| Classâ…¡malocclusion is patho-occlusion in clinic. One of its significance characters is the mandibular retraction. Among adolescents with mandibular retraction, 46 percent of them suffer from Classâ…¡malocclusion . The abnormity influences the patients'countenances and functions severely. According to the abnormity's nature, extent and formation in different periods, it's important for patients to be treated by submaxilla anterior guidance .Owing to the different retention modes, submaxilla anterior guidance activator can be classified as removable appliance and fixed appliance. Most of the appliances which used in the earlier period were removable, and the treatment of mandibular retraction needed two-phases treatment. In recent years, a great number of orthodontic doctors pay close attention to fixed appliance which prescented by Forsus ,for such appliance is small in size, has more durable and homogeneous elastic foce and easy to control, too. What's more, the installation is easier and the course of treatment is shorter in general. In a word, fixed appliance suggests the new developmental trend of the orthopaedic treatment appliance . At present, the study of Forsus appliance steps into clinical research phase. None report about vitodynamics study in mandibular anerior guidance is found. Numerical simulation analysis is one important means in oral biomechanical study, it is a technique combines Mathematical Sciences and Computer Technology and it has been widely used in vitodynamical study. On the basis of considering visvoelasto, by using the simulated analysis of the Forsus orthopedic force system, the different mechanical effects can be analysed under different anterior guidance operating conditions, and the analysis improves the clinical use of the appliance as well .In this study, Forsus-Dent-uper and lower jaw-TMJ integral 3D model with the character of isotropy and non-linear was builded. To some extent the model also is built with the character of visvoelasto.The study shows that there is no obvious stress attenuation, or distinct stress relaxation region,that is, the rebuilding process of jaw bones is slow. The larger the angle between the datum line and loading point is the more obvious mental region's protrusive bias would be. Those who with mandible anticlockwise rotation have more obvious protrusive bias compares with mandible clockwise rotation ones. When Forsus is used, the range of loading angle is from0 to25 degree would be better. In cases with rotation center lies in the Incisal border of lower incisors, a antrorse rotation of the lower jaw would do good to the therapy of type II patho-occlusion. For patients with unfavorable vegetative form ,by adjusting the loading angle of Forsus applicaton, the lower mandible's expedient automatic rotation orientation would be increased . All the above does good to improve the latero-countenance. The condylar's remodeling compass is in the extent of 1.0 to 3mm. Though the remodeling tendency of condylar is significant, this changement is finite. When the orthopedic force-vector through the center of abutment tooth crown's buccal surface, adding a anti-incline couple of Mt/F = 9 and a anti-rotation couple of Mr/F = 5 would won the molar's translation.A model of Forsus-Dent-uperand lower jaw-TMJ with some visvelasto-plastic characters is built in this study and it is isotopic, non-linear, three diamensional and integral. It has high geometric and mechanics similarities and could be splited and used in the form of modules. All the above contributes to a research platform for further study of the vitodynamics effect of Forsus in mandible anterior guidance .At the same time, the study offers favourable reference for the clinical application and improvement of Forsus by using simulated analysis on the disposition of the orthopedic forcess system under different anterior guidance operating condition. |
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