BACKGROUND:Post and core restoration is a common choice for tooth defects,but the repair effects of various post and core materials are different. OBJECTIVE:To evaluate the stress distribution at the post and core,tooth root,and bonding agent site of post and core models made of different elastic modulus post and core materials using finite element method. METHODS:A three-dimensional root canal treated maxillary central incisor model was built using three-dimensional modeling software,which was restored with a full ceramic crown.The post and core materials in the restoration used nanoceramic resin(elastic modulus=12.8 GPa),composite resin(elastic modulus=16 GPa),hybrid ceramic(elastic modulus=34.7 GPa),glass ceramic(elastic modulus=95 GPa),titanium alloy(elastic modulus=112 GPa),and zirconia(elastic modulus=209.3 GPa).The model was fixed in cortical bone.A 100 N concentrated force of 45° from the long axis of the tooth was applied to 1/3 of the crown and tongue side of the central incisor.The stress distribution of the post and core,dentin,and tooth-root bonding agent in the model was repaired by the maximum principal stress criterion. RESULTS AND CONCLUSION:(1)When the post and core materials with higher elastic modulus was used,the post-core stress in the repair model was more concentrated.When the elastic modulus of the post and core materials(nanoceramic resin and composite resin)was close to dentin,the stress distribution of the post and core was more uniform.The stress distribution of dentin in all restoration models was similar regardless of post and core materials.When the post and core with higher elastic modulus was used,more stress concentration was shown at the post and root bonding agent in the repair model.(2)The maximum stress values at the post and core,tooth root,and the bonding agent site of post and tooth root in the nanoceramic resin model were 31.00,33.21,and 0.51 MPa,respectively.The maximum stress values at the post and core,tooth root,and the bonding agent between the post and tooth root in the composite resin model were 36.84,33.14,and 0.59 MPa,respectively.In the mixed ceramic model,the maximum stress values at the post and core,tooth root,and the bonding agent between the post and tooth root were 64.05,32.83,and 1.00 MPa,respectively.In the glass ceramic model,the maximum stress values at the post and core,tooth root,and the bonding agent between the post and tooth root were 112.30,32.69,and 1.73 MPa,respectively.In the titanium alloy model,the maximum stress values of the post and core,tooth root,and the bonding agent between the post and tooth root were 120.00,32.17,and 1.86 MPa,respectively.In the zirconia model,the maximum stress values of the post and core,tooth root,and the bonding agent between the post and tooth root were 148.80,31.85,and 2.28 MPa,respectively.(3)The higher the elastic modulus of the post and core material,the higher the maximum stress at the post and core during restoration.The elastic modulus of the post and core material had no significant effect on the maximum stress of the dental bonding agent and dentin.

Objective: To investigate the clinical efficacy of spinal endoscopic surgery for lumbar posterior ring apophysis separation (PRAS) via percutaneous transforaminal approach. Methods: A retrospective case series study was conducted to analyze the clinical data of 32 patients with lumbar PRAS admitted to the First Affiliated Hospital of Fujian Medical University from September 2016 to March 2018. There were 20 males and 12 females, aged 20-47 years [(33.7 ± 6.6)years]. All patients had single-segment lesions. The injured segments were at L_3/4 in seven patients, L_4/5 in 14 patients, L₅/S₁ in 11 patients. All patients were treated with spinal endoscopic surgery via percutaneous transforaminal approach. The incision length, operation time, intraoperative blood loss, intraoperative fluoroscopy times of C-arm X-ray machine and operational complications were recorded. At 24 hours, 3 months and 12 months after operation, the efficacy was evaluated by visual analogue score (VAS), Oswestry dysfunction index (ODI) and modified MacNab criteria. Results: All patients were followed up for 12-30 months, with an average of 15.5 months. The incision length was 7-9.5 mm [(8.0±0.9)mm], the average operation time was 60-155 minutes [(80.5±13.2) minutes], the average intraoperative blood loss was 5-25 ml [(10.6±5.7)ml] and the average number of fluoroscopy was 5-25 times [(9.4±3.4) times]. The patients were permitted to move wearing hard waist 8-12 hours after operation and returned to normal work and life 6 weeks after operation. Postoperative dysesthesia was noted in one patient, who recovered after neurotrophy and physiotherapy after one week. There were no complications such as open surgery conversion, intervertebral space infection, nerve root injury and dural sac laceration. The VAS and ODI at 24 hours, 3 months and 12 months after operation [low back pain VAS: (3.4±1.5)point, (1.8±1.1)points, (1.7±0.9)points; leg pain VAS: (1.8±1.0)points, (1.6±0.8)points, (1.4±0.6)points; ODI: (26.8±9.7)%, (13.9±4.3)%, (12.8±2.8)%] were significantly improved compared with those before operation [ back pain VAS: (7.3±2.1)points, leg pain VAS: (7.9±2.7)points; ODI: (56.2±15.6)%] (P<0.05). According to the modified MacNab criteria, the results were excellent in 25 patients, good in five patients, and fair in two patients, with the excellent and good rate of 94%. Conclusion Spinal endoscopic surgery for lumbar PRAS via percutaneous transforaminal approach is an effective method with advantages of small incision, less complications, effective pain relief and fast functional recovery.

Objective:To analyze the clinical characteristics of adult Chinese patients with syncope.Methods:This is a cross-sectional survey study. Patients with preliminary diagnosis of syncope in the Emergency Department, Geriatrics and Cardiology Outpatient Department, or Syncope Unit of 37 hospitals in 19 provinces, autonomous regions and the Hong Kong Special Administrative Region from June 2018 to March 2021 were included in this study. The clinical features of these patients with syncope were analyzed.Results:A total of 4 950 consecutive patients with syncope were included in this study. The age was (56.3±16.8)years, and 2 604 cases (52.6%) were male. The most common type of syncope was neurally mediated syncope (2 345 (47.4%)), followed by cardiac syncope (1 085 (21.9%)), orthostatic hypotensive syncope (311 (6.3%)), and unexplained syncope accounted for nearly one third (1 155 (23.3%)). Predisposing syncope was more common in patients under 65 years of age(2 066(72.4%) vs. 786(27.6%),χ 2=136.5, P<0.001). Presyncope was more common in patients with neurally mediated syncope (1 972(79.0%) vs.1 908(73.9%), χ 2=17.756, P<0.001). Premonitory symptoms were more common in women(1 837(80.0%) vs. 1 863(73.0%),χ 2=33.432, P<0.001). Presyncope syndrome was more common in patients under 65 years of age (2 482(77.8%) vs. 1 218(73.4%),χ 2=17.523, P=0.001). Cyanosis was more common in ≥65 years old patients (271(18.2%) vs. 369(12.7%), χ 2=23.235, P<0.001). Urinary incontinence was more common in old patients aged ≥65 years(252(15.2%) vs. 345(10.8%), χ 2=19.313, P<0.001). Family history was more common in patients with cardiogenic syncope compared with other types of syncope (264(24.3%) vs. 754(19.5%), χ 2=11.899, P=0.001). Hypertention(1 480(30.5%)), coronary heart disease(1 057(21.4%)), atrial flutter and atrial fibrillation(359(7.2%)), second degree atrioventricular block(236(4.8%)) were common complications of syncope. The proportion of patients with coronary heart disease was significantly higher in cardiac syncope than that of other types of syncope(417(38.4%) vs. 640(16.6%), χ 2=241.376, P<0.001). Other common complications included cerebrovascular diseases (551 (11.1%)) and diabetes mellitus (632(12.8%)). Conclusions:Neurally mediated syncope is the most common syncope in adult Chinese population. Patients with predisposing conditions and premonitory conditions are younger. Presyncope is more common in women. The proportion of family history and coronary heart disease is higher in patients with cardiogenic syncope.