Three-Dimensional Finite Element Analysis Of Stress Distribution In Different Crown To Implant Ratio Of Short-Length Implants In Moderately Atrophic Maxillary Sinus Region

Objective:. The purpose of this study was to investigate the biomechanical feasibility in different crown to implant ratio (C/IR) of a short implant when the short implant placed in a moderately atrophic maxillary sinus region for repairing a first molar by using three-dimensional finite element method.Methods:(1)According to the different C/IR(1:1、1.5:1、2:1、2.5:1、3:1)and different density of cancellous bone establish 5 3-D finite element models of maxillary sinus and maxillary molar region which contains BICONΦ 6x5.7mm implants by UG NX 8.5 software. The maxillary sinus and maxillary molar region was divided into three parts. They were graft bone, cortical bone and cancellous bone. (2) A functional loading force of 150 N was applied to the occlusal node at the center top surface of the superstructure. A defined force of 50 N inclined to the posterior by 45° relative to the implant axis.(3) Evaluate the maximum Von-Mises in implants and maxillary sinus and maxillary molar region by using ANSYS WORKBENCH 16.1 software.Results:(1) With the vertical load, the stress-distribution of the 5 models were basically same. The maximum Von-Mises of the implant appeared at the neck of the implant. And The maximum Von-Mises of maxillary molar region appeared at the crest cortical bone.With the increasing of the C/IR, the maximum Von-Mises of the Models changes little. So do the density of the cancellous bone.(2) With the oblique load, the maximum Von-Mises of the implant appeared mostly at the one side of the implant. And the maximum Von-Mises of maxillary molar region appeared at the one side of the crest cortical bone.The maximum value of Von-Mises stress in implant and cortical bone increased significantly in each model with the C/IR increasing. But the maximum value of Von-Mises stress in cancellous bone decreased in each model with the decreasing of the density of cancellous bone.Conclusion:It is feasible for using a short implant in maxillary sinus lift. With the oblique load, the C/IR had a significantly influence to the implant and the density of the cancellous bone also had a bad effect to the stress-distribution. These phenomenon may lead to the break of the implant and the lost of the bone level. In That way, we should reduce the buccolingual width and the cusp of the crown when we confronted with a patient who has a longer C/IR and poor dental bone.