Abstract:The results of the present study indicate that treatment with tissue-level implants is potentially more advantageous than with bone-level implants for implant-supported fixed prostheses.
“…Distal cantilever designs generally yielded the highest von Mises stresses in implants (111.6 MPa and 88.9 MPa ) in MD-PEKK and MD-Zr models respectively with concentrated stress adjacent to the distal offset extension, while fixed-fixed bridges without offset extensions showed the best biomechanical behavior with equally distributed stress patterns at the implant prosthetic interface and the lowest von Mises stress in implants(56.6 MPa and 48.9 MPa ) in MF-PEKK and MF-Zr models respectively. This might be attributed to the considerable bending moment, hinging effect together with rotational forces especially at the most distal areas [ 19 ].…”
Section: Discussionmentioning
confidence: 99%
“…The prosthesis-abutments assembly was cement-retained (virtual cement gap ) , where abutments are considered perfectly bonded to the prosthesis [ 19 , 33 ]. (Fig.…”
Section: Methodsmentioning
confidence: 99%
“…In literature, a diversity of FEA studies discussed the potential effect of different designs and cantilever extensions on stress distribution. Many authors reported detrimental effects of horizontal cantilever on implants and supporting structures, [ 19 – 21 ] while other limited studies concluded that increasing cantilever length did not cause distinct stress increase, however it might decrease stress values at distally tilted posterior implants and monolithic zirconia framework [ 22 , 23 ].…”
Background
The aim of this study is to evaluate the biomechanical behavior of the mesial and distal off-axial extensions of implant-retained prostheses in the posterior maxilla with different prosthetic materials using finite element analysis (FEA).
Methods
Three dimensional (3D) finite element models with three implant configurations and prosthetic designs (fixed-fixed, mesial cantilever, and distal cantilever) were designed and modelled depending upon cone beam computed tomography (CBCT) images of an intact maxilla of an anonymous patient. Implant prostheses with two materials; Monolithic zirconia (Zr) and polyetherketoneketone (PEKK) were also modeled .The 3D modeling software Mimics Innovation Suite (Mimics 14.0 / 3-matic 7.01; Materialise, Leuven, Belgium) was used. All the models were imported into the FE package Marc/Mentat (ver. 2015; MSC Software, Los Angeles, Calif). Then, individual models were subjected to separate axial loads of 300 N. Von mises stress values were computed for the prostheses, implants, and bone under axial loading.
Results
The highest von Mises stresses in implant (111.6 MPa) and bone (100.0 MPa) were recorded in distal cantilever model with PEKK material, while the lowest values in implant (48.9 MPa) and bone (19.6 MPa) were displayed in fixed fixed model with zirconia material. The distal cantilever model with zirconia material yielded the most elevated levels of von Mises stresses within the prosthesis (105 MPa), while the least stresses in prosthesis (35.4 MPa) were recorded in fixed fixed models with PEKK material.
Conclusions
In the light of this study, the combination of fixed fixed implant prosthesis without cantilever using a rigid zirconia material exhibits better biomechanical behavior and stress distribution around bone and implants. As a prosthetic material, low elastic modulus PEKK transmitted more stress to implants and surrounding bone especially with distal cantilever.
“…Distal cantilever designs generally yielded the highest von Mises stresses in implants (111.6 MPa and 88.9 MPa ) in MD-PEKK and MD-Zr models respectively with concentrated stress adjacent to the distal offset extension, while fixed-fixed bridges without offset extensions showed the best biomechanical behavior with equally distributed stress patterns at the implant prosthetic interface and the lowest von Mises stress in implants(56.6 MPa and 48.9 MPa ) in MF-PEKK and MF-Zr models respectively. This might be attributed to the considerable bending moment, hinging effect together with rotational forces especially at the most distal areas [ 19 ].…”
Section: Discussionmentioning
confidence: 99%
“…The prosthesis-abutments assembly was cement-retained (virtual cement gap ) , where abutments are considered perfectly bonded to the prosthesis [ 19 , 33 ]. (Fig.…”
Section: Methodsmentioning
confidence: 99%
“…In literature, a diversity of FEA studies discussed the potential effect of different designs and cantilever extensions on stress distribution. Many authors reported detrimental effects of horizontal cantilever on implants and supporting structures, [ 19 – 21 ] while other limited studies concluded that increasing cantilever length did not cause distinct stress increase, however it might decrease stress values at distally tilted posterior implants and monolithic zirconia framework [ 22 , 23 ].…”
Background
The aim of this study is to evaluate the biomechanical behavior of the mesial and distal off-axial extensions of implant-retained prostheses in the posterior maxilla with different prosthetic materials using finite element analysis (FEA).
Methods
Three dimensional (3D) finite element models with three implant configurations and prosthetic designs (fixed-fixed, mesial cantilever, and distal cantilever) were designed and modelled depending upon cone beam computed tomography (CBCT) images of an intact maxilla of an anonymous patient. Implant prostheses with two materials; Monolithic zirconia (Zr) and polyetherketoneketone (PEKK) were also modeled .The 3D modeling software Mimics Innovation Suite (Mimics 14.0 / 3-matic 7.01; Materialise, Leuven, Belgium) was used. All the models were imported into the FE package Marc/Mentat (ver. 2015; MSC Software, Los Angeles, Calif). Then, individual models were subjected to separate axial loads of 300 N. Von mises stress values were computed for the prostheses, implants, and bone under axial loading.
Results
The highest von Mises stresses in implant (111.6 MPa) and bone (100.0 MPa) were recorded in distal cantilever model with PEKK material, while the lowest values in implant (48.9 MPa) and bone (19.6 MPa) were displayed in fixed fixed model with zirconia material. The distal cantilever model with zirconia material yielded the most elevated levels of von Mises stresses within the prosthesis (105 MPa), while the least stresses in prosthesis (35.4 MPa) were recorded in fixed fixed models with PEKK material.
Conclusions
In the light of this study, the combination of fixed fixed implant prosthesis without cantilever using a rigid zirconia material exhibits better biomechanical behavior and stress distribution around bone and implants. As a prosthetic material, low elastic modulus PEKK transmitted more stress to implants and surrounding bone especially with distal cantilever.
“…To have a better insight into our experimental results, nite element method was implemented for numerical modeling of the both drilling methods. Finite element analysis is inherently an approximation tool; however, applicable approximations and simpli cations can be employed and still have realistic models in which important aspects of the problem are taken into account [17,18]. Since we knew the chip removal mechanism is identical in 2-dimensional and 3-dimentional models [19], to avoid timeconsuming and expensive simulations, we considered 2-dimensional models [19][20][21].…”
Background: A potential method in drilling of bone is ultrasonic-assisted drilling. In addition, during the drilling of bone, which is common in clinical surgeries, excessive heat generation and drilling force may lead to damages in bone tissue, and thus to failure of implants and fixation screws or delay in healing process. The aim of this study was to appraise efficiency of ultrasonic-assisted drilling in comparison to conventional drilling.Methods: In addition to investigating drilling force and temperature elevation, their effects on arising osteonecrosis and micro-cracks were explored in ultrasonic-assisted and conventional drilling through histopathologic assessment and microscopic imaging. In this regard, three drilling speeds and two drilling feed-rates were considered as drilling variables in the in-vitro experiments. Moreover, numerical modeling gave an insight into temperature distribution during drilling process in the both methods and compared three different vibration amplitudes. Results: Although temperature elevations were lower in the conventional drilling, the ultrasonic-assisted drilling had lesser drilling forces. Furthermore, the latter method had smaller osteonecrosis regions, and did not have micro-cracks in cortical bone and destructions in structure of cancellous bone.Conclusions: The ultrasonic-assisted drilling, which caused lesser damages to the bone tissue in both cortical and cancellous bone, was more comparatively advantageous.
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