3-D FEA Of Mandibular First Molar By Two Marginal Design Endocrowns

Objective The purpose of this experiment was to provide a theory basis for clinical practice by establishing two marginal designed first mandibular molar endocrowns with different thickness and height of axial wall,and hence to study the resistance ability and stress distribution through three-dimension finite element analysis.Methods An adult male volunteer was selected with sound tooth.By scanning his maxillofacial region by Cone-beam CT,the first mandibular molar was chosen as object,and 223 images were selected which slice thickness at 0.25 mm.After inputting the images into Mimics software,a preliminary model was established.Then by using the software such as Geomagic Studio and NX,the model was accomplished.Two marginal endocrowns were built with different axial wall thickness(t= 1mm?2mm?3mm)and height(h=2mm?3mm?4mm).Group A was butt joint design,while group B was shoulder surround design(n=18),and both were pressed under a mechanics loading to simulate chewing with a load of 100 N.The two loading directions were paralleling to the long axis of the tooth and 45 degrees to the long axis.Compare the stess distribution,principal maximum stress and equivalent stress by 3-D FEA method under the two loads.Results 1.The models of the first mandibular molar restored by endocrown were built through CBCT and some computer softwares,which could reflect the real oral condition accurately.2.Group A showed the lower equivalent stress than group B at the same thickness and height under the vertical load.3.Under lateral load,group A showed higher root equivalent stress than group B at the same thickness and height of 2mm and 3mm.When the height was 4mm,the consequence was reversed.Conclusions 1.The butt joint marginal endocrown showed higher ability to resist the vertical force than shoulder surrounded endocrown.2.The butt joint marginal endocrown had higher ability to resist lateral force when the axial wall height was 2mm or 3mm.It can be used as the first choice expecting the axial wall was higher than 4mm.