The use of polyetheretherketone for the manufacture of removable implant dentures

INTRODUCTION: The industry of temporary prosthetics for dental implantation in the postoperative period at the present stage of the development of dentistry has achieved significant results. However, up to now, there are still cases of insufficient effectiveness of temporary prosthetics, which is expressed in a reduced service life and a violation of the retention of temporary structures, the need for a relatively large number of corrections of their basis, as well as inflammatory and atrophic changes in the mucous membrane of the prosthetic bed and loss of bone tissue in the jaws in the projection of the mechanical pressure of the prosthesis. AIM: To determine the effectiveness of the use of polyetheretherketone for the manufacture of immediate prostheses based on temporary dental implants. MATERIALS AND METHODS: Dental implants in the upper jaw were installed in 76 patients with a diagnosis of full absence of teeth. For temporary rehabilitation for the period of osteointegration, temporary implants were installed in the amount of 2 pieces and temporary removable dentures were made. RESULTS: The use of polyetheretherketone revealed a 25% decrease in dentures breakdowns, an increase in the number of temporary implants viability by 37.5%, and a decrease in bone tissue atrophy by 19% to 22%. CONCLUSIONS: It is advisable to use polyetheretherketone for the manufacture of removable implant dentures.

Rubber bark dust-zeolite composite improved mechanic strength of soft paddy soil through improved microstructure

<p>Soft paddy soils are not a stable soil structure that leads to the decline of rice production in Kedah, Malaysia. The soil had high compressibility and water content, and low soil strength thus the agricultural machines could not be operated above this soil. Therefore, this study was conducted to improve the mechanical strength of soft soils in paddy fields using an organic amendment. The organic amendment used in this study was made from amended materials comprising clinoptilolite, kieserite, humic acid, and rubber bark dust. The study was carried out in the paddy field area of Alor Pudak district, Kedah, Malaysia, and it was divided into five treatments of amendment dose, i.e: 0 kg (control or P0), 125 kg (P1), 250 kg (P2), 375 kg (P3) and 500 kg (P4) with each plot size about 0.20 ha. The soil samples were then analyzed using X-ray diffraction (XRD), scanning electron microscope (SEM), and the unconsolidated undrained triaxial compression test (UU-test) to characterize their amended properties. The XRD results clearly exhibited changes in the mineralogical composition of all treated plots with an increasing smectite content (1200 to 1300 intensity). Furthermore, the SEM results showed that clay particles in the treated plots have been flocculated to form close-knit, more stable soil structures. After the organic amendment application, the mechanical strength of the treated plots increased to an optimum level (50 kPa in P2) for resisting mechanical pressure from agricultural machinery. Overall, this study of the efficacy of organic amendment offers new insight into a soft paddy soil remediation method that is more effective and economical than the conventional method.</p>

Piezoelectric Nanogenerators based on Lead Zirconate Titanate nanostructures: An insight into the effect of potential barrier and morphology on the output power generation

The high internal resistance of the perovskite materials used in Nanogenerators (NGs) lowers the power generation. It severely restricts their application for mechanical energy harvesting from the ambient source. In this work, we demonstrate a flexible Piezoelectric NG (PENG) with an improved device structure. Hydrothermally grown one-dimensional Lead Zirconate Titanate (Pb(ZrTi)O3) of different morphologies are used as the generating material. The morphology of the PZT nanostructures, engineered from nanoparticles to needle-shaped nanowires to increase the surface to volume ratio, provides effective mechanical contact with the electrode. The reduction of the internal resistance of the PENG has been achieved by two ways: i) fabrication of interdigitated electrodes (IDE) to increase the interfacial polarization and ii) lowering of Schottky barrier height (SBH) at the junction of the PZT nanostructure and the metal electrode by varying the electrode materials of different work functions. We find that lowering of the SBH at the interface contributes to an increased piezo voltage generation. The flexible nano needles-based PENG can deliver output voltage 9.5 V and power density 615 μW/cm2 on application low mechanical pressure (~1 kPa) by tapping motion. The internal resistance of the device is ~0.65 MΩ. It can charge a 35 μF super-capacitor up to 5 V within 20 s. This study provides a systematic pathway to solve the bottlenecks in the piezoelectric nanogenerators due to the high internal resistance.

Sandwich Integration Technique for the Pressure Sensor Detection of Occlusal Force In Vitro

Bite force measurement is an important parameter when checking the function and integrity of the masticatory system, whereas it is currently very difficult to measure bite force during functional movement. Hence, the purpose of this study is to explore the potential technique and device for the measurement and intervention of the continuous bite forces on functional and dynamic occlusal condition. A portable biosensor by sandwich technique was designed, and the validity, reliability, and sensitivity were determined by mechanical pressure loading tests; meanwhile, the pressure signal is acquired by, and transmitted to, voltage changes by the electrical measurements of the sensors. The result is that, when the mechanical stress detection device is thicker than 3.5 mm, it shows relatively ideal mechanical properties; however, when the thickness is less than 3.0 mm, there is a risk of cracking. Mechanical stress changing and voltage variation had a regularity and positive relationship in this study. The mechanical stress-measuring device made by medical and industrial cross has a good application prospect for the measurement of bite force during function.

A Granular Thermodynamic Model to Describe the Temperature/Mechanical Characteristics of Sandy Soil

Based on the granular-solid-hydrodynamic theory, the constitutive model considering the thermo-hydro-mechanical (THM) coupled action is established, and the dilatancy property of sandy soil under coupled high mechanical pressure and temperature is simulated. The relationship between the energy dissipation and the macroscopic stress-strain changes at the grain level of saturated sandy soil is connected by defining the transfer coefficient and the energy function, without considering the concepts of yield surface and hardening parameters in classical plastic mechanics. Additionally, the changes in temperature, relative density and confining pressure during the shearing process cause particle rolling, slipping and friction. The energy dissipation in this process is described by defining the concept of particle entropy and particle temperature. In the calculation, the isotropic compression test, drained and undrained shear test of sandy soil under high stress are simulated respectively. The validity of the model is proved by comparing with the test results. Meanwhile, the stress-strain relationship and pore pressure variation law of sandy soil under different temperatures are predicted. The results show that the effect of temperature on shear strength is limited, and the pore pressure will gradually increase and become stable with the increase of temperature. Thus, this work establishes the soil THM coupled model from the perspective of micro energy dissipation, which can provide new theoretical support for the prediction of natural disasters such as landslides and debris flow.

Determination of functional structure of soft-bottom marine macrobenthic communities of the Samsun Shelf Area using biological traits analysis

Biological Traits Analysis (BTA) was used to investigate the functional structure of marine macrobenthic communities along the Samsun Shelf Area (SSA). Benthic samples were collected seasonally from five different locations and at four different depths using a Van Veen grab sampler. Macrofaunal communities distributed in the SSA were assessed using 10 biological traits to identify characteristic traits for each depth and location. It was found that variability of benthic ecosystem functions in the SSA was driven by biological traits such as maximum size, living habit, sediment position, feeding mode and type of reproductive behavior. Bivalves, polychaetes and crustaceans of small to medium size, biodepositing, burying themselves in the sediment (burrowers) and feeding in suspension were relatively more abundant at depths of 0–60 m. However, the biomass of Amphiura, Abra, Papillicardium and some polychaetes characterized by medium to large sizes, diffusive mixing, free living and feeding on deposit and subsurface deposit showed higher values at depths below 60 m. In general, it is concluded that the functional structure of the benthic infauna in the SSA has adapted to physical disturbance, and communities distributed in this area consist mainly of taxa resistant to mechanical pressure.

Retinal Changes before and after Silicone Oil Removal in Eyes with Rhegmatogenous Retinal Detachment Using Swept-Source Optical Coherence Tomography

This study aimed to evaluate and compare the retinal and choroidal thickness and vessel density (VD) changes between silicone oil (SO) tamponade and after SO removal using swept-source optical coherence tomography (SS-OCT) and OCT angiography (OCTA). Thirty patients who underwent pars plana vitrectomy for retinal detachment (RD) with SO tamponade were included. SS-OCT and OCTA were conducted before RD surgery, during SO tamponade, and after SO removal. A 3-dimensional volumetric wide scan protocol was used for the analysis. The segmented retina, choroidal thickness map, and peripapillary thickness were then measured. For the OCTA analysis, 4.5 × 4.5 mm scans were used. Superficial and deep capillary plexus VDs in unaffected fellow eyes and eyes after SO removal were compared. During the SO tamponade period, the thickness of the parafoveal total retina, ganglion cell-inner plexiform layer, and peripapillary retinal nerve fiber layer (ppRNFL) were significantly thinner than those of unaffected fellow eyes (p < 0.05). The parafoveal layer thickness thinning recovered up to three to six months after SO removal. Moreover, six months after SO removal, the parafoveal thickness was not significantly different compared to that of unaffected fellow eyes (p > 0.05). However, the ppRNFL thickness was significantly decreased during SO tamponade and remained unrecovered six months after SO removal. There was no significant difference in the VD on the OCTA. Thus, SO tamponade and removal for RD resulted in a change in the retinal and peripapillary thickness. This may be due to the mechanical pressure effect of SO.

Dependency of active pressure and equation of state on stiffness of wall

Autonomous motion and motility are hallmarks of active matter. Active agents, such as biological cells and synthetic colloidal particles, consume internal energy or extract energy from the environment to generate self-propulsion and locomotion. These systems are persistently out of equilibrium due to continuous energy consumption. It is known that pressure is not always a state function for generic active matter. Torque interaction between active constituents and confinement renders the pressure of the system a boundary-dependent property. The mechanical pressure of anisotropic active particles depends on their microscopic interactions with a solid wall. Using self-propelled dumbbells confined by solid walls as a model system, we perform numerical simulations to explore how variations in the wall stiffness influence the mechanical pressure of dry active matter. In contrast to previous findings, we find that mechanical pressure can be independent of the interaction of anisotropic active particles with walls, even in the presence of intrinsic torque interaction. Particularly, the dependency of pressure on the wall stiffness vanishes when the stiffness is above a critical level. In such a limit, the dynamics of dumbbells near the walls are randomized due to the large torque experienced by the dumbbells, leading to the recovery of pressure as a state variable of density.