| Objective:On the basis of Cone Beam Computed Tomography(CBCT)scanning data,the three-dimensional reconstruction of the skull,and the three-dimensional cephalometry of three-dimensional model of mandible were performed.Comparing analysis the measurement results of before and after surgery.To investigate the effect of mandibular angle osteotomy on the morphological changes of mandible,and to evaluate its clinical effect.It provides some reference for clinical mandibular angle osteotomy and plastic surgery.Methods: According to include and exclude criteria,the complete CBCT data of 20 female patients(aged 20-35 years with an average age of 25.5 years)admitted to the Affiliate Friendship Plastic Surgery Hospital of Nanjing Medical University from January 2016 to June 2018 who underwent curved mandibular angle osteotomy combined with splitting cortiectomy were selected.Firstly,CBCT scanning data were imported into ProPlanCMF,a three-dimensional design software,for reconstruction.Then,the three-dimensional model was segmented and fixed,and the corresponding reference plane was determined.Seven items reflecting mandibular morphology before and after surgery were measured respectively,including the distance between mandibular angles(Go-Go),length of ascending ramus of mandible(Cd-Go),length of mandibular body(Go-Me),maximum width of Angle area(Go-Ri),gonial angle(Ar-Go-Me),mandibular plane angle(MP-FH)andmandibular eversion angle(MR-MA).All the items were measured for three times by the same examiner,with each interval of 3 days.The mean value of thethree times of measurement was taken as the measured result.All the data were analyzed by the means of SPSS12.0,linear correlation analysis and paired t test were used to evaluate the change of andibular morphology.Results: 1.Three-dimensional images showed sharp edges and rough surfaces of the mandible osteotomy surface within 10 days after surgery.With thickening and regeneration of the bone cortex in the mandibular angle area,the rough and sharp osteotomy surface disappeared,and was replaced by the smooth surface with smooth edges,forming a soft and natural new shape of the mandibular angle in 6 months after the surgery.2.The measurement results of the mandible pre-and postoperative 10 days showed as follows:Go-Go decreased(from 102.94±5.07 mm to 94.53±4.60mm);both sides of Cd-Go decreased(from 60.97±5.54 mm to 47.18±5.59 mm on the left side,and from 62.51±5.58 mm to 48.03±5.86 mm on the right side);both sides of Go-Me became longer,(from 72.97±2.71 to 79.01±4.02 mm on the left side,and from74.23±2.71 mm to 79.14±3.99 mm on the right side),both sides of Go-Ridecreased(from 38.76±3.90 mm to 33.89±3.64 mm on the left side,and from39.13±3.20 mm to 33.44±3.17 mm on the right side);both sides of Ar-Go-Me increased(from 109.44±4.06°to 124.11±4.89°on the left side,and from110.25±4.00°to 124.35±4.80°on the right side);both sides of MP-FH increased(from16.48±3.81°to 26.39±4.52°on the left side,and from 15.81±4.04°to 26.33±5.19°on the right side);and both sides of MR-MAdecreased(from 12.08±2.72°to 0.76±1.06°on the left side,and from 11.45±2.63° to 0.78±1.10°on the right side).The paired t-test results showed that there was significant difference between before and after operation(P<0.05),while there was no difference between left and right sides(P>0.05).The results showed that the distance between mandibular angles,the length of ascending ramus of mandible,the mandibular eversion angle and themaximum width of angle area decreased,while the gonial angle,the mandibular plane angle and the length of mandibular body increased,and bilateral mandibular symmetry was obtained after surger.3.Compared within 10 days after operation,the measurement items also changed 6months after operation.A slight changes in Go-Go(from 95.53±4.60 mm to 95.02±4.97 mm),both sides of Cd-Go become longer(from 47.18±5.59 mm to47.33±5.57 mm on the left,and from 48.03±5.86 mm to 49.40±6.14 mm on the right);both sides of Go-Me become longer(from 79.01±4.02 mm to 79.23±4.06 mm on the left and from 79.14±3.99 mm to 79.37±4.38 mm on the right);both sides of Go-Ri become larger(from 33.89±3.64 mm to 34.10 ± 3.60 mm on the left and from33.44±3.17 mm to 33.58 ± 3.12 mm on the right);decreased on both sides of the Ar-Go-Me(from 124.11±4.89° to 123.89±5.02° on the left and from 124.35±4.80°to 124.02 ± 3.98° on the right);On both sides of the MP-FH decreased(from26.39±4.52°to 26.19±4.52°on the left and from 26.33±5.19° to 25.97±5.27° on the right);.On the contrary,MR-MA increased from 0.76±1.06° to 0.86±1.07° on the left and from 0.78±1.10° to 0.83±1.011° on the right.There was no statistical difference between the above measurement items 6 months after surgery and 10 days after surgery(P > 0.05),and no statistical difference between the left and right sides(P >0.05).This indicated that the morphology of mandible changed with bone regeneration in the surface of osteotomy after surgery,bilateral symmetry did not change,and bone regeneration did not affect the postoperative effect.Conclusion: 1.Curved mandibular angle osteotomy combined with splitting cortiectomy can effectively remove the bone in mandibular angle area and increase the height of mandibular angle points.Thus the distance between mandibular angles,the length of ascending ramus of mandible,the length of mandibular body,and themaximum width of angle area can be reduced.At the same time,the gonial angle,mandibular plane angle and the length of mandibular body were enlarged to achieve changing facial contour.2.There was bone healing on the osteotomy surface after operation,and new callus and cortex could be formed on the surface,which could change the shape of mandible and make the osteotomy line and the osteotomy surface more smooth and natural without affecting the shape of the facial contour of postoperation.3.The mandibular three-dimensional model which reconstructed based on CBCT data,not only display the three-dimensional anatomical structure that cannot be presented on X-ray film visually and comprehensively by means zoom,rotation and other operations,but also precise and accurate show the change of the shape of the mandible from the sagittal,coronal and horizontal plane with arbitrary cutting and rotation.The measurement of mandible is more accurate and reliable,and the surgical plan of mandibular angle osteotomy can be accurately planned preoperatively,and the operative effect can be quantitatively evaluated postoperatively. |
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