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Cement Interface (cement + interface)
Selected AbstractsAn experimental analogue to model the fibrous tissue layer in cemented hip replacementsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2004Victor Waide Abstract Fibrous tissue at the bone,cement interface of cemented joint replacements has been reported frequently in cases of revisions made necessary by aseptic loosening. This work describes the development of in vitro specimens suitable for biomechanical modeling of cemented femoral hip replacements with a fibrous tissue layer at the bone,cement interface. In particular, a series of uniaxial compression tests were performed on silicone elastomer specimens to identify a suitable analogue with similar mechanical characteristics to those reported for the fibrous tissue layer. A method was developed to apply the silicone elastomer at the bone,cement interface. This was examined for two types of cemented hip replacements implanted in composite femurs. The selected thickness of the elastomer layers was in the range of those found in clinical cases of aseptic loosening. Specimens produced by these methods could be used in preclinical biomechanical tests (such as stability or stress shielding tests) to assess the effects of a soft-tissue layer, to model in vitro a long-term-implant scenario, and to provide validation for similar finite element studies. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 69B: 232,240, 2004 [source] Stress analysis in a post-restored tooth utilizing the finite element methodJOURNAL OF ORAL REHABILITATION, Issue 5 2003M. Toparli summary ,This study utilized the finite element method (FEM) to predict distribution of stresses in dentin of an endodontically treated tooth, restored with cast post and cores. For this investigation an axisymmetric model of a maxillary second pre-molar that included an alveolar bone was analysed. The three tooth models evaluated were Ti,Ti alloy, NiCr,AuPd alloy and Ti,NiCr alloy as post-material and crown material with porcelain. A load of 200 N at an angle of 45° to the longitudinal axis was applied on the occlusal margin of each model. The tooth was assumed isotropic, homogenous and elastic. The author prepared a calculation program using fortran 77. Investigation of the stress distributions was made in five regions; namely bottom of post, top of post, cole, metal,cement interface and metal,porcelain interface. The distributions of radial and axial stresses were plotted with length of radial. [source] Effect of three adhesive primers for a noble metal on the shear bond strengths of three resin cementsJOURNAL OF ORAL REHABILITATION, Issue 1 2001K. Yoshida The purpose of this study was to evaluate the durability and shear bond strengths of the different combinations of three adhesive primers and three resin cements to a silver,palladium,copper,gold (Ag,Pd,Cu,Au) alloy. The adhesive primers Alloy Primer® (AP), Metal PrimerII® (MPII) and Metaltite® (MT), and the resin cements BistiteII® (BRII), Panavia Fluoro Cement® (PFC) and Super-Bond C&B® (SB) were used. Two sizes of casting alloy disks were either non-primed or primed and cemented with each of the three resin cements. The specimens were stored in a 37 °C water bath for 24 h and then immersed alternately in 4 and 60 °C water baths for 1 min each for up to 100 000 thermal cycles. Shear mode testing at a crosshead speed of 0·5 mm/min was then performed. The application of MPII or MT was effective for improving the shear bond strength between each of the three resin cements and the Ag,Pd,Cu,Au alloy compared with non-primed specimens. However, when primed with MPII or MT and cemented with SB, the bond strength at 100 000 thermal cycles was significantly lower than that at thermal cycle 0. When primed with AP, the specimens cemented with BRII or PFC showed lower bond strength than non-primed specimens and failed at the metal,resin cement interface at 100 000 thermal cycles. On the other hand, AP was effective in enhancing the shear bond strength of SB to the Ag,Pd,Cu,Au alloy. The five combined uses of an adhesive metal primer and resin cement (combinations of MPII or MT and BRII or PFC and AP and SB) are applicable to the cementation of prosthodontic restorations without complicated surface modification of the noble alloy. [source] Precooling of the femoral canal enhances shear strength at the cement,prosthesis interface and reduces the polymerization temperatureJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 9 2006Pang-Hsin Hsieh Abstract Preheating of the femoral stem in total hip arthroplasty improves the cement,prosthesis bond by decreasing the interfacial porosity. The main concern, however, is the potential thermal osteonecrosis because of an increased polymerization temperature. In this study, the effects of femoral canal precooling on the characteristics of the cement,stem interface were evaluated in an experimental model for three test conditions: precooling of the femoral canal, preheating of the stem (44°C), and a control in which stems were inserted at room temperature without thermal manipulation of the implant, cement, or bone. Compared to the control group, precooling of the femoral canal and preheating of the stem had similar effects on the cement,stem interface, with greater interfacial shear strength and a reduced porosity. Femoral canal precooling also produced a lower temperature at the cement,bone interface. No difference was found in the ultimate compressive strength of bone cement for the three preparation conditions. Based on this laboratory model, precooling of the femoral canal could improve shear strength and porosity at the stem,cement interface, minimize thermal injury, and maintain the mechanical strength of the cement. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Mechanical characteristics of the bone,graft,cement interface after impaction allograftingJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2005Hanspeter Frei Impaction allografting is an attractive procedure for the treatment of failed total hip replacements. The graft,cement,host bone interface after impaction allografting has not been characterized, although it is a potential site of subsidence for this type of revision total hip reconstruction. In six human cadaveric femurs, the cancellous bone was removed proximally and local diaphyseal lytic defects were simulated. After the impaction grafting procedure, the specimens were sectioned in 6 mm transverse sections and pushout tests were performed. From the adjacent sections the percentage cement contact of the PMMA cement with the endosteal bone surface was determined. The host bone interface mechanical properties varied significantly along the femur largely due to different interface morphologies. The apparent host bone interface shear strength was highest around the lesser trochanter and lowest around the tip of the stem. A significant positive correlation was found between the percentage cement contact and the apparent host bone interface shear strength (r2 = 0.52). The sections failed in 69% of the cases through a pure host bone interface failure without cement or allograft failure, 19% failed with local cement failure, and 12% with a local allograft failure. The apparent host bone interface strength was on average 89% lower than values reported for primary total hip replacements and were similar to cemented revisions proximally and lower distally. This study showed that cement penetration to the endosteal surface enhanced the host bone,graft interface. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source] Clinical and radiological outcomes after revision to the low-contact-stress mobile-bearing total knee arthroplastyANZ JOURNAL OF SURGERY, Issue 5 2009David J. Whitehead Abstract Background:, The aim of the present study was to investigate the short,medium-term clinical and radiological outcomes in revision total knee arthroplasty using a mobile-bearing implant. Methods:, Forty patients (42 knees) who had revisions using the New Jersey low-contact-stress (LCS) mobile-bearing total knee arthroplasty between 1996 and 2000 were reviewed. Results:, The average age at revision was 71 years (range, 38,86 years) and the average follow up was 6 years (range, 5,9 years). Of the 34 patients reviewed clinically, six had excellent results, and 20 had good results, to give a total of 76% excellent or good results. There were five (15%) fair results and three (9%) poor results. Seven patients required revision of the components. There was one case of instability within the first year of revision, which required only exchange of the polyethylene bearing to achieve a satisfactory clinical outcome. Of the 31 knees reviewed radiologically, progressive radiolucent lines were seen at the bone,cement interface in five (16%) of the femoral components and in two (6%) of the tibial components. Conclusion:, Unconstrained LCS mobile-bearing total knee arthroplasty can be used in revision surgery with satisfactory results after medium-term follow up (level of evidence: therapeutic level III). [source] | ||||||||||