Search

The effect of hybrid micro fillers on two body abrasive wear of PA66/PA6 blend based composites was investigated. Three composites: Blend (PA66/PA6) (80/20 wt%), Blend/10 wt% PTFE and Blend/10 wt% PTFE/5 wt% MoS2 were considered for the investigation. These micro composites were prepared by using melt mix method using twin screw extrusion technique. The two-body abrasion wear behavior of these micro composites was investigated using 180 grit SiC abrasion paper in a multipass condition as per ASTM G99 standard under the influence of variable abrasion load at a constant velocity of 0.5 m/s. It is found from the experimentation that the volumetric wear loss is totally dependent on abrading load. Further, it is found that Blend/PTFE composites exhibited good abrasion wear behaviour due to excellent Ratner-Lancaster (σe) factor. Micro ploughing and micro cutting were noticed during the morphological study through SEM images. Among the micro composites studied, Blend/10 wt% PTFE exhibited better abrasive wear resistance compared to other composites.

Background There is a paucity of data on the long-term performance of highly cross-linked polyethylene (HXLPE). Therefore, this study evaluated 10-year 1) functional, 2) radiographic, and 3) surgical outcomes in patients who underwent total hip arthroplasty with sequentially irradiated and annealed HXLPE. Methods A retrospective, multicenter study was conducted on patients who underwent primary total hip arthroplasty and received HXLPE polymer (n = 151). Two-dimensional radiographic linear and volumetric wear analyses were quantified using the Martell Hip Analysis software, while functional outcomes were assessed by analyzing postoperative Short-Form-12 (SF-12) Physical and Mental Health Surveys and Harris Hip Scores. Radiographic outcomes included yearly linear (mm/y) and volumetric (mm3/y) wear rates. Surgical outcomes included additional operations and survivorship. Results SF-12 scores were within 1 standard deviation (SD) of the normal population (SF-12 Physical: 47.0; SF-12 Mental: 52.0), while the Harris Hip Scores of 89.5 was borderline between “good” and “excellent.” Total and annual linear wear rates were 0.164 mm (SD: 0.199 mm) and 0.015 mm/y (SD: 0.018 mm/y), respectively. The mean total volumetric wear rate was 141.4 mm3 (SD: 165.0) and 12.6 mm3/y (SD: 14.9 mm3/y) when broken down into a yearly rate. Eleven patients required revisions, resulting in an all-cause polyethylene survivorship of 92.7%, with a polyethylene wear survivorship of 100.0%. Conclusions Our results demonstrate clinically undetectable linear and volumetric wear rates after 10 years in those who received the unique sequentially irradiated and annealed HXLPE. Furthermore, high rates of survivorship coupled with low all-cause revision rates illustrate the polymers' capability to potentially increase implant longevity.

In this article, the methodology of using probabilistic models of the grinding tool wear process is presented. Probabilistic modeling with empirical data allowed determining the values of other important process features. Among them, the distribution of active grains lifetime or distribution of cumulative attritious wear of the grinding grain apex could be distinguished. The results of modeling and wear analysis of grinding wheels as well as experimental results on peripheral grinding with zoned grinding wheels are presented. The analyzed grinding wheels consisted of three layers: two identical external layers with conventional structure and one internal layer containing the addition of abrasive aggregates. The external layers were profiled by chamfering the edges. As a result, their nominal surfaces were conical. The internal layer had a cylindrical shape and was designed for smoothing the surface after machining with external part. The tools were designed to increase the grinding efficiency and hence a good quality of machined surfaces could be acquired. For the experimental tests, the Ti6Al4V titanium alloy was used. It was found that the change in the shape and position of the grinding zone, as a result of volumetric wheel wear, caused a significant change in fracturing intensity. In the case of multilayer grinding tools, the wear process depends on the physical properties of each layer and their participation during machining of the workpiece. The presented methodology could be applied to a study on the machining process stages, which concerns temporary states and their variability according to the machining time.This makes it possible to reduce the cost of developing new tools dedicated to specific applications.

Oxidized zirconium (OxZr) femoral heads were developed to emulate the superior wear and scratch properties of ceramics while eliminating their unwanted tendency for brittle fracturing. Studies using OxZr have demonstrated reduced linear and volumetric wear of polyethylene (PE) liners when compared with cobalt chrome, ceramic, and steel femoral heads. The purpose of this systematic review was to determine the difference in revision rates, radiologically determined linear wear rates, and patient-reported outcomes among OxZr and alternative bearing materials. Following the Preferred Reporting Items for Systematic Review and Meta-Analysis protocols, a systematic review of published literature through April 24, 2018 was conducted. Among the 862 cases included at a mean weighted follow-up of 4.78 years, the revision THA rate and patient-reported outcomes were similar among OxZr and alternative bearing materials. One of the five studies demonstrated significantly lower linear wear rates in the OxZr group when paired with ultrahigh molecular-weight PE (OxZr 0.03 mm/y vs. stainless-steel 0.11 mm/y; p

Risky gait activities lead to severe wear in orthopaedic implants during postoperative periods. The aim of the present study is to predict the linear and volumetric wear of zirconia (ZrO2) vs alumina (Al2O3) hip implants subject to risky and normal gait activities. Initially, the gait loads pertaining to risky gait activities were converted to equivalent normal loads. Then using the computed normal loads, friction and wear coefficients of ZrO2 ball against Al2O3 disc were calculated from Pin-on-Disc (POD) tribometer under dry and lubricating conditions. Saline solution, a bio-lubricant was utilized for lubrication purpose to mimic synovial fluid properties. Nineteen gait activities stair ascending or descending, carrying load, lifting load and ladder up or down etc., grouped as A, B, C and D were used to determine friction and wear coefficients. Finite Element Method (FEM) was employed to predict the wear of the bearing couple. The developed contact pressure for these gait activities was then utilized to compute linear and volumetric wear for 2 million cycles. Our findings suggests that, patients regularly involved in group C and D type gait activities were likely to cause more wear which may accelerate early implant failure. Refereed/Peer-reviewed

ZrN coatings were formed by magnetron sputtering at various rates of nitrogen flow in the reaction chamber: 3, 4, 5, and 6 cm3/min. The thickness of the ZrN coatings was approximately 3 μm. Using atomic force microscopy (AFM), we studied the surface morphology; roughness; coefficient of friction Сfr; specific volumetric wear ω of ZrN coatings with the construction of Сfr dependencies on the number of scan cycles; and specific volumetric wear on load, probe speed, number of scan cycles. It was found that the coating obtained at a nitrogen flow rate of 3 cm3/min has the lowest values of Сfr and ω.

Objectives The objective of this study is to test the wear of dual-cured bulkfill and flowable bulkfill composites. Materials and methods Six dual-cured bulkfill composites, Cention, Cention-Exp, Activa, Fill-up, Hyperfil Injectafill, and two flowable bulkfill composites Tetric Evoflow BulkFill and G-aenial Universal Flo were tested in this study (n = 8). Each composite was applied into an aluminum sample holder and cured with a Valo Grand (1230 mW/cm2 ) or self-cured according to manufacturer's recommendations, and stored in water for 3 weeks. The samples were subjected to 120 000 load cycles of 49 N (CS-4) against spherical steatite antagonists and simultaneously subjected to 4440 thermocycles (5°C-55°C). At intervals between load cycles, polyvinyl siloxane impressions were taken and scanned with a True Definition Laser Scanner. The volumetric wear was calculated using image software (Geomagic). Microscopic images of selected wear facets and their corresponding worn antagonists were obtained using SEM. All data were analyzed using analysis of variance (ANOVA) and Tukey post hoc test for multiple comparison (α = .05; β = .2). Results The load cycles volumetric wear-increase was linear. Two-way ANOVA showed significant main effects (material and light-cured) and significant interactions. Self-cured materials (mean = 0.38 mm3 ) showed more wear than light-cured materials (mean = 0.35mm3 ). Conclusions The bioactive materials except Activa light-cured showed significantly more wear than the flowable composites. Clinical significance This study demonstrated that most of the dual-cured composites, if light-cured, showed the same wear as the flowable composites used as control. Therefore, to obtain adequate wear resistance the dual-cured composites should be routinely light-cured.

Using atomic force microscopy, wear is performed and the results of determining wear resistances of 100-nm-thick Cu and SiO2 coatings and 3-μm-thick ZrN are presented. The dependences of the specific volumetric wear on the normal mechanical stress at the contact of an AFM probe with the surface during wear are found.

This paper presents an experimental approach to predict the friction and wear coefficients followed by finite element modeling (FE) to analyze the wear of silicon nitride sliding against alumina bearing components up to 2 years considering risky gait activities. First, the friction and wear coefficients were determined for four loading conditions - 15, 20, 25 and 30 N for 20 km (equivalent to 2 years of implant life) using ball-on-disc (BOD) tribometer with 0.9% (NaCl) saline solution to simulate a lubricating bearing contact similar to hip joint. These BOD loads were equivalent to gait loads which were named as four groups- A (as similar to sitting down or getting up), B (as similar to stair ascending and descending with load), C (as similar to carrying load 50 kg) and D (as similar to load transfer 50 kg). Interestingly, the experimental results showed the friction and wear coefficients obtained from BOD tests were found to be much lower for higher gait loads due to the formation of discontinuous tribofilm on the worn surface. Later, finite element simulation was carried out and the findings revealed that physically demanding gait activity of load transfer 50 kg had the least maximum linear and volumetric wear. Group A gait activity showed maximum linear and volumetric wear among all the groups. From these results, it is quite evident that, people engaged in physically demanding gait activities, may prefer silicon nitride and alumina combination for hip joint replacement which showed reduced wear for risky activities. Refereed/Peer-reviewed

Aim To develop the mathematical model for root canal preparation using Endodontic file. Method The process of obturation consist of the filling of the root canal cavity using heated and softened gutta-percha to get the fluid tight seal in between the canal wall and filled gutta-percha. Any obturation process to perform before it requires the preparation of the root canal which involves the removing dead tissue, substrates and debris from the decayed root canal. The various geometric parameters viz. Taper, relative angle for orientation of cross-section between two planes, pitch and polar symmetry constant of the Endodontic file etc. Geometric parameters are derived. The various performance parameters like Endodontic file life assessment, cutting force components (tangential and normal), substrate removal rate, torque exerted by Endodontic file etc are also derived successfully. The Endodontic file life is estimated based on two approaches viz. speed and volumetric wear approach. Conclusion The mathematical model described is helpful for the Endodontic experts, researchers, design engineers etc. However the applicability of the described mathematical model limited to assumption of study. The gap between root canal to be prepared and Endodontic file is zero while preparation. The Endodontic file weight, speed of rotation and substrate removal rate is assumed to be constant. The mathematical model for Endodontic file discussed above proved to be efficient tool for studying the root canal preparation. The various geometric parameters and the various performance parameters are derived.

The wear of a novel temporomandibular joint (TMJ) prosthesis was evaluated in an animal model. The prosthesis consisted of an additively manufactured titanium alloy (Ti6 Al4 V) mandibular condyle and glenoid fossa created through selective laser melting, with a machined vitamin E-enriched ultra-high molecular weight polyethylene (UHMWPE) surface attached to the fossa. Thirteen TMJ prosthesis were implanted in sheep, six of which had condylar heads coated with HadSat® diamond-like carbon (H-DLC). Euthanasia took place after 288 days, equaling 22 years of human mastication. Linear and volumetric wear analysis of the fossa was performed by optical scanning. The condylar head surfaces were assessed by scanning electron and confocal laser microscopy. The average linear UHMWPE wear, when combined with the coated condyle, was 0.67 ± 0.28 mm (range: 0.34-1.15 mm), not significantly differing (p = .3765, t-test) from the non-coated combination average (0.88 ± 0.41 mm; range: 0.28-1.48 mm). The respective mean volumetric wear volumes were 25.29 ± 11.43 mm3 and 45.85 ± 22.01 mm3 , not significantly differing (p = .1448, t-test). Analysis of the coated condylar surface produced a mean Ra of 0.12 ± 0.04 μm and Sa of 0.69 ± 0.07 μm. The non-coated condylar surface measured a mean Ra of 0.28 ± 0.17 μm and Sa of 2.40 ± 2.08 μm. Both Sa (p = .0083, Mann-Whitney U test) and Ra (p = .0182, Mann-Whitney U test), differed significantly. The prosthesis exhibits acceptable wear resistance and addition of the H-DLC-coating significantly improved long-term condylar surface smoothness. ispartof: JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS vol:110 issue:6 pages:1425-1438 ispartof: location:United States status: published

Modular hip implants can improve construct stability and the rate of volumetric wear in Total Hip Arthroplasty (THA), however, there is still a 0.2-10% risk of dislocation. We report the unusual case of a 54-year-old lady who presented with a dislocated migrated ceramic liner following a twisting injury. She had undergone a ceramic-on-ceramic THA five years earlier. This diagnosis of the dislocated liner was confirmed with computed tomography (CT) scanning. Review of National Joint Registry data showed ceramic-on-ceramic acetabular liner dissociation to be rarer than in those with metal-on-polyethylene (incidence 0.27 vs. 0.46 per 1000 prosthesis years). We suggest the liner may have migrated in retrograde along the iliopsoas. We recommend the use of cross-sectional imaging (CT) to assist in confirming the diagnosis and planning future surgery.

Aims A retrospective study was conducted to measure short-term in vivo linear and volumetric wear of polyethylene (PE) inserts in 101 total knee arthroplasty (TKA) patients using model-based radiostereometric analysis (MBRSA). Patients and Methods Nonweightbearing supine RSA exams were performed postoperatively and at six, 12, and 24 months. Weightbearing standing RSA exams were performed on select patients at 12 and 24 months. Wear was measured both linearly (joint space) and volumetrically (digital model overlap) at each available follow-up. Precision of both methods was assessed by comparing double RSA exams. Patient age, sex, body mass index, and Oxford Knee Scores were analyzed for any association with PE wear. Results Linear wear occurred at 0.015 mm/year (supine) and 0.220 mm/year (standing). Volumetric wear occurred at 10.3 mm3/year (supine) and 39.3 mm3/year (standing). Wear occurred primarily on the medial side of the joint. Weightbearing imaging greatly improved the reliability of measurement. Clinical precision of volumetric wear was 34 mm3. No significant associations were found between patient demographics or function scores and measured wear. Conclusion In vivo volumetric wear of TKAs can be assessed at short-term follow-up using MBRSA. Cite this article: Bone Joint J 2019;101-B:1348–1355.

This paper builds a theoretical model for crossed steel wires in frictional wear with the considerations of interwire elliptical contact, the wear movement effect and the dependence of wear coefficient on contact stress. A stepwise solution procedure based on an efficient method is proposed to numerically solve the theoretical model, realizing the accurate simulation of wear evolution step by step. The results show that the cross angle between wires has significant influences on the wear scar and mechanical property of the wires. The non-perpendicularly crossed arrangements between wires leads to narrow and long elliptical wear regions at a small cross angle, which are more even than the concentrated ones at a large cross angle. Compared with the moving wire, the static wire suffers a greater cross-sectional area loss and larger volumetric wear, and is in a greater risk of fracture failure, especially under large cross angle conditions. Local concentrations of contact stress occur in the contact zone border and vary with the cross angle and the moving wire's position, resulting in a changing dangerous area for the risk of contact fatigue. An increment in the cross angle results in larger contact stress, elastic deformation, subsurface stress of wires, and a deeper dangerous zone for local stress yielding from the wire surface.

A leading cause of long-term failure of total knee replacements (TKRs) is osteolysis caused by polyethylene wear particles. The current gold standard for preclinical wear testing of TKRs is mechanical knee simulators. The definition of the femoral center of flexion-extension rotation (CoR) has been identified as one possible source of variability within TKR wear tests, since the femoral curvature varies from distal to posterior. The magnitude of the influence on wear due to changes in location of femoral CoR has not been investigated in depth. During this study, a computational framework utilizing finite element analysis for modelling wear of TKRs was developed and used to investigate the influence of the location of femoral CoR on TKR polyethylene wear during standardized displacement controlled testing (ISO 14243–3:2014). The study was carried out using a 40-point Latin Hypercube Design of Experiments approach. Volumetric wear was highly correlated to femoral CoR in both the superior/inferior and anterior/posterior directions, with a stronger relationship in the superior/inferior direction. In addition, wear scars showing linear penetration were examined, with large differences in simulations at the extreme ends of the sampling region. In this study, it was found that variations in the location of the femoral center of rotation can represent a large source of variability in the preclinical testing and evaluation of the wear performance of total knee replacements. This study represents the first attempt at quantifying the effect on wear of different femoral center of rotations across a large sampling space.

In this study, the wear properties of compacted graphite cast iron (CGI), which is being extensively used in recent years owing to its excellent mechanical properties, were compared with the wear properties of spheroidal graphite cast iron (SGI). Wear test specimens were prepared for this purpose. The volumetric wear amounts were examined by subjecting to three different wear forces, wear time and number of revolutions of abrasive disc. Also, the hardness measurements and spectral analysis of the specimens were performed. After the wear tests, SEM photographs were taken from the wear surfaces and main surfaces. The wear results were presented in graphical form and discussed. The wear resistance of the CGI material was found to be approximately ten times better than the wear resistance of the SGI material. The compacted graphite cast iron was more sensitive to the friction velocity, while the spheroidal cast iron was more sensitive to the friction time.

Background The wear properties of knee implants need to be thoroughly evaluated prior to clinical use to ensure implant longevity. ISO 14243-1:2009 and ASTM F3141-17 are the two standards typically used for evaluating wear, with the ISO standard being more common; ASTM F3141-17 was first released in 2015. The aim of this study is to compare differences between these two standards in terms of wearing on a knee prosthesis. Methods Using finite element analysis based on Archard's law, this study evaluated anterior-posterior and internal-external motion, contact area, contact force, contact stress, volumetric wear rate, wear depth, and wear distribution on the knee prosthesis. Findings The results show that simulations performed according to ASTM F3141 produced knee kinematics that were more similar to human gait. The maximum wear depth occurred on the medial side of the tibia. However, the region of peak contact stress did not always correspond with the region of the maximum wear depth, indicating that considering the contact stress alone is not sufficient for evaluating wear as the sliding distance also plays an important role. The resulting wear region from the ASTM F3141 simulation was smaller but deeper than the wear region from the simulation per ISO 14243-1. However, the volumetric wear rates were very similar, with 13.48–55.26 mm3/million for ASTM F3141 and 13.64–54.9 mm3/million for ISO 14243-1. Interpretation The resulting rate of wear is almost identical between ISO 14243-1 and ASTM F3141. However, there are differences in wear contours and wear depth.

– The wear on the acetabular liner surface of total hip prosthesis due to human activity cannot be avoided. Salat is an obligation religious activity for Muslims performed five times daily, without exception for patients who used the total hip prosthesis. Salat consists of standing, bowing, prostrating and sitting on the leg motions. Many researchers have investigated the wear on the liner surface for daily activity but not for salat activity. This study has aimed to calculate wear on the acetabular liner surface due to salat activity. A new linear wear model has been proposed in order to estimate the linear wear or the wear depth on the acetabular liner surface. In addition, a volumetric wear model or volume loss on the acetabular liner surface has also been developed based on the new linear wear model. These wear model are used to calculate wear on the acetabular liner surface due to walking and salat activities. Results show that the linear wear due to salat activity is lower than walking activity, because of the intensity of salat activity is lower than walking. However, the combinations of both wear due to walking activity and salat activity need to be considered.

Computational modeling of polyethylene wear based on patient-specific gait kinematics and component orientation remains lacking. This study aimed to quantify the polyethylene wear among 48 total hip arthroplasty (THA) using patient-specific data through a computational model incorporating the cross-shear effect. Strong patient variations were observed in volumetric wear rate (54.1 ± 13.9 mm3/year) and linear wear rate (0.20 ± 0.08 mm/year). Regression analysis demonstrated that axial plane rotation, in light of its influence on cross-shear effect, plays an important role in polyethylene wear. The computational model based on patient-specific gait kinematics and component orientation provides a useful tool to investigate the in-vivo polyethylene wear.

Summary Objective Orthodontic bite turbos are used to separate the maxillary and mandibular arch when disocclusion is needed for brackets placement or extrusion of teeth. Bite turbos should have adequate wear resistance to maintain disocclusion but also avoid abrasion of the opposing enamel. The objective of this study was to measure the wear of three materials used as bite turbos and opposing enamel wear. Materials and methods 10 mm × 8 mm × 4 mm specimens (n = 8) of Transbond™LR (3M™) Transbond™ Plus (3M™) and Triad®gel (Dentsply) were prepared in silicone molds. Cusps of extracted premolars were prepared to a standard cone shape. Extracted maxillary incisors were used as reference for flat enamel surfaces. The experiments were performed on the modified UAB wear testing device at 20N for 200,000 cycles at 1 Hz. All surfaces were scanned with a non-contact profilometer at 10micron resolution. Volumetric wear was measured with superimposition software and data analysed with one-way ANOVA and Tukey post-hoc. Results Significant differences were seen in the wear of materials and opposing enamels (P Transbond™ Plus (.317 ± .062 mm3) > Transbond™ LR (.136 ± .027 mm3) > Enamel (.053 ± .04 mm3). Opposing enamel ranked: Transbond™ LR (.158 ± .086 mm3) = Enamel (.128 ± .035 mm3) = Transbond™ Plus (.126 ± .025 mm3) > Triad®gel (.039 ± .008 mm3). Conclusions All bite turbo materials wore more than natural enamel but caused equal or less wear to opposing enamel than tooth-tooth contact. Triad®gel underwent 2.5× and 6× the wear of Transbond™ Plus and Transbond™ LR respectively. The bite turbo material used may be selected based on preference for longevity.