Peri-implant bone resorption has been reported around some implants after loading, which could create problems for the peri-implant soft and hard tissues’ long-term stability. The reasons for this are still not known. However, relevant importance could be given to this due to the presence of a bacterial contamination at the micro-gap level between implant and abutment. In this regard, external and internal implant–abutment assemblies have been shown to be much more permeable to bacterial colonization than Cone-Morse or conical connections. The placement of a subcrestal implant could have aesthetic advantages, therefore allowing a better prosthetic emergence profile. In literature, controversial experimental and clinical results have been reported on bone resorption around implants placed equicrestally and subcrestally. Interestingly, Finite Element Analysis (FEA) studies revealed to be extremely useful for assessing the peri-implant bone strain and stress. Thus, this study conducted a FEA evaluation of implants with a Cone-Morse implant–abutment assembly inserted into a bone block model mimicking equicrestal (0 mm) and subcrestal placements (−1 and −2 mm). Results demonstrated that maximum stresses were observed in the cortical bone around equicrestally placed implants, with the lowest in the 2 mm subcrestally placed implant and intermediate stresses within the 1 mm subcrestally placed implant. The cortical bone resulted more stressed under lateral loads than axial loads. In conclusion, this FEA study suggested a subcrestal implant placement ranging between −1 and −2 mm to obtain an adequate peri-implant stress pattern.
The aim of biomechanics applied to implantology is to determine the deformative and tensional states by solving the equilibrium equations within the mandibular bone and the osseointegrated implant to ensure its stability and improve the success rate. The finite element method is a powerful numerical technique that uses computing power to derive approximate solutions for the analysis of components with very complex geometry, loads, materials, and especially the biomechanical problems analysis, which is challenging to find in vivo or in vitro. This study performs a complete FEA survey on 3 implants Cono-in with 3 different diameters 3.4 mm, 4.5 mm, and 5.2 mm with abutments inclined to 15° and evaluates the tensions that are generated in the system as a result of the application of chewing loads. In this study, the extent of the stresses developed in the peri-crestal zone of the implants with the variation of the occlusal overstress acting on them was also evaluated. Autodesk Inventor Nastran Software was used to perform this type of localized finite element analysis; With this type of analysis, it was possible to analyze the peri-crestal area of the implant more precisely through a more accurate reconstruction of the mesh element, which allowed us to solve the FEA solution mathematically. The results showed how the application of the inclined load with respect to the vertical load on a larger diameter system leads to an increase in stress.
The natural distribution of stress in the femur is altered when total hip arthroplasty (THA) is performed. In fact, when a stem is inserted inside the femur, there is a variation in stress due to the difference in rigidity between the material with which the stem is made and the femur. This generates the phenomenon of stress shielding. The aim of this study is to design an optimized prosthesis that guarantees an excellent rotational stability and a reduced stress shielding. Methods: Through the finite element method (FEM), the mechanical behavior of the stem subjected to the loads described by ISO 7206-4:2010 is studied. Results: Through topological optimization, there is a reduction in stress shielding in the proximal zone of 31.46%. The addition of ridges on the dorsal side of the stem also improves rotational stability by 27.82%. Conclusions: The decrease in stiffness that is recorded with the optimized stem guarantees a greater distribution of stress on the bone. The presence of dorsal ridges also favors the corticalization of the bone as it loads the bone near the dorsal, ensuring further stability. The perforated prosthesis presented in this study shows an increase in primary stability and an improvement in rotational stability as there is also a bone regrowth inside the prosthesis.
The natural distribution of stress in the femur is altered when total hip arthroplasty (THA) is performed. In fact, when a stem is inserted inside the femur, there is a variation in stress due to the difference in rigidity between the material with which the stem is made and the femur. This generates the phenomenon of stress-shielding. The aim of this study is to design an optimized prosthesis that guarantees excellent rotational stability and re-duced stress shielding. Methods: through the finite element method (FEM) the mechanical behavior of the stem subjected to the loads described by ISO 7206-4: 2010 is studied. Re-sults: Through topological optimization, there is a reduction in stress shielding in the proximal zone of 31.46%. The addition of ridges on the dorsal side of the stem also im-proves rotational stability by 27.82%. Conclusions: The decrease in stiffness that is rec-orded with the optimized stem, guarantees a greater distribution of stress on the bone. The presence of dorsal ridges also favors the corticalization of the bone as it loads the bone near the dorsal ensuring further stability. The perforated prosthesis presented in this study, shows an increase in primary stability and an improvement in rotational stability. As there is also a bone regrowth inside the prosthesis.
Total Hip Arthroplasty (THA) is a common surgical procedure used to treat hip osteoar-thritis and other joint conditions that cause pain and functional limitation. Traditionally, THA has been most performed in elderly patients, but in recent years there has been an in-crease in hip arthroplasties in young patients. Femoral prosthesis rupture is a rare but sig-nificant complication that can also occur in young patients undergoing total hip arthro-plasty (THA). Some of the factors that can contribute to femoral prosthesis ruptures include abnormal overload, defects in the design lack of geometric fit, type of materials used in the stem and femoral head connection. The aim of this study is to analyze the criticalities in the contact between the femoral head and the stem neck. In particular, the two types of con-tacts will be taken into consideration: proximal and distal and through the finite element method (FEA) the criticalities will be defined. The results show that in the proximal contact the voltages are higher than 500 Mpa. This is due to the fact that there are higher circum-ferential voltages. In addition, to prevent bacterial infiltration or debris from the outside, the distal connection is the recommended one.
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