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Finite element comparison of the effect of absorbers' design in the surrounding bone of dental implants.

牙种植体周围骨吸收器设计效果的有限元比较。

  • 影响因子:2.44
  • DOI:10.1002/cnm.3270
  • 作者列表:"Ashrafi M","Ghalichi F","Mirzakouchaki B","Arruga A","Doblare M
  • 发表时间:2020-01-01
Abstract

:Despite the high success rate achieved in current dental implantation, there are still important problems to solve like incomplete early osteointegration, bone damage, and long-term implant loosening. Highly compliant stress absorbers are a possible solution to these problems. Although several works examined the stress-strain distribution in bone without and with absorbers to show their favorable results, none of them analyzed their impact on long-term remodeling. Here, we analyze this effect by comparing the evolution of stress and bone mass density without and with different designs of absorbers with those of the healthy tooth. Several finite element models with ABAQUS, corresponding to each design considered, were built to obtain the mechanical conditions in bone and implant. Then a mechanobiological bone remodeling model that considers damage accumulation and its repair during the remodeling process was used to compute the bone density redistribution. This approach allows assessing both the short-term density loss and the relative micromovement between bone and implant. We analyze the stress distributions in both bone and implant as well as the relative micromovement of the implant. We also present the evolution of damage and bone volume fraction. These results show that the addition of absorbers can reduce the stress in the bone around the implant. The obtained results also show that using stress absorbers reduces damage in bone, while increasing the number of absorbers does not necessarily improves damage reduction. We conclude that using implants with a correct design of absorbers prevents damage and stress shielding, reducing implant loosening.

摘要

: 尽管目前的种植牙成功率很高,但仍有重要问题需要解决,如早期骨整合不完整、骨损伤和长期种植体松动。高度柔顺的应力吸收器是这些问题的可能解决方案。虽然一些工作检查了没有吸收剂和具有吸收剂的骨中的应力-应变分布以显示其有利的结果,但它们都没有分析它们对长期重塑的影响。在这里,我们通过比较没有和不同设计的吸收剂与健康牙齿的吸收剂的应力和骨密度的演变来分析这种影响。建立了与考虑的每个设计相对应的ABAQUS有限元模型,以获得骨和植入物的力学条件。然后使用在重建过程中考虑损伤积累及其修复的力学生物学骨重建模型来计算骨密度再分配。这种方法允许评估短期密度损失和骨与植入物之间的相对微运动。我们分析了骨和植入物的应力分布以及植入物的相对微运动。我们还介绍了损伤和骨体积分数的演变。这些结果表明,添加吸收剂可以降低植入物周围骨中的应力。所获得的结果还表明,使用应力吸收器减少骨中的损伤,而增加吸收器的数量并不一定改善损伤减少。我们的结论是,使用具有正确设计的吸收剂的植入物可以防止损伤和应力屏蔽,减少植入物松动。

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发表时间:2020-01-01
来源期刊:European radiology
DOI:10.1007/s00330-019-06319-0
作者列表:["Delattre BMA","Boudabbous S","Hansen C","Neroladaki A","Hachulla AL","Vargas MI"]

METHODS:OBJECTIVES:The aim was to evaluate the image quality and sensitivity to artifacts of compressed sensing (CS) acceleration technique, applied to 3D or breath-hold sequences in different clinical applications from brain to knee. METHODS:CS with an acceleration from 30 to 60% and conventional MRI sequences were performed in 10 different applications in 107 patients, leading to 120 comparisons. Readers were blinded to the technique for quantitative (contrast-to-noise ratio or functional measurements for cardiac cine) and qualitative (image quality, artifacts, diagnostic findings, and preference) image analyses. RESULTS:No statistically significant difference in image quality or artifacts was found for each sequence except for the cardiac cine CS for one of both readers and for the wrist 3D proton density (PD)-weighted CS sequence which showed less motion artifacts due to the reduced acquisition time. The contrast-to-noise ratio was lower for the elbow CS sequence but not statistically different in all other applications. Diagnostic findings were similar between conventional and CS sequence for all the comparisons except for four cases where motion artifacts corrupted either the conventional or the CS sequence. CONCLUSIONS:The evaluated CS sequences are ready to be used in clinical daily practice except for the elbow application which requires a lower acceleration. The CS factor should be tuned for each organ and sequence to obtain good image quality. It leads to 30% to 60% acceleration in the applications evaluated in this study which has a significant impact on clinical workflow. KEY POINTS:• Clinical implementation of compressed sensing (CS) reduced scan times of at least 30% with only minor penalty in image quality and no change in diagnostic findings. • The CS acceleration factor has to be tuned separately for each organ and sequence to guarantee similar image quality than conventional acquisition. • At least 30% and up to 60% acceleration is feasible in specific sequences in clinical routine.

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影响因子:2.98
发表时间:2020-01-01
DOI:10.1136/neurintsurg-2019-014962
作者列表:["Guo W","Liu H","Tan Z","Zhang X","Gao J","Zhang L","Guo H","Bai H","Cui W","Liu X","Wu X","Luo J","Qu Y"]

METHODS:BACKGROUND:The main surgical techniques for spontaneous basal ganglia hemorrhage include stereotactic aspiration, endoscopic aspiration, and craniotomy. However, credible evidence is still needed to validate the effect of these techniques. OBJECTIVE:To explore the long-term outcomes of the three surgical techniques in the treatment of spontaneous basal ganglia hemorrhage. METHODS:Five hundred and sixteen patients with spontaneous basal ganglia hemorrhage who received stereotactic aspiration, endoscopic aspiration, or craniotomy were reviewed retrospectively. Six-month mortality and the modified Rankin Scale score were the primary and secondary outcomes, respectively. A multivariate logistic regression model was used to assess the effects of different surgical techniques on patient outcomes. RESULTS:For the entire cohort, the 6-month mortality in the endoscopic aspiration group was significantly lower than that in the stereotactic aspiration group (odds ratio (OR) 4.280, 95% CI 2.186 to 8.380); the 6-month mortality in the endoscopic aspiration group was lower than that in the craniotomy group, but the difference was not significant (OR=1.930, 95% CI 0.835 to 4.465). A further subgroup analysis was stratified by hematoma volume. The mortality in the endoscopic aspiration group was significantly lower than in the stereotactic aspiration group in the medium (≥40-<80 mL) (OR=2.438, 95% CI 1.101 to 5.402) and large hematoma subgroup (≥80 mL) (OR=66.532, 95% CI 6.345 to 697.675). Compared with the endoscopic aspiration group, a trend towards increased mortality was observed in the large hematoma subgroup of the craniotomy group (OR=8.721, 95% CI 0.933 to 81.551). CONCLUSION:Endoscopic aspiration can decrease the 6-month mortality of spontaneous basal ganglia hemorrhage, especially in patients with a hematoma volume ≥40 mL.

影响因子:0.96
发表时间:2020-02-01
DOI:10.1002/jcu.22762
作者列表:["Meng L","Zhao D","Yang Z","Wang B"]

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