The CBCT Study On The Changes Of Hyoid Position Before And After Orthognathic Surgery In Patients With Skeletal Class ? Malocclusion

Objective: A study of BSSRO(Bilateral Sagittal Split Ramus Osteotomy)in patients with III malocclusion by CBCT(Cone Beam Computed Tomography)was performed one week before operation(T0)and one week after operation(T1).The correlation of hyoid position change 10 months after operation(T2)and the relationship between mandibular retrogression and hyoid position were analyzed.In order to evaluate the long-term effect and stability of orthognathic surgery,better guide clinical orthognathic surgery.Patients planning simple mandibular retrograde surgery should consider the possibility of OSAHS(Obstructive Sleep Apnea Hypopnea Syndrome,obstructive sleep apnea hypopnea syndrome.For patients who need a large amount of mandibular retreat during surgery,we may consider simultaneous maxillary anterior surgery to compensate for the large amount of retrogression of the mandible.To prevent or reduce the occurrence of obstructive sleep apnea hypopnea syndrome by reducing hypohyoid movement.Materials and methods: From May 2015 to December 2018,16 patients with orthodontic and orthognathic malocclusion were diagnosed by clinical and imaging examination in maxillofacial surgery ward of Dalian Stomatological Hospital.The age was 18-28 years old,male 10 cases,female 6 cases.All the subjects were divided into two groups according to the amount of mandibular receding during operation: group I(group I),the amount of mandibular retrogression was smaller than that of 5mm),IIgroup(n = 9,the amount of mandibular recession was in 5mm-10mm).All subjects underwent three-dimensional conical beam computed tomography(CBCT,)in our radiology department before orthognathic surgery(T0),one week after operation(T1)and 10 months after operation(T2).The CBCT images were processed and measured by Invivo five software.The images were rotated under the Supper Ceph interface to make the left and right ear points and orbital points overlap.Adjust the basic symmetry of left and right and then transform into CBCT lateral cephalic CCB(Cephalogram from CBCT,CBCT).After reconstruction,rendering and grayscale adjustment can be carried out to help recognize the anatomical structure.Then the CBCT image is saved to JPG format.In this paper,the CCB of T0 ?T1 ?T2 CBCT transform cranial lateral position is introduced into the software of Geometry Sketchpad,and the 2D projection measurement and analysis are carried out,and the same coordinate system is established for measurement.All the measured data were statistically analyzed by SPSS25.0software.The changes of hyoid position with time and the relationship between mandibular receding volume and hyoid position were observed.Results:1.The position of hyoid bone in group I and group II showed a backward movement and a downward movement in comparison with that in the first week(T0)after mandibular retrogression.The position of hyoid bone in 10 months after mandibular retrogression(T2)was significantly higher than that in one week before operation(T0).The position of hyoid bone moved backward and downward(.(P < 0.05)2.The position of hyoid bone in group I and group II,ten months after operation(T2),the hyoid moved forward and upward compared to the first week after surgery(T1).In the 3.II group,the hyoid bone moved vertically 1 week(T1)and 10 months(T2)compared with the preoperative week(T0)(P < 0.05).The difference of distance between 1 week(T1)and 10 months(T2)after operation in II group was smaller than that in one week before operation(T0).The difference of hyoid movement distance in group I.Conclusion:1.The position of hyoid bone immediately after mandibular retrogression was compared with the position of hyoid bone before operation and theposition of hyoid bone after long-term follow-up.2.The results of follow-up showed that the position of hyoid bone tended to move forward and upward,but it was still located in the lower part of the preoperation,and the amount of mandible receding within a certain range(10mm)did not affect the movement trend of hyoid bone.3.The position of hyoid was lower in patients with greater distance of mandibular recession than that in patients with lower distance of mandibular retraction.