| Part I: The Development of Measuring System for the Muscular Pressure Exerting on the Deciduous Dental ArchObjective:Forces acting on the teeth in the dentition are produced, principally, by the perioral musculature, the tongue, and also by the masticatory muscles via the opposing teeth. The forces could be decomposed into 6 vectors: mesio-distal directions, bucco-lingual directions and infra-superior directions. Teeth could be drawn into appropriate position of the jaws by the forces to form dental arches during they erupted. Normally the 6 vectors were in a state of balance while they played an important role in sustaining the position of the teeth. There are tongue, orbicularis and buccinators beside the dental arch. These muscles accompany with the dentition every day while they play an important role in guiding teeth eruption and occlusion formation and keeping dental arch shape and stability. The pressures from lips, cheeks and tongue are called perioral force and tongue pressure. Compared with occlusional force, which means vertical vector force, perioral force and tongue pressure exert their influence on the dental arch by horizontal vector direction. The previous researches have studied the pressure exerted on the mixed dentition and permanent dentition and manifested primarily therelationship between the force and malocclusion. But so far there is no corresponding study on the deciduous dentition. The main purpose of this study was to develop and test a system for the measurement of forces from lips, cheeks and tongue on the deciduous dentition in order to offer a fine devise to study the relationship between the deciduous perioral and lingual forces and skeletodental morphology. Methods:The PC muscular force measuring system consists of the strain gauges pressure transducer and the PCLab biological signal real time collecting, processing system. The wire-resistance strain gauges were positioned on the upper and inferior surface of an Nb strip welded with an steel base, 0.5mm thickness and 3mm. wide and 2 mm. long, to detect the distortion of the spring strip. The watch-spring is about 3mm. wide and 5 mm. long. The strain gauges were incorporated with two fine resistances and then formed a wheatstone bridge circuit and applied to design and manufacture a new pressure transducer, which is more suitable for the deciduous teeth. The transducer's thickness is less than 1 mm (0.7mm). The physical capability of this muscular measuring system, such as its thermal effect on zero balance, waterproof ability and relationship between load and strain, were tested respectively. Calibration was made out of the mouth using standard weights. Results:The resistance value of the transducer is more than 200MO whether the transducer is in air or in normal saline for a long time. The linearity between load and strain is fine while the transducer bears the pressure from 0 to 500g/cm2. The drift on zero balance of the PC real muscular measuring system is only about 0.001 mv/h. Conclusion:The PC muscular measuring system can be especially used as a device of detecting the muscular forces acting on the deciduous teeth from the lips, cheeks and tongue, which have many advantages, such as thin thickness, little dimension, good waterproof ability, fine linearity between load and strain, little drift and wide range for the measurement.Part II: Perioral and Lingual Forces Measurement in Normal Deciduous SubjectsObjective:The purpose of this part was to apply the deciduous muscular force measuring system in the study of a group of children with normal deciduous occlusion in order to test this system and obtain pressure data Then such data would be used for the discussion of the distribution mode of these muscular pressures beside the dentition and the head position effect on the muscular pressure. At the same time these data would also be used to value the interaction between muscular pressure and formation of dental arch and jaw. Methods:30 volunteers, whose occlusions were completely at the... |
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