The creating of biomechanical model of the abdominal cavity, which allows us to predict the amount of intra-abdominal pressure during various physiological and pathological conditions is an urgent task. Development of such a model is closely connected with the nature of intra-abdominal pressure. In the scientific literature, we can find studies which state that the abdominal cavity can be represented as a container filled with an incompressible fluid. However, the degree of compressibility of the abdominal contents has not yet been studied enough. This work is devoted to experimental research, which attempts to determine the amount of compression of the abdominal cavity volume during contraction of the anterolateral abdominal wall muscles (abdominal press). As the initial data, we used computed tomography scans of the abdomen of the volunteer, obtained as a result of X-ray studies in a relaxed state and in contraction of abdominal press. Then, these tomographic images were analyzed using an application that was created in a Matlab software. The experimental data revealed a decrease of abdominal space volume of the volunteer only by 2 %. This result leads to the conclusion that the abdominal contents can be considered as incompressible. This proves the validity of the previously mentioned approval that as a model of human abdominal cavity we can use a container filled with an incompressible fluid.

Key words: abdominal contents, incompressibility, tomographic image processing

Clinical experience shows cases of loss of cementation of artificial crowns of dental implants. To study the reasons for breaking strength of cement fixing crowns, it is appropriate to use mathematical finite element analysis of the stress–strain state of all elements of prosthetic design with functional loads. The three-dimensional mathematical modelling of the stress–strain state of the implant and prosthetic construction with cement fixing crowns to the abutment was conducted. The parameters of the stress–strain state in artificial crown, the implant, and fixing cement at vertical and inclined functional load 150 N were studied. The optimal parameters of the stress–strain state at vertical load and deformation changes in cement at offset of the load on 45 degrees. There recommended optimum position of the implant relatively covering artificial crown for the prevention of its loss of cementation under functional load.

Key words: dental implant fixing cement, artificial crown, mathematical modelling, stress–strain state.

The article is devoted to modern concepts of the relationship of parodontal disease and bruxism caused by disorder of biomechanics of the mandible. The aim of this work was to evaluate the efficiency of a rehabilitation program including basic rehabilitation complex, photodynamic therapy with «Lamifaren” gel, music therapy, physiotherapy for the muscles of the maxillofacial region, the fluctuarization, and amplipulse therapy in patients with chronic generalized periodontitis and bruxism. Materials and methods: the study used the such diagnostic methods as dental computed tomography, electromyography. Treatment was provided with using photodynamic therapy, amplipulse therapy, music therapy, physical therapy, fluctuorization. The results of a complex examination, diagnosis and treatment of 85 patients with chronic generalized periodontitis  of moderate severity and bruxism are presented. The characteristic clinical and functional features of these patients is given. The program of medical rehabilitation is developed. The results of the study: the efficiency of the proposed rehabilitation program was determined. Positive dynamics of clinical symptoms was more expressed in patients, who were treated with the proposed programme of medical rehabilitation, than in patients, who received basic rehabilitation complex. It was observed the reduction of treatment time on average 8 days. Clinically, it was observed disappearance of swelling and hyperemia of the gingiva, pain and bleeding at eating, restoration of tightly-elastic consistency of the gingiva, correct configuration of marginal papillae and the entire gingival margin. Multiplie application of the basic rehabilitation complex, photodynamic therapy with «Lamifaren” gel, music therapy, physical therapy for the muscles of the maxillofacial region of fluctuorization and amplipulse therapy in patients with chronic generalized periodontitis of moderate severity and bruxism showed a significant increase in clinical efficiency of the treatment. Conclusion: the high efficiency of the proposed rehabilitation program with physical therapy technologies in the treatment of chronic generalized periodontitis and bruxism caused by disorder of biomechanics of the mandible was proved.

Key words: biomechanics of the mandible, chronic generalized parodontitis, bruxism, amplipulse therapy, photodynamic therapy, fluctuatization.

The paper suggests a post-resection prosthesis–obturator for the upper human jaw made from polyamide. The authors propose a Vertex ThermoSens polyamide reinforcement by nanostructured titanium dioxide in an amount up to 1 wt. %. The new material reduces the level of pathogenic bioflory development on the prosthesis and improves the quality of orthopedic treatment of patients with acquired maxillary defects by reducing the inflammatory complications. Also, the mechanical properties of the obtained material are investigated in the electromechanical system Instron 5965. Tests are carried out according to GOST 31572–2012 with loading rate of 5 mm per min. Loading is carried out to achieve the traverse displacement up the value of 4 mm, then the test is stopped and unloaded sample is removed from equipment. Young's modulus and maximum stress for reinforced polyamide are resulted. The properties of the new material are compared with acrylic plastic. The boundary value problem of linear theory of elasticity for prosthesis-obturator within small deformations is stated. The problem is solved by finite element method. To construct a 3D-model of the prosthesis, the scanner Artec Eva is used. The result shows that the proposed prosthesis has the required mechanical properties and can carry the functional stress. Based on studies, the suggested material can be recommended for clinical use in the manufacture of complicated mandibular prostheses and devices.

Key words: prosthesis–obturator, nanostructured titanium dioxide, polyamide, finite element method.

Many theoretical models about the bone remodelling employ the analysis of several variables including the surface density Sv and vascular porosity fv. The model previously assumed (Nutini, 2015) constructed a system of three equations considering just such variables (Sv and fv) into the analysis of Vito Volterra (Volterra, 1926) in his mathematical model ‘predator/prey’. The proposed remodelling model, therefore, connects the subpopulations involved in the remodelling process (osteoblasts and osteoclasts), into an oscillatory behavior that may be considered by the variation of surface density of the system as a useful indicator of the remodelling process. This paper shall further define the implicit remodelling mechanism in the proposed theoretical model, analyzing the signals that guide and control the bone multicellular units and considering two basic parameters required for the creation of the information network at the base of the bone remodelling itself. The two systems are identified by the functional equilibrium of the bone multicellular unit’s variable in the process of remodelling (rBMU) and from the functional variable dynamic balance of the osteoblastic/ osteoclastic subpopulations (qBMU): both include the signal form that acts on the bone multicellular unit and enable an appropriate form of bone remodelling.

Key words: bone remodelling, bone multicellular unit, theoretical model, coupling mechanisms, surface density, vascular porosity.

Evaluation of bone regenerate maturity was performed according to the rate of velocity reduction of regenerate blood supply at functional load on the extremity and according to the intensity of this load when blood flow was accelerated during this load and was related to reduction of mean dynamical artery opening. In treatment of adult patients with closed humerus fractures by Ilizarov method (n = 20), micromotion of fragments in axial extremity load 10 kgf was 219 ± 39 microns, in tibial bones fractures (n = 30) – 71 ± 18 microns, after tibial lengthening (n = 15) – 54 ± 14 microns. During further treatment periods, micromotion of bone fragments was decreased while compaction of bone regenerate. Rate of compaction was higher on humerus and was lower after extremity lengthening in adult patients of 1st group. During fixation, patients tolerance to load on humerus was increased from 5 to 15 kgf. Tolerance threshold of load was determined by sense of discomfort appearance at patient’s regenerate area and by increase of blood velocity. In patients with tibial bones fractures, this tolerance threshold was increased during treatment from 20 to 40 kgf, after extremity lengthening – from 10 to 30–40 kgf. Fundamental differences in the dynamics of micromotion bone and endurability of functional load in injuries of the shoulder and lower leg were identified.

Key words: regenerate blood supply, functional load, Ilizarov method, bones fractures, extremity lengthening.

Earlier, it was discovered an interconnection of the functional condition of the limb and linear blood flow velocity in the middle cerebral arteries of contralateral side of the brain. The present study is done to analyze the causes for decrease of blood flow velocity in the middle cerebral arteries with age. The studied parameters of blood flow velocity were evaluated using the method of ultrasound Doppler with a probe of 2 MHz. The examinations were done at rest and during functional muscular test (squeezing elastic wrist exerciser) in 30 apparently healthy people aged 18–60 and in 30 patients aged 5–62 with congenital growth delay of one of the lower limbs during its surgical lengthening by the Ilizarov method by 3–7 cm (on average by 4.5 cm). Decrease of blood flow velocity in the middle cerebral arteries with age was discovered in the healthy people, and even more significant – in the orthopaedic patients. We also discovered an interconnection of values of blood flow velocity in the middle cerebral arteries of the contralateral side of the brain and degree of longitudinal growth delay of the affected limb. We concluded that decrease of blood flow velocity is a necessary condition to conserve cerebral blood flow auto-regulation; in case it gets affected with age and also in patients during treatment their performance significantly decreases.

Key words: cerebral blood supply, adaptation reserve, performance, limb lengthening.

Sound transmission in the middle ear is mechanical process. In this article, two problems are considered: the development of a biomechanical model of stapes functioning as elastic and a rigid body in norm and its fixation at process of otosclerosis and modelling of system of the transmission of sound through the stapes and stapes prosthesis in stapedoplasty. Modelling of the elastic state stirrup showed that at fixing the stirrup, displacement shift to the bone head and the strain reaches the maximum at the base of the leg stirrup, as well as stress. Information obtained at these biomechanical studies correlates well with the literature on the morphological changes of the stapes in otosclerosis. The kinematic model of the stapes movement as a rigid body allowed us to provide conditions for preservation of stapedius muscle in stapedotomy in contrast to the classical scheme of intersection. Clinical studies on a group of 340 operations have shown that the process of improving the hearing after the stapedoplasty with preserving stapedius tendon is more intense compared with the classic version of its intersection. As a result, the proposed biomechanical models are useful for theory of the stapedoplasty and practice otosurgery.

Key words: otosclerosis, stapes operation, biomechanical model, stapedoplasty, stapedotomy, stapes prosthesis, stapedius tendon preservation. 

Research of biomechanical processes depends on the observer (as, in principle, generally in mechanics). The problem of determining time of completion of the process is formulated. In this paper, this time is determined by the achievement of predetermined value of the parameter defining the process. Completion of the process can be predicted by observation of changes of determining the parameter or is based on kinetic modelling of this implementation at instrumental accompaniment of biomechanical process. The process is essentially random under the same conditions if observer does not monitor course of the process. This situation is due to the fact that the biomechanical processes as biological and biotechnological processes are linked to the activity of organs or microorganisms. It leads to ambiguity of procedure and results of implementations. In this case, time of reaching of predetermined value of determining parameter of the process can be predicted only at given probability. Series of experiments or observations of repeatable implementations is necessary for research of these processes as random. As a rule, the required information is limited both by number of realizations and the number of observations on temporary sections of the process. Simple (kinetically modelled) random processes can be described by the ordinary functions of the system of limited number of random parameters based on kinetic models for implementations. The cardinal question is the reliability of distribution of random variables. In this paper, criterion of reliability of distribution of the random parameters in case of small sample is proposed, and the method of determining time of completion of biomechanical processes with given probability. The proposed method makes possibility for development and implementation of deterministic and probabilistic formulations of optimization problems for simple biomechanical processes.

Key words: biomechanical processes, kinetics, observer position, time of completion, deterministic and probabilistic approaches, law of distribution, small sample, criterion of reliability.

Computed optical topography has been used for quantitative evaluation of motor pathology manifestations in postural orthostatic stereotypes. Spatial characteristics of the trunk and spine in orthostatic position were investigated by 7–14 topographic images with prolonged standing up to 3.5 minutes. Monitoring of postural activity was carried out in a natural position and under the conditions of modeled limb length discrepancy with the interval from 10 to 20 seconds. Orthopedically normal persons (n = 55) at the age of 6–30 years, and 36 patients with children cerebral paralysis of the same age have been examined before and after the functional load as non-stop random-rate walking for 30 minutes. As it has been established, the diagnostic criterion of “standardized deviations” based only on the variability assessment of the studied sign in the population, does not adequately reflect the signs of motor pathology in orthostatic activity. It is necessary to determine the individual variability of the studied parameter in the structure of a specific motor stereotype in order to assess the pathologic manifestations in postural activity. The developed stability indicator (SI) of the postural parameter is directly related to the absolute values of its variability, and it reflects the degree of the locomotorium characteristic approximation to a useful adaptive result. In the structure of functional organizing of the postural orthostatic stereotypes, the variability of spatial characteristics of vertically and horizontally oriented kinematic trunk elements is in degree-related dependence on their mathematically expected values. The normative values of SI for the index of affecting the shape of the trunk are more than –2.0 relative units in the frontal plane, and the values of variation are less than 0.4δ. Under the conditions of motor pathology, the strength of power dependence decreases that characterizes manifestations of the motor disorders associated with the extrapyramidal system dysfunctions, then the values of SI are recorded less than –2.0 relative units and the values of variance more than 0.4δ.

Key words: motor pathology in postural activity, orthostatic motor stereotype, computed optical topography, variability and stability of postural characteristics, stability indicator of the postural parameter.