| Purpose:1.A three-dimensional finite element method was used to establish the model of mandible containing TMJ after BSSRO with internal fixation,which was the base to study the biomechanics of the mandible and TMJ after BSSRO.2.From the view of biomechanics,observation of the trend of the condyle displacement in two types of split patterns with different amount of advancement under BSSRO.3.In the finite element model,analysis of the changes of condyle in two types of split patterns with same advancement under BSSRO;and in same split pattern with different amount of advancement.In order to improve the clinical operation,and provide the theoretical base to avoid displacement of condyle and articular disc.The research object and methods:Research object: Dry bone of mandible,three-dimensional finite element model of mandible with temporomandibular jointResearch methods and procedures:1.Establishment of the three-dimensional finite element model with temporomandibular joint(1)Selection the intact dry mandible as specimen which had intact anatomic structure of bone and full dentition.(2)CBCT scan was used to get the data of DICOM that combined with three-dimensional finite element model to establish the model directly which contained mandible and TMJ.2.Simulating BSSRO on modelSimulation of BSSRO In the model,cutting the mandible into three parts which contained two proximal segments and a distal segment,then fixed with titanium plates and screws.Type 1 was split in posterior border of the mandibular ramus;and type 2 was split in lingual side near the mylohyoid sulcus.3.Simulation of displacement of osteotomy segmentSimulation of distal segment advanced to correction of mandibular retrognathia with setting boundary constraint and masticatory muscles load.4.Biomechanical analysis and comparison(1)Analysis of the trend of the condyle displacement in same split pattern with different amount of advancement under BSSRO.(2)Analysis of the trend of the condyle displacement in two types of split patterns with same advancement under BSSRO.Result1.The establishment of three-dimensional finite element model of mandible with TMJ which had geometric similarity and similarity of biological,and simulated the BSSRO to advance distal segment.In order to lay the foundation for further research.2.The displacement of different regions of the condyle in different amount of advancement with two types of split patterns was studied.3.There was statistical significance in medial part of condyle(P<0.05)compared the displacement of condyle between advanced distal part 3mm and 8mm with type 1 split.Conclusion1.No matter what type of split was and what amount of distal segment advanced,the trend of condyle displacement was the same: condyle moved counterclockwise and intercondylar angle(ICA)measured as the angle formed by intersection of the medial extensions of the lines through the long axis of each condyle decreased.2.The displacement in medial of condyle was relevant to amount of advancement with type 1 split,the tendency is the variation of medial part of condyle varies largely when amount of advancement increased.(P<0.05).3.The change of condyle displacement was no obvious relevant to amount of advancement with type 2 split(P>0.05). |
