scholarly journals Effect of crown-to-implant ratio and crown height space on marginal bone stress: a finite element analysis

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
José Joaquim da Rocha Ferreira ◽  
Luís Filipe Meira Machado ◽  
José Manuel Oliveira ◽  
João Carlos Tomás Ramos
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Reference Model ◽  
Stress Generation ◽  
P Value ◽  
Crown Height ◽  
Element Analysis ◽  
Bone Stress ◽  
Bone Level ◽  
Marginal Bone Level

Abstract Background Crown-to-implant ratio and crown height space, associated with the use of short implants, have been related with marginal bone loss. However, it is unclear which of the two entities would play the most important role on the bone remodelling process. Using a finite element analysis, the present work aims to help clarifying how those two factors contribute for the stress generation at the marginal bone level. A numerical model (reference model), with a crown-to-implant ratio of 4, was double validated and submitted to a numerical calculation. Then, it was modified in two different ways: (a) by decreasing the prosthetic height obtaining crown-to-implant ratios of 3, 2.5 and 2 and (b) by increasing the implants length obtaining a crown-to-implant ratio of 2.08. The new models were also submitted to numerical calculations. Results The reference model showed a marginal bone stress of 96.9 MPa. The increase in the implants’ length did not show statistically significant differences in the marginal bone stress (p-value = 0.2364). The decrease in the prosthetic height was accompanied with a statistically significant decrease in the marginal bone stresses (p-value = 2.2e− 16). Conclusions The results represent a paradigm change as the crown height space appears to be more responsible for marginal bone stress than the high crown-to-implant ratios or the implants’ length. New prosthetic designs should be attempted to decrease the stress generated at the marginal bone level.

Failure analysis of simple overlap bonding joints and numerical investigation of the adhered tip geometry effect on the joint strength

2021 ◽  
Vol 63 (11) ◽  
pp. 1007-1011
Author(s):  
İsmail Saraç
Keyword(s):  
Finite Element Analysis ◽  
Experimental Study ◽  
Finite Element ◽  
Reference Model ◽  
Lap Joints ◽  
Shear Stresses ◽  
Element Analysis ◽  
Single Lap Joints ◽  
Failure Loads ◽  
Previous Experimental Study

Abstract This study was carried out in two stages. In the first step, a numerical study was performed to verify the previous experimental study. In accordance with the previous experimental study data, single lap joints models were created using the ANSYS finite element analysis program. Then, nonlinear stress and failure analyses were performed by applying the failure loads obtained in the experimental study. The maximum stress theory was used to find finite element failure loads of the single lap joints models. As a result of the finite element analysis, an approximate 80 % agreement was found between experimental and numerical results. In the second step of the study, in order to increase the bond strength, different overlap end geometry models were produced and peel and shear stresses in the adhesive layer were compared according to the reference model. As a result of the analyses, significant strength increases were calculated according to the reference model. The strength increase in model 3 and model 5 was found to be 80 % and 67 %, respectively, relative to the reference model.

Improvement and FEA of New Type of Osteointegrated Implant for Higher Amputated Leg Attachment

2007 ◽  
Vol 342-343 ◽  
pp. 829-832
Author(s):  
J.M. Luo ◽  
L. Zheng ◽  
X.H. Shi ◽  
Yao Wu ◽  
Xing Dong Zhang
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Distal Part ◽  
Element Analysis ◽  
Bone Stress ◽  
Traditional Design ◽  
Maximal Stress ◽  
New Type ◽  
Scan Data ◽  
Leg Prosthesis

Stress concentration is one of the main mechanical problems leading to the failure of clinical application for osteointegrated implant of percutaneous osteointegrated prosthesis, which is especially marked for higher amputated leg prosthesis. Traditionally design was composed of only the distal part. To improve the biomechanical safety, a new design with the lag part similar to the lag screw was introduced. Based on CT scan data, relatively accurate model of femur for finite element analysis (FEA) were obtained. The FEA results with the new implant demonstrated that compared to traditional design, the declination of bone stress peak ranged from 15.68% to 28.67%, perpendicular deformation from 34.73% to 72.16%, and maximal stress of implant from 14.51% to 23.36% with the increasing of loads from 3750N to 2000N. So the new design of osteointegrated implant would be more secure mechanically, in the case of higher amputated leg attachment.

Finite element analysis of calibration factors for the modified incremental strain method

2003 ◽  
Vol 38 (1) ◽  
pp. 45-51 ◽  
Author(s):  
B-W Hwang ◽  
C-M Suh ◽  
S-H Kim
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Boundary Conditions ◽  
Reference Model ◽  
Strain Relaxation ◽  
Hole Drilling ◽  
Element Analysis ◽  
Bending Load ◽  
Incremental Strain ◽  
Strain Method

To modify the incremental strain method used to evaluate non-uniform residual stress, a finite element analysis (FEA) of the reference model used to describe a hole-drilling test was conducted. The calibration factors for the x and y directions were obtained from the analysis and then their differences were compared under various loading conditions. A hole-drilling test using a steel plate as the reference specimen was introduced, and under the pure bending load, strain relaxation was measured at each hole-drilling step to determine the calibration factors. Although the calibration factors in the x and y directions varied with the boundary conditions used in the FEA, their differences were reduced to zero for all depths when the prescribed loads as the boundary conditions in the x and y directions became the same. In addition, it was analytically and experimentally confirmed that the calibration factors did not vary with the direction. Accordingly, by making the calibration factors equal in the x and y directions in the modified equation for the incremental strain method, no singularity is produced in the stress calculations.

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