The Effect Of Bone Condition And Implant Size On The Stress Distribution Of Short Implants With Different Osseointegration Rates:A Finite Element Analysis

Objective: Using three-dimensional finite element analysis method to simulate four osseointegration rates and establish an anisotropic jaw bone model,the effect of bone condition and implant size on the stress distribution of short implants with different osseointegration rates was investigated to provide some reference for the clinical application of short implants from the perspective of biomechanics.Experiment One: Effect of bone condition on stress distribution in anisotropic bone with short implants of different osseointegration rates.Materials and methods: Using Solidworks 2019 3D modeling software,an anisotropic jaw model representing three bone conditions Ⅱ,Ⅲ and IV and a 4.1 mm × 6 mm implant model were created to simulate four osseointegration rates of 25%,50%,75% and 100%.A force of 200 N vertically downward and 100 N at an inclination of 45° was applied to the center of the implant abutment,respectively.Setting the ultimate stress of the cortical bone and the yield strength of the implant.The maximum Von mises stress in the implant and jaw bone,the safety of cortical bone and implants,the maximum strain in the cancellous bone,the maximum principal stress in the jaw bone,the minimum principal stress in the jaw bone,the maximum shear stress in the jaw bone,and the maximum displacement of the implant were analyzed in abaqus2020 finite element software.Results: 1.The laws of variation of maximum Von mises stress,maximum principal stress,minimum principal stress,and maximum shear stress in cortical bone with bone condition were Type IV bone > Type Ⅲ bone > Type Ⅱ bone,and the laws of variation with osseointegration rate were 100% > 75% > 50% > 25%.2.Under vertical loading,the cortical bone ultimate stress was not exceeded at ≥25% osseointegration rate for type Ⅱ bone,≥50% osseointegration rate for type Ⅲ bone,and 100% osseointegration rate for type IV bone;under inclined loading,the cortical bone ultimate stress was not exceeded at ≥50% osseointegration rate for type Ⅱ bone and 100% osseointegration rate for type Ⅲ bone,and the cortical bone ultimate stress was exceeded even at 100% osseointegration rate for type IV bone.3.The maximum Von mises stress of the implant increases with the deterioration of bone condition and the increase of osseointegration rate,but does not exceed its yield strength.4.The maximum strain of cancellous bone and the maximum displacement of implant decreased with the increase of osseointegration rate,and increased with the deterioration of bone condition.5.The stress of cortical bone increased under oblique load.Experiment Two: Effect of implant diameter and length on stress distribution in anisotropic bone with short implants of different osseointegration rates.Materials and methods: Using Solidworks 2019 3D modeling software,an anisotropic jaw bone model representing type Ⅲ bone and implant models with diameters of 4.1 mm,4.8 mm,and lengths of 6 mm,8 mm,and 10 mm were created respectively,and four osseointegration rates of 25%,50%,75%,and 100% were simulated.The loading method and data analysis were the same as in Experiment one.Results: 1.The maximum Von mises stress in cortical bone decreases with the increase of implant diameter and length.Under vertical loading,increasing the length decreased the cortical bone stress more;under tilt loading,increasing the diameter decreased the cortical bone stress more.2.Under vertical loading,all implant models did not exceed the cortical bone ultimate stress when the osseointegration rate was ≥50%,and the4.8mm×10mm implant did not exceed the cortical bone ultimate stress even when the osseointegration rate was 25%;under inclined loading,the 4.1mm×6mm implant did not exceed the cortical bone ultimate stress when the osseointegration rate was 100%,while other implant models did not exceed the cortical bone ultimate stress when the osseointegration rate was ≥75%.3.The maximum principal stress,minimum principal stress,and maximum shear stress of cortical bone decreased with increasing the length and diameter of the implant,but the maximum principal stress increased when the length of the implant increased from 8 mm to 10 mm under tilt loading.4.The strain on cancellous bone and the maximum displacement of the implant became smaller with increasing implant length and diameter,and decreased with increasing osseointegration rate.5.The stress on cortical bone increased under tilt loading.Conclusions: 1.The maximum stress on the cortical bone becomes higher as the bone condition deteriorates.4.1 mm x 6 mm short implants are safer in type Ⅱ bone with ≥ 50%osseointegration and in type Ⅲ bone with 100% osseointegration,and are not recommended for use in type IV bone.2.The osseointegration rate affects the stress distribution of the bone around the implant.The maximum stress in cortical bone increases with increasing osseointegration rate.The higher osseointegration rate of the implant,without exceeding the ultimate stress of the cortical bone,reduces cancellous bone strain and implant displacement,which facilitates the stability of the implant.3.Diameter and length affect the stress distribution at the implant bone interface.The cortical bone stresses decrease with increasing diameter and length.In Type Ⅲ bone,4.1mm × 6 mm short implants are safer at 100% osseointegration,and 4.1 mm × 8 mm,4.8mm × 6 mm,and 4.8 mm × 8 mm short implants are safer at ≥75% osseointegration.