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Objective@#To compare the biomechanical characteristics of four-implants mandibular overdentures supported by Locator attachment or bar-clip attachment under different mechanical loads using three-dimensional finite element analysis method.@*Methods@#Two different models of four-implants supported mandibular overdentures using Locator attachment and bar-clip attachment (hereinafter called Locator model and bar-clip model) were established. Each model was subjected to five different mechanical loading conditions: 100 N vertical loading in central incisor (vertical load of incisor), 100 N vertical loading or oblique loading in canine (vertical or oblique loads of canines), 100 N vertical or oblique loading in mandibular first molar (vertical or oblique loads of mandibular first molar). The stress distributions in implants, peri-implant bone and mucosa were recorded under the above five conditions to evaluate the effects of different attachments on the biomechanical properties of implant-supported mandibular overdentures.@*Results@#Regardless of loading conditions and types of attachments, the stress concentration in implants were located at the neck of implants, and the stress concentration in peri-implant bone was located in the cortical bone. The stress values in mucosa were always much smaller than those in implants and cortical bone. Regardless of loading positions (on canine or on mandibular first molar), the maximum stress at the bone interface around the implant under lateral loading was much higher than that under vertical loading. Under various loading conditions, the stress in implants and cortical bone of the Locator model (the highest von Mise stress value was respectively 79.5 and 22.3 MPa) were lower than that of bar-clip model (the highest von Mise stress value was 110.3 and 28.7 MPa respectively) while the maximum compressive stress in mucosa (0.198 MPa) in Locator model was slightly higher than that in the bar-clip model (0.137 MPa).@*Conclusions@#In clinical practice, the lateral force applied to the implant-retained overdenture should be minimized to avoid complications caused by pathological loads. Under the same loading condition, the stress distributions in overdenture using Locator attachment are more dispersed, which is more conducive to long-term stability of implants.
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Objective@#To analyze the stress distribution of different types of bone tissue around porous titanium implant in different mechanical loads and to further evaluate the biomechanical properties of porous titanium implant.@*Methods@#Finite element (FE) models of implant restorations for the maxillary first premolar was established, and the diameter of implants in the models was 4.1 mm. Five models was constructed according to diameter of implant central pillar and the thickness of outer porosity: solid group (group A), central pillar 1.5 and 3.1 mm and outer porosity 30% (group B and C), central pillar 1.5 and 3.1 mm and outer porosity 40% (group D and E). Different loads (150 N vertical force, 50 N lateral force) were applied to the occlusal surface of implant restorations in type Ⅲ bone and maximal von Mises stress was evaluated. Meanwhile, a couple of simplified maxillary part models varied in four types of bone were constructed with the implants bearing load of simulation ultimate force to evaluate the stress distribution of different types of bone.@*Results@#With different mechanical loading, the stress value of bone tissue around porous implant (group B-E) was greater than that in the solid structure (group A). Under the load of simulation ultimate force, the maximum stress of the bone rised with the increase of porosity and thickness of the porous implant. And the maximum stress value of the surrounding bone tissue changed with the change of bone. Under vertical loading, the maximal von Mises stress of the bone around solid implants of group A was 17.56 MPa, which was a little lower than that of group B and C. And the maximal equivalent von Mises stress of group D and E was 69.24 MPa. The results of lateral force and simulation ultimate force loading were similar. The stress of the bone tissue around implant increased with the decrease of bone quality. The maximum stress value of group D implant was 134.95 MPa.@*Conclusions@#Porous structure of the implant is conducive to transmit stress to surrounding bone tissue and increases the mechanical stimulation of bone. However, if the value and direction of load are inappropriate or quality of bone is poor, pathological stress may be produced.
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Objective To observe the clinical efficacy and safety of ticagrelor,a new antiplatelet agent,in patients with ST-Segment elevation myocardial infarction (STEMI) underwent emergency PCI.Methods Selected 174 patients with STEMI receiving emergency PCI treatment from January 2013 to July 2014 in Nanjing General Hospital of Nanjing Military Area Command,and randomly divided into clopidogrel group (preoperative taking 600 mg of clopidogrel,n =88) and ticagrelor group (preoperative taking 180 mg of ticagrelor,n =86).Compared platelet inhibition rate,renal function before and after treatment,major clinical cardiovascular events and bleeding events 30 d after treatment,adverse drug reactions of two groups.Results (1) Arachidonic acid pathway inhibition rate of the two groups were compared,the difference was not statistically significant (P ＞0.05).Compared two groups of patients with adenosine phosphate pathway inhibition rate,ticagrelor group was higher,the difference was statistically significant ((71.82 ± 19.97) ％ vs.(38.96 ± 27.55) ％;t =-7.569,P ＜0.001).(2) Compared major cardiovascular events of ticagrelor group(5 cases) and clopidogrel group (15 cases),ticagrelor group was decreased.There was significant differences (P =0.02) between the two groups.Bleeding events compared to between ticagrelor group (15 cases) and clopidogrel group (11 cases),no statistically significant difference was found(P =0.617).Conclusion Clinical efficacy of ticagrelor in acute ST-segment elevation myocardial infarction treated with primary PCI is superior to clopidogrel in which can reduce the risk of cardiovascular events in patients and without an increase in severe bleeding.
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Objective To explore the disparity of severity of cardiac dysfunction and recovery among different glycometabolic patients in the early phase of acute myocardial infarction (AMI) . Methods Consecutive 111 AMI patients without known diabetes underwent continuous glucose monitoring. Patients with different glycometabolic status were compared in terms of cadiac dysfunction and recovery at admission and 3month follow up. Results Compared to patients with normglycemia and transient hyperglycemia, patitents with persistent hyperglycemia were more likely to grade Killip Ⅱ or above,which were 13.3% (4/30) ,33. 3% ( 12/36) ,55. 6% (25/45), 20. 0% ( 6/30), 41.7% ( 15/36 ) and 93.3% (42/45) ( Ps ＜ 0. 01 ). In-hospital left ventricular ejection fraction (LVEF), mitral valve protodiastolic E peak velocities (E) and its ratio to late diastolic (E/A) decreased significantly ( LVEF :0. 52 ± 0. 02,0. 48 ± 0. 01 and 0. 37 ± 0. 02; E: [0. 65 ± 0. 41]m/s,[0.55 ± 0.02] m/s and [0.39 ±0. 12]m/s;E/A:1. 15 ±0.08,1.02 ±0.06 and 0.61 ±0.02,respectively) ( Ps ＜ 0. 01 ), whereas LVESV and WMSI increased significantly ( LVESV: [25.83 ± 0. 51] ml,[31.26 ± 1.23] ml, [37, 72 ± 1.01] ml; WMSI: 1.5 ± 0. 3,1.8 ± 0. 2 and 2. 6 ± 0. 4, respectively) ( Ps ＜ 0. 01 )There months after AMI,patitents with persistent hyperglycemia were more likely to grade NYHA Ⅱ or above compared to patients with normglycemia and transient hyperglycemia [67.5% (27/40), 10.0% (3/30) and 11.8% (4/34),respectively] (P ＜0. 01 ). Echocardiographic recovery was observed in each group,but less in persistent hyperglycemia patients. Conclusion Cardiac function of patients with persistent hyperglycemia suffered more severely from AMI and difficult to recover.
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One hundred and eleven patients with acute myocardial infarction and without known diabetes mellitus who underwent continuous glucose monitoring were divided into normoglycemia(n = 30),transient hyperglycemia(n = 36),and persistent hyperglycemia(n = 45)groups.Compared with other two groups,higher mean blood glucose,standard deviation of blood glucose,largest amplitude of glycemic excursions,mean amplitude of glycemic excursions,and absolute mean of daily differences were observed in the patients with persistent hyperglycemia group(all P<0.01),who were more likely to be female with the history of hypertension and old myocardial infarction(all P<0.05).It was shown that the levels of aspartate aminotransferase,creatine phosphokinase(CK),CK-MB,total cholesterol,triglyceride,low-density lipoprotein cholesterol,HbA1C,and C reactive protein levels were higher in these patients(P<0.01).
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Objective To approach the effect of hyperglycemia on admission on the prognosis in female pa-tients with acute myocardial infarction (AMI) during hospital stay. Methods 171 female AMI patients without a history of diabetes mellitus from January 1998 to December 2007 were divided into 3 groups according to the blood glucose level on admission. Group Ⅰ included 69 cases with blood glucose <6. 1 mmol/L,group Ⅱ included 49 cases with blood glucose between 6.1 and 7.8 mmol/L,and group Ⅲ included 53 cases with blood glucose >7.8 mmoL/ L. The basic clinical profile, infarct sites, the incidence rates of the main complications and the mortality of the pa-rhythmia among group Ⅲ ,group Ⅰ and group Ⅱ were significantly different ( the incidence rate of cardiac failure was 30.43% (21/69) ,32.65% (16/49) and 58.49% (31/53), the incidence rate of cardiogenic shock was 5.80% (4/69) ,8.16% (4/49) and 24.53% (13/53) ; the incidence rate of severe arrhythmia was 24.64% (17/69) ,30. 61% (15/49) and 54.72% ( 29/53), respeetivley in group Ⅰ, group Ⅱ and group Ⅲ, P < 0.05 for each). The in-hospital mortality in group Ⅲ (28.30% (15/53) ) was remarkably higher than group Ⅰ ( 13.04% (6/69)) ,with significant difference ( P < 0.05 ). Conclusions Elevated blood glucose level on admission is associated with s markedly increased risk of cardiac failure,severe arrhythmia,cardiogenic shock and mortality during hospital stay in female patients suffering from AMI.
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Objective To study the change of diastolic cardiac function in diabetic patients and to determine the diagnostic value of plasma brain natriuretic peptide (BNP) and atria natriuretic peptide (ANP) for diastolic heart failure in patients with type 2 diabetes mellitus.Methods Twelve healthy subjects and seventy-one diabetic patients were included in the study.Plasma BNP and ANP were measured with immunoradiometic assay.Results Plasma levels ofBNP andANP increased significantly with increased severity of diastolic heart dysfunction.The ratio of E/A had significant negative correlation with the plasma levels of BNP (r=0.669,P＜0.001) and ANP (r=0.579,P＜0.01).AUC of ANP and BNP in ROC model was 91.9% and 65.3%,respectively.Conclusions The plasma level of BNP might be a valuable predictor for differential diagnosis of diastolic cardiac function in diabetic patients.
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Objective To observe pre-syncopal limited tolerance and cardiovascular responses to head-up tilt combined with lower body negative pressure (HUT/LBNP) following exposure to head-down tilt (HDT, -1 Gz). Method Exposures to HUT/LBNP (-60 mmHg) in control session (without preceding 30 s -1 Gz treatment) and in simulated push-pull effect (PPE) session (with preceding 30 s -1 Gz treatment) were performed in 8 healthy adults. The changes of hemodynamic parameters were monitored by electrical impedance instrument during the experiments. Result The mean endurance time in presyncopal symptom limited HUT/LBNP in control session and in simulated PPE session were 8.4±2.1 min and 4.5±2.4 min, respectively, the two means were significantly different (P< 0.01). In simulated PPE session, as compared with baseline, heart rate (HR) during HDT was significantly lowered (P<0.01), while stroke volume (SV) and cardiac output (CO) were increased significantly (P<0.01). During HUT/LBNP, the increased percentage (relative to baseline) of HR in PPE session was lower than these in control session (P<0.05); the decreased percentages of SV and CO during HUT/LBNP in PPE session were both higher than those in control session (P<0.05). During HUT/LBNP, arterial pulse pressure (PP) of control session was significantly decreased than the value of baseline value (P<0.05); Total peripheral resistance (TPR) of PPE session was significantly increased than baseline value (P<0.05). Conclusion Tolerance time before the appearance of presyncopal symptoms during HUT/LBNP decreases and cardiovascular responses to HUT/LBNP are impaired, preceding exposure to HDT.
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Objective To investigate changes of learning ability and somatostatin (SS) changes after positive acceleration (+Gz) exposures. Mehtod Eighty male SD rats were randomly divided into 3groups: control group(Con), +6 Gz/3 min group ( +6 Gz), and +10 Gz/3 min group ( +10 Gz),8 rats in each group. Changes of learning ability in rats were observed at 0 d, 2 d, 4 d and 6 d after + Gz exposure. SS in hippocampus was measured by RIA at 0 d, 2 d and 4 d after + Gz exposures ( there were 8 rats every time, in each group). Result In Y-maze test,number of correct response decreased significantly (P ＜0.01 ), and total reaction time increased significantly(P ＜0.01 ) in +6Gz and +10 Gz groups as compared with control group; number of correct response and total reaction time in +10 Gz group changed significantly at 0 d(P ＜0.01 or P ＜0.05) as compared with +6Gz group. RIA showed that, content of SS in hippocampus declined at 0 d and 2 d(P ＜0.05 or P ＜0.01) in +6 Gz and + 10 Gz groups as compared with control group. Conclusion + Gz exposure could impair learning ability of rats, and inhibit expression of SS in hippocampus.
