Cone Bean Computed Tomography Study On The Effects Of Two Kinds Of Expansion Appliances On Tooth、Alveolar Bone And Basal Bone

ObjectiveUse of CBCT to evaluate the clinical effect of tooth-supported expansion appliance(Hyrax)and combined-supported expansion appliance(Hass)for rapid maxillary expansion functionally.Preoperative and postoperative CBCT scans were performed on patients with early permanent dentition with crowding and posterior crossbite,and the thickness of alveolar bone and the length of basal bone were measured to evaluate the clinical application effect of the two kinds of expansion appliances,so as to provide some experimental data for orthodontists to choose the best one.Methods1.Sample design:a total of 44 patients admitted to the orthodontics department of the Affiliated Stomatological Hospital of Binzhou medical college were selected.The subjects were randomly divided into two groups,22 in each group,namely the Hass group and the Hyrax group.In the Hass group,there were 14 males and 8 females,with an average age of 13.8 years and 3.2 years.Cone-beam Computed Tomography records were taken before and 3 months after expansion through Planmeca Romexis Viewer orthodontic software to analyze including basal bone,alveolar bone and tooth tipping.2.Instrument usage:all the subjects are using the same Binzhou Medical School Affiliated Hospital dental CBCT scanning,the three dimensional imaging scans conditions for voltage 90V k,exposure time of 10.00 s,current 10mA,radiation dose of 1245mGycm2.The patient be told to keep the body upright,straight ahead,instruments used to patients with skull fixing device to fixed head,adjust the cursor positioning system to ensure that the orbital plane parallel to the ground.Finally all these works was done by one man.3.The conditions of dental arch expansion:check the patients’ oral hygiene,and determine the absence of teeth without lesions,bad dental prosthesis,etc.The degree of dental arch stenosis was examined,and rapid arch expansion therapy was performed for patients with maxillary dysplasia or posterior crossbites.4.Expansion before:all the patients informed consent,and sign in the treatment of informed consent and maxillofacial CBCT taken and stored.Put the separator in between maxillary canines and premolars and between premolar and the first premolar.A week later return to remove separator.5.The method of expansion:turn the screw with the key every day,1/4 turn each time,twice a day,once in the morning and once in the evening.When the palatal tip of the upper posterior teeth comes into contact with the buccal tip of the lower posterior teeth,the expansion stops.later,use self-curing denture acrylic fixed.CBCT scan is performed after expansion for three months.6.Data processing:the data with x±s,SPSS24.0 software was used to conduct paired sample t test on the data to analyze the changes of relevant indicators in the two groups after expansion.P<0.05 was considered statistically significant.Results1.The bilateral width between the crown of the first premolar and the first molar was increased in both groups.The thickness of buccal alveolar bone of first molars decreased and that of palatal alveolar bone increased.2.The dental effect of the two groups was greater than that of the bone effect,and the bone effect of the Hass group was slightly greater than that of the Hyrax group.The changes of the two groups in the premolar area of Hyrax group were greater than that of the Hass group,and there was a statistical difference between the two groups.3.Compared with the Hass group,the Hyrax group had more posterior tooth inclination,and the hyrax group had a greater influence on the arch width and buccal alveolar bone thickness of the first molar.Compared with the hass group,the hyrax group had more tooth inclination and buccal alveolar bone absorption in the premolar area and molar area.Conclusion1.The tooth-supporting and hybrid-supported expansion appliances has the same effect on the expansion of the maxillary arch.Both arching methods can effectively expand the transverse width of the arch.2.The combined-supported expander has a greater effect on the bone.The expander will cause more of the first molar and the alveolar process to tilt.When clinically selecting the expander,the appropriate expander should be selected for treatment according to the specific conditions of the patient.