Abstracts-International Society of Biomechanics XIV Congress 1993
MECHANICAL PROPERTIES OF A NEW PROCESSED XENOGRAFT Franvise DUCLOS and Georges POUMARAT Groupe Biomecanique et Instrumentation, Universitb Blaise Pacal 63 177 Aubikre CEDEX, FRANCE The aim of this work is to determine the mechanical properties of a new highly purified bone xenograft (T650 prepared by TR4NSPHYTO S.A) derived from calf cancellous bone according to different immersion procedures. The T650 samples were randomly assigned to three groups: group 1 (n=19) immersed in human titrated blood, group 2 (n=26) in physiologic saline, group 3 (n=29) in a 40% (V/V) glycerin solution in water, 30 minutes prior to testing. Compressive tests were performed using a model HlOFM HOUNSFIELD material testing machine at room temperature (2OtiO). The force was applied on the right angle on the upper face of bone (25* 15 mm). The tests were performed at constant deformation rate of 0.01 mm.min” . Destructive testing was preceded by a series of 10 conditioning cycles (0.1 Hz) to an inframaximal stress (1.3 MPa). There is no significant difference in apparent density and Young’s modulus. Ultimate stress is different for the 3 groups (PC O.Ol), specially between groups 2 and 3. The main effect of hydration concerns the ultimate strain. Immersion in physiologic saline induces an important water absorption by collagen. In regards of the importance of ultimate strain of grafts for surgeon an immersion in the patient’s blood must be considered as the most appropriate technique.
ABRASIVE WEAROF DIFFERENT DENTAL ALLOYS E.Fem&dez, F.J.Gil, M.Cortada+, J.Sabris+ Dept. Ciencia de 10s Materiales e Ingenieria Universidad Polit&nica de CatalGa. Spain. +F. de Cdontologia.
and J.A.Planell. Metalikgica. E.T.S.Ingenieros
Wear is one of the main surface failure mechanism in materials and it will play a leading role in substitutive dental bicmaterials. The aim of the present study is to compare the abrasive wear of different metallic materials used in dental applications. The study has been carried out according to the DIN 53516 standard for abrasive wear using a crossed-cylinder apparatus. The linear speed used has been 0.3 m/s which is low enough in order to avoid fusion and oxidative wear. The load used has been 1 Kg which is also low in order to avoid feezing wear. The measured wear is only abrasive. The samples used were cylinders of 15.4 ~TI diameter and 7 mn height. The weight loss has been evaluated and different testing times: 10, 20, 30, 40, 50 and 60 minutes. Using the density of each material the values of volume loss required by the DIN 53516 standard have been evaluated. It can be noticed that the volume loss is linear with testing time. The prsent results show that the abrasive wear of alloys based on precious metals such as Pt, Pd, Au and Ag is higher than for Ti and Ti based alloys. The alloy with highest wear resistance is the Co-Cr which exhibits as well as the highest hardness and Younq*s modulus.
GAIT ANALYSIS IN PARAPLEGICS WALKING WITH RGO ORTHOSIS Maurizio Ferrarin, Marco Rabuffetti, Antonio Pedotti and Marco Lusvardi* Centro di Bioingegneria, Fnd. Pro Juventute IRCCS, Politecnico di Milano, Italy. *Officine Ortopediche Rizzoli, Bologna, Italy Restoration of walking in paraplegic patients is a complex task. Although good results have recently been achieved with new ot-thoses for reciprocal gait, further improvements must be performed in terms of optimal adaptation to the single subject and choice of the best locomotor strategy. Attempting to face these problems in the present study a group of paraplegic patients walking with RGO orthosis and upper limb aids has been assessed with a multifactorial movement analysis system consisting on an ELITE system for kinematic analysis, a force platform for Ground Reaction Force (GRF) detection and a PC to store, process and graphically represent all data collected during movement. A couple of TV cameras were used for each side of the patient to allow a 3D analysis of orthosis, pelvis, upper limbs, arm aids and head. Besides a general description of walking pattern, the differences between the use of crutches and walking frame were investigated. General spatiotemporal parameter of gait and time course of joint angular displacement were computed. Torsion and lateral bending of the spine were also estimated. Combining kinematic and kinetic data torque and power at hip, shoulder and elbow joints were estimated. Finally load impulses (integral of vertical component of GRF) on feet and walking aids were computed. Results show bigger peak of force on arms when crutches are used, while the impulse on arms is bigger with frame. Joint angle ranges are quite similar in both cases, even if the pattern on elbow joint is different because of the linkage between the two arms when frame is used. Analysis of torque and power at hip joints allowed us to study the transfer of energy through the posterior reciprocator bowden cable.