The Experts below are selected from a list of 1815 Experts worldwide ranked by ideXlab platform
Michele Nieri - One of the best experts on this subject based on the ideXlab platform.
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Implant prosthetic rehabilitation in partially edentulous patients with Bone Atrophy. An umbrella review based on systematic reviews of randomised controlled trials.
European journal of oral implantology, 2018Co-Authors: Mauro Merli, Marco Moscatelli, Umberto Pagliaro, Giorgia Mariotti, Ilaria Merli, Michele NieriAbstract:PURPOSE To summarise systematic reviews that assess the effects of different interventions for implant prosthetic rehabilitation in partially edentulous patients with the presence of Bone Atrophy. MATERIALS AND METHODS Only systematic reviews of randomised controlled trials (RCTs) dealing with partially edentulous adult patients presenting Bone defects were included. Treatments of interest were Bone augmentation procedures, use of short, tilted or zygomatic implants, sinus lift and transposition of the inferior alveolar nerve. Outcome variables considered were: prosthetic and implant failure, complications, radiological and clinical peri-implant Bone level variation, aesthetic and functional satisfaction, and vestibular peri-implant soft tissue recession. A search of systematic reviews of RCTs selected from MEDLINE, the Cochrane Database of Systematic Review, and the Prospero register published in the past 5 years (May 2012 - May 2017) was performed. Systematic reviews were also manually searched. Independent data extraction by two authors using predefined data fields, including ROBIS risk of bias, was executed. RESULTS A total of 12 systematic reviews of RCTs were identified for inclusion in the overview. Eight reviews were considered at low risk of bias. Short implants (≤ 8 mm) were associated with a notable decrease in complications compared to long implants with Bone augmentation procedures. Many trials compared different sinus lift procedures and different Bone augmentation techniques. None of these indicated that one procedure could reduce prosthetic or implant failures when compared to the other. The use of a membrane can contribute to the regeneration of the hard tissue in horizontal augmentation. Different membranes or Bone substitutes did not give substantially different results. No data are available regarding comparisons involving zygomatic implants or tilted implants or transposition of the alveolar nerve. CONCLUSIONS Overall, the evidence is not sufficiently robust to determine the best treatment for implant prosthetic rehabilitation in partially edentulous patients presenting Bone Atrophy. In terms of vertical defects, if the short implants can be used they should be used because the number of complications are reduced compared to longer implants with sinus lift or Bone augmentation. Nevertheless, caution should be exercised because long-term follow-up studies were not available. No conclusions can be drawn regarding the comparison between different vertical Bone augmentation techniques in atrophic posterior mandible because quantitative meta-analyses were not performed. With regards to horizontal defects, the use of a membrane appears to increase the regeneration of the hard tissue but no differences were detected in prosthesis or implant failures or in complications.
Mitsuo Niinomi - One of the best experts on this subject based on the ideXlab platform.
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Low Modulus Titanium Alloys for Inhibiting Bone Atrophy
Biomaterials Science and Engineering, 2011Co-Authors: Mitsuo NiinomiAbstract:Metallic biomaterials constitute approximately 70% 80% of all implant materials, and thus represent a very important class of biomaterials. Among the various metallic biomaterials such as stainless steels and Co-Cr alloys, titanium and its alloys exhibit the best biocompatibility. Consequantly, titanium and its alloys have been the fucus of attension for biomedical materials, especially for use in load bearing implants such as artificial hip joints, Bone plates and screws, spinal instruments, and dental implants. The Young’s moduli of metallic biomaterials are generally much higher than that of the human cortical Bone (hereafter, Bone) (Niinomi, 2002a). If the Young’s modulus of a load bearing implant made of metallic biomaterials is higher than that of the cortical Bone, Bone Atrophy occurs because of the stress shielding between the implant and Bone (Sumitomo, 2008). Stress shielding causes loosening of the implants such as artificial joints or Bone re-fracture after extraction of the implants. Therefore, the Young’s modulus of the metallic biomaterials must be equal to that of the natural Bone. Titanium and its alloys possess lower Young’s moduli than those of other mettalic biomaterials such as stainless steels and Co-Cr alloys. -type titanium alloys, in particular, having a single phase exhibit much smaller Young’s moduli compared with and ( + -type titanium alloys (Niinomi, 2002b). As such, the -type titanium alloys are particulary promissing for biomedical applications. A number of -type titanium alloys composed of non-toxic and non-allergic elements with low Young’s modulus have been developed and even more are currently under development (Niinomi, 2011a). Much of the current research in the biomaterials field has been directed at lowering the Young’s modulus of the -type titanium alloys for biomedical applications. The mechanical biocompatibility factors such as fatigue strength, fretting fatigue strength, tensile properties, wear resistance, fracture toughness, etc., including the Young’s modulus are very important factors for the practical application of the allloys in biomaterials as well as the biological biocompatibilities (Niinomi, 2008a). Among the mechanical biocompatibility factors, the endurance, i.e., the fatigue strength is one of the most important factors (Niinomi, 20007). The development of metallic biomaterials with improved fatigue strength and a simaltaneously low Young’s modulus is desirable for biomedical applications. The effect of the Young’s modulus of the metallic implant should be clarified by animal experiments prior to medical applications, and recently, these kinds of studies have begun to be implemented (Niinomi, 2002b).
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titanium based biomaterials for preventing stress shielding between implant devices and Bone
International Journal of Biomaterials, 2011Co-Authors: Mitsuo Niinomi, Masaaki NakaiAbstract:β-type titanium alloys with low Young's modulus are required to inhibit Bone Atrophy and enhance Bone remodeling for implants used to substitute failed hard tissue. At the same time, these titanium alloys are required to have high static and dynamic strength. On the other hand, metallic biomaterials with variable Young's modulus are required to satisfy the needs of both patients and surgeons, namely, low and high Young's moduli, respectively. In this paper, we have discussed effective methods to improve the static and dynamic strength while maintaining low Young's modulus for β-type titanium alloys used in biomedical applications. Then, the advantage of low Young's modulus of β-type titanium alloys in biomedical applications has been discussed from the perspective of inhibiting Bone Atrophy and enhancing Bone remodeling. Further, we have discussed the development of β-type titanium alloys with a self-adjusting Young's modulus for use in removable implants.
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effect of young s modulus in metallic implants on Atrophy and Bone remodeling
2010Co-Authors: Mitsuo Niinomi, Tomokazu HattoriAbstract:The Young’s modulus equal to that of the cortical Bone can be achieved at the direction of a single crystal of Ti–29Nb–13Ta–4.6Zr (TNTZ). The fatigue life of TNTZ can be sufficiently improved by keeping its Young’s modulus low enough by short-time aging after severe cold rolling. Silane coupling treatment highly improves the strength of porous titanium and poly(methyl methacrylate) composite by keeping its Young’s modulus just equal to that of the cortical Bone. TNTZ with low Young’s modulus inhibits the Bone Atrophy and enhances Bone remodeling.
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experiment study on fracture fixation with low rigidity titanium alloy plate fixation of tibia fracture model in rabbit
Journal of Materials Science: Materials in Medicine, 2008Co-Authors: Nozomu Sumitomo, K Noritake, Tomokazu Hattori, Keizo Morikawa, Sigeo Niwa, Keiji Sato, Mitsuo NiinomiAbstract:In order to investigate Bone tissue reaction to the low rigidity titanium alloy of TNTZ in Bone plate fixation, animal experiment with rabbit was performed with X-ray follow-up and histological observation. Experimental fractures were made in rabbit tibiae, and fixed by different Bone plates of SUS316L, Ti–6Al–4V and TNTZ. Although there was no significant difference in fracture healing, Bone Atrophy was observed in cortical Bone especially under the Bone plate, which was different in time course among three materials. The Bone Atrophy under the Bone plate was confirmed as porous or poor Bone tissue in histological observation. In addition, the diameter of the tibia Bone was increased in TNTZ as the result of Bone remodeling with a new cortical Bone. It is confirmed that the elastic modulus of the Bone plate will naturally influence Bone tissue reaction to the Bone plate fixation according to the Wolff’s law of functional restoration.
Mauro Merli - One of the best experts on this subject based on the ideXlab platform.
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Implant prosthetic rehabilitation in partially edentulous patients with Bone Atrophy. An umbrella review based on systematic reviews of randomised controlled trials.
European journal of oral implantology, 2018Co-Authors: Mauro Merli, Marco Moscatelli, Umberto Pagliaro, Giorgia Mariotti, Ilaria Merli, Michele NieriAbstract:PURPOSE To summarise systematic reviews that assess the effects of different interventions for implant prosthetic rehabilitation in partially edentulous patients with the presence of Bone Atrophy. MATERIALS AND METHODS Only systematic reviews of randomised controlled trials (RCTs) dealing with partially edentulous adult patients presenting Bone defects were included. Treatments of interest were Bone augmentation procedures, use of short, tilted or zygomatic implants, sinus lift and transposition of the inferior alveolar nerve. Outcome variables considered were: prosthetic and implant failure, complications, radiological and clinical peri-implant Bone level variation, aesthetic and functional satisfaction, and vestibular peri-implant soft tissue recession. A search of systematic reviews of RCTs selected from MEDLINE, the Cochrane Database of Systematic Review, and the Prospero register published in the past 5 years (May 2012 - May 2017) was performed. Systematic reviews were also manually searched. Independent data extraction by two authors using predefined data fields, including ROBIS risk of bias, was executed. RESULTS A total of 12 systematic reviews of RCTs were identified for inclusion in the overview. Eight reviews were considered at low risk of bias. Short implants (≤ 8 mm) were associated with a notable decrease in complications compared to long implants with Bone augmentation procedures. Many trials compared different sinus lift procedures and different Bone augmentation techniques. None of these indicated that one procedure could reduce prosthetic or implant failures when compared to the other. The use of a membrane can contribute to the regeneration of the hard tissue in horizontal augmentation. Different membranes or Bone substitutes did not give substantially different results. No data are available regarding comparisons involving zygomatic implants or tilted implants or transposition of the alveolar nerve. CONCLUSIONS Overall, the evidence is not sufficiently robust to determine the best treatment for implant prosthetic rehabilitation in partially edentulous patients presenting Bone Atrophy. In terms of vertical defects, if the short implants can be used they should be used because the number of complications are reduced compared to longer implants with sinus lift or Bone augmentation. Nevertheless, caution should be exercised because long-term follow-up studies were not available. No conclusions can be drawn regarding the comparison between different vertical Bone augmentation techniques in atrophic posterior mandible because quantitative meta-analyses were not performed. With regards to horizontal defects, the use of a membrane appears to increase the regeneration of the hard tissue but no differences were detected in prosthesis or implant failures or in complications.
Peter Rüegsegger - One of the best experts on this subject based on the ideXlab platform.
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Mechanical consequences of different scenarios for simulated Bone Atrophy and recovery in the distal radius
Bone, 2003Co-Authors: W. Pistoia, Van B Bert Rietbergen, Peter RüegseggerAbstract:Metabolic Bone diseases such as osteoporosis usually cause a decrease in Bone mass and a deterioration of Bone microarchitecture leading to a decline in Bone strength. Methods to predict Bone strength in patients are currently based on Bone mass only. It has been suggested that an improved prediction of Bone strength might be possible if structural changes are taken into account as well. In this study we evaluated which structural parameters (other than Bone mass) are the best predictors for changes in Bone mechanical properties of the human radius after different Bone Atrophy scenarios and whether the original strength of the affected Bone can be recovered if Bone loss is restored by thickening of the remaining structures. To answer these questions, a human radius was measured with a microcomputer tomography scanner to extract the full three-dimensional architecture of the distal radius at an isotropic resolution of 80 microm. Eight models with modified Bone architecture were created and the mechanical variations due to these modifications were studied using microfinite element (micro-FE) simulations. In four models mass was lowered by 20%, either by reducing cortical thickness, trabecular thickness, or number of trabeculae or by overall thinning of structures. In the other four models Bone mass was restored to the original value using a trabecular Bone thickening procedure. The micro-FE analyses revealed that most load was carried by the cortical Bone. For this reason, Bone strength was affected most in the reduced cortical thickness model. For the same reason, the trabecular Bone Atrophy scenarios, all of which affected Bone strength in a very similar way, resulted in less dramatic Bone strength reduction. The restoration of Bone mass did not recover the original Bone strength. These findings demonstrate that the importance of different parameters for the prediction of Bone strength also depends on the mechanical loading. This could explain why results of earlier studies on the importance of structural parameters can be inconsistent and site-dependent.
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Analysis of mechanical properties of cancellous Bone under conditions of simulated Bone Atrophy
Journal of biomechanics, 1996Co-Authors: Ralph Müller, Peter RüegseggerAbstract:Abstract The mechanical properties of cancellous Bone have been shown to depend on Bone density and on the anisotropy of the trabecular Bone structure. By means of high-resolution quantitative computed tomography (QCT), providing a nominal resolution of 0.17 mm, it became possible to assess both apparent density and trabecular microstructure of intact Bones. In order to study the influence of age- and disease-related Bone loss on the mechanical properties of cancellous Bone, a more phenomenological approach was used to develop a novel Bone resorption algorithm, called simulated Bone Atrophy. The algorithm, which is principlally based on constrained Gauss filtration of segmented data volumes, was applied to create derived microstructural models. The mechanical behavior of the cancellous Bone can be expressed as a function of the anisotropic Bone properties of the microstructural model on the continuum level. To study the influence of Bone Atrophy on Bone strength we compared three models: the originally noninvasively measured Bone biopsy and two derived models simulating moderate and pronounced Atrophy. For the comparison of the three models, the apparent Young's moduli in the three orthogonal directions were predicted for each model with the help of three-dimensional finite-element analysis. Realistic results for the apparent Young's moduli were found for the tissue moduli chosen. The results siggest that the prediction of anisotropic material properties of cancellous Bone based on noninvasive measurements of trabecular microstructures and the application of simulated Bone Atrophy may be helpful to understand the influence of age- and disease-related Bone loss on Bone strength.
Adolph V. Lombardi - One of the best experts on this subject based on the ideXlab platform.
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Tapered design for the cementless total hip arthroplasty femoral component
Clinical orthopaedics and related research, 1997Co-Authors: Thomas H. Mallory, William C. Head, Adolph V. LombardiAbstract:The long-term behavior of total hip arthroplasty ultimately is determined by adaptive Bone remodeling. Stress adaptation creating various degrees of metaphyseal Bone Atrophy has occurred with prostheses designed for tight distal fit and fill. This phenomenon has been explained as Bone adaptation resolving the conflict between femoral component stiffness and Bone flexibility. However, clinical observations indicate that a different premise may be operational when prostheses with tapered geometries are used. The results of four published reports (748 arthroplasties) using cementless femoral components of a tapered design were reviewed. The review found a low incidence of aseptic loosening (0.5%) and significant thigh pain (0.5%), and a radiographic incidence of proximal Bone Atrophy of 6%. In no case was the metaphyseal Bone Atrophy described as severe or extensive. These findings challenge the premise that reactive Bone adaptation is related to the issues of femoral component stiffness exclusively and propose that femoral component geometry may have an influence on Bone adaptation.