Objective:To establish a model of mandibular impact third molar extraction with common dental materials for pre-clinical trai-ning.Methods:Based on the characteristics of the common dental materials,the anatomy and extraction skill of mandibular impact third molar,the dental model for mandibular impact third molar extraction was designed and made.Then,this dental model was placed in the head-simulation model as required,and used by the dentists and the students.The questionnaire was designed and used to evalu-ate the effects of the model.Results:A new method of designing and making a dental model for mandibular impact third molar extraction with the common dental materials was established successfully.The questionnaire results showed that all the dentists and students agreed that this model could simulate the mandibular third molar extraction procedure.Conclusion:Simulation model of the mandibular third molar extraction can help students for the following clinical practice.

Objective:To investigate the survival rate and clinical failure reasons of onlay and occlusal veneer restorations retrospectively,and to put forward valuable suggestions for the selection of clinical in-dications.Methods:A total of 102 patients and 124 teeth treated by one of the authors from 2016 to 2019 were subjected to CAD/CAM lithium silicate reinforced glass-ceramic onlay or veneer restorations of premolars and molars,including 43 teeth with pulp vitality,81 endodontic treated teeth,and occlusal thickness of restoration was 1.5 mm.After four years of restoration,retrospective surveys were conducted to record the survival rate of restorations,the causes of restoration failure,and patient satisfaction rates,and the survival rate of restorations between vital teeth and endodontic treated teeth and among restored teeth was statistically analyzed by Chi-square test.Results:The survival rates of restorations on vital teeth and endodontic treated teeth were 95.5％and 90.0％,respectively,the average survival rate was 90.2％.The survival rates of vital teeth were higher than those of endodontic treated teeth without statis-tical difference.There was also no statistically significant difference among the tooth locations.The cau-ses of failure included the cracking of the restoration,the loss of the restoration,the fracture of the abut-ment teeth,secondary caries below the adjacent contact point,and food impaction caused by the loose-ning of the adjacent contact point.The overall patient satisfaction rate was 91.5％.Conclusion:The 4-year survival rate of glass-ceramic onlays and occlusal veneers is lower than that of the full crown restora-tion,and there are more complications than that of the single-crown restorations.The design of the resto-ration should be carefully selected based on the vitality of the abutment tooth and the remaining amount of tooth tissue.When there is too little tooth structure left,a post and crown should be selected for restora-tion.Adequate strength and thickness of the restoration should be ensured to prevent food impaction.Due to the small amount of abutment tooth preparation,it has the advantages of less stimulation of the pulp and periodontal tissue,and can be recommended as a trial restoration.

Objective    To analyze the effect of modified Blalock-Taussig shunt on the treatment of cyanotic congenital heart diseases in neonates. Methods    The clinical data of 33 neonates undergoing modified Blalock-Taussig shunt between January 1, 2013 and December 31, 2017 were reviewed, including 28 males and 5 females with the age of 3.0-28.0 (18.0±6.1) d and weight of 1.9-3.7 (2.9±0.5) kg. Results    There were 3 (9.1%) in-hospital deaths. Ten (30.3%) patients required early unplanned reoperations after surgery. Five (15.2%) patients were lost to follow-up. In the multivariate analysis, preoperative acidosis, emergency operation and postoperative bedside thoracotomy were independent risk factors of early death. During the follow-up of 18.0-93.0 (40.2±22.5) months, there was no death and 9 (36.0%) survival patients underwent corrective surgery and stage-two palliative surgery. In the multivariate analysis, preoperative hyperhemoglobinemia was an independent risk factor of nonadministration of the corrective surgery and stage-two palliative surgery. Receiver operating characteristic curve showed that preoperative hyperhemoglobinemia was significant in determining whether secondary surgery was possible. Conclusion    The modified Blalock-Taussig shunt is effective in promoting development of pulmonary arteries and preparing for the secondary surgery. The rate of mortality and postoperative complications after the neonatal modified Blalock-Taussig shunt remains high. The rate of secondary surgery is still low during follow-up.