Femur Auxetic Meta-Implants with Tuned Micromotion Distribution

Stress shielding and micromotions are the most significant problems occurring at the bone-implants interface due to a mismatch of their mechanical properties. Mechanical 3D metamaterials, with their exceptional behaviour and characteristics, can provide an opportunity to solve the mismatch of mechanical properties between the bone and implant. In this study, a new porous femoral hip meta-implant with graded Poisson’s ratio distribution was introduced and its results were compared to three other femoral hip implants (one solid implant, and two porous meta-implants, one with positive and the other with a negative distribution of Poisson’s ratio) in terms of stress and micromotion distributions. For this aim, first, a well-known auxetic 3D re-entrant structure was studied analytically, and precise closed-form analytical relationships for its elastic modulus and Poisson’s ratio were derived. The results of the analytical solution for mechanical properties of the 3D re-entrant structure presented great improvements in comparison to previous analytical studies on the structure. Moreover, the implementation of the re-entrant structure in the hip implant provided very smooth results for stress and strain distributions in the lattice meta-implants and could solve the stress shielding problem which occurred in the solid implant. The lattice meta-implant based on the graded unit cell distribution presented smoother stress-strain distribution in comparison with the other lattice meta-implants. Moreover, the graded lattice meta-implant gave minimum areas of local stress and local strain concentration at the contact region of the implants with the internal bone surfaces. Among all the cases, the graded meta-implant also gave micromotion levels which are the closest to values reported to be desirable for bone growth (40 µm).     

Elaboration and Characterization of Vitreous Fertilizers and Study of Their Impact on the Growth,Photosynthesis, and Yield of Wheat (Triticum durum L.)

Four different phosphate glass formulations (F₀, F₁, F₂, and F₃) were developed according o wheat nutrient requirements to be used as controlled-release fertilizers. These glasses contain macro-elements (P₂O₅-K₂O-CaO-MgO), with the addition of microelements (Fe-Mn-Zn-B-Cu-Mo) in each formulation. The effects of these elements’ addition on thermal properties, glass structure, and dissolution behaviors were investigated. Results showed that these glasses are composed essentially of metaphosphate chains and that the addition of micronutrients could change the chemical durability of phosphate glasses. A greenhouse experiment was performed using wheat (Triticum durum L.) to evaluate the efficiency of the four glasses, with or without application of chemical nitrogen (N) (N + VF and VF, respectively). The different formulas were tested using two rates of 0.3 and 1 g per plant. In addition to the vitreous fertilizer formulations, two other treatments were applied: control treatment with no amendment and Nitrogen-Phosphorus-Potassium treatment with the application of the conventional fertilizers on the base of optimal rates. After four months of cultivation, vitreous fertilizers application significantly improved growth (7% to 88%), photosynthetic (8% to 49%) parameters, and yield (29% to 33%) compared to NPK treatment and to the control. It has been found that formulas F₁, F₂, and F₃ may constitute a potential alternative to conventional fertilization due to their positive impact on wheat production and can be used in practice as an environmentally controlled-release fertilizer.     

Promoted hydrogel formation of lignin-containing arabinoxylan aerogel using cellulose nanofibers as a functional biomaterial

In this work, three-dimensional (3D) aerogels and hydrogels based on lignin-containing arabinoxylan (AX) and cellulose nanofibers (CNF) were prepared. The effects of the CNF and the crosslinking with citric acid (CA) of various contents (1, 3, 5 wt%) were evaluated. All the aerogels possessed highly porous (above 98%) and lightweight structures. The AX-CNF hydrogel with a CA content of 1 wt% revealed a favorable network structure with respect to the swelling ratio; nanofiber addition resulted in a five-fold increase in the degree of swelling (68 g of water per g). The compressive properties were improved when the higher CA content (5 wt%) was used; when combined with CNF, there was a seven-fold enhancement in the compressive strength. The AX-CNF hydrogels were prepared using a green and straightforward method that utilizes sustainable resources efficiently. Therefore, such natural hydrogels could find application potential, for example in the field of soft tissue engineering.

Plant biomimicking assembly: the use of cellulose nanofibers as a functional biomaterial for promoted hydrogel formation from lignin-containing arabinoxylan-based aerogels.     

Vagus nerve stimulation in drug-resistant epilepsy: the efficacy and adverse effects in a 5-year follow-up study in Iran

Drug-resistant epilepsy seems like a different disease compared with easy to control epilepsy, and new strategies are needed to help these patients. Vagus nerve stimulation (VNS) therapy is the most frequently used neurostimulation modality for patients with drug-resistant epilepsy who are not eligible for seizure surgery. In this study, we aimed to evaluate the efficacy and adverse effects of VNS in patients with drug-resistant epilepsy in an open-label, prospective, long-term study in Iran. We selected 48 patients with partial-onset drug-resistant epilepsy. Implantations were performed in the neurosurgery department of Loghman Hospital, Tehran, Iran. Follow-up visits were done on monthly bases for 5 years. Forty-four patients completed the study. Mean age of patients was 24.4 years. Mean years of epilepsy history was 14 years. The mean number of anti-epileptic drugs did not significantly change over five years (p = 0.15). There was no exacerbation of epilepsy; however, one patient discontinued his therapy due to unsatisfactory results. Five patient had more than 50 %, and 26 patients (59 %) had 25–49 % reduction in the frequency of monthly seizures persistently. Overall mean frequency of monthly seizures decreased by 57.8, 59.6, 65, 65.9, and 67 %, in 1st, 2nd, 3rd, 4th, and 5th years of follow-up, respectively. Most common side effects were as follows: hoarseness (25 %) and throat discomfort (10 %). We found VNS as a safe and effective therapy for drug-resistant epilepsy, with an approximate long-term decrease in mean seizure frequency of 57.8–67 %. Thus, VNS is recommended for suitable patients in developing countries.     

Effect of Different Intraorifice Barriers and Bleaching Agents on the Fracture Resistance of Endodontically Treated Anterior Teeth

Introduction

Intraorifice barriers (IOBs) are usually used before internal bleaching for coronal sealing and the prevention of cervical resorption. The aim of this study was to investigate the effect of different IOBs on the fracture resistance (FR) of endodontically treated anterior teeth bleached with various bleaching agents (BAs).