Des malocclusions pourraient etre a l'origine de dereglements posturaux, temoignant d'une influence des signaux issus de l'appareil manducateur sur le controle postural. Notre approche consiste a rechercher des signes directionnels (biais posturaux, biais d'orientation) de malocclusions d'expression transversale, censees occasionner un flux afferent asymetrique. Dans cette investigation, des mastications unilaterales forcees sont utilisees comme modele.Cette approche se justifie dans le cadre theorique qui stipule que le flux continu des messages nerveux visuels, vestibulaires et proprioceptifs contribue a l'elaboration dynamique de references spatiales qui guident la perception et l'action. En temoignent les biais d'orientation constates lors des lesions de structures cerebrales integrant ces messages, ou les illusions de position provoquees chez le sujet sain par stimulation optocinetique ou vibration des tendons. Dans ce champ d'etude, l'accent est souvent mis sur les relations entre la cognition spatiale et la posture.L'experience compare les effets de modalites occlusales asymetriques sur la posture et les representations spatiales. Elle porte sur 50 adultes (23 ans en moyenne), dont la preference manuelle a ete exploree par un questionnaire detaille. Les troubles posturaux, la mastication preferentielle, l'oeil directeur et les pathologies visuelles ont ete relevees. Le protocole comprend 4 conditions occlusales, dont l'ordre de presentation est contrebalance : repos mandibulaire, intercuspidation maximale, mastications laterales droite et gauche. La posture statique est evaluee par stabilometrie normalisee, la posture dynamique par un test de pietinement. Deux indices d'orientation spatiale sont mesures : le droit devant subjectif et la verticale visuelle subjective.Les resultats confortent l'idee d'une influence de la mastication forcee sur la posture chez le sujet sain. L'effet concerne le cout plutot que la precision du controle, suggerant une compensation de la perturbation induite. L'ensemble des donnees recueillies facilitera l'interpretation de celles des cas cliniques dont l'etude est maintenant envisagee.

Located at the center of the neck and the pharyngeal column and, thanks to its attachments, tied to the base of the skull, to the mandible, to the tongue, to the larynx, and to the scapular belt, the hyoid bone is intimately related to an extensive tendino-muscular complex. From this strategic position, the hyoid bone participates in all functional and nutritional activities of the oro-facial complex. Heavily involved in the physiology of the pharyngeal column, it appears to enjoy a remarkable stability in relation to its surrounding structures as it participates in the critical process of vertical ontogenetic development. Deceptively simple in its shape and location it is anything but. While it would be easy to scorn it as a vestigial organ of little importance, the hyoid bone is actually an ancient witness of the evolution of the first human vertebrae and a vestige of the 2nd and 3rd brachial arches. Like a toy buffeted by powerful groups of muscles and tendons, the hyoid bone occupies a crossroads position where it is solicited by many vital functions, the most critical of which is respiration. Its functional behavior seems to have evolved considerably over the course of phylogeny. By piecing together the conceptions of many authors, we can conclude that the similarities--and, later, the differences--existing between the human fetus and those of other primates, and, then between young children and young primates, are related to an essentially different status quo, which modifies the delicate equilibrium of the pharyngeal region. In metamorphosing from a sagittal equilibrium to one that is vertical, this very status quo maintains an open respiratory airway during each time frame, continuously permitting the articulation and modulation of sounds, particularly during the vertical period. The hyoid bone is unpaired, in a mid-line position, symmetrical, and located just below the mandible with which it shares, to an astonishing extent, certain morphological characteristics. Its maturation and its ossification occur slowly and late even though it migrates much more rapidly to a vertical position than does the bulk of the cervical complex. True articulations between the body and the horns of the hyoid bone persist for a very long time; and so the junction between the small horns doesn't fully calcify until about the age of 50; and, in spite of its appearance, the hyoid bone is extremely supple, a quality that allows it to make substantial contributions to functional activity. If the hyoid bone itself scarcely moves during normal respiration, modern research attributes an increasing role to it in the maintenance of the equilibrium of the pharyngeal column. It seems to be called upon to respond to a number of demands that it manages to satisfy as it helps to maintain the permeability of the pharyngeal column and thus make respiration possible. In so doing, the hyoid bone adjusts its positioning, and, perhaps most important, its orientation to the physiological requirements imposed by pharyngeal obstruction and mouth breathing. Intimately connected to the larynx, the hyoid bone plays a part in phonation that has long been recognized. Recent studies now also show that the contribution the hyoid bone makes to respiratory equilibrium is far more important than its small size would suggest.

Located at the center of the neck and the pharyngeal column and, thanks to its attachments, tied to the base of the skull, to the mandible, to the tongue, to the larynx, and to the scapular belt, the hyoid bone is intimately related to an extensive tendino-muscular complex. From this strategic position, the hyoid bone participates in all functional and nutritional activities of the oro-facial complex. Heavily involved in the physiology of the pharyngeal column, it appears to enjoy a remarkable stability in relation to its surrounding structures as it participates in the critical process of vertical ontogenetic development. Deceptively simple in its shape and location it is anything but. While it would be easy to scorn it as a vestigial organ of little importance, the hyoid bone is actually an ancient witness of the evolution of the first human vertebrae and a vestige of the 2nd and 3rd brachial arches. Like a toy buffeted by powerful groups of muscles and tendons, the hyoid bone occupies a crossroads position where it is solicited by many vital functions, the most critical of which is respiration. Its functional behavior seems to have evolved considerably over the course of phylogeny. By piecing together the conceptions of many authors, we can conclude that the similarities--and, later, the differences--existing between the human fetus and those of other primates, and, then between young children and young primates, are related to an essentially different status quo, which modifies the delicate equilibrium of the pharyngeal region. In metamorphosing from a sagittal equilibrium to one that is vertical, this very status quo maintains an open respiratory airway during each time frame, continuously permitting the articulation and modulation of sounds, particularly during the vertical period. The hyoid bone is unpaired, in a mid-line position, symmetrical, and located just below the mandible with which it shares, to an astonishing extent, certain morphological characteristics. Its maturation and its ossification occur slowly and late even though it migrates much more rapidly to a vertical position than does the bulk of the cervical complex. True articulations between the body and the horns of the hyoid bone persist for a very long time; and so the junction between the small horns doesn't fully calcify until about the age of 50; and, in spite of its appearance, the hyoid bone is extremely supple, a quality that allows it to make substantial contributions to functional activity. If the hyoid bone itself scarcely moves during normal respiration, modern research attributes an increasing role to it in the maintenance of the equilibrium of the pharyngeal column. It seems to be called upon to respond to a number of demands that it manages to satisfy as it helps to maintain the permeability of the pharyngeal column and thus make respiration possible. In so doing, the hyoid bone adjusts its positioning, and, perhaps most important, its orientation to the physiological requirements imposed by pharyngeal obstruction and mouth breathing. Intimately connected to the larynx, the hyoid bone plays a part in phonation that has long been recognized. Recent studies now also show that the contribution the hyoid bone makes to respiratory equilibrium is far more important than its small size would suggest.

In dentofacial orthopedics, rehabilitation concerns the performance of the orofacial functions. Orthodontists will therefore speak of rehabilitation of functions, or functional therapy. Orofacial functions seem to obey a hierarchical system in accordance with their physiological importance; the impact of their disorders on both muscular behavior and facial morphogenesis, proportionally to their physiological importance. Therefore, priority will be given at a very early stage to the rehabilitation of respiration: restoring nasal ventilation is indeed an essential condition to obtain balanced oral functions because oral ventilation conditions both muscular posture and the performance of other functions. A little later, affective immaturity symptoms closely linked to various persisting bad suction habits will be looked after. At last, the rehabilitation of phonation and chewing both affected by the previous dysfunctions will participate in acquiring correct lingual position. The age for intervention will before all depend on the dysfunctional etiopathogeny. The morphological context, the importance of the malocclusion, and some orthodontic appliances also play a role in the the dysfunctional requests and the alterations of oral behavior.

Organic plagiocephaly is caused by premature synostosis of the coronal suture. The subject is dealt with in the context of a desire to categorize these types of asymmetries and to find asymmetry indices using computed tomography scan images. From a cephalometric point of view, the authors looked for a reproducible reference, independent of the structures to be studied-the vestibular orientation, which is based on the definition of a mediolabyrinthic plane, making it possible to assess the symmetry. One of the problems encountered in this study of the cranial vault is related to the difficulty of determining reproducible cranial indicators. Consequently, the authors propose an alternative method for studying the asymmetry using the tracing, measurement of radiuses, and the ratio between symmetrical radiuses from the origin of the vestibular indicator. When it came to putting this tool into practice, the authors opted to design a customized instrument. The tool was then applied to dry skulls considered to be symmetrical and to a few cases of plagiocephaly before and after surgery. The study of dry skulls, used as a reference, demonstrates the general shape of the curve representative of the symmetry evolution over the entire vault in healthy models. Analysis of pathological cases reveals the asymmetry of the cranial profiles (for example, homolateral frontal flattening, contralateral frontal prominence). It also makes it possible to assess the anterior, posterior, low, or high location of asymmetries of the vault. This analysis enables quantitative assessment of asymmetries using ratios, along with objective evaluation of postoperative results, with demonstration of surgical improvements and overcorrections. This analysis could make it possible to characterize asymmetries according to their shape. An attempted quantitative classification system for plagiocephalies according to four degrees of severity is proposed. The proposed analysis permits an objective, reproducible, and quantitative method for studying cranial vault asymmetries. A study on a larger population would make it possible to confirm these hypotheses and put forward new ones. Prospects for development could relate to study of all asymmetry problems affecting the base of the skull and the face.

In dentofacial orthopedics, rehabilitation concerns the performance of the orofacial functions. Orthodontists will therefore speak of rehabilitation of functions, or functional therapy. Orofacial functions seem to obey a hierarchical system in accordance with their physiological importance; the impact of their disorders on both muscular behavior and facial morphogenesis, proportionally to their physiological importance. Therefore, priority will be given at a very early stage to the rehabilitation of respiration: restoring nasal ventilation is indeed an essential condition to obtain balanced oral functions because oral ventilation conditions both muscular posture and the performance of other functions. A little later, affective immaturity symptoms closely linked to various persisting bad suction habits will be looked after. At last, the rehabilitation of phonation and chewing both affected by the previous dysfunctions will participate in acquiring correct lingual position. The age for intervention will before all depend on the dysfunctional etiopathogeny. The morphological context, the importance of the malocclusion, and some orthodontic appliances also play a role in the the dysfunctional requests and the alterations of oral behavior.

Cranio-facial dissymmetries especially concern orthodontics and orthognathic surgeons, but also all clinicians. A review of the conventional ways to study cranio-facial dissymmetries and their limits are presented. Progress of medical scanning allow to acceed to new methods of investigation and evaluation of cranio-facial morphology and dissymmetries. A cranio-facial dissymmetries analysis is suggested, based on CT, vestibular orientation, and an architectural and structural analysis, based on nervous indicators of the trigeminal nerve.