A Study On The Effect Of Fixed Expansion Of The Upper And Lower Jaw And Expansion Of The Invisible Appliance

The study consists of two parts.Part I : Comparison of the needed time between fixed expander and clear alignment on dental arch expansion.Part II The change of airway,tympanic cavity,maxillofacial hard tissue after the maxillomandibular slow expansion in CBCT.Part ? : Comparison of the needed time between fixed expander and clear aligner on dental arch expansion.Objective:With the development of orthodontic,clear aligners therapy has been developing and becomes more and more popular in patients.However,we wonder if this new therapy can save patients' time,how efficient it has,and how to manage it.This study will make a comparison of the needed time on dental arch expansion between fixed appliance and clear aligner.Methods:Patientswas treated with fixed expander(Hyrax expander).After the treatment,clear aligner company will make a plan according to the tooth data.Finally,the invisible appliance plan is compared with the actual treatment effect,and the time required for each to achieve the expansion effect is calculated and compared.Results: The fixed appliance usually reaches the required width in about 3 months,and the clear aligner takes at least 6-10 months to complete the expansion.The statistical analysis shows that p<0.05.clear aligner and expansion efficiency is not as good as fixed expansion.Conclusion: The efficiency of clear aligner is not as good as that of fixed appliance,but the arch expansion and the simultaneous alignment of the teeth are advantages that the fixed appliance does not have.Part ? The change of airway,tympanic cavity and maxillofacial hard tissue after the maxillomandibular slow expansion in CBCT.Objective: At present,there are many studies on the changes of soft and hard tissues in the mouth and face caused by RME,but there are still few studies on the changes caused by the maxillomandibular slow expansion.In this study,the CBCT of patients before and after the maxillomandibular expansion was measured to study the volume change of airway,the tympanic cavity and maxillofacial hard tissue.Methods: The patient was treated with maxillomandibular slow expansion.CBCT was taken after the expansion.The airway volume,minimum cross-sectional area,before and after orthodontic treatment were measured by dolphin 11.9 software,and the left and right tympanic cavity volume was measured by the eustachian tube.At the same time,the bone tissue of the maxillofacial region was measured to explore the changes before and after the expansion.Result:1: There was no significant difference in the volume before and after the expansion.However,the minimum cross cross-sectional area has significant difference 2: There was no significant difference in the volume of the tympanic cavity on the side of the eustachian tube before and after the maxillomandibular slow expansion 3.There was partial bone reconstruction of the maxilla before and after the maxillomandibular slow expansion,while the mandible had no bone changesConclusion:In the people whose middle palate suture closure,the upper and lower jaws still have a bony arch expansion effect after the slow expansion of the upper and lower jaws,but there is no bony effect on the mandible,which has a positive effect on the airway,and the eustachian tube changes are not clear.