Osseointegration of dental implants in 3D-printed synthetic onlay grafts customized according to bone metabolic activity in recipient site

Onlay grafts made of monolithic microporous monetite bioresorbable bioceramics have the capacity to conduct bone augmentation. However, there is heterogeneity in the graft behaviour in vivo that seems to correlate with the host anatomy. In this study, we sought to investigate the metabolic activity of the regenerated bone in monolithic monetite onlays by using positron emission tomography–computed tomography (PET-CT) in rats. This information was used to optimize the design of monetite onlays with different macroporous architecture that were then fabricated using a 3D-printing technique. In vivo, bone augmentation was attempted with these customized onlays in rabbits. PET-CT findings demonstrated that bone metabolism in the calvarial bone showed higher activity in the inferior and lateral areas of the onlays. Histological observations revealed higher bone volume (up to 47%), less heterogeneity and more implant osseointegration (up to 38%) in the augmented bone with the customized monetite onlays. Our results demonstrated for the first time that it is possible to achieve osseointegration of dental implants in bone augmented with 3D-printed synthetic onlays. It was also observed that designing the macropore geometry according to the bone metabolic activity was a key parameter in increasing the volume of bone augmented within monetite onlays.     

Bone Strength During Growth: Influence of Growth Rate on Cortical Porosity and Mineralization

Although it is well accepted that bone architecture adapts to withstand the loads placed on it, the manner in which this occurs in the immature growing skeleton is not fully understood. To investigate the possible mechanisms, we have compared morphometric differences between tibiae from chickens with fast and those with slow growth potential and also distinguished between the effects of genetic potential and growth rate on their impact on bone quality. Two different fast-growing (ad lib modern) strains, one additionally feed-restricted and one slow-growing (control) strain of chicken, were compared at 15 and 42 days of age. The ad lib modern strains had similar final body weights and were approximately twice the weight of the control and restricted-fed birds. Tibiae from the control and restricted birds had a higher ash content and lower porosity than the ad lib modern strain at 42 days. The porosity was a result of rapid primary osteon formation at the periosteal surface and incomplete infilling of the resultant canal by osteoblasts. When adjusted to average body weight of contemporaries, bones from the control strain and the restricted-fed modern birds were stiffer and at least as strong as those from the fast growing ad lib-fed birds. In conclusion, rapid bone deposition at the periosteal surface was associated with decreased mineralization, increased cortical porosity, and altered biomechanical properties. Our results also indicate that growth rate, and not genetic potential, of the fast growing birds was responsible for the rapid periosteal bone deposition.     

Thermal conductivity measurements for small molecule organic solid materials using modulated differential scanning calorimetry (MDSC) and data corrections for sample porosity

A method for measuring the thermal conductivity (k) of small molecule organic solid materials using modulated differential scanning calorimetry (MDSC) is demonstrated. Sample preparation required powder consolidation, unavoidably introducing air voids into compacts. Supporting equations for the technique were modified to include a porosity term (?), and the theoretical quadratic relationship between k and ? was confirmed by experimental measurements for 18 representative materials. Zero-porosity extrapolation was used to approximate values of “true” thermal conductivity for non-porous solids (k_?=0). Zero-porosity-extrapolated values ranged from 0.1273 W/(K m) to 0.3472 W/(K m) for all materials, consistent with expected values of k for non-porous organic polymers.     

低孔率血流导向支架对兔腹主动脉分支动脉开口的影响

目的 评估低孔率血流导向支架对分支动脉开口的影响.方法 30只新西兰大白兔随机分入实验组(n=20)和对照组(n=10).低孔率血流导向支架植入实验组腹主动脉并覆盖分支开口,对照组动物只进行造影不植入支架.3个月后对所有动物再次造影并处死行病理学检查.结果 支架所覆盖的分支在造影随访中均无闭塞,分支开口处新生内膜增生程度和支架孔率呈负相关(r=-0.507,P=0.005),这些新生内膜主要由平滑肌细胞和胶原纤维组成.结论 造影显示低孔率血流导向支架所覆盖的分支开口在术后3个月无闭塞,但病理显示支架可引起分支开口处内膜增生.     

Graft copolymers of ethyl methacrylate on waxy maize starch derivatives as novel excipients for matrix tablets: Physicochemical and technological characterisation

Nowadays, graft copolymers are being used as an interesting option when developing a direct compression excipient for controlled release matrix tablets. New graft copolymers of ethyl methacrylate (EMA) on waxy maize starch (MS) and hydroxypropylstarch (MHS) were synthesised by free radical polymerization and alternatively dried in a vacuum oven (OD) or freeze-dried (FD). This paper evaluates the performance of these new macromolecules and discusses the effect of the carbohydrate nature and drying process on their physicochemical and technological properties. Grafting of EMA on the carbohydrate backbone was confirmed by IR and NMR spectroscopy, and the grafting yields revealed that graft copolymers present mainly a hydrophobic character. The graft copolymerization also leads to more amorphous materials with larger particle size and lower apparent density and water content than carbohydrates (MS, MHS). All the products show a lack of flow, except MHSEMA derivatives. MSEMA copolymers underwent much plastic flow and less elastic recovery than MHSEMA copolymers. Concerning the effect of drying method, FD derivatives were characterised by higher plastic deformation and less elasticity than OD derivatives. Tablets obtained from graft copolymers showed higher crushing strength and disintegration time than tablets obtained from raw starches. This behaviour suggests that these copolymers could be used as excipients in matrix tablets obtained by direct compression and with a potential use in controlled release.     

The influence of precursor addition order on the porosity of sol–gel bioactive glasses

Objective

The superior textural properties of sol–gel derived bioactive glasses compared to conventional melt quench glasses accounts for their accelerated bioactivity in vitro. Several studies have explored ways to improve the surface properties of sol–gel glasses in order to maximise their efficiency for bone and tooth regeneration. In this study, we investigated the effect of order of network modifying precursor addition on the textural properties of sol–gel derived bioactive glasses.

壳聚糖-脱细胞真皮三维材料作为骨组织工程支架材料的研究

目的观察MC3T3-El成骨前体细胞在壳聚糖-脱细胞真皮三维支架材料上的黏附情况,并评价其细胞相容性。方法通过冷冻干燥制备壳聚糖-脱细胞真皮三维支架材料,并测试其孔隙率、密度和吸水率,通过扫描电镜分析支架的微观形貌。采用体外培养细胞的方法,将MC3T3-E1细胞直接接种到壳聚糖-脱细胞真皮三维支架材料上,培养2,3,4,5h,各时间点各取3个样品,测定细胞在支架上的黏附率,确定最佳的细胞贴壁时间。将细胞接种到支架上,共培养1,3,5,7,9,11,13d,采用MTS方法绘制细胞增殖曲线,组织化学染色观察细胞形态,并利用材料试验机测试不同时间材料细胞复合物的压缩弹性模量。结果壳聚糖-脱细胞真皮材料具有连通的多孔结构,孔隙率为92.8%,密度为97.96g/L,吸水率为(2169±100)%。细胞相容性实验显示,成骨细胞易于在支架材料上黏附、增殖。结论壳聚糖-脱细胞真皮材料具有连通的孔隙,孔径较均匀,MC3T3-El成骨前体细胞易在壳聚糖-脱细胞真皮三维支架材料上黏附、增殖,表明该支架材料具有良好的细胞相容性。     

Comparison of the effects of different drying techniques on properties of granules and tablets made on a production scale

The aims of this study were to compare the properties of granules prepared in a high-shear granulator and dried by using different methods (fluid-bed and microwave-vacuum drying) and to compare the properties of tablets pressed from such granules. Experiments on a production scale were performed with Collette Ultima Pro 600 single-pot processing equipment and a Glatt WSG 200 fluid-bed granulator and drier. The particles granulated in the traditional high-shear granulator and dried in a vacuum chamber had a higher porosity and higher bulk and tapped densities, as a consequence of the special characteristics of the drying process. They retained their spherical form, in contrast with the particles dried via the fluid-bed technology. The two types of granules required different compressing forces for tabletting.     

低孔率球囊扩张支架对犬颈总动脉瘤腔压力的影响

目的观察低孔率球囊扩张支架对犬颈总动脉瘤腔压力的影响。方法自行设计中央部分网孔加密而两端与普通类型支架相同（正常孔率区）的低孔率支架,据中央网孔密度高低分为A、B、C三型。取10只犬,于每只犬的双侧颈总动脉建立3个侧壁宽颈动脉瘤模型。将24个成功的动脉瘤按平衡不完全随机设计分为4组：置入A型支架组、B型支架组、C型支架组和空白对照组（仅测压,不置人支架）。采用微导管尾端连接的生物信号分析仪记录瘤腔内和载瘤动脉内的压力变化。结果①18个动脉瘤成功置入支架。置入后即刻造影显示,支架中央低孔率区完全覆盖动脉瘤瘤颈,支架贴壁良好,载瘤动脉血流通畅。所有动脉瘤内血流减慢,其中12个（66．7％）瘤体减小。置入支架组均无血栓形成及支架移位。②3个支架组支架置入前、置入后动脉瘤内的压力差异均无统计学意义,与空白对照组比较差异亦无统计学意义。在支架置人过程中,3个支架组动脉瘤内压力均比对照组及自身置入前、置入后升高（P〈0．05,P〈0．01）;而3个支架组间差异无统计学意义（P〉0．05）。③支架置入后载瘤动脉内压力,3个支架组间比较差异无统计学意义,与空白对照组比较,差异亦无统计学意义。支架置入后,各组自身比较,动脉瘤内压力与载瘤动脉内压力差异亦无统计学意义。结论低孔率支架置入后,可使动脉瘤内血流速度减慢,血液流空时间延长。不影响动脉瘤和载瘤动脉内压力的变化,仅在支架释放的过程中可引起动脉瘤腔内压力的短暂性升高。