| Objectives:The diagnostic obturator was used to explore the feasibility in restoring the same natural and aesthetical facial morphology on the repaired side and the healthy side.The prosthesis was generated by mirroring technology and photosensitive resin as material,and was based on a three-dimensional model of maxillofacial soft and hard tissue reconstructed by CBCT data of patients with left maxillary defects,combined with optical model of upper and lower jaw.Exploratory 3D FEA models including maxillofacial soft and hard tissue,optical model and digital obturator of patients with left maxillary defect were to establish.The stress between the soft tissue and the hard side of the repaired side was compared with that of the healthy side by different sizes and directions loading.The final shape of the polishing surface were determined by the uniform stress distribution and the size on the repaired side which was no more than that of the healthy side.3D FEA provides theoretical basis for subsequent aesthetic analysis and application of this prosthesis in clinical practice.Using the 3D reconstruction analysis software and precise medical mode anthropometry,the craniofacial three-dimensional model of the patient were measured and analyzed in three states of the pre repair defect,wearing the traditional and digital prostheses.To investigate the effect of obturator made on different processes on the facial morphology of patients,further more accurately and objectively verify the feasibility of digital prosthesis to reconstruct the same aesthetic facial morphology of the patients with the same reprosthetic side and the healthy side.Methods:Experiment 1:The three-dimensional models of soft and hard tissue in patients with left upper maxillary defects were reconstructed by CBCT data in Mimics software.The optical model of the upper and lower jaw was obtained by scanning the plaster model with 3 Shape laser scanner.The above two models were matched to get three-dimensional models including residual dentition,defect cavity,bilateral gingiva,mucosa and other soft tissues.The digital diagnostic obturator model was designed in the 3 Shape software by mirroring technology.This prosthesis was made by using VisiJetS300 liquid photosensitive resin as consumables and SLA 3D Systems printer.Finally,the prosthesis was worn in the mouth of the patient.Experiment 2:A three-dimensional finite element model including craniofacial and facial soft and hard tissue,optical model and digital prosthesis was established in ANSYS software.The size and distribution of the von mises stress between the soft tissue and the corresponding healthy side and the prosthetic surface were calculated after vertical and lateral light,medium and severe loading.The healthy side was used as a standard control to ensure that the stress distribution on the repaired side was uniform and the size was no more than that of the healthy side.Experiment 3:Based on the concept of individualized precision medical treatment,the bilateral upper and lower lips and hard tissue morphology of the craniofacial 3D model in the patients with pre repair defect and wearing traditional and digital prosthesis were measured and analyzed by Mimics software.The healthy side was a standard control,when observing the wearing of the prostheses,the maxillofacial morphology of repair side was closer to the healthy side.Results:Experiment 1:Based on CBCT images and maxillary and mandibular plaster models,diagnostic obturator including gingiva,mucosa and other soft tissues were designed and made based on digital three-dimensional reconstruction,scanning technology and SLA principles.After wearing,the patients could restore the same middle face shape as the healthy side.Experiment 2:The accurate three-dimensional finite element model including 3623133 elements and 635849 nodes were obtained,which consists of the soft and hard tissue of patient’s maxillofacial,optical model and digital obturator.In general,the two sides of the model were loaded with different sizes and directions,the results showed that the von mises stress distribution was uniform and the size of the repair side was no more than that of the healthy side.Experiment 3:Compared with the healthy side,the upper and lower lip crest of the defect side inclined to 3.10mm and 2.30mm,the red lip thickened 1.26mm,1.00mm,the upper lip width narrowed 3,10mm,the soft tissue of the lip and buccal fell 4.21mm.After the digital prosthesis was used,the difference between the healthy and repair sides of the upper lip crest,lip thickness and the protrusion of soft tissue were less than 1.00mm,and the lower lip was less than 0.3mm,while the difference of the traditional prosthesis was larger than that of the former.Compared with the healthy side,the distance from each marker to three planes of the digital hard tissue model was no more than 1.00mm,while the traditional obturator difference was 2.03mm.Conclusions:1.Compared with the traditional prosthesis,the patients’maxillofacial morphology of repair side was closer to the healthy side after wearing digital obturator,which shows that the prosthesis could restore the natural and aesthetic facial morphology of the patients;2.The digital prosthetic model is solid foundation for subsequent biomechanical and aesthetic analysis;3.A 3D FEA model with high accuracy and good geometrical similarity is established by ANSYS software.The model containing the maxillofacial soft and hard tissue,optical models and digital obturator supplemented previous the vacancy of FEA without the soft tissue,improved the accuracy of the biomechanical analysis,made the experimental results closer to the objective and more representative,and laid a good foundation for the follow-up finite element analysis;4.Combined with three dimensional measurement and analysis technology and precise medical anthropometry,the face shape of the subjects can measured multidimensional and objectively. |
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