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1

Examinations on retention of overdentures with elastic frictional attachments

Chladek W., Chladek G., Wrzuś-Wieliński M., Żmudzki J.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 1

205-213

EN

Purpose: of this paper was to evaluate the effectiveness of the overdentures equipped with silicone elastic frictional attachments. Design/methodology/approach: The examinations of retention characteristics of traditional attachments, elastic frictional attachments and models of overdentures have been carried out using Zwick testing machine. Retention forces and work essential for separating the attachments have been determined as well. Next the force – displacement characteristics for overdenture model have been registered for two places where the force was applied and for three inclination angles of the line of application of force. Findings: The obtained results of laboratory examinations gave evidence of high effectiveness of elastic frictional attachments. Research limitations/implications: It has not been possible to register mechanical characteristics due to limitations of clinical conditions. Wide analysis of retention characteristics requires examinations carried out in laboratory conditions. Practical implications: Thorough analysis of force - displacement characteristics enables to understand better the mechanisms which are essential for the effectiveness of particular attachments. Applying such knowledge in practice helps to use more effectively the properties of silicone rubbers for making the elastic frictional attachments. Originality/value: The presented method of evaluating the effectiveness of attachments is based on determining retention work of the attachments and it allows to compare quite objectively even relatively different solutions. The so far used criterion of measuring vertical retention force makes it possible to compare only the solutions which are based on similar mechanical principles.

2

Badania modelowe jako narzędzie identyfikacji sił mięśni żwaczowych

Wojnarowski J., Margielewicz J., Chladek W.

Acta Mechanica et Automatica

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2010

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Vol. 4, no. 3

138-142

PL

W pracy przedstawiono metodykę identyfikacji sił mięśni żwaczowych narządu żucia. W zaproponowanym podejściu przeprowadzono ocenę sił mięśniowych narządu żucia, z uwzględnieniem oddziaływania układu nerwowego. Taki sposób prowadzenia badań modelowych jest alternatywnym ujęciem problemu równowagi biostatycznej narządu żucia, w stosunku do dotychczas stosowanych metod obliczeniowych. Dodatkowo podczas przeprowadzonych obliczeń numerycznych uwzględniono ograniczenia, związane z maksymalną wydolnością poszczególnych mięśni żwaczowych. Wyniki obliczeń numerycznych przedstawiono w postaci przebiegów czasowych sił mięśni narządu żucia oraz charakterystyki odwzorowującej wpływ przyłożenia zewnętrznego obciążenia do łuku zębowego żuchwy.

EN

The paper presents a methodology to identify the forces of masticatory muscles. The proposed approach was evaluated masticatory muscle forces, including the impact of the nervous system. This method of research is an alternative model of the problem of balance of masticatory biostatic, with respect to existing methods of calculations. In addition, in carrying out numerical calculations take into account constraints related to the maximum capacity of the individual muscles. The results of numerical calculations are presented in the form of time histories of forces of masticatory muscles and the characteristics of mapping decisions and brokering the impact of application of external load to the arch of the mandible.

3

Ocena cech materiałowych krążków stawowych stawu skroniowo-żuchwowego

Chladek W., Margielewicz J., Czerwik I.

Inżynieria Materiałowa

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2009

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Vol. 30, nr 3

201-206

PL

W pracy przedstawiono wyniki badania właściwości mechanicznych krążków stawowych stawu skroniowo-żuchwowego. Biorąc pod uwagę podobieństwo cech funkcjonalnych ludzkiej i wieprzowej żuchwy, badania zrealizowano na krążkach wieprzowych wyreparowanych bezpośrednio po uboju zwierzęcia (rys. 1, tab. 1). Kierując się rożnymi warunkami pracy poszczególnych fragmentów krążka, jako miejsca istotne wytypowano przednie i tylne struktury obwodowe krążków oraz ich części centralne. Testy prowadzono na uniwersalnej maszynie wytrzymałościowej Zwick przy piłowych charakterystykach zmian siły w zakresie od 0 do 3 N zachodzących z prędkością 1 N/s. Oceniano wpływ kolejnych cykli na kształt pętli histerezy ?(?) oraz zmiany właściwości tłumiących, decydujących w istotny sposób o dystrybucji obciążeń na kość panewki i głowy żuchwy. Na podstawie uzyskanych charakterystyk naprężeniowo-odkształceniowych (rys. 4) określono sztywność oraz efektywny moduł Younga tkanek w strefie pomiaru. Wykazano, że charakterystyki naprężeniowo-odkształceniowe tkanek krążków istotnie zależą od miejsca pomiaru, jak i historii obciążenia. Największe zmiany zachodzą w pierwszych czterech cyklach, a za ustabilizowany cykl można uznać dopiero piąty cykl obciążenia. Wynik ten wskazuje na konieczność weryfikacji wielu danych, wprowadzanych do warunków brzegowych, które zostały uzyskane w próbach statycznych. Niewłaściwym postępowaniem jest również uśrednianie cech materiałowych dla całej objętości krążka. Przy obciążaniu krążków uzyskano zdecydowanie rożne wartości efektywnego modułu Younga dla poszczególnych fragmentów. Wartości te wynosiły dla strefy tylnej 4,44 MPa, środkowej 1,97 MPa oraz przedniej 2,99 MPa (tab. 2) Zarejestrowane przebiegi cykliczne, ujmujące zmiany siły i odkształcenia, były asumptem do sformułowania modelu matematycznego materiału, z jakiego wykonany jest krążek stawu skroniowo-żuchwowego. Największe spadki szerokości pętli histerezy zaobserwowano w strefie przedniej oraz tylnej. W części tylnej dla dziesiątego cyklu pole powierzchni histerezy jest prawie dwukrotnie mniejsze w stosunku do cyklu drugiego, natomiast w strefie przedniej pole powierzchni maleje prawie trzykrotne (tab. 4). W praktyce zjawisko wzrostu sztywności prowadzi do pogorszenia właściwości tłumiących tkanek krążka stawowego. Najsztywniejszy miejscem krążka jest jego część tylna, gdzie sztywność w piątym cyklu obciążenia wy- nosiła 87,1 N/mm. Środek krążka wykazał najmniejszą sztywność, przyjmując wartość 38,7 N/mm (tab. 2). Zgodność modelowego odwzorowania cykli pracy krążka, potwierdziła przeprowadzona weryfikacja, podczas której porównano wyniki symulacji numerycznych z zarejestrowanymi danymi doświadczalnymi. Pozwala to na stwierdzenie, że przyjęty model reologiczny, jak również zidentyfikowane jego parametry dobrze odwzorowują cykle pracy krążka.

EN

The paper presents the results of examination of mechanical properties of the temporomandibular joint discs. Taking into account the similarity of func- tional characteristics of human and pig mandible, the research was taken on pig's discs after animal slaughter (Fig. 1, Tab 1). Knowing about the fact that all parts of a disc have different conditions of work, the anterior, posteriori and central parts of encircling structure of the disc were thought to be the most crucial. All the tests were made with the use of an all-purpose strength machine Zwick, at pile characteristics of force change in scope between 0 and 3 N at speed of 1 N/s. These are the influence of individual cycles on the shape of the hysteresis loop and the changes of damping properties chich in a very important way determinate distribution of the load on the acetabu- lum bone and the head of the mandible, which were evaluated here. On the basis of the stress-strain results (Fig. 4), stiffness and the effective Young module of tissues in the measurement area were estimated. It was proved that stress-strain characteristics of discs' tissues significantly depend on the area of measurement and the history of load. The largest changes can be noticed during the first four cycles, and the one which may be called the stable is the fifth cycle of load. The result shows that it is necessary to verify all data inserted to bank conditions which were obtained through the static tests, and that it is inappropriate to take the average material characteristics to use on the whole volume of the disc. While loading discs, completely different valu- es of the effective Young module were obtained for separate parts. They were like these: for the posterior part 4.44 MPa, for the central part 1.97 MPa and for the anterior part 2.99 MPa (Tab. 2). The recorded cycles which included changes of force and strain were the cause to form a mathematical model of material of which the disc of the temporomandibular joint is made. The greatest falls in the width of the hysteresis loop was noticed in the anterior and posterior areas. In the posterior area for the tenth cycle the surface of the hysteresis is almost twice as small as it was in the second cycle, whereas In the anterior area the surface makes smaller almost three times (Tab. 4). In fact the growth of stiffness leads to worsening of dampening properties of the joint disc tissues. The stiffest part of the disc is its posterior part, where the stiffness in the fifth cycle of load was 87.1 N/mm. The central disc part was the least stiff and it took only 38.7 N/mm (Tab. 2). The compliance of the model cycles of the disc work was confirmed by verification during chich the results of numerical simulations with the test data were compared. His allows to state that the reological model with its identified parameters repro- duces the cycles of the disc work very well.

4

Attachments of implant retained tissue supported denture under biting forces

Żmudzki J., Chladek W., Krukowska J.

Archives of Computational Materials Science and Surface Engineering

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2009

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Vol. 1, nr 1

13-20

EN

Purpose: In implant retained soft tissue supported type dentures functioning of attachments, presented by their producers as mechanically bio-compatible because of the ensured freedom of rotational displacements is accompanied by numerous problems that seem to be caused by excessive bearing of occlusal loads. Design/methodology/approach: For the purposes of attachments loadings evaluation, built was a threedimensional FEM model of a denture situated on an atrophic prosthetic foundation with joint supports assumed in the area of denture attachment to implants. Analysis of attachments loadings has been carried out under unilateral oblique occlusal forces of 100N in molars and incisors zones. Findings: Used methodology made it possible to determine attachments loading in a quantitative manner. In spite of free rotational movements implantological supports bear significant part of horizontal occlusal forces components, which reach the value of 66N during chewing processes. Research limitations/implications: Examined was only the most commonly used type of attachments. Hence, further studies, apart from constrains enabling rotational movements introduced should be also an axial compliance which is already offered by some types of attachments, and which additionally enables sedimentation of the denture towards the axes of implants. Practical implications: Analysis of loadings related to implantological attachments in case of assuming only a vertical component of occlusal forces leads to a significant underestimation of implantological supports loads values. In the presented analysis, taking into account the influence of the obliquely acting occlusal forces that occur in real chewing conditions, it has been proved that freedom of rotational movements of overdenture's attachments does not allow to use the natural supports of mucous membrane. That explains the reason of attachments and acrylic resin dentures damages, as well as the significant number of lost implants of upper denture resulting from biomechanical causes. In clinical practice, achieved should be the most anterior implants' placement, and especially in case of flat ridges because of the lack of any bearing surface. Originality/value: Determined loadings of supports might constitute a starting point for further biomechanical evaluation of attachments solutions that function according to similar principles, without the necessity of building complex models of the whole system.

5

Stresses present in bone surrounding dental implants in FEM model experiments

Żmudzki J., Walke W., Chladek W.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 27, nr 1

71-74

EN

Purpose: Appropriate selection of material and geometric characteristics of intraosseus pillar implant part creates a possibility to control the bone tissue loading. Design/methodology/approach: A basic tool that is commonly used the evaluation of bone loading state is the linear FEM analysis. It requires setting of appropriate experiment conditions. Hence, an analysis has been carried out in order to determine the influence of dividing method of finite elements (tetragonal type 187 in Ansys system v.11) on stresses in pillar and surrounding bone tissue. Findings: Seeking of loading values cortical bone tissue is highly affected by the increase of mesh density on the edge of implant insertion into the cortex bone. Loading stresses values have significantly increased along with increased mesh density, whereas the differences have even reach 47 MPa. Research limitations/implications: Research has been carried out only for the Ansys system in the linear range assuming standard shape and mechanical characteristics of implant and bone, as well as regarding the after the osseointegration phase because if the presumed complete adherence of the pillar to the bone. Practical implications: Excessive increase of mesh density leads to overestimation of loading stresses values and further to an unjustified increase of pillars' diameter. At the other hand, too large elements might lead, through an underestimation of loading stress level, to overloading atrophy of bone tissue. Originality/value: This paper points out the necessity of more determined activities aimed on defining appropriate and uniform FEM experiment conditions that would enable achievement of more real results of model researches and their comparability.

6

Loading of overdenture attachments under simulated biting forces

Żmudzki J., Chladek W., Krukowska J.

Archives of Materials Science and Engineering

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2008

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Vol. 32, nr 1

33-36

EN

Purpose: The basis for effectiveness evaluation of over-denture attachments is the determination of loads on supports, and denture mobility. In cases of denture stabilized on two prosthetic supports, for most of the attachments constructions that are available on the market, the margin of dentures mobility is limited to rotation around axes of the attachments. Design/methodology/approach: Determining attachments loadings during bearing of biting forces that accompany chewing processes was carried out by means of Finite Element Method model analysis. A three-dimensional model of a denture supported on mucous membrane and joint supports assumes to be fixed in places of denture anchoring to implants. This model was loaded on one side with unilateral oblique 100 N force at molars zone. Findings: Maximum loading at pillar accompanies biting forces acting in a lateral direction toward buccal side. Research limitations/implications: Researches were carried out exclusively for attachments not showing any resilience in any direction, without any rotational constrains. Hence, in further researches, at the first place, determined should be the influence of the vertical resiliency used in some of the commercial attachments on loads bearing. Practical implications: Appropriate determining of loadings levels on over-denture attachments, requires necessarily that the oblique biting forces will be taken into account. In case of an assumption of only vertically oriented biting forces, there is a significant underestimation of the most dangerous horizontal loadings of prosthetic supports. Originality/value: Presented displacements of denture and pillars loading as vertical and horizontal reactions causing pillar bending and leverage at the bone, constitute a starting point for evaluation of denture’s behavior and strength estimation of analyzed types of attachments for implants and the surrounding bone.

7

Estimation of stresses in layers of dentures' relining materials

Żmudzki J., Chladek W., Krukowska J.

Archives of Materials Science and Engineering

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2008

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Vol. 30, nr 1

21-24

EN

Purpose: Durability tests of materials relining dentures should be carried out in conditions reflecting the real loading that accompanies bite force transmission. The influence of geometry resulting from a denture foundation shape on real stresses in relining has not been so far found. Design/methodology/approach: Using FEM modeling, identified were the stress levels in relining layers in conditions reflecting biting loading for two opposite cases of bone foundation atrophy. Findings: The equivalent Huber-Mises` stresses have not reached their critical values, although tangential stresses on the interfacial where relining is bonded with denture base have reached 440kPa, which, for some of the commercial types of relining denotes the bonding strength. Research limitations/implications: The linear elastic mechanical characteristics were assumed. Hence, during further research, taken into account should be the “stiffening” of characteristics in the upper loadings range, which is typical for silicones. Practical implications: In case of a convex foundation the biggest danger will be caused by any bond defects occurring in the central area because in that area shear of bond has reached the highest values. Originality/value: Values of stresses components identified in this paper reflect the real shear conditions of relining bonding with denture base and might constitute a determinant for strength tests.

8

Effort changes of lower complete denture material caused by relining

Żmudzki J., Chladek W., Krukowska J.

Archives of Materials Science and Engineering

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2008

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Vol. 31, nr 2

79-82

EN

Purpose: Influence of dentures relining on saddles material effort in case of bone foundation not affected by any atrophic changes has been examined. Design/methodology/approach: Stresses levels in material of denture saddles bearing structure have been determined for any cases where alveolar ridges of mandible are well preserved. This research has been carried out in simulated conditions of biting loads, by means of a FEM. Compared were not-relined vs. relined saddles for two variants of bottom denture saddles margins, i.e. ended smoothly and with an extension that increases the amount of material of the bearing structure. Analyzed was also the influence on deformability of relining layers. Findings: Equivalent Huber-Misses stresses on a good saddles surface in case of a not-relined denture have slightly exceeded the level of 2 MPa, whereas in case of a relined denture with a soft margin they have reached 4 MPa; and for variant of relined denture with extended margin they reached a level of 14 MPa. Modulus of elasticity of the relining has not influenced significantly the effort of saddles material. Research limitations/implications: Assumed were vertical loading forces of 100 N simplified denture geometry without separating any complex shapes of artificial teeth. Practical implications: Increase of the bearing surface of relined saddles by means of extended margins results in stress concentration. Hence, attempts should be made to form the margins and teeth profiles changes at their base smoothly. All micro damages in endangered areas of saddles’ margins should be removed. Originality/value: Relining of low dentures’ saddles in a well preserved bone foundation does not directly result in excedance of allowable stress levels for prosthetic acrylic resins. Hence, the causes of failures should be sought in the impact of geometrical notches, or potentially existing damages that initiate degradation processes.

9

Mechanical properties of temporomandibular joint disc on the basis of porcine preparation investigations

Chladek W., Czerwik I.

Acta of Bioengineering and Biomechanics

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2008

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Vol. 10, nr 4

15-20

EN

The paper presents the results of a study on mechanical properties of porcine temporomandibular joint discs. Taking into account anatomical properties, three typical spots were selected for the investigation: the posterior, anterior and central parts of the disc. The main focus was on the influence of samples' preparation on the changes in mechanical properties. Complete undamaged discs, cylindricallycut disc samples of 5 mm in diameter as well as discs of locally broken continuity in the upper layer around the measuring zone were prepared. Periodic compression was applied during testing, by varying the force in a sawtooth control signal. The rate of increasing the force applied equalled 1 N/s with a maximum value of 3 N. Based on the stress and strain characteristics obtained, the object's rigidity, Young's modulus of the samples, and effective Young's modulus of joint discs were calculated. Results showed that the stress and strain characteristics of the discs' substance depend on sample preparation, measurement location and load history within a given number of cycles. Only the fifth load cycle may be considered as stabilized. The most rigid proved to be the posterior part of the disc, as the rigidity of the samples, of an incised disc and of a complete disc in the fifth loading cycle amounted to 117.9 N/mm, 88.8 N/mm and 87.1 N/mm, respectively. A central part of the disc exhibited the lowest rigidity, whose values for the samples, for an incised disc and for a complete disc reached 87.9 N/mm, 70.6 N/mm, and 38.7 N/mm, respectively. Excision of the samples resulted in their dehydration, which led to increased rigidity, as reflected by Young's modulus values. In the posterior part of the disc, the modulus value was 12.56 MPa, while in the anterior part and in the center, these values reached 7.25 MPa and 6.99 MPa, respectively. Excised discs also exhibited dehydration effects during examination. While loading complete discs, the lowest effective values of Young's modulus were obtained, despite the influence of the tissues adjacent to the loaded zone, counteracting deformation. The values were 4.44 MPa, 1.97 MPa and 2.99 MPa for the posterior, central and anterior parts, respectively. Present data allow the conclusion that the error introduced due to breaking the tissue continuity is greater than the error resulting from ignoring substance continuity when applying local loads to an undamaged disc. Therefore, it seems more sensible to adopt the effective Young's modulus values in numerical analyses rather than to apply the results obtained for the samples cut out of discs.

10

Kinematical analysis of mandibular motion in a sagittal plane

Margielewicz. J., Chladek W., Lipski T.

Acta of Bioengineering and Biomechanics

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2008

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Vol. 10, nr 1

9-19

EN

The paper presents a kinematical model enabling the analysis of mandibular motion in a sagittal plane. Based on the recorded trajectories of incisors, the configuration coordinates were identified. The configuration coordinates explicitly identify the position and orientation of the mandible during motion. Such values are basic to the evaluation of alteration in muscle length and to the orientation of forces in particular muscles. This paper also deals with the influence of the coefficients of the weight matrix on the character of the solutions of the configuration coordinates applied in the model study of the kinematical chain. The results of the numerical calculations obtained demonstrated that the trajectory representation was in a considerable concordance with the data recorded.

11

Elastic silicone matrices as a tool for load relief in overdenture implants

Żmudzki J., Chladek W.

Acta of Bioengineering and Biomechanics

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2008

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Vol. 10, nr 4

7-14

EN

The objective of this study was to analyze how the elasticity of matrices attaching to an overdenture affects implants and how the location of implants affects their loading. The attachments proposed made from elastic matrix increase the denture stability and simultaneously preserve the mechanisms of occlusion load transfer in compliance with principles usually applied in the denture used in the case of edentulous maxilla or mandible. It was revealed that denture dislodgement caused by occlusion forces did not result in the force being greater than the attachment retention force determined empirically. Our analysis also demonstrates that in the case where the implants are inserted in such a way that they are shifted too much to the back area of the tooth arc, an increase in the implant bending occurs, with the supporting capacities of alveolar processes not being fully utilized. This fact suggests the necessity to increase the susceptibility of attachments in a posterior location.

12

Przyczyny mechanicznego niszczenia jednoczęściowych bikortykalnych wszczepów dentystycznych

Chladek W.

Inżynieria Materiałowa

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2007

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Vol. 28, nr 2

79-83

PL

W praktyce klinicznej stwierdzono występowanie przypadków złamań jednoczęściowych, bikortykalnych wszczepów dentystycznych. Wszczepy tego typu kotwione są dwupunktowo w kości korowej, następnie bez fazy gojenia osadzana jest na nich nadbudowa protetyczna. Równoległość filarów niezbędną do osadzenia nadbudowy uzyskuje się przez odpowiednie doginanie nakostnej części wszczepu. Celem badań było przeprowadzenie laboratoryjnych i numerycznych eksperymentów wyjaśniających przyczynę ich zniszczenia. Na podstawie mikroskopowych badań przełomów stwierdzono, że zniszczenie nastąpiło wskutek procesów zmęczenia materiału. We wszystkich przypadkach inicjacja pęknięć następowała w ostrych karbach występujących w strefach dna gwintu. Badania wpływu zaniku tkanki kostnej wokół wszczepu na jego wytężenie, przeprowadzone metodą elementów skończonych, wykazały pojawienie się niebezpiecznych wartości naprężeń w chwili, gdy zanik tkanki kostnej osiągnął ostatni zwój gwintu. Negatywne skutki płytkiego osadzenia ostatniego zwoju gwintu potwierdziły również symulacyjne próby zmęczeniowe. Nie stwierdzono natomiast wyraźnego wpływu wyginania trzonu implantu na jego trwałość.

EN

In clinical practice cases of fractures of one-element bi-cortical dental have been stated. This type of implants is anchored at two points on core bone, then, without the healing phase a prosthetic superstructure is placed. Parallelism of the columns that is necessary for superstructure placement is achieved by appropriate bending of the part of the implant protruding off the bone. The aim of the studies was carrying out of laboratory and numerical experiments explaining the cause of their failure. On the Basis of microscope examinations of the cracks is has been proved that the failure resulted from material fatigue processes. In all cases cracks have been initiated on sharp indentation occurring in the areas of the bottom of the thread. For examinations of the influence of bone tissue resorption adjacent to implant on its effort the method of finite elements modeling have been employed. These examinations have shown that the values have reached critical safety limits while the bone tissue has resorpted to the last thread. Negative effects of the shallow placement of the last thread have also confirmed the carried out simulation fatigue tests. No significant influence of implant bending core on its durability has been observed.

13

Wpływ przecięcia tkanek na wyniki badań właściwości mechanicznych krążków stawu skroniowo-żuchwowego

Chladek W., Czerwika I.

Engineering of Biomaterials

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2007

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Vol. 10, no. 67-68

16-18

14

Influence of surface modification on friction coefficient of the titanium–elastomer couple

Chladek W., Hadasik E., Chladek G.

Acta of Bioengineering and Biomechanics

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2007

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Vol. 9, nr 2

17-25

EN

This paper presents the results of a study of the friction coefficient of titanium–elastomer couple. The study was carried out with a view to potential future utilization of its results for constructing retentive elements of implanted prostheses. Changes in the friction force were recorded while removing titanium specimens placed between two silicone counter specimens made of Ufi Gel. The influence of the titanium specimen movement speed in relation that of to the counter specimens and the influence of clamping force on the friction force were assessed. Additionally, the surface roughness of titanium specimens differed; in one case, titanium was coated with polyethylene. The effect of introducing artificial saliva between the cooperating surfaces on the friction force and friction coefficient was analyzed as well. Based on the characteristics recorded, the possibilities of shaping the friction coefficient have been assessed, since it is the friction coefficient that determines effective operation of a friction couple through increasing the titanium specimen roughness. The artificial saliva being introduced between the specimens reduces considerably the friction coefficient through a change of the phenomenon model. An increase in the pressure force for the specimens of high roughness entails a reduction of the friction coefficient. The study carried out allows us to identify the roughness parameters, which in turn will enable obtaining the prescribed retention force for friction/membrane couplings.

15

Evaluation method of saliva and oral cavity mucous membrane in the aspect of holding a denture on an atrophic base

Chladek W., Lipski T., Kasperski J.

Acta of Bioengineering and Biomechanics

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2007

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Vol. 9, nr 1

53-60

EN

The paper presents application of the authors’ own method of investigating the secretion and elasticity of saliva as well as resilience of mucous membrane in evaluation of force holding the lower denture in the base. The object of research is a complete mucus lower denture cooperating with the base with a tooth-caving that is on the decline. Results of the tests of a horizontal force knocking the denture off the base were assumed as objective effectiveness evaluation criteria. Clinical investigation has been carried out in a group of 126 patients using diagnostic devices constructed according to the authors’ own conception. The elasticity of saliva was determined by measuring the length up to the break point where saliva loses elasticity, the sample volume being 55.26 mm3. The amount of saliva was determined on the basis of the area on which saliva remains and that is created by pressing the saliva with a force of 140 N by means of a 0.22 mm thick circular filter paper with a diameter of 8 mm. The filtering paper had earlier been put for 30 seconds on a mucous membrane in the area of molars. The resilience was determined on the basis of the penetrator’s cavity dented by a force of 1 N into the mucous membrane. Results obtained during the examination of a group of patients enabled an unambiguous numerical description of the characteristic features of oral cavity environment. A statistically significant influence of all investigated factors on the force necessary to knock the denture off the base has been determined. A significance hierarchy of the factors investigated as well as the ranges of variability in the parameters measured have been defined. The resilience of the mucous membrane has affected the denture knocking off force the most. It had a value of 0.4 mm up to 2.1 mm during an impact of a pointwise pressure of an average value of 0.99 mm. Then, the influence of the amount of the secreted saliva has been observed. The amount of the saliva gathered on the filter paper was expressed in terms of a “flood” area obtained after pressing the paper and amounted to 180 mm2 up to 660 mm2, with the average of 468.75 mm2. The least important factor was the elasticity determined by the break length of a saliva sample. The lengths of breakpoints measured were from 4.8 mm for saliva with a dominant serum secretion content up to 24.1 mm for saliva with a dominant mucus secretion content. The average value for the whole population examined was estimated at 14.19 mm.

16

Stress distribution in anchoring regions of posts cooperating with overdentures

Chladek W., Chladek G., Krukowska J., Lipski T.

Acta of Bioengineering and Biomechanics

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2005

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Vol. 7, nr 1

35-45

EN

The paper presents the results of model research of mechanical compatibility of selected overdenture structures. The tests based on finite elements method were conducted on flat models reflecting the areas of posts anchoring m a sagittal piane. The reference point was the structure of a prosthesis seated on ball-and-socket joints secured in tooth roots. As altemative solutions, dentures placed on two cylindrical implants supporting ball-and-socket joints were compared with a denture attached to a joint which consisted of a straight axis bar and an elastic clip as well as with a denture supported by a joint of elevated retention, built of a doubly bent axis bar and three elastic bar clips. Taking advantage of the MES Algor program functions, the diverse materiał structures of the systems investigated were modelled. Next. the reduced stresses and principal maximum stresses generated m osseous tissues, in the implants anchoring area. were determined. The value of the mechamcal stimulator decisive to the osseous tissue remodelling was assumed as au evaluatiou criterion. It was assumed that making use of patient's own tooth roots to attach implants IS an optimal solution which, in terms of mechanics, IS practically identical to the alveolodental ligament of a healthy tooth. The application of the other methods of implanted prosthesis attachment always creates a risk of undesirable changes, mostly in the upper area of post insertion into the osseous tissue. The least favourably, in the light of stresses comparison, looks the joint of a doubly refracted axis, where the probability of adverse changes of the osseous tissue in a short time is high. This indicates the necessity to carry on words in order to improve this solution characterized by good retention.

17

Experimental evaluation of occlusal forces

Chladek W., Lipski T., Karasiński A.

Acta of Bioengineering and Biomechanics

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2001

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Vol. 3, nr 1

25-37

EN

The paper presents the results of measuring the occlusion forces in the group of 163 subjects being tested. In the research, the method based on the dependence of the plastic deformity and force intending the spherical penetrator upon each other in a metal sample was implemented. The results obtained allowed us to estimate the distribution of occlusion forces along the alveolar ridge and to define the dimensions of the maximum forces applied, while biting and gnawing. The biting force between the first incisors for different angles of parting mandible was also measured.

18

System modelowania wybranych stanów mechanicznych żuchwy ludzkiej

Chladek W.

Zeszyty Naukowe. Hutnictwo / Politechnika Śląska

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2000

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z. 59

1-108

PL

W pracy przedstawiono sposób kompleksowego podejścia do zagadnienia równowagi żuchwy ludzkiej. W warunkach naturalnych stan równowagi żuchwy zapewniany jest przez selektywne pobudzanie grup włókien odpowiadających poszczególnym mięśniom żwaczowym. W zastosowanym modelu podjęto próbę zastąpienia funkcji układu nerwowego "logiką" dostosowania się wartości reakcji więzów sprężystych do struktury przestrzeni obiektu dla zadanych obciążeń i przyjętych sztywności więzów. Etapem wyjściowym do modelowej oceny stanów mechanicznych żuchwy było zebranie danych dotyczących charakterystyk obiektów naturalnych, takich jak wielkości sił zwarciowych, kierunki działania sił w mięśniach żwaczowych oraz cechy geometryczne modelowanego obiektu. Aktywność mięśni zwierających i wielkość reakcji w stawach określono na podstawie analizy wartości wprowadzonego w pracy bezwymiarowego współczynnika "Wa". Współczynnik ten, odpowiadający stosunkowi wybranej składowej reakcji do siły okluzyjnej, umożliwia oszacowanie udziału rozważanej składowej w wysiłku układu stomatognatycznego, związanego z generowaniem sił zwarciowych. Obliczenia przeprowadzono dla sił przyłożonych w punktach odpowiadających położeniu kolejnych zębów po prawej stronie łuku zębowego. Wyniki badań modelowych przedstawiono w formie wykresów i tablic ujmujących aktywność więzów w kierunkach osi prostokątnego układu współrzędnych, dla różnych systemów podparć. Analiza wartości współczynników aktywności więzów uzyskanych dla modeli żuchw o budowie zróżnicowanej w sposób zgodny z formami spotykanymi w naturze wykazała odpowiedzi więzów na zadane obciążenia, logicznie związane z rozpoznanymi reakcjami rzeczywistych obiektów. Dowodzi to, że opracowany system pozwala, poprzez analizy numeryczne oparte na metodzie elementów skończonych, ocenić wielkość wybranych sił czynnych i biernych utrzymujących równowagę żuchwy w zadanym położeniu.

EN

The present dissertation shows a comprehensive approach to the human mandible equilibrium issue. In normal conditions the state of equilibrium is provided by selective stimulation of fiber groups corresponding to the individual muscles of mastication. According to the chosen methodology of the computational model, the nerve system is substituted with the response of elastic constraints, logically ocnnected with the object spatial structure and imposed loading. The starting point for a model assessment of the mandible mechanical states was the acquisition of data describing the properties of natural objects (e.g. the values of occlusive forces, directions of forces in masticatory muscles, geometrical features of the object modeled). The research of occlusive forces values revealed individual diversity, which makes an unambiguous description of the forces very difficult. The occlusive muscles activity and quantity of reaction in joints were derived basing on the analysis of values of the nondimentional coefficient "Wa" (introduced in the present dissertation). The coefficient (corresponding with ratio of chosen reaction component to (occlusive force) enables to estimate the participation of the considered component in the stomatognathic system effort (the effort of occlusive forces generation). The computations realized for the forces applied in the points corresponding with locations of successive teeth along the right side of dental arch. Results of model research are shown in graphs and tables expressing the constraints activity in directions of cartesian co-ordinates for different support systems. Analysis of constraints activity coefficients values obtained for mandible models with natural diverse structure proved the logical connection of constraints responses to imposed loadings with recognized reactions of real objects. It shows, that the system proposed is able to evaluate the value of chosen active and passive forces, which keep the equilibrium of mandible in the arbitrary position, using the numerical analyses based on finite elements method.

19

Finite element analysis of mandible equilibrium depending on the way of its loading and supporting

Chladek W., Żmudzki J, Lipski T.

Acta of Bioengineering and Biomechanics

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2000

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Vol. 2, nr 1

63-69

EN

Results of FEA of mandible equilibrium and mandible without one-sided support at temporoman-ibular joint were presented. Models were loaded with occlusal forces whose values were experimentally itablished. Forces of muscles were simulated by elastic supports with an assumption that reactions ould lead to active forces generated by the system of muscles.

20

Biomechaniczne aspekty funkcjonowania rekonstrukcji uzębienia wykonanej z zastosowaniem implantów i wkładów koronowo-korzeniowych.

Chladek W., Grosman F., Ilewicz L., Lipski T.

Inżynieria Materiałowa

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1999

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R. XX, nr 3-4

196-201

PL

W pracy przedstawiono wyniki badań oddziaływania wybranych konstrukcji metalowych stosowanych w rekonstrukcji uzębienia na zmiany rozkładów w tkankach naturalnych. Wykorzystując metodę elementów skończonych, zamodelowano wpływ sił okluzyjnych na naprężenia w układzie kostnym w strefie kotwiczenia implantów stomatologicznych systemu Branemarka stanowiących filary implantoprotezy pojedynczego zęba. Analizie poddano takie czynniki, jak długość implantu oraz kierunek jego wprowadzenia. Stwierdzono istotną różnicę wytężenia tkanki kostnej w stosunku do stanu naturalnego. Uzyskane wyniki wskazują na możliwość wpływania na wielkość naprężeń poprzez odpowiedni dobór długości wszczepu. Kolejnym analizowanym sposobem przywracania wydolności narządu żucia były metody całkowitej rekonstrukcji korony zęba wykorzystujące prefabrykowane wkłady koronowo-korzenne. Przy zastosowaniu tych metod, biomechaniczne warunki pracy przyzębia nie ulegają zmianie. Zmienia się natomiast sposób obciążenia pozostałych tkanek zęba własnego. Stwierdzono, że zarówno dla zębów jednokorzeniowych, jak i wielokorzeniowych, metalowe konstrukcje poprawiające retencję materiału rekonstrukcyjnego przejmują rolę twardych tkanek zęba. Ze względu na zdarzające się przypadki pęknięcia korzenia z założonym wkładem, następujące przeważnie w wyniku urazu, przeanalizowano wpływ długości części korzeniowej wkładu na wytężenie ścianki korzenia. Stwierdzono, że zbyt bliska odległość końca wkładu od otworu fizjologicznego będzie sprzyjać mechanicznym uszkodzeniom korzenia. Wyniki przedstawiono w postaci map i wykresów naprężeń redukowanych.

EN

Investigation results of interaction of selected metal structures used in the dentition reconstruction on the changes in the stress distribution in natural tissues are presented in this article. Using the final elements method an influence of occlusion forces on stresses in the osseous system in the zone of hooking the dental implants of Branemark's system being the implantoprosthesis pillar of a single tooth has been modelled. The length of an implant and the direction of its insertion were the factors subjected to an analysis. A significant difference of the bone tissue effort was found in comparison to the natural state. the obtained results show that is possible to influence the value of stresses by an appropriate selection of the implant length. Methods of the total reconstruction of the tooth crown using prefabricated crown-root inlays were another analysed way of restoring efficiency of masticatory organ. By using those methods, biomechanical working conditions of the parodontium do not undergo changes. However, a way of loading of the other tissues of the natural tooth is changed. It has been found that for both monoradicular and multiradicular teeth, metal structures improving retention of the reconstruction material take over the function of hard tissues of a tooth. Due to cases of cracking of a root with the inserted inlay, occuring mainly as a result of trauma, an influence of the length of the radicular part of an inlay on effort of the root wall was analysed. It has been found that too close distance of the inlay end from a physiological opening will favour mechanical damages of the root. The results were presented in the form of maps and diagrams of reduced stresses.