training needs, so as to provide reference for the design of pre-job training for clinical nursing teachers.Methods:A cross-sectional survey method was used to investigate 172 clinical nursing teachers in a tertiary general hospital in Harbin from April 2020 to June 2020 with multi-level pre-job training mode. The status quo of pre-job training and the training needs of teachers were analyzed. SPSS 17.0 was used to process the original data statistically.Results:Among the 172 respondents, 138 teachers (80.2%) were under 35 years old, and 133 teachers (77.3%) had a bachelor's degree or less; 89 teachers (51.7%) confirmed that hospitals or departments would carry out pre-job training in a planned and organized way, 10 teachers (5.8%) said that hospitals or departments had never organized training, 41 teachers (23.8%) had never participated in pre-job training, and 80 teachers (46.5%) had participated in pre-job training 1-3 times. There were 5 duplicates in the first 8 training contents of in-hospital training and in-department training, including knowledge of common diseases, nursing procedures, communication skills, hospital rules and regulations, and teaching methods. The total score of training demand was (154.51± 40.35) points, and the overall demand rate was 81.3%, which was at the high level. The dimensions with the highest scoring rate were legal system and humanistic literacy, with a scoring rate of 83.0%. The dimension with the lowest score was teaching management, with a score of 74.9%. The scoring rate of training needs with the highest points won nine items respectively on students' basic quality (self-supervision, willingness to learn, professional quality, etc.) (84.7%), training of legal knowledge (84.4%), incompatibility of drugs commonly used in department (84.3%), nurse etiquette (83.3%), nursing risk prevention (83.1%), evaluation methods of student education (83.1%), nurse-patient communication skills (83.0%), nurses and patients medication observation points of commonly used drugs in the department (83.0%), and effects of commonly used drugs in department (82.9%). Among the top three training forms, 84 students (48.8%) received online learning, 74 students (43.0%) received lectures from experienced teachers in hospitals, and 72 students (41.9%) received experience exchange and sharing seminars.Conclusion:The talent structure of clinical nursing teachers in this hospital is relatively young, and the first education level is low. Therefore, the pre-job training of clinical nursing teachers should be strengthened vigorously. The awareness rate and participation rate of pre-job training are average, so we should strengthen the release of training information from various channels, improve the awareness rate of training activities, clarify the encouragement or reward measures to participate in pre-job training activities, and improve the participation rate of training activities. Pre-job training content is repeated at every level, with a gap between the training needs of teachers in clinical nursing teaching. It's suggested that the teaching hospitals combine with their training objects of training needs, take the online-offline mixed mode of training, reasonably plan training contents as a whole at all levels, avoid training content repetition and waste of teachers, and organize teachers to timely exchange and share experiences.