Interradicular Angle And Root Trunk Height Of First Mandibular Molar On Its Immediate Loading After Immediate Implant:a 3-D Finite Element Analysis

Objective: To determine the effect of different root morphology of first mandibular molar on its immediate loading after immediate implant based on the three dimensional(3-D)finite element method.Methods: Two groups of first mandibular molars with different interradicular angle and root trunk height were used to establish the model after immediate implant,and immediate loading of the first mandibular molars were built.The 2 groups of tooth were further divided according to their different interradicular angle(IA)and root trunk height(RT).Load of 100 N was applied to the occlusal surface in 4 different directions,including axial,oblique 45°,lingual,and mesial directions.The displacements of implant and the Von Mises stresses of bone were analyzed with finite element analysis software ANSYS.Results: The 3-D finite element model of immediate loading of first mandibular molar after immediate implant was established successfully.The results of the analysis indicated that with the increase of root separation and the shorter root trunk height,the maximum displacement of the implant and maximum Von Mises stresses of the implant bone interface were in a downward trend.The maximum displacement of the implant reached 0.441 mm when the mesial loading at IA of 10°,and the minimum displacement was only 0.015 mm when the axial loading at IA of 42°in the group of interradicular angle.The maximum displacement of the implant reached 0.520 mm when the mesial loading at RT of 5.3 mm,and the minimum displacement was only 0.016 mm when the axial loading at RT of 1.5mm in the group of root trunk.The stresses concentrated upon the cortical bone of the neck of implant and the weak cancellous bone beside thread.Conclusion: Interradicular angle and root trunk height of mandibular first molar exert certain effects on the formation of osseointegration in the implant.The decrease of available bone in interradicular septa enhances the risk of failure in the immediate loading of mandibular first molar after immediate implant.