A Preliminary Study On Dental Implant Restoration And The Repair Mode With Different Bone Density

Objective:Three dimension finite element models were built to study the stress distribution on implant-bone interface and the deviation of displacement of implant in bone with different cortical bone thicken, and investigate the biomechanical properties of implants with different bone density in uncoupled and splinted crown,thus to provide reference for molar restoration in clinics.Materials and Methods:This study built simplified twelve different mandible models.Three-dimension finite element analysis method was used.Two dental implants in the shape of cylinder(4.0×13mm)and/or thread(4.8×10mm)were implanted into the mandibular bone at the position of the first molar and the second molar with differrent cortical bone thickenss.A force load of 100N vertically and a force load of 45N under 45°lingually inclined to occlusal were applied respectedly to study the stress distribution on implant-bone interface and the deviation of displacement of implant.Results:(1)Whether axial loading or oblique loading,both the stress distribution characteristics of implant-bone interfaces of two implant systems were that the stress value was gradually diminished from the implant cervix to the root tip,and the peak Von-Mises stress district of the bone was concentrated on the implant neck.The maximum stress values of various repair modes were all within the normal physiological limits. Maximum Von-mises stress values b＞a+b＞a when different repair modes were used in the same bone.Maximum Von-mises stress valuesⅣ＞Ⅲ＞Ⅱ＞Ⅰwhen the same repair mode was used under different bone density.(2)Whether axial loading or oblique loading,the max-value of displacement of the implant long axis occurred at cortical bone.When the force was loaded vertically,the values of displacement were characterized by diminishing from the implant cervix to the root tip gradually.When the force was loaded obliquely,the same characteristic was observed in the bone of typeⅠ,Ⅱ,Ⅲ,but in the bone of typeⅣ,the values of displacement were increased before diminished.The max-value of displacement after force loaded wasⅣ＞Ⅲ＞Ⅱ＞Ⅰwhen the same repair mode was used under different bone density.The max-values of displacement in the bone of typeⅠ,Ⅱwere all less than 3um.In the bone of typeⅢ,The max-values of displacement by a and a+b were more than 3um,the max-values of displacement were less than 3um by using mode b.(3)When the force was loaded obliquely,Maximum Von-mises stress values on implant-bone interface and the max-values of displacement were both higher compared with loaded vertically.(4)When different repair modes were used in homologous bone,the max-values of displacement by different repair modes were manifested as a＞a+b＞b.Conclusion:1.More attention should be paid to implant restoration when the molar loss occurs in the bone of typeⅢandⅣ.2.Mode uncoupled b is the optimal choice for molar restoration when the molar loss occurs in the bone of typeⅠ,ⅡandⅢ,according to the displacement of the implant.