Elastic Liner Research Articles

Analytical poro‐elastic solution of deep lined tunnels in anisotropic rock with consideration of tunnel face advance

AbstractThis paper aims at deriving a closed‐form solution for deep lined tunnels within a saturated anisotropic poro‐elastic medium. The derivation of the solution is carried out with the assumption of plane strain conditions along the tunnel axis, an isotropic elastic liner, a steady‐state flow, and perfect contact between the liner and rock. For this purpose, the complex potential function approach pioneered by Lekhnitskii for the anisotropic elastic body was used to develop the mechanical response of the rock mass. A complex hydraulic potential function is also introduced to solve the steady state fluid flow. Then the well‐known Biot theory is chosen to describe the hydro‐mechanical coupling of the anisotropic saturated rock. The stress and displacement solutions of both the liner and the surrounding rock, considering the tunnel face advance with respect to the considered section, are derived based on the principle of the convergence‐confining method. Comparisons with previous closed‐form solutions for isotropic case and finite element solution for anisotropic case were made to show the accuracy of the current closed form solution. Sensitivity analysis is performed based on this analytical solution to highlight the effect of some rock parameters on the stress and displacement of the liner.

MANUFACTURE OF REMOVABLE DENTURES WITH A TWO-LAYER BASE

In the case of unfavorable anatomical conditions on the part of prosthetic tissues (sharp bone protrusions, exostoses, a sharp ridge of the inner oblique line, an unyielding mucous membrane, etc.), the manufacture of removable prostheses with an elastic plastic lining is shown. The lining can be applied to the entire base or to certain areas of it. The bases of removable prostheses, consisting of two basic materials, are commonly called two-layer. Elastic polymer materials are used to make the lining in prostheses with a two-layer base. Modern elastic materials for double-layer bases of prostheses are divided by chemical composition into acrylic, silicone, fluoro-rubber, PVC and polyurethane. Depending on the nature of the initiation of the polymerization reaction, elastic materials of cold polymerization (self-hardening) and hot polymerization are isolated.

Numerical Modeling and Simulation of a Poroelastic Journal Bearing Lubricated By Nanofluids with Couple-Stresses

In this paper we present a numerical simulation of a porous journal bearing considering the fluid film – poroelastic matrix interaction and the non-Newtonian rheological behavior of nanolubricant consisting of base fluid and nanoparticles (NPs). The flow of nanolubricant in the bearing clearance space is described by the Vijay Kumar Stokes micro-continuum theory which considers the characteristic size of nanoparticles such as fullerenes dispersed in a base oil. The flow of the nanolubricant in the porous medium is modeled by the modified Darcy’s law where the Beavers–Joseph slip conditions are applied at the fluid film-porous matrix interface. The deformation of the fluid-film porous matrix interface due to hydrodynamic pressure is calculated by using a simplified analytical thin elastic liner model. The hydrodynamic behavior of lubricating film is governed by the modified Reynolds equation obtained from the momentum, moment of momentum, and mass conservation laws using the classical Reynolds derivation process. The bearing porosity is introduced into the governing modified Reynolds equation by means of the Morgan-Cameron approximation. The steady-state analysis shows that for an imposed operating eccentricity, the load capacity increases with the characteristic size and the concentration of NPs while the attitude angle, the leakage flow rate, and the coefficient of friction decrease. On the other hand, the permeability decreases the hydrodynamic pressure, the load capacity, and the leakage flow rate, and increases the attitude angle and the coefficient of friction.

Possibilities of orthopedic technical care for extremity lengthening and reconstruction

Orthopedic technical care plays acrucial role in improving function and mobility for patients undergoing limb lengthening and reconstruction. The treatment strategy is based on aprecise classification of the defect, taking into account factors such as joint instability, muscle pathology and limb length discrepancy. The selection of orthopedic aids depends on the specific deformity, its classification and the individual needs of the patient. Through interdisciplinary decision-making and customized adaptations of prostheses and orthoses, optimal function and aesthetically pleasing outcomes can be achieved. The utilization of custom-made technical components, such as traction devices combined with elastic liners, is essential for long-term treatment success and can support surgical interventions. The treating physician's expertise is crucial in selecting the appropriate orthopedic technical device following limb lengthening and reconstruction.

Performance of hydrodynamic textured journal bearing with the combined influence of elastic deformation and pseudo-plastic lubricant

This study outlines the performances of finite-length journal bearing with textured liner, shear-thinning Rabinowitsch lubricants, and considers the elastic deformation of the bearing liner. The yielded nonlinear Rabinowitsch-Reynolds PDE system has been solved using the finite difference method combined with Elrod’s algorithm for the case of cylindrical textures. The static performance of hydrodynamic lubrication, in this case, involves different parameters such as depth of texture, eccentricity ratio, elastic deformation factor, rheological index, etc. Results showed that, at a fixed eccentricity ratio, texturing of the bearing’s converging area enhances significantly the load-carrying capacity and reduces the friction coefficient compared to the smooth bearing surface (up to [Formula: see text] in load capacity and [Formula: see text] in friction coefficient). On the other hand, using a lubricant with more pronounced shear-thinning behavior and/or elastic liner reduces the journal bearing performances (up to [Formula: see text] in load capacity and [Formula: see text] in pressure). By applying the optimization technique (particle swarm optimization), an optimal arrangement of textures that can compensate for these losses in performance even at high eccentricity has been found. This optimal texture with dimensionless dimple’s depth set to 1 [Formula: see text] improves the load capacity with [Formula: see text] for a lubricant with a rheological index [Formula: see text] and elastic bearing liner with deformation parameter [Formula: see text].

Contribution of geosynthetic to the shear strength of geosynthetic encased stone columns

This paper presents a numerical study to evaluate the contribution of geosynthetic to the shear strength of geosynthetic encased stone column (GESC) under direct shear loading conditions. The backfill soil was characterised using the linearly elastic–plastic Mohr–Coulomb model. The geosynthetic encasement was simulated using linearly elastic liner elements. The interaction between the geosynthetic encasement and soils on both sides was modelled through two interfaces. The three-dimensional numerical model was validated using experimental data from direct shear tests of GESC models. The shear stress–strain response and the development of longitudinal and circumferential strains of GESC during the shear process were first discussed, and then a parametric study was conducted to investigate the effects of various design parameters on the shear strength of GESC and the contribution of geosynthetic. Results indicate that the shear resistance provided by the geosynthetic encasement develops slowly, which depends on the mobilisation of tensile strains. At the failure condition, the longitudinal strains are larger than the circumferential strains, which indicates that the longitudinal tensile rupture is more critical for GESC under shear loading. The vertical stress, geosynthetic encasement stiffness and stone column diameter and spacing have the most important influences on the shear strength contribution of geosynthetic encasement.

PROBLEMS OF PROVIDING ORTHOPEDIC DENTAL CARE TO PATIENTS WITH CHRONIC RECURRENT APHTHOSIS STOMATITIS (LITERATURE REVIEW)

Abstract. According to the World Health Organization, chronic recurrent aphthous stomatitis remains an acute unresolved medical problem of the population and affects up to 20%. Such a large volume of patients stimulates the development of new treatment methods. In domestic and foreign literature, the possibilities of orthopedic treatment for chronic recurrent aphthous stomatitis are presented only in separate works. In this case, the question is not about the rejection of prosthetics. It is necessary for chronic aphthous stomatitis to choose the appropriate design of the prosthesis, which will eliminate the possibility of injury to the oral mucosa and the occurrence of an allergic reaction. Rational prosthetics is possible and necessary in terms of preventing the occurrence of relapses of chronic stomatitis. According to many authors, when preparing the oral cavity for prosthetics with chronic recurrent aphthous stomatitis, it is important to determine the amount of possible orthopedic care. There are recommendations for the elimination of possible traumatic factors, the correct restoration of the height of the lower face when providing orthopedic dental care to patients with chronic recurrent aphthous stomatitis. To prevent exacerbations in preparation for dental procedures, researchers suggest treating the oral cavity with gels or solutions containing an anesthetic. In many literature sources, when prosthetics with removable lamellar dentures of extensive defects in the dentition or the complete absence of teeth, it is necessary to use two-layer bases made of colorless plastic with an elastic lining. Aim of the study: to analyze domestic and foreign literature on the issues of orthopedic treatment of patients suffering from chronic recurrent aphthous stomatitis. Material and methods. An analysis of the literature on this issue was carried out, where a significant place is given to the importance of oral hygiene, weakening the toxic-allergic effect of polymers, improving the technology for manufacturing removable lamellar dentures, the use of magnetic therapy and low-intensity laser radiation. Conclusions. An analysis of the literature data and our own observations confirms the need for further study of the issue of providing qualified dental orthopedic care to patients with chronic recurrent aphthous stomatitis and ways to accelerate adaptation to removable partial or full dentures in patients with this pathology.

Numerical Analysis of Deep Tunnels in Viscoplastic Rock Mass Considering the Creep and Shrinkage of the Concrete Lining

This paper aims to show, through numerical parameter analysis on a finite-element method with axisymmetry hypothesis, the long-term effect involving the creep and shrinkage of the concrete lining in deep tunnel problems. The excavation process is simulated by the deactivation and activation method. A viscoplastic constitutive model for the rock mass and an elastic and viscoelastic constitutive model for the lining are used in the software ansys. Perzyna’s viscoplastic constitutive model with an associated flow rule with von Mises yield surface is considered. The viscoelastic model is implemented in ansys using the customization feature. The shrinkage is given by the CEB-FIP MC90 formulation and the creep part is modeled through a Generalized Kelvin chain, according to the solidification theory of Bažant and Prasannan, whose parameters are adjusted with the creep function of the CEB-FIP MC90. Compared with an elastic lining, the viscoelastic line showed a difference (in average terms), in the equilibrium convergence at the end of tunnel construction between 6% and 37%. This value increases to 8% and 72% in the long-term convergence.

PERIODIC REINFORCEMENT OF TWO PRE-STRESSED STRIPS BY FINISHED SUPPORTING ELEMENTS

The qualitative and quantitative influence of initial (residual) stresses on the law of distribution of contact characteristics at interaction of elastic finished overlays (stringers), at their placement, with two prestressed strips which are clamped by one edge. In general, the research was carried out for the theory of great initial (ultimate) and two variants of the theory of small initial deformations within the framework of linearized theory of elasticity with the elastic potential having arbitrary structure for compressible and incompressible bodies. Fourier integral methods, methods for solving harmonic differential equations, singular integral-differential equations and numerical methods were used too. It is assumed that in the contact area the initial stress state, with a certain degree of accuracy, is considered homogeneous. We make the assumption that the elastic band with initial (residual) stresses is in the conditions of plane deformation. Also, for an elastic lining loaded with both vertical and horizontal forces, the generally accepted model of beam bending in combination with the model of uniaxial stress-strain state of the elastic lining is valid. A singular integral-differential equation with the Gilbert kernel was derived, which allows us to solve this problem. We find the analytical solution of the equation in the form of series from the Jacobi function. Numerical studies were performed for materials with elastic potentials of harmonic type (compressible bodies) and elastic potentials of Bartenev-Khazanovich and Treloar (incompressible bodies). Numerical studies have been performed for materials with elastic potentials of harmonic type (compressible bodies) and elastic potentials of Bartenev-Khazanovich and Treloir (incompressible bodies). We have considered the case when all periodically placed pads that support elastic bands with the initial stresses were loaded with tangential force. Analysis of numerical results shows a significant effect of initial (residual) stresses on the distribution of contact characteristics of periodically reinforced strips with thin reinforcing elements. The results obtained can be used for engineering calculations for the strength and durability of structures, taking into account the initial stresses for a wide range of structural materials.

Pressure-driven wrinkling of soft inner-lined tubes

A simple equation modelling an inextensible elastic lining of an inner-lined tube subject to an imposed pressure difference is derived from a consideration of the idealised elastic properties of the lining and the pressure and soft-substrate forces. Two cases are considered in detail, one with prominent wrinkling and a second one in which wrinkling is absent and only buckling remains. Bifurcation diagrams are computed via numerical continuation for both cases. Wrinkling, buckling, folding, and mixed-mode solutions are found and organised according to system-response measures including tension, in-plane compression, maximum curvature and energy. Approximate wrinkle solutions are constructed using weakly nonlinear theory, in excellent agreement with numerics. Our approach explains how the wavelength of the wrinkles is selected as a function of the parameters in compressed wrinkling systems and shows how localised folds and mixed-mode states form in secondary bifurcations from wrinkled states. Our model aims to capture the wrinkling response of arterial endothelium to blood pressure changes but applies much more broadly.

Design of combined lower limb elastic compression device and comparative study with elastic bandage

To compared with the modified Robert Jones bandage of 3M elastic bandage, to evaluate the fitness, convenience, safety and comfort of the modular combination lower limb elastic compression device. Forty healthy adult college students, including 28 males and 12 females, aged 16 to 25 (20.3±2.2) years old and weighing 40 to 81 (60.4±20.2) kg, were randomly divided into two groups with 40 samples in each group. According to the body surface parameters of Chinese lower limbs and guided by the concept of modularization, a group of modular combined lower limb elastic compression device was designed. Each module was combined to evaluate the fitness of the modular combined compression device in thelength and circumference of the lower limbs. The left and right lower limbs were randomly paired and divided into groups, with 40 samples in each group. The convenience of the operation time, adjustment times and required time were compared between two groups. The safety of the two groups after 24 hours of application of pressure injury was compared. The subjective pain feeling changes within 24 hours were recorded by visual analogue scale (VAS) to evaluate the comfort. The device was composed of several elastic compression outer lining modules with different length and width of 15 cm, an inner lining module for buffering, positioning and attaching the main body, and an elastic ankle compression module. The length of the elastic compression outer lining module covers the circumference of the human lower limbs. The length of a single outer lining module increased from 15 cm to 80 cm every 5 cm interval, and the length of a single inner lining module increased from 62 cm to 83 cm every 3 cm interval. After the modules were selected and combined, the length and circumference of the lower limbs can reach 100% fitness. The operation time of the first placement(118.23±7.33) s and re operation(60.08±5.88) s of experimental group were significantly shorter than those of control group (164.68±8.93) s and re operation (131.23±7.91) s. The adjustment times (3) and operation time (3.50±0.71) s of experimental group were significantly shorter than those of control group(11)and operation time(139.00±5.66) s (P<0.05), but there was no significant difference between two groups (P>0.05). The VAS score of experimental group was significantly lower than that of control group at each time point (P<0.01). The modular combined elastic compression device has good fitness, better placement and flexible adjustment, convenience and safety, and better comfort than modified Robert Jones bandage of 3M elastic bandage.

Analytical Solution for Lined Circular Tunnels in Deep Viscoelastic Burgers Rock Considering the Longitudinal Discontinuous Excavation and Sequential Installation of Liners

Tunneling stoppage often occurs during tunnel construction, especially in weak and rheological ground. The discontinuous excavation caused by the stoppage usually has a certain impact on the tunnel convergence and supporting pressure. This study develops a closed-form analytical solution for a deep-buried circular tunnel excavated in viscoelastic rock, in which the progress of longitudinal discontinuous excavation (the stoppage that occurs during tunneling) and the sequential installation of double elastic liners are considered. In the derivation, the change in the advance rate of the tunnel face before and after stopping is also considered. Corresponding to the whole construction process, the solution is solved step by step in five stages, and a generalized derivation procedure for any viscoelastic model is provided depending on the integral equation theory. Particularly for the Burgers model, explicit expressions for the time-dependent rock displacement and stress as well as the pressure on the two liners are presented, which can be reduced to the previous viscoelastic solutions with a constant advance rate or without the face effect. For validation purpose, comparisons are made between the proposed solution and previous existing solutions as well as the numerical results obtained by the finite-difference simulations. Additionally, to further verify the applicability of the presented solution in tunnel applications, the time-dependent tunnel convergence and liner stress of the four typical cross sections in the Saint Martin La Porte access adit are predicted, which are in good agreement with the corresponding field monitoring data. Compared with previous solutions, the proposed solution is more comprehensive and suitable for more complex tunnels with various excavation methods, rheological rocks, and supporting forms.

Radial deformation analysis of couple stress fluid operated multi-lobe hydrodynamic journal bearing

In high speed rotating machine parts the elasticity of the bearings supporting the journal plays key role. The present work is related to couple stress fluid (CSF) operated multi-lobe elastic hydrodynamic (HD) journal bearing. In this work the evaluation of radial deformation in the three dimensional elastic liner of bearing has been done. Here finite element method is used to solve the Reynolds equation along with the elasticity equation, to evaluate radial deformation in the liner. The iterative process used for the convergence of pressure in the rigid as well as in elastic case, however the present work focuses on the amount of radial deformation obtained while operating at different eccentricities. The results of radial deformation shows that increase or decrease in the amount of deformation is different for both upper and lower lobe with increase in couple stress parameter and eccentricity ratio. Further it directly influences the performance of bearing system by effecting the fluid flow zone. Hence the elasticity of the liner must be consider for better performance evaluation along with couple stress fluid. The radial deformation results of two lobe journal bearing presented in this work will lead to the better bearing designs by the bearing designers.

Оцінка ефективності застосування еластичної підкладки як засобу для скорочення термінів адаптації до знімних пластинчастих протезів в процесі ранньої ортопедичної реабілітації пацієнтів

Objectives. Study of ways to increase the efficiency of immediate prosthetic treatment of patients with asymmetric distally unlimited defects of dental rows by using clinical relining of partial removable dentures with elastic material to reduce the time of adaptation to dentures and normalize the functional activity of the masticatory muscles. Materials and methods. The efficiency of clinical relining of partial removable dentures using an elastic lining with Ufi Gel P from VOCO (Germany) was evaluated by electromyographic examination with BioEMG III electromyograph from BioRESEARCH Associates, Inc. (USA). The bioelectrical activity of the temporal and masseter muscles was evaluated during maximum voluntary clenching and mastication. The quantitative indicators of the amplitude of biopotentials (μV) and the qualitative characteristics of the chewing cycles were evaluated. Results. Our study has revealed that patients with asymmetric distally unlimited defects of dental rows had shown a significant decrease in the amplitude of biopotentials of the masticatory muscles compared to patients in the control group during maximum voluntary clenching and chewing, as well as a significant asymmetry of the bioelectric activity of the masticatory muscles on the right and left. During mastication there were significant differences in the size and duration of chewing cycles, a decrease in the duration of rest periods and the average number of chewing movements increased almost two times compared with intact dentition. A month after prosthetics, the indicators of bioelectrical activity of the masticatory muscles improved in both study groups of patients, but the most significant increase in amplitude was observed in the second group with a soft lining. There was also revealed a significant increase in the symmetry of bioelectric activity of the masticatory muscles, an improvement in the characteristics of the masticatory cycles and normalization of the activity and rest periods duration ratio in patients of the second group, while in patients of the 1st clinical group the indicators of symmetry did not change significantly. The average number of chewing movements required to chew the hazelnut kernel decreased to 38.7±16.2 and 29.3±10.7 respectively, in groups 1 and 2, which indicates an increase of masticatory efficiency. Conclusions. In the framework of this study, the high efficiency of elastic lining for the successful rehabilitation of patients with asymmetric distally unlimited defects in case of early prosthodontic interventions was proved. Our observations have shown that the use of the soft lining significantly increases the functional parameters of the masticatory system, shortens the period of adaptation to removable dentures and supports the formation of the alveolar processes relief without irregularities.

Функциональный анализ результатов использования эластической подкладки «Ufi Gel P» компании «VOCO» (Германия) как средства для сокращения сроков адаптации к съемным пластиночным протезам в процессе ортопедической реабилитации пациентов с асимметричными дистально неограниченными дефектами зубных рядов на ранних этапахФункциональный анализ результатов использования эластической подкладки «Ufi Gel P» компании «VOCO» (Германия) как средства для сокращения сроков адаптации к съемным пластиночным протезам в процессе

Objectives. Study of ways to increase the efficiency of immediate prosthetic treatment of patients with asymmetric distally unlimited defects of dental rows by using clinical relining of partial removable dentures with Ufi Gel P material from VOCO (Germany) to reduce the time of adaptation to dentures and normalize the functional activity of the masticatory muscles. Materials and methods. The efficiency of clinical relining of partial removable dentures using an elastic lining with Ufi Gel P from VOCO (Germany) was evaluated by electromyographic examination with BioEMG III electromyograph from BioRESEARCH Associates, Inc. (USA). The bioelectrical activity of the temporal and masseter muscles was evaluated during maximum voluntary clenching and mastication. The quantitative indicators of the amplitude of biopotentials (μV) and the qualitative characteristics of the chewing cycles were evaluated. Results. Our study has revealed that patients with asymmetric distally unlimited defects of dental rows had shown a significant decrease in the amplitude of biopotentials of the masticatory muscles compared to patients in the control group during maximum voluntary clenching and chewing, as well as a significant asymmetry of the bioelectric activity of the masticatory muscles on the right and left. During mastication there were significant differences in the size and duration of chewing cycles, a decrease in the duration of rest periods and the average number of chewing movements increased almost two times compared with intact dentition. A month after prosthetics, the indicators of bioelectrical activity of the masticatory muscles improved in both study groups of patients, but the most significant increase in amplitude was observed in the second group with a soft lining. There was also revealed a significant increase in the symmetry of bioelectric activity of the masticatory muscles, an improvement in the characteristics of the masticatory cycles and normalization of the activity and rest periods duration ratio in patients of the second group, while in patients of the 1st clinical group the indicators of symmetry did not change significantly. The average number of chewing movements required to chew the hazelnut kernel decreased to 38.7±16.2 and 29.3±10.7 respectively, in groups 1 and 2, which indicates an increase of masticatory efficiency. Conclusions. In the framework of this study, the high efficiency of Ufi Gel P (VOCO) elastic lining for the successful rehabilitation of patients with asymmetric distally unlimited defects in case of early prosthodontic interventions was proved. Our observations have shown that the use of the Ufi Gel P (VOCO) soft lining significantly increases the functional parameters of the masticatory system, shortens the period of adaptation to removable dentures and supports the formation of the alveolar processes relief without irregularities.

Structural failure performance of the confined liner with a non-uniformly annular gap subjected to a point load under a thermal rise field

The present investigation focuses on the failure performance of the confined liner with a non-uniform annular gap. The liner is subjected to a radial point load under a temperature rise field. An admissible displacement function is assumed to establish the nonlinear equilibrium equations. The principle of minimum potential energy is employed to obtain the analytical expressions of the critical buckling load (failure load) for the elastic liner encased in the rigid medium. It is found that the temperature rise field has a substantial increase in the critical buckling load. Subsequently, the buckling and post-buckling load-displacement equilibrium paths are plotted by the analytical solutions, and such equilibrium paths can also be traced by developing a two-dimensional (2D) finite element model (FEM). The maximum load (buckling load) obtained from the numerical results show excellent agreement with that from the proposed analytical solutions, and other closed-form expressions. Furthermore, the liners with inelastic material properties and geometric nonlinearities are considered numerically, and the critical buckling load shows its sensitivity to the initial gap, the initial out-of-roundness imperfection, and Young's modulus of the medium. Finally, the effect of friction is examined and plays a small role in the critical buckling load.

Elastic and inelastic buckling of thin-walled steel liners encased in circular host pipes under external pressure and thermal effects

This study aims to develop an analytical solution for the elastic buckling pressure and its corresponding equilibrium path of confined, thin-walled liners subjected to temperature variations. The admissible radial displacement function and the minimum potential energy of liners are employed to establish the equations of equilibrium. The steel liners are modelled with two-dimensional finite elements for both elastic and inelastic behaviors. The elastic buckling pressure and the equilibrium path from the computational model are in excellent agreement with the analytical predictions. The analytical solutions for elastic liners and the numerical results for inelastic liners with material and geometric nonlinearities compare well with their respective test results available in the literature. Parametric studies are performed in terms of temperature variation, out-of-roundness imperfection, non-uniform liner-pipe gap, pipe supporting medium flexibility, and steel liner yield strength.

Development of the theory of laying a hoisting rope on the drum of a mining hoisting machine

For new designs of mine hoisting machines, the development of scientifically-based solutions to increase the rope capacity and reduce the size of the machines is relevant. Based on the theory of laying the rope on a lined cylindrical drum developed by the authors, it is shown that when choosing a groove profile and winding pitch for a non-lined drum, it is necessary to use a geometric rope laying model, and for taking into account the elastic lining, it is necessary to use a physical model of static interaction of a rope with a scallop of the groove. It is recommended to use the U-tilda-groove profile, which will allow a 4.5 % increase in the drum capacity while maintaining the rope’s curvature radius that is permissible under safety rules during its installation.

Justification of the algorithm for selecting the parameters of the elastic lining of the drums of mine hoisting machines

When calculating the stress-strain state of a cylindrical drum of a mine hoisting machine loaded with a metal rope, the stiffness parameters of the elastic lining and frontal surface are taken into account. It is defined that, depending on the values of the radial and bending stiffness of the frontal surface, two zones can be distinguished. If the parameters of the frontal surface fall into the first of them, the stresses in the shell slightly differ from the stresses in the hinged supported shell. The second zone is characterized by a sharp (up to 70%) increase in stresses. An algorithm has been developed for selecting rational parameters of a lined drum, which allows to reduce the stresses in the metal shell by up to 20%.

Antibacterial and antifungal effects of chitosan nanoparticles on tissue conditioners of complete dentures

IntroductionOne of the most serious problems in dentistry is the growth of bacteria and fungi on complete dentures. The growth in question takes place on the surface of the elastic liners of their tissue conditioners. However, this problem can be solved by adding nanoparticles with antibacterial and antifungal properties to the tissue conditioners. Materials and methodsAfter bacterial and fungal microorganisms were cultured, the suspensions obtained were incubated for 24 and 48 h respectively. It was conducted under incubation conditions with a tissue conditioner containing chitosan nanoparticles. The growth rate of microorganisms was measured in the culture medium using a spectrophotometer. ResultsDifferent concentrations of chitosan nanoparticles led to the inhibition of fungal and bacterial growth in within both 24 and 48 h. ConclusionChitosan nanoparticles have an inhibitory effect on the growth of bacteria and pathogenic fungi.