Objective To investigate the influence of micro-implant length and screw angle on stress distribution and displacement of micro-implant bone interface when micro-implant was implanted in zygomatic alveolar ridge and bear a certain load,in order to provide certain theoretical basis for micro-implant selection and further optimization design in clinical practice.Methods A three-dimensional finite element model of the jaw in the zygomatic alveolar ridge region was established using ANSYS software.At the same time,35 kinds of micro-threaded implants with length of 8,9,10,11,12 mm and angle of 30°,45°,60°,75°,90°,105°,120° were estab-lished.The micro-implant was simulated to be implanted in the jaw bone,and the implantation model was established.Stress analysis was performed on the bone interface of the micro-implant.Results The maximum stress of micro-implant bone interface occurred in the bone cortex.The maximum stress value of buccal cortical bone,cancellous bone and micro-implant displacement decreased with the increase of screw length.The angle of screw had little effect on the maximum stress and displacement of micro-implant-bone interface.Conclusion The screw length has an impact on stress distribution of micro-implant bone interface.The micro-implant with longer length can improve its stability in zygomatic alveolar ridge.

Objective To investigate the influence of micro-implant length and screw angle on stress distribution and displacement of micro-implant bone interface when micro-implant was implanted in zygomatic alveolar ridge and bear a certain load,in order to provide certain theoretical basis for micro-implant selection and further optimization design in clinical practice.Methods A three-dimensional finite element model of the jaw in the zygomatic alveolar ridge region was established using ANSYS software.At the same time,35 kinds of micro-threaded implants with length of 8,9,10,11,12 mm and angle of 30°,45°,60°,75°,90°,105°,120° were estab-lished.The micro-implant was simulated to be implanted in the jaw bone,and the implantation model was established.Stress analysis was performed on the bone interface of the micro-implant.Results The maximum stress of micro-implant bone interface occurred in the bone cortex.The maximum stress value of buccal cortical bone,cancellous bone and micro-implant displacement decreased with the increase of screw length.The angle of screw had little effect on the maximum stress and displacement of micro-implant-bone interface.Conclusion The screw length has an impact on stress distribution of micro-implant bone interface.The micro-implant with longer length can improve its stability in zygomatic alveolar ridge.

Objective To study the protective effect of helmet on human head injury under continuous frontal blast shock wave.Methods A finite element head-helmet coupling model was established to analyze the effects of helmets on biomechanical response parameters such as intracranial pressure and cranial pressure under single frontal blast and continuous frontal blast shock wave.The dynamic changing law of brain tissues in the blast environment was discussed to evaluate the protective performance of helmets on human head.Results In the case of single frontal blast impact,the helmet could effectively reduce intracranial pressure in the frontal lobe,occipital lobe,and parietal lobe by 32%,38%,and 19%,respectively,as well as peak stress at the rear of the skull.In the case of continuous frontal blast impact,the helmet could reduce intracranial pressure in the parietal lobe and occipital lobe by 36%and 21%,respectively,but its effect on intracranial pressure in the frontal lobe was limited due to the lack of facial protection.Conclusions Compared to single blast shock wave,continuous frontal blast shock wave has a more severe impact on craniocerebral injury due to its long effective effects on the head.Since the shock wave propagates from different directions and heights,the protective effect of the helmet on the face is minimal.This study can provide important references for biomechanical research of human head injury under continuous frontal blast shock wave and the design of new helmets.

Objective To study the protective effect of helmet on human head injury under continuous frontal blast shock wave.Methods A finite element head-helmet coupling model was established to analyze the effects of helmets on biomechanical response parameters such as intracranial pressure and cranial pressure under single frontal blast and continuous frontal blast shock wave.The dynamic changing law of brain tissues in the blast environment was discussed to evaluate the protective performance of helmets on human head.Results In the case of single frontal blast impact,the helmet could effectively reduce intracranial pressure in the frontal lobe,occipital lobe,and parietal lobe by 32%,38%,and 19%,respectively,as well as peak stress at the rear of the skull.In the case of continuous frontal blast impact,the helmet could reduce intracranial pressure in the parietal lobe and occipital lobe by 36%and 21%,respectively,but its effect on intracranial pressure in the frontal lobe was limited due to the lack of facial protection.Conclusions Compared to single blast shock wave,continuous frontal blast shock wave has a more severe impact on craniocerebral injury due to its long effective effects on the head.Since the shock wave propagates from different directions and heights,the protective effect of the helmet on the face is minimal.This study can provide important references for biomechanical research of human head injury under continuous frontal blast shock wave and the design of new helmets.

Objective:To investigate the clinical phenotypes, therapy and genetic features of aldehyde dehydrogenase 7 family member A1 (ALDH7A1) gene mutations in five cases of pyridoxine dependent epilepsy (PDE) with diagnosis confirmed by next generation sequencing.Methods:Retrospective analysis was carried out on clinical data of five cases of PDE children with early epilepsy onset who were treated in the Department of Neurology of Children′s Hospital Affiliated to Zhengzhou University from February 2018 to November 2019. Next generation sequencing approach was used for genetic sequencing of proband ALDH7A1 gene and the first generation Sanger was used for validation of family members. And the characteristics of gene mutations were analyzed.Results:Among the five children diagnosed with PDE, the male to female ratio was 4 ∶ 1 and ages at clinic visit ranged from two months to 10 months old. In clinical phenotypes, all five cases experienced onset in neonatal period, with repeated seizures, manifested as myoclonus, spasms or focal paroxysm. The administration of antiepileptic drugs performed poorly in seizure control while long term oral intake of large dose pyridoxine showed better efficacy. All the five cases of children came from compound heterozygous mutations of father and mother, i.e. slicing homozygous mutation c.247-2(IVS2)A>T, missense mutation c.584A>G (p.N195S) and nonsense mutation c.1003C>T(p.R335 *), missense mutation c.1553G>C(p.R518T) and c.1547A>G(p.Y516C), missense mutation c.1547A>G(p.Y516C) and frameshift mutation c.1566_1568delTAC, missense mutation c.1061A>G(p.Y354C) and nonsense mutation c.841C>T(p.Q281X, 259), among which c.247-2(IVS2)A>T was novel splicing site mutation not reported before. Conclusions:PDE is induced by ALDH7A gene mutation. Early clinical manifestations are mostly onset of refractory epilepsy in neonatal period. Antiepileptic drugs perform poorly in terms of efficacy while pyridoxine can control seizure effectively. Gene analysis should be conducted on such patients for confirmed diagnosis.

Objective To investigate the feasibility of centerline measurement method in estimating aortic diameter at the proximal landing zone in Stanford B type aortic dissection. Methods CT angiography materials of 30 patients with type B aortic dissection were randomly selected from the hospital database (24 males with a median age of 49.5 years), which were retrospectively analyzed with multiplanar reformation (MPR) and centerline technique by two experts in vascular radiology. Difference between two measurement techniques was analyzed by using mixed linear model, and the agreement of measurements between two readers as well as between two techniques were evaluated by Bland-Altman plots. Results The diameters measured with MPR method by two experts were (29.73±2.99) mm and (29.86±2.95) mm respectively, while the diameters measured with centerline measurement method by two experts were (29.66 ±2.81) mm and (29.71 ±2.91) mm respectively. No statistically significant differences in the diameter value existed between the two measurement methods, although the results determined by centerline measurement method were more stable. Conclusion In determining aortic diameter at the proximal landing zone in Stanford B type aortic dissection, the centerline analysis provides a checking method for MPR measurement.