title: The role of the fluid phase in the viscous response of bovine periodontal ligament.
abstract: The mechanical response of the periodontal ligament (PDL) is complex. This tissue responds as a hyperelastic solid when pulled in tension while demonstrating a viscous behavior under compression. This intricacy is reflected in the tissue's morphology, which comprises fibers, glycosaminoglycans, a jagged interface with the surrounding porous bone and an extensive vascular network. In the present study we offer an analysis of the viscous behavior and the interplay between the fibrous matrix and its fluid phase. Cylindrical specimens comprising layers of dentine, PDL and bone were extracted from bovine first molars and affixed to a tensile-compressive loading machine. The viscous properties of the tissue were analyzed (1) by subjecting the specimens to sinusoidal displacements at various frequencies and (2) by cycling the specimens in 'fully saturated' and in 'partially dry' conditions. Both modes assisted in determining the contribution of the fluid phase to the mechanical response. It was concluded that: (1) PDL showed pseudo-plastic viscous features for cyclic compressive loading, (2) these viscous features essentially resulted from interactions between the porous matrix and unbound fluid content of the tissue. Removing the liquid from the PDL largely eliminates its damping effect in compression.
authors.affiliation: Laboratoire de Mécanique Appliquée et D'analyse de Fiabilité, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland.
authors.forename: Marzio
authors.initials: M
authors.lastname: Bergomi
authors.forename: Joël
authors.initials: J
authors.lastname: Cugnoni
authors.forename: John
authors.initials: J
authors.lastname: Botsis
authors.forename: Urs C
authors.initials: UC
authors.lastname: Belser
authors.forename: H W
authors.initials: HW
authors.lastname: Anselm Wiskott
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001826:Body Fluids / Q000502:physiology; D002417:Cattle; D019245:Compressive Strength; D066298:In Vitro Techniques; D008954:Models, Biological; D010513:Periodontal Ligament / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength; D014783:Viscosity