Browse Articles

The aim of this study is to investigate the effect of alloplatic graft and platelet rich fibrin (PRF) , alone or in combination, on bone regeneration in Wistar rats femural defects. Bone defects were prepared in adults male of 20 Wistar rats. In a group of ten, the defect was filled with synthetic ceramic graft as an alloplastic graft; the others 10 were grafted with this alloplastic graft mixed with PRF. All animals were sacrificed on the 90th postoperative day and the femural bones were removed, histologic sections were prepared and the experimental sites were examined microscopically. Histologic examination revealed more new bone formation in the defects filled with alloplastic graft mixed with PRF than in the defects grafted with alloplastic graft alone. The platelet rich fibrin combination effectively induces new bone formation.

Most of the fixation implants for tibia fracture are made of various metallic alloys based on titanium or even stainless steel. But modern technologies and advanced materials offer endless opportunities of using polymers combined with various fillers to enhance and adjust mechanical properties in order to be as suitable and convenient for any patient.

Polylactic acid (PLA) is one of the most extensively used biodegradable aliphatic polyester produced from renewable resources, such as corn starch. Due to its qualities, PLA is a leading biomaterial for numerous applications in medicine as well as in industry, replacing conventional petrochemical - based polymers. The purpose of this paper is to highlight the mechanical properties, such as tensile stress, of pure PLA specimens in comparison with PLA based-composites, with three different added materials in PLA mass: Copper, Aluminum and Graphene, as well as the influence of filament angle deposition on these properties. In order to check if the the filling density of the specimen influences the ultimate tensile stress (UTS), three different filling percentages (60%, 80% and 100%) have been chosen in the experimental tests. In this context, the mechanical characteristics of four different filament types based on PLA material, starting from pure PLA to PLA with Aluminum, Copper or Graphene filler are compared. Understanding and controlling these parameters is essential for the successful use of PLA and PLA-based composites in different areas such as medical applications, sport equipments and light industry.These tests have been performed due to the fact there is a lack of information concerning the mechanical properties. In the scientific literature, such information is only available for expensive printing systems; for open source printers (as those used in these tests), the information is poor and for some new materials, even inexistant. According to the technical specifications, for an expensive printer the cost may exceed 3000 Euros, with a minimum layer resolution of 100 m, this type of printer can reliably reproduce many 3D objects accurately, in quiter conditions.

This work are made for determine the possibility of generating the specific parts of a threaded assembly. If aspects of CAD generating specific elements was analysed over time in several works, the technological aspects of making components by printing processes 3D through optical polymerization process is less studied. Generating the threaded appeared as a necessity for the reconditioning technology or made components of the processing machines. To determine the technological aspects of 3D printing are arranged to achieve specific factors of the technological process, but also from the specific elements of a trapezoidal thread or spiral for translate granular material in supply process are determined experimentally. In the first part analyses the constructive generation process of a spiral element. In the second part are identified the specific aspects that can generation influence on the process of realization by 3D DLP printing of the two studied elements. The third part is affected to printing and determining the dimensions of the analysed components. We will determine the specific value that can influence the process of making them in rapport with printing process. The last part is affected by the conclusions. It can be noticed that both the orientation and the precision of generating solid models have a great influence on the made parts.

The purpose of this study was to assess the accuracy of two 3D printed dental models manufactured after intraoral/IO and extraoral/EO scanning. A dental study model (KaVo Dental GmbH/Germany) was used as a reference for this research; this model was scanned with an industrial scanner (XT H 225 ST/Industrial CT scan/Nikon Metrology Inc./U.S.A.) and a reference STL file was generated (coded M1). Two 3D printed models (Form2/FormLabs Inc./U.S.A.) were produced via IO scanning (TRIOS 3 Battery Cart/3 Shape/Denmark), respectively via EO scanning (Swing Dental Scanner/Dof Inc./South Korea) of the reference dental model. The 3D printed models obtained were scanned with the industrial scanner, resulting in other two STL files (coded M2, respectively M3). All the STL files obtained (reference M1; M2; M3) were compared in pairs, using a 3D analysis software. Good results were achieved in obtaining 3D printed dental models via IO or EO scanning, yet, the 3D printed dental model obtained via IO scanning (M3) showed slightly improved dimensional compatibility with the reference model (M1) in comparison with the 3D printed dental model manufactured via EO scanning (M2).

In recent years, in many areas of civil engineering applications, fuzzy logic models have been used. The aim of this paper is to develop a fuzzy logic model to predict the adhesion stress in polymer concrete. Availability of experimental data was required to develop the relationship between the mixture variables of polymer concrete and its measured properties. The basic parameters considered in this study were epoxy resin, silica fume, aggregate sort I and aggregate sort II dosage. Using Mamdani fuzzy model, with the said parameters, we effectively predicted the adhesion stress in polymer concrete accurately by taking into account the parameters of the problem. In these circumstances, data can be acquired in a short period of time without wasting material, with decreased design cost, all this without attempting experiments and thus saving time. This study showed that the model used has a good prediction and generalization capacity with acceptable errors.

The article presents the process by which, with the help of 3D printing technology, the piston of the differential injection device was produced using ABS material. It was made with fused filament fabrication (FFF) technology, and the smoothing process was used to improve the surface quality. The piston is part of a complex equipment for underground fertilization of agricultural crops.

At young ages the spinal column, which is the central support system of the human body, is susceptible to malformations, especially if the children are sitting in an incorrect position for long period. Our study examines the case of several elementary school students from a developed rural area. The aim of this study to analyze the impact of long sitting hours (5-6 hours) in incorrect position at on the normal standing up position at elementary school students. The study group for our study consisted of 80 elementary school students were recruited from a local rural elementary school. Each student was evaluated using a Kinect based system to determine their general standing up position. For 14 weeks, twice a week, each student has executed 5 type of Schroth exercises to improve their general body position. The first evaluation has shown that the students general standing up position is affected from the long sitting hours in the school benches. Most of them have shown misalignments at the shoulder and hip levels. In many cases one of the shoulders was higher than the other and the same is true for the hips as well. After 14 weeks of physiotherapy based on Schroth exercises the miss alignments were reduced to a bare minim. The results have shown that long sitting hours in incorrect positions can affect the spinal column and the standing up posture of the human body. In many cases malicious postures start to develop from childhood. If not treated they can transform in hyper-kyphotic and scoliotic postures which can induce other complications. If these malicious postures are observed in early stages of the children and with only 2 hours a week of physiotherapy based on Schroth exercise the postures can be corrected and the hyper-kyphotic and scoliotic postures can be avoided.

Finite element analysis is the most commonly used methods in orthopedic biomechanical research. The study aims at improving the common understanding of the behavior of the pelvis and the biomechanics of the pelvic ring in a healthy and osteoporosis configuration. We performed a finite element analysis using the ANSYS program. The study mainly focused on bones and the joints and the complex modelling of the ligaments was ignored. The results of our study showed that the stress distribution of the pelvis with osteoporosis was changed compared with normal pelvis. In addition to, in the healthy bone, where the maximum stress values are concentrated around the obturator foramen (anterior arch of the pelvic ring), in the osteoporotic bone, the maximum stress also appear at the posterior arch of the pelvic ring (especially in the sacrum.

The topic of this paper refers to the influence of the plasticizer and the processing mode upon the characteristics of the poly(vinyl chloride) (PVC) composites. Thereby, in this study two types of industrial plasticizers were used to highlight their influence upon the properties of final composites. The employed lubricant was stearic acid, the most common and cheapest additive used in the industry for cables manufacturing. For economic reasons, calcium carbonate of 2 m size was used as reinforcing agent. Further on, two sets of samples were prepared, targeting the influence of the processing mode upon the properties of final composites. Beside the structure (by FT-infrared), thermal behavior (thermal analyses and differential scanning calorimetry) and mechanical properties (dynamic mechanical analyses, tensile strength and elongation at break) of PVC composites, the limiting oxygen index (LOI) and the overall morphology of the samples were also investigated.