Three-dimensional Finite Element Study Of Mandibular Biomechanics And Rigid Internal Fixation Of Mandibular Fractures

Object:To analyze the stress distribution of the mandible at the condition of central occlusion,labial teeth occlusion,premolar and molar occlusion,and biomechanics of four kinds of fixation of the mandibular fractures with the finite-element method,evaluate the effect of the different fixation methods and so as to provide theoretically direction for the treatment of the mandibular fracture.Methods:Establish the three dimensional finite element models of mandibule,and then analysis the stress distribution of the mandible with the cmputer.Establish the three dimensional finite element models of mandibular fractures and four kinds of rigid internal fixation(RIF)of the mandibular fractures through modifying the three dimensional finite element model of mandible,then to analysis the stress distribution and the mobility of fracture segment in mandibular symphysis,body and angle fractures with four kinds of fixation methods and the different occlusion conditions with the computer,so as to evaluate the effect of four kinds of fixation methods.Result:1 Under the four kinds of occlusal condition there was higher stress value in the region of mandibular angle,condyle neck,coronoid process,simoid notch, alveolar crest and external oblique line;at occlusal side of mandible,compressive stress region,tension stress region and minimum stress region changed,on the other side the minimum stress was at the borderline of the middle and lower 1/3 of the mandible,compressive stress act at the lower border of the mandible and tension stress act at the alveolar border of the mandible.2 When the mandibular symphysis fractures were fixed with biomechanical miniplates,the mobility of the fracture segment under the premolar and molar occlusion is 0.3791944mm and0.175192mm individual.When the mandibular body fractures were fixed with biomechanical miniplates,the mobility of the fracture segment under labial teeth occlusion is 0.3611944 mm,the mobility of the fracture segment is 0.2336944 mm,0.2243583 mm and 1.1647222mm under the molar occlusion of injured side and the molar and premolar occlusion of uninjured side individual.When the mandibular angle fractures were fixed with biomechanical miniplates,the mobility of the fracture segment under occlusion of molar and premolar of uninjured side is 0.17615 mm and 0.384944mm individual.3 When the mandibular body and angle fractures were fixed with two pieces of titanium miniplates,the mobility of the fracture segment under the premolar occlusion of uninjured side is 0.2575917mm;and 0.174578mm individual.4 When the mandibular body and angle fracture fixed with one piece re-establish plate,the mobility of the fracture segment under premolar occlusion of uninjured side is 0.2023444 mm and 0.316389mm individual.5 When the mandibular body and angle fracture were fixed with one piece of miniplate and one piece of re-establish plate,the mobility of the fracture segment under the premolar occlusion of uninjured side is 0.1694333mm and 0.170133mm individual.Conclusion:1 Under the central occlusal condition and the not work side of other occlusal conditions,compressive forces act at the lower border of the mandible and forces of tension act at the alveolar border of the mandible;The minimum stress was at the mandible borderline of the middle and lower 1/3 of the mandilble.But the work side of other occlusal condition,compressive stress region,tension stress region and minimum stress region changed.Under occlusal condition there were higher stress value in the region of the mandibular angle condyle neck,coronoid process,simoid notch,alveolar crest and external oblique line.2 When the mandibular symphysis fracture was fixed with two pieces of biomechanical miniplates,the mobility of the fracture segment under molar and premoalr occlusion was beyong the permission of union of fracture.When the mandibular body fracture were fixed with biomechanical miniplates,the mobility of the fracture segment was beyond the permission of union of fracture under labial teeth occlusion,the molars occlusion of injured and uninjured side and premolar occlusion of uninjured side.When the mandibular angle fracture fixed with biomechanical miniplates,the mobility of the fracture segment was beyond the permission rang of union of fracture,under the premolar and molar occlusion of unjured side.. 3 When the mandibular body and angle fracture fixed with two pieces of titanium miniplates,the mobility of the fracture segment was beyond the permission range of union of fracture under premolar occlusion of uninjured side.4 When the mandibular body and angle fracture fixed with one piece of re-establish plate,the mobility of the fracture segment was beyond the permission range of union of fracture under occlusion of premolar of unj ured side.5 When the mandibular body and angle fracture fixed with one piece of miniplate and one piece of re-establish plate,the mobility of the fracture segment was beyond the permission range of union of fracture under occlusion of premolar of unjured side.6 the mandibular symphysis fracture under premolar occlusion,the mandibular body and angle fracture under the premolar occlusion of uninjured side make great disadvantage to the fracture,the patients should avoid these occlusion conditions.7 When the mandibular symphysis fracture was fixed with two pieces of titanium miniplates,the stress of premolar occlusion should be less than 140N.When the mandibular body and angle fracture fixed with two pieces of titanium miniplates,the stress of premolar occlusion of uninjured side should be less than 60N and 100N individual.8 When the mandibular symphysis fracture was fixed with two pieces of biomechanical miniplates,the stress of premolar occlusion should be less than 40N. When the mandibular body and angle fracture fixed with two pieces of biomechanical miniplates,the stress of premolar occlusion of uninjured side should be less than 20N and 60N individual.9 When the mandibular symphysis fracture was fixed with one piece of re-establish plate,the stress of premolar occlusion should be less than 120N.When the mandibular body and angle fracture fixed with one piece of re-establish plate,the stress of premolar occlusion of uninjured side should be less than 80N and 60N individual.10 When the mandibular symphysis fracture was fixed with one piece of miniplate and one piece of re-establish plate,the stress of premolar occlusion should be less than 200N.When the mandibular body and angle fracture fixed with one piece of miniplate and one piece of re-establish plate,the stress of premolar occlusion of uninjured side should be less than 80N individual.