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1

Force ratio in masticatory muscles after total replacement of the temporomandibular joint

Vilimek M., Horak Z., Baca W.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 3

131--136

EN

The temporomandibular (TM) joint is one of the most active joints in the human body, and any defect in this joint has a significant impact on the quality of life. The objective of this study was to analyze changes in the force ratio after TM joint replacement on contralateral TM joint loading. Implantation of an artificial TM joint often requires removal of 3 of the 4 masticatory muscles (activators). In order to perform true loading of the TM joint, loading during mastication was investigated. Input kinematic variables and mastication force were experimentally examined. The inverse dynamics approach and static optimization technique were used for solution of the redundant mechanism. Muscle forces, and reactions in the TM joint were calculated. We modified the model for several different tasks. The m. temporalis and m. masseter were removed individually and together and the forces of mastication on the TM joint were calculated for each variation. To evaluate the results, a parametric numerical FE analysis was created to compare the magnitude of the TM joint loading during the bite process for four different muscle resections. The results show an influence relative to the extent of muscle resection on contralateral TM joint loading in a total TM joint replacement. The biggest increase in the loading magnitude on the contralateral TM joint is most evident after m. masseter and m. temporalis resection. The results from all simulations support our hypothesis that the greater the extent of muscle resection the greater the magnitude of contralateral TM joint overloading.

2

Thermoplastic elastomer blends based on waste rubber and low-density polyethylene

Hrdlicka Z., Kuta A., Hajek J.

Polimery

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2010

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T. 55, nr 11-12

832-838

EN

Materials based on waste rubber from discarded tires and low-density polyethylene (PE-LD) have been studied. The blends were prepared via compounding of molten PE-LD with ground rubber (average particle size 0.4 mm) in an internal mixer. The products behaved like thermoplastic elastomers. To improve mechanical properties of the blends, various compatibilisers (dicumyl peroxide, sulfur system) were added. The best materials had tensile strength 8.6 MPa and elongation at break 260 %.

PL

W ramach pracy badano materiały wykonane z wykorzystaniem odpadów opon i polietylenu małej gęstości (PE-LD). Mieszanki sporządzano łącząc w mieszalniku stopiony PE-LD z rozdrobnioną gumą (średni rozmiar cząstek wynosił 0,4 mm) w temperaturze 150 °C, w przypadku mieszanek bez kompatybilizatora, a 180 °C w przypadku mieszanek z kompatybilizatorem. Uzyskany produkt miał cechy elastomeru termoplastycznego. Zbadano wpływ rodzaju i ilości użytego kompatybilizatora na właściwości mechaniczne otrzymanych mieszanek. Najlepszy materiał charakteryzował się wytrzymałością na rozciąganie o wartości 8,6 MPa i wydłużeniem przy zerwaniu 260 %.

3

Znaczenie warunków podparcia i obciążenia w modelowych badaniach MES protez zębowych typu overdenture

Żmudzki J., Chladek G.

Aktualne Problemy Biomechaniki

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2009

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z. 3

239--245

PL

W badaniach modelowych FEM protez overdenture założenie więzów ograniczających ruchomość protezy w sposób zgodny z zasadami ich funkcjonowania pozwala na rozpoznanie obciążeń złączy, przy znacznym uproszczeniu modelu numerycznego. Dla powszechnie dostępnych w sprzedaży typów złączy podczas transmisji sił żucia stwierdzono występowanie znacznych wartości obciążeń bocznych, co stanowi bezpośrednie wyjaśnienie przyczyn niepowodzeń mechanicznych. Założenie pionowych kierunków sił zgryzowych prowadzi do znacznego niedoszacowania obciążeń złączy.

EN

In overdenture FEM analysis, assumption of constrains reducing denture movement according to the rules of their functioning allows to determine loads of attachments, at the same time significantly simplifying numerical model. For commonly available types of attachments - during occlusal forces transmission found has been an occurrence of considerable lateral loads, which directly explains the causes of mechanical failures. Assumption of vertical occlusal forces directions leads to remarkable underestimating of attachments loads.

4

Measurement of strains and stresses in fixed partial dentures

Colosi H., Constantiniuc M., Bejan M., Cretu A.

Acta of Bioengineering and Biomechanics

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2000

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Vol. 2, nr 2

51-57

EN

The purpose of this study was to determine strain distribution in fixed partial dentures (FPD). The results of strain measurements in some specific regions of the FPD served as input data for an original computer-aided method of modelling and simulation of masticatory dynamics and strain distribution in FPD during mastication. The principal experimental findings show a proportional relation between the loads applied and the specific linear deformations of the surfaces of each FPD being analyzed.