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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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Aim To investigate the effect of p38 MAPK AS-ODNs on the expression of GLT-1 during the induction of brain ischemic tolerance induced by cerebral ischemic preconditioning (CIP).Methods Eighty healthy male Wistar rats with permanent occlusion of the bilateral vertebral arteries were randomly divided into 6 groups: ①Sham group (n=10);②CIP group (n=10);③ischemic insult (Ⅱ) group (n=10);④CIP+Ⅱ group (n=10);⑤p38 MAPK AS-ODNs+CIP+Ⅱ group (n=30);⑥p38 MAPK S-ODNs+CIP+Ⅱ group (n=10).Group ⑤ was divided into 5 nmol, 10 nmol and 15 nmol subgroups according to the dose of p38 MAPK AS-ODNs (n=10).The dose of p38 MAPK S-ODNs was 15 nmol.All the rats were sacrificed 6 h and 2 d after the sham operation or the last time of global brain ischemia reperfusion.Western blot and immunohistochemistry analysis were used for detecting the expression of p-p38 MAPK and GLT-1 protein.Results CIP moderately up-regulated the expression of p-p38 MAPK and significantly up-regulated the expression of GLT-1 protein, inhibited the excessively up-regulation of p-p38 MAPK and the down-regulation of GLT-1 induced by ischemic insult.p38 MAPK AS-ODNs significantly inhibited the up-regulation of p-p38 MAPK and GLT-1 protein in a dose-dependent manner during the induction of brain ischemic tolerance by CIP.Conclusion p38 MAPK AS-ODNs inhibit the up-regulation of GLT-1 during the induction of brain ischemic tolerance induced by CIP.
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Objective:To observe the effect of icariin on the osteoporosis of the ovariectomized rats,and to explore the mechanism.Methods:Fifty female rats aged 6 months were randomly divided into sham operation group, model group,positive drug group,low dose of icariin group and high dose of icariin group (n= 10).The rats in positive drug group were given with 1 mg· kg-1 nilestriol every week;the rats in low and high doses of icariin groups were given with 50 and 100 mg · kg-1 icariin every day.The bilateral ovaries of rats were excised by operation to establish the osteoporosis models.2 weeks after operation,the rats were treated with icariin for 12 weeks,and then they were sacrificed by drawing blood from abdominal aorta under anesthesia condion.The bone mineral density (BMD),serum biochemical indicators,bone histomorphology and the expressions of apoptosis-related proteins were detected.Results:Compared with sham operation group,the BMD of the rats in model group was decreased (P <0.01),the serum calcium level was decreased (P <0.05),and the serum phosphorus level was increased (P <0.05),and the serum BGP,ALP,NO and NOS levels were significantly decreased (P <0.05 or P <0.01).Compared with model group,the BMD of the rats in positive drug group and high dose of icariin group were obviously increased (P < 0.01 ), the serum calcium levels were increased, the phosphorus levels were decreased (P <0.05),and the BGP and ALP levels were increased significantly (P < 0.05 ). Compared with control group,the cortical in model group was thinned,the width of bone trabecula was reduced,the Bax and Caspase-3 expression levels in bone tissue were increased,and the Bcl-2 expression level was decreased.Compared with model group,the cortical in icariin group was thicked,the width of bone trabecula was increased,the Bax and Caspase-3 expression levels were decreased,and the Bcl-2 expression level was increased (P <0.05 or P <0.01). Conclusion:Icariin can protect the osteoporosis of ovariectomized rats,the function may be related to the inhibition of apoptosis.
