A Clinical Study Of Establishing The Midsagittal Plane Of Maxillofacial Bones With Digital Three-dimensional Technology

Objective: To use digital three-dimensional technology to establish multiple median sagittal planes(MSP,Media Sagittal Plane)to evaluate the skeletal symmetry of normal patients.Taking the whole skeleton to the local skeleton(maxillofacial bone,mandible,condyle)as the research unit,analyze the accuracy of different MSPs in assessing the symmetry of the corresponding bones.At the same time,based on the symmetry differences of different MSP skeletons,to establish an ideal MSP for the overall and local skeleton of the maxillofacial region,it can provide reference and help for the clinical diagnosis and treatment of the reconstruction of maxillofacial bone defects and unilateral maxillofacial lesions.Methods: The maxillofacial spiral CT data of 30 normal maxillofacial patients were collected respectively,and the maxillofacial CT image data of 30 patients were imported in DICOM format file using Mimics Research 21.0software,and the corresponding area was reconstructed.Bone(maxillofacial bone,mandible,condyle),locate the MSP on the 3D original model through the corresponding anatomical landmarks,each object needs to establish multiple common maxillofacial MSPs(Part 1,whole head group: N-ANS-PNS,N-ANSS,N-Ba-S;Parts II and III,Mandible and Condyle Group: B-Co-Go,Me-B-Sim,Mf-Go-Sim,Po-B-Go),Using the corresponding MSP as the mirror plane,a mirror model was established through the "mirror" operation,and the original bone model and the mirrored model were overlapped and compared by 3-Matic Research software,and the results of color graphics and overlap difference data were obtained.Statistical test to analyze the statistical difference between the original model and the mirrored model.Result 1: Taking the whole head skeleton of the maxillofacial region as the research unit,and using N-ANS-PNS,N-ANS-S,and N-Ba-S as the MSP,the overlap between the mirror model and the original model was statistically different(P < 0.05): The differences in the overlapping degrees of the plane NANS-PNS and N-ANS-S groups were significantly lower than those of the plane N-Ba-S group models(all P < 0.05).The plane N-ANS-PNS group has the lowest dispersion 0.06～0.72(mm),the plane N-ANS-S group has the middle dispersion0.08～1.23(mm),and the plane N-Ba-S group has the highest dispersion 0.13～3.34(mm).Result 2: The mandibular bone is the research unit,and the most ideal MSP(plane N-ANS-PNS)in the first part of the results and the MSP constructed from the anatomical Points on the mandibular surface(plane B-Co-Go,Me-B-Sim,Mf-Go-Sim,Po-B-Go)as the mirror plane,after the "mirror" operation of the Mimics software,the difference in the overlap between the mandibular mirror model and the original model was tested by Friedman rank sum test,and there was statistical significance(P = 0.015.P < 0.05).The difference in the overlap of plane 4(Mf-Go-Sim)was significantly lower than that of the whole head ideal MSP(plane N-ANS-PNS)(P = 0.019,P < 0.05).Plane 4(Mf-Go-Sim)and Plane(N-ANS-PNS)serve as mirror planes of the whole maxillofacial skeleton at the same time,and there is statistical significance by t-test analysis(P = 0.013,P <0.05),Plane 4(Mf-Go-Sim)overlap difference was 0.50±0.05(mm),higher than the plane(N-ANS-PNS)overlap difference 0.37±0.04(mm).Result 3: Taking the condyle as the research unit,the degree of overlap between the mirror model generated by the mandibular MSP(plane B-Co-Go,Me-B-Sim,Mf-Go-Sim,Po-B-Go)and the original model was selected.The difference was statistically significant by Friedman rank sum test(P < 0.05): 1)There was a statistical difference between the plane 1/plane 2 data(P = 0.003,P< 0.05),that is,plane 1(B-Co-Go)as the The application effect of the condylar mirror plane was better than that of plane 2(Me-B-Sim);2)There was a statistical difference between plane 1/plane 3 data(P = 0.012,P < 0.05),that is,plane 1(BCo-Go))as the condyle mirror plane is better than plane 3(Mf-Go-Sim);3)There is a statistically significant difference between plane 1/plane 4 data(P =0.001,P < 0.01),that is,plane 1(B-Co-Go)as a condylar mirror plane was significantly better than plane 3(Mf-Go-Sim).Conclusion: 1)There are differences in the results of evaluating the symmetry of the maxillofacial bones based on different MSPs;2)The whole maxillofacial skeleton,mandible and condyle all have their respective ideal MSPs.The ideal MSP of the whole maxillofacial skeleton can’t completely replace the dominant MSP of the maxillofacial partial skeleton;3)Taking the bones of the maxillofacial region as the research unit,the median sagittal plane using the plane N-ANS-PNS as the real MSP has little error,high accuracy and stability;the mandibular bones For the research unit,the plane Mf-Go-Sim is used as the MSP for higher accuracy;for the condyle as the research unit,the plane B-Co-Go is used as the MSP for higher accuracy and stability;4)Digital3D technology can accurately Establishing a three-dimensional head model of maxillofacial skeleton,applying "mirror" technology combined with threedimensional color graphic analysis can effectively and intuitively evaluate the accuracy and authenticity of MSP.