A comparative investigation of the influence of certain arm positions on hand pinch grips in the standing and sitting positions of dentists.

Hand pinch grips in the standing and sitting positions on a group of 46 healthy males of 20 to 26 years old were measured. The results were as follows: 1. Hand pinch grip forces are higher when the subject is standing than when he is sitting. 2. Hand pinch grip forces, depending on the position of the arm in the working space, are higher when the arm is supported than the corresponding forces of the unsupported arm. 3. There is an effect due to the position of the arm in relation to the frontal position of the subject's thorax. In the standing position, the forces are maximum when the forearm has a 60 degrees angle towards the frontal position, while in the sitting position pinch grip forces are maximum when the forearm is perpendicular (90 degrees ) to the frontal position. 4. A handle which permits all fingers to be spread in a pinch grip is capable of having an applied force 50% greater than if the thumb and either forefinger or middlefinger grips the handle. In such a handle each finger is required to apply less force to contribute to the total needed for the task, and therefore there is a diminished likelihood of the onset of fatigue.

The influence of arm position on the pinch grip strength of female dentists in standing and sitting positions.

The objective of this study was to measure and compare hand pinch grip forces in standing and sitting postures for a group of 77 healthy female dentists of 25 to 55 years old. The equipment used consisted of a gripping device with strain gauges, a measuring device and a printer. The results can be described as follows. With respect to absolute values the hand pinch forces are higher when the subject is standing with her arm supported, than when she is sitting. In the standing position the measured forces were maximum when the forearm was at 60 degrees angle towards the frontal position, while in the sitting position the pinch grip forces were maximum with the forearm vertical (90 degrees ) with respect to the frontal position. The above data can be used to design the dentist's working area.

Determination of central dynamic moments of inertia of body segments.

This paper has been described an automatised method for determination of central dynamic moments of inertia of body segments. The method has been established for measuring female subjects. The body is sectioned into 16 segments, which are modelled using geometric solids. Measuring has been performed on 120 female subjects. Dynamic moments of inertia have been determined for all three axes of local co-ordinate systems in segments' centres of mass. The results are statistically analysed and divided into five percentile groups. Method described in this work represents simple, quickly and reliable manner of dynamic anthropomeasures determination.

The compact formulation of anthropodynamical measures in physiological anthropology.

In this paper, an interdisciplinary combination of several state-of-art methods from biomechanics, modeling and multibody dynamics of the humans is described. The description of the human figure in the motion is a very important part of biomechanical analysis. In such current methods it is necessary to us mass moment of inertia as a part of the fundamental dynamic anthropomeasure when describing this motion. The goal of this work is to use and modify existing techniques and to investigate what have to be analyzed to make them work together. First, some general definitions and descriptions of mass moment of inertia adapted to anthropometric values of our population. Second, there is also a review of some simple models by means of which it is possible to calculate distribution of the body-part masses during the motion. The results are given in the form of equations and tables which present the functions between selected body parts anthropodynamical measures and percentile distribution values of males as well as females of Croatian population.

Three dimensional model of the human mandible.

A new biomechanical three-dimensional (3D) model for the human mandible is proposed. A simple two-dimensional model cannot explain the biomechanics of the human mandible, where muscular forces through occlusion and condylar surfaces are in a state of dynamical 3D equilibrium. All forces are resolved into components according to a selected coordinate system. The muscular forces, which during clenching act on the jaw, along with the necessary force level for chewing, also act as some kind of stabilizers of the mandibular condyles preventing dislocation and loading of nonarticular tissues.

Dynamic effects of food consistency on chewing motions.

The purpose of the study was to find evidence of how different types of food consistency affect chewing motions, especially the forward, downward and sidewise extents of motion of the lower jaw. Nineteen individuals with intact tooth sequence, aged from 20 to 37 years, were asked to chew three types of food of different consistency (banana, bread, carrot). The motions of the lower jaw were recorded by ELITE system, i.e. the measurement instrument that by stereo-photo-grametric procedures calculates space co-ordinates of markers on faces of the study subjects. The system enables continuous recording of lower jaw motions in three dimensions, without any possibility of the study subjects' influencing the operation of the instrument, which significantly decreases the possibility of error. Study results have shown that in all 19 subjects a greater food consistency increases the extent of chewing motion. In each individual study subject different average values were found for equal shifts of lower jaw when chewing the same type of food. Although varying from subject to subject, the chewing cycle depends to a great extent on food consistency. By increasing the consistency of a bite, the extent of lower jaw motion has increased in every single study subject.

The biomechanics of the kidney: the isothermal function of the capsule adipose renis.

The paper describes the research in the field of thermodynamics. It deals with the function of capsule adipose renis. This homogenous tissue of low temperature acts as an independent thermal conductor. In fact, by encapsulating the kidney, it acts as a vacuum-flask, providing insulation for the kidney from two surrounding thermal areas, the warmer being on the interperitoneum and the cooler on the skin surface.

A biomechanical aspect of the lumbal approach to the kidney.

Functional differences between surgically attacked musculature of the lumbal region and intact musculature of the contralateral side were assessed in 71 patients by the method of Multic-Labar, Moire topography, electromyography and X-ray analysis of the thoraco-lumbar spine. The following conclusions were derived from the results obtained. In the intact musculature of the lumbal segment of the spine, sliding forces reached 200 kN in males an 170 kN in females aged >25 and <30 years. In younger and older age groups, the values were lower, assuming a form of the ascending and descending limb of a parabole, respectively. Upon healing, the lumbal musculature damaged by surgical resection showed decreased values of the pulling and sliding forces by 15 and 25 kN on an average, respectively, as definite values independent of age and sex. Kinematic alterations included myogenic geneses of a stationary form, with normal innervation, involving the whole damaged musculature. Summa summarum, results of analyses suggested the values of kinematic forces of pulling and sliding forces of the musculature damaged by surgical resection to be definitely significantly reduced, thus confirming the premise of the study.

Biomechanical analysis of hip function after Chiari pelvic osteotomy.

The reasons are discussed for differences in functional results of the pelvic osteotomy after Chiari, regardless of the fact that the CE and AC angles were equal in all patients. When lateralization and distal displacement of the greater trochanter were performed in addition to the pelvic osteotomy, the functional results proved to be better. Biomechanical analysis of the relationship between gluteal force and body weight revealed that these relations change; in all examined cases where lateralization and distal displacement of the greater trochanter were performed, the relationship proved postoperatively to be considerably more favorable. In the same group of patients, the relationship between the force of reaction and body weight was also changed after surgery. Therefore, lateralization and distal displacement of the greater trochanter are important factors for the undisturbed functioning of a hip; in all examined patients the functional results were better when lateralization and distal displacement of the greater trochanter were performed.

[Modified Küntscher's nail for the proximal femur fixation after corrective osteotomies in children (author's transl)]. / Modifizierter Küntschernagel zur Fixierung des proximalen Teiles des Femurs nach korrektiven Osteotomien bei Kindern.

The authors describe the development in the design of the modified Küntscher's nail with two fins on its upper part, assigned for the fixation of proximal femur after corrective osteotomies in children. Detailed explanation about the nails construction and its biomechanical characteristics are presented. The fixation of the nail in the proximal and distal femoral part, as well as on the site of osteotomy is particularly analyzed. On the base 423 operated cases, where the modified Küntscher's nail was applied, the authors conclusion is that the nail is very suitable for the correction of proximal femur deformities in children.

[The vomer and its role in the transfer of pressure in the masticatory system]. / Raonik i njegov udio u prijenosnom sustavu zvacnih opterecenja.

Dimensions of certain parts of the orofacial skeleton and vomer were obtained by a bioanthropologic measurement for which native preparations of whole and parasagitally sawed up skulls were used. The application of a harmonic frame of the skull and the main dimensions of the vomer allowed the construction of an ideal model of the vomer using Araldit B. The photoelasticimetric procedure and pressure load to the model were used for the determination of possible pressure tensions, if any, occurring during mastification, namely the share of the vomer in the transfer of these tensions to the base of the cranium. The study has shown that even the vomer (besides other bones of the orofacial skeleton) has its share in the transfer of pressure tensions to the base of the cranium on a level with its symmetry, and that concurrently, like a rigid support, tightens the hard palate, thus considerably adding to the stability of this part of the orofacial skeleton. The vomer has a relatively high inertia (up to 1.8 cm) and the bottom stability limit at which the vomer resists to bending figures out between the set values of 684 i 1045 N, which means that a millimetre thick vomer would not bend at chosen elasticity modules or axial force values lower than (0.75 to 1.5) x 10(6) N/cm2.