Application And Analysis Of MAO Using Geometric Mathematical DOTs To Guide The Aesthetic Osteotomy Line

Mandibular Angle osteotomy is popular in young Asian females.It is still difficult to locate the osteotmy line during the operations.The limited surgical field and the misjudgements make the procedure liable to complications and unfavorable results.This study intends to develop geometric mathematical osteotomy guide templates based on aesthetic standards using varied technologies(computer-assisted design;3D printing;artificial intelligence).The new method might provide a possible osteotomy method which strongly suggested the effectiveness,safety,individualization,and accuracy.Five parts were carried out:PartⅠ: 3D Aesthetic measurement of the young females in ShanghaiObjective: To observe the maxillofacial characteristics of young females in Shanghai.To analyze the contour characteristics of different types of mandibular shape ramous.To explore the measurement data of mandibular aesthetics and mandibular hypertrophy in order to form a clinical database,which providing data for mandibular osteotomy.Methods: CT DICOM data of 200 young women in Shanghai were collected and divided into "attractive group","prominent group" and "normal group".3D reconstruction and 3D measurement were performed through computer aided software,including 6 soft tissue items and 11 bone tissue items.There were statistically differences between the measurements of attractive females and prominent females.Results: There were differences in the measurement indexes among three groups.The mandibular angle of attractive female is small and delicate,and show significantly different to the normal female in the measurements.The angle area of prominent female had significant evagination(∠Co-Go-Me<110°,∠A ngle GO-ME-Go>72°)Conclusions: Three-dimensional measurement can be used to evaluate mandibular contour.Angle of∠Co-Go-Me,∠Go-Me-Go are related to the shape of the mandible.The shape of the mandible should conform to the following characteristics: 1)Mandibular angle(∠Co-Go-Me)is between 115-128°in the lateral view;the mandibular expansion angle(∠Go-Me-Go)less than 72°;2)No significant eversion or retrogression can be observed in mandibular angle area;3)Osteotomy curve should be both smooth and natural.Part II: Application of Geometric Mathematical Method with Computer Aided DesignObjective: To establish the three-dimensional location of the new mandibular angle(Go’)and the osteotomy line based on geometric mathematics.To explore the shape of the osteotomy line and the formula of osteotomy plan.Methods: The mandibular contour of attractive people was fitted by the curve analysis software.Three-dimensional reconstruction of the patient’s head CT was carried out in Medraw software.Combined with the facial contour characteristics of the attractive female and the geometric relationship among the key points,a design scheme of the mandibular osteotomy line was obtained.Results: The functions of cubic polynomial and logarithmic can be used to simulate the shape of mandibular contour curve in attractive post-operative females.The triangular area formula and spatial vector formula can be used to accurately locate the new mandibular angle.Conclusions: The position of osteotomy line based on geometric calculation and the shape of osteotomy line based on curve fitting can provide objective reference for the decision of osteotomy line and the design of osteotomy plan.Part III: Application of geometric mathematical 3D printing osteotomy guide plate in MAOObjective: To develop mandibular osteotomy guides(DOTs)based on aesthetic geometric mathematical model.To assess the application value of DOTs mandibular osteotomy.Methods: The Osteotomy guide templates were 3D printed with the material of polylactic acid(PLA)or resin based on geometric mathematical design.The DOTs were placed in the operation area to guide the osteotomy during the operations.Both preoperative and postoperative data of preoperative period were analyzed to evaluate the clinical application effect compared to the traditional open-handed osteotomy group.Results: The DOTs group(22cases)was compared to the traditional open-handed osteotomy group(11cases).postoperative measurement showed closer to the design value in DOTs group.Moreover,the application of guide plate can shorten the osteotomy time and improve the postoperative effect.No serious complications occurred in the cases carried out.Conclusions: The application of DOTs can provide a reliable guide surface for the surgeon,and convert the preoperative design to the intraoperative process.The DOTs can reduce the difficulty and risk of surgery and improve the accuracy of surgery.Part IV: Application of psychological Assessment in preoperative period of MAOObjective: To evaluate the psychological state of patients during preoperative period by using the psychological questionnaire.To understand the psychological expectation and treatment motivation of women with mandibular angle hypertrophy.To investigate the effect of mandibular osteotomy on physical and mental health of patients.Methods: Scales of Psychological Assessment(SCL-90,SAS,SDS)were used to evaluate the psychological level of patients through the operation.The improvement of postoperative psychological level was analyzed.Results: The psychological evaluation of 36 patients suggested that 44.4 % of patients had anxiety,and 50.0 % had depression before operation.Patients’ postoperative negative emotions such as depression,anxiety and hostility were significantly improved compared with the preoperative scales.The anxiety/depression score of postoperative patients showed no significant difference compared to the norm level.Conclusions: Mandibular osteotomy can improve the mental health of patients and reduce the anxiety/depression score.Preoperative psychological assessment and intervention can help correct patients’ bad cognition,avoid doctor-patient conflict and improve patients’ satisfaction Part V: Application of Artificial intelligence technology in mandibular plastic surgeryObjective: To construct the mandibular contour extraction and curve analysis platform based on photos by using face recognition technology and neural convolution network technology.To provide possibility of batch processing and constructing for mandibular contour database.Methods: The face detection technology based on JVCR algorithm is used to automatically identify and extract the mandibular contour of photos.The mandibular curve was measured and analyzed mathematically based on neural convolution network.The AI measurement values were compared with the measured values to verify the accuracy of the measurement.Results: By observing the results of the test set,JVCR can accurately extract the mandibular curve contour of the frontal and lateral parts.There is no significant difference between AI measurements and actual measurements.Conclusions: JVCR algorithm can be used for face detection.The mandibular angle contour can be extracted through photos automatically.Artificial intelligence technology can provide more efficient and convenient means for preoperative evaluation of mandibular osteotomy.