The Feasibility Study On The Treatment Of Dento-maxillofacial Deformities By Surgery-first Approach With Computer Assisted

Objective: To discuss the application of computer-assisted technology associated with traditional model surgery technology in creating a highly simulated dentofacial model with accurate dentition-jaw position relationship and precise dental morphology.And utilize this model to explore the feasibility of model surgery technology guiding surgery-first approach for the treatment of dentofacial deformity.Methods and materials: A human skull specimen with complete dentition was prepared.After three-dimensional spiral CT scan for the specimen,the CT data was downloaded as the form of DICOM and input into the software Pro Plan CMF 3.0(Materialise,Belgium)for 3D modeling and model segmentation.Then the data was imported into a rapid prototyping machine to 3D print/create a resin model(RP model)that was equally proportional to the skull specimen.And then a plaster cast of the upper and lower jaw dentitions for the skull specimen was made.Finally,the plaster cast was combined with the RP model to create a highly simulated dentofacial model using facebow transfer technology.The three-dimensional coordinate system was used in the measurement and comparison of the accuracy of the distances between the corresponding marker points between the skull specimen and the highly simulated dentofacial model.A highly simulated dentofacial model with clinical feasibility was made and model surgery technology was applied,in order to utilize the surgery-first approach to guide the treatment of dentofacial deformity.Results: The eight pairs of data of the distances in three-dimensional direction,between the corresponding marker points,the skull specimen and the highly simulated dentofacial model were compared,and the measured differences were statistically analyzed.For the comparison of the eight pairs of original data,the maximum difference(absolute value)was 0.943,the minimum difference was 0.290,and the average difference(absolute value)was 0.568;the absolute value of the maximum difference between the average values was 0.862 and the minimum difference was 0.296.A total of 2 patients with dentofacial deformity were selected from the Department of Oral and Maxillofacial Surgery,the First Affiliated Hospital of Fujian Medical University and the Department of Oral and Maxillofacial Surgery,School and Hospital of Stomatology,Fujian Medical University during the period of 2016.9-2017.9.The preoperative and postoperative simulations and predictions were performed for the 2 patients by a model surgery technology with a highly simulated dentofacial model,and guide plates were made for the combined treatment from orthognathics to orthodontics with surgery-first approach.The patients' face shape had been significantly improved,and the occlusal relationship has been adjusted smoothly.The patients and their families were very satisfied with the treatment effect.Conclusion: The highly simulated dentofacial model generated by combining the RP model 3D printed by the computer software and the plaster models of the patients' upper and lower jaw dentition can better simulate the positional relationship between the maxillofacial bones and the dentition.The accuracy of highly simulated dentofacial model is sufficient for clinical applications,and the insufficiency of purely digitized software applications such as a lack of physical sensation,inability to perform crash tests,etc.has been improved.On this basis,the treatment plan can be designed more intuitively and reliably,the position of the teeth before and after treatment can be changed,and the postoperative appearance can be predicted,thus a reference can be provided for the preoperative simulation under the surgery-first approach.