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Periodontal biomechanics
Abstracts of the Fourth Meeting of the European Society of Biomechanics
516
analysis of neurone pool active state. Indicators for myopathies and neuropathies derived from surface EMG signals are under investigation. A new kind of detecting dynamic contraction components non-invasively in correlation with surface EMG signals may open new diagnostic possibilities. CLINICAL
BIOMECHANICS
AS RELATED TO THE HUMAN
SPINE
ALF L. NACHEMSON(Department of Orthopaedic Surgery, Sahlgren Hospital, S-41 3 45 Gbteborg, Sweden) In this lecture an account will be given of the developments of biomechanical knowledge in this field that have occurred over the last thirty years, during which time the author has been active doing spine research. Particular emphasis will be placed on the more practical applicability of the new knowledge. Spine mechanics in relation to both etiology and treatment of scoliosis will be discussed. New data in fact strongly support the mechanical factor as one of the important contributions, together with faulty balance, in the pathogenesis and progression of adolescent idiopathic scoliosis, while the mechanics of various treatment modalities is of more general knowledge. The same is true for spine fractures. Mechanical factors are also important for low back pain, the current epidemic pain problem in the modern industrialized societies. Through experimental and clinical work we know much about the stresses and strains which the vulnerable lumbar motion segments have to bear. Various types of spine models, some of them validated by in uiuo experiments, have widened our knowledge. This will then greatly increase the possibility in the future of properly treating this condition, with due account also for the various biological factors. PERIODONTAL
BIOMECHANICS
D. C. A. PICTON (University College London Dental School, London, U.K.) The periodontal ligament is a connective tissue, some 200 pm thick, which suspends the tooth in the socket. The predominant orientation of the oblique collagen fibres is from the socket towards the root end, but blood vessels are numerous. Under load tooth and alveolar bone, independently or when ankylosed, behave elastically. The ligament conveys viscoelastic properties. Ramp force causes relatively free movement up to 0.8 N, followed by much less displacement of the tooth. Analysis of relaxation curves by ‘curve stripping’ indicates functionally three Voigt elements. Impact loads cause less displacement, the ligament being relatively rigid. Sustained loads cause creep followed by prolonged recovery. Loading history is important, a series of axial loads ( > 1 min - ‘) causes progressive intrusion and less displacement. No loads for 3 h cause extrusion and reduced mobility. Tension, compression and haemodynamic damping contribute to a varying extent depending on loading conditions. ISSUES IN SPORTS BIOMECHANICS JAMESG. HAY (University of Iowa, Iowa City, IA 52242, U.S.A.) This paper will address three major issues in sports biomechanics-the development of a satisfactory procedure for the qualitative analysis of human movements; the problems inherent in providing biomechanical support services to coaches and athletes; and the relative merits of cross-sectional and longitudinal analyses in sports biomechanics research. FUNCTIONAL SAVIO
ADAPTATION
OF CORTICAL
BONE, TENDONS
AND LIGAMENTS
L.-Y. Woo (University of California, San Diego and San Diego Veterans Administration Center, La Jolla, CA, U.S.A.)
Medical
In this study the results of three animal experiments on functional adaptations of hard and soft tissues to different levels of stress (or strain) are described: (1) Plate immobilization of long bone reduced bone stresses causing significant atrophy without altering mechanical properties. (2) Immobilization reduced the mechanical properties of the ligament substance and the structural strength of the bone-ligament junctions. However, rapid recovery was seen for the ligament substance following remobilization. (3) Moderate exercise training for a short duration had minimal effect on the mechanical properties of bones and extensor tendons, while intense exercise for a longer duration caused bone hypertrophy and improvement of tendon mechanical properties. Based on the experimental results, we are able to construct a non-linear curve to represent the functional adaptation of connective tissues. Acknowledgmenr
Supported by RR&D of the Veterans Admin., NIB Grants AM14918 and AM33097, and the Bone and Joint Disease Foundation.
516
analysis of neurone pool active state. Indicators for myopathies and neuropathies derived from surface EMG signals are under investigation. A new kind of detecting dynamic contraction components non-invasively in correlation with surface EMG signals may open new diagnostic possibilities. CLINICAL
BIOMECHANICS
AS RELATED TO THE HUMAN
SPINE
ALF L. NACHEMSON(Department of Orthopaedic Surgery, Sahlgren Hospital, S-41 3 45 Gbteborg, Sweden) In this lecture an account will be given of the developments of biomechanical knowledge in this field that have occurred over the last thirty years, during which time the author has been active doing spine research. Particular emphasis will be placed on the more practical applicability of the new knowledge. Spine mechanics in relation to both etiology and treatment of scoliosis will be discussed. New data in fact strongly support the mechanical factor as one of the important contributions, together with faulty balance, in the pathogenesis and progression of adolescent idiopathic scoliosis, while the mechanics of various treatment modalities is of more general knowledge. The same is true for spine fractures. Mechanical factors are also important for low back pain, the current epidemic pain problem in the modern industrialized societies. Through experimental and clinical work we know much about the stresses and strains which the vulnerable lumbar motion segments have to bear. Various types of spine models, some of them validated by in uiuo experiments, have widened our knowledge. This will then greatly increase the possibility in the future of properly treating this condition, with due account also for the various biological factors. PERIODONTAL
BIOMECHANICS
D. C. A. PICTON (University College London Dental School, London, U.K.) The periodontal ligament is a connective tissue, some 200 pm thick, which suspends the tooth in the socket. The predominant orientation of the oblique collagen fibres is from the socket towards the root end, but blood vessels are numerous. Under load tooth and alveolar bone, independently or when ankylosed, behave elastically. The ligament conveys viscoelastic properties. Ramp force causes relatively free movement up to 0.8 N, followed by much less displacement of the tooth. Analysis of relaxation curves by ‘curve stripping’ indicates functionally three Voigt elements. Impact loads cause less displacement, the ligament being relatively rigid. Sustained loads cause creep followed by prolonged recovery. Loading history is important, a series of axial loads ( > 1 min - ‘) causes progressive intrusion and less displacement. No loads for 3 h cause extrusion and reduced mobility. Tension, compression and haemodynamic damping contribute to a varying extent depending on loading conditions. ISSUES IN SPORTS BIOMECHANICS JAMESG. HAY (University of Iowa, Iowa City, IA 52242, U.S.A.) This paper will address three major issues in sports biomechanics-the development of a satisfactory procedure for the qualitative analysis of human movements; the problems inherent in providing biomechanical support services to coaches and athletes; and the relative merits of cross-sectional and longitudinal analyses in sports biomechanics research. FUNCTIONAL SAVIO
ADAPTATION
OF CORTICAL
BONE, TENDONS
AND LIGAMENTS
L.-Y. Woo (University of California, San Diego and San Diego Veterans Administration Center, La Jolla, CA, U.S.A.)
Medical
In this study the results of three animal experiments on functional adaptations of hard and soft tissues to different levels of stress (or strain) are described: (1) Plate immobilization of long bone reduced bone stresses causing significant atrophy without altering mechanical properties. (2) Immobilization reduced the mechanical properties of the ligament substance and the structural strength of the bone-ligament junctions. However, rapid recovery was seen for the ligament substance following remobilization. (3) Moderate exercise training for a short duration had minimal effect on the mechanical properties of bones and extensor tendons, while intense exercise for a longer duration caused bone hypertrophy and improvement of tendon mechanical properties. Based on the experimental results, we are able to construct a non-linear curve to represent the functional adaptation of connective tissues. Acknowledgmenr
Supported by RR&D of the Veterans Admin., NIB Grants AM14918 and AM33097, and the Bone and Joint Disease Foundation.