title: Craniomandibular System and Postural Balance after 3-Day Dry Immersion.
abstract: The objective of the study was to determine the influence of simulated microgravity by exposure to dry immersion on the craniomandibular system. Twelve healthy male volunteers participated in a 3-day dry immersion study. Before and immediately after exposure we measured maximal bite force using piezoresistive sensors. The mechanical properties of the jaw and cervical muscles were evaluated before, during, and after dry immersion using MyotonPRO. Because recent studies reported the effects of jaw motor activity on the postural stability of humans, stabilometric measurements of center of pressure were performed before and after dry immersion in two mandibular positions: rest position without jaw clenching, and intercuspidal position during voluntary teeth clenching. Results revealed no significant changes of maximal bite force after dry immersion. All postural parameters were significantly altered by dry immersion. There were however no significant differences in stabilometric data according to mandibular position. Moreover the masseter tonicity increased immediately after the end of dry immersion period. Dry immersion could be used as a valid model for studying the effects of microgravity on human subjects. However, 3 days appear insufficient in duration to evaluate the effects of weightlessness on maximal bite force. Our research suggests a link between postural disturbance after dry immersion and masseter tonicity.
authors.affiliation: Université Claude Bernard Lyon 1, Lyon, France.|Université de Strasbourg, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Strasbourg, France.
authors.forename: Loïc
authors.initials: L
authors.lastname: Treffel
authors.affiliation: Institute of Biomedical Problems, Moscow, Russia.|Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6214 - Institut National de la Santé et de la Recherche Médicale 1083, Université d'Angers, Angers, France.
authors.forename: Liubov
authors.initials: L
authors.lastname: Dmitrieva
authors.affiliation: Centre National d'Etudes Spatiales, Paris, France.
authors.forename: Guillemette
authors.initials: G
authors.lastname: Gauquelin-Koch
authors.affiliation: Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6214 - Institut National de la Santé et de la Recherche Médicale 1083, Université d'Angers, Angers, France.|Centre de Recherche Clinique, Centre Hospitalo-Universitaire d'Angers, Angers, France.
authors.forename: Marc-Antoine
authors.initials: MA
authors.lastname: Custaud
authors.affiliation: Université de Strasbourg, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Strasbourg, France.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Blanc
authors.affiliation: Université Claude Bernard Lyon 1, Lyon, France.|Centre International d'Ostéopathie, Saint-Etienne, France.
authors.forename: Claude
authors.initials: C
authors.lastname: Gharib
authors.affiliation: Université Claude Bernard Lyon 1, Lyon, France.|Service d'Odontologie, Hospices Civils de Lyon, Lyon, France.
authors.forename: Catherine
authors.initials: C
authors.lastname: Millet
mesh_terms: D000328:Adult; D001732:Bite Force; D004576:Electromyography; D006801:Humans; D007101:Immersion; D008297:Male; D008334:Mandible / Q000502:physiology; D008406:Masseter Muscle / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D009129:Muscle Tonus / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D018474:Weightlessness Simulation