Three-body Wear Research Articles

Effect of an adhesive primer on the integrity of occlusal veneer-metal interface and wear of composite resin veneered restorations

This study examines the influence of a metal-resin bonding agent on the wear rate of composite resin veneer. The specimens were prepared with a silver-based casting alloy and a light-cured composite veneering material. After application of repeated loading through a three-body wear testing device, the amount of wear was measured. The results showed no significant difference in wear between bonded and nonbonded specimens on the 1.5 mm areas of the veneer-metal interface. However, the bonded specimens exhibited significantly lower wear values at the veneer-metal interface. The use of an adhesive primer effectively enhanced the integrity of the occlusal veneer-metal junction.

Localized three-body wear of six types of composite resin veneering materials

The wear resistance of six types of composite resin veneering materials was determined in vitro by use of a three-body wear-testing device. This investigation examined the wear characteristics of the veneering composite resins in heavy occlusal contact areas. After repeated cyclic loading, wear values were measured with a profilometer, and surface textures were evaluated with a scanning electron microscope. All of the composite resin veneering materials were significantly more wear resistant than unfilled acrylic resin; but the composite resin materials demonstrated rougher surfaces than unfilled resin. Three of the composite resins exhibited fractures in the contact areas.

Particulate Metallic Debris in Cemented Total Hip Arthroplasty

Several studies conducted by the authors in the last six years demonstrate that the generation of metallic debris is more severe with titanium alloy than with cobalt-chrome alloy femoral components in cemented total hip arthroplasty (THA). The debris is generated from the articulating surface, particularly if entrapped acrylic debris produces three-body wear, and from the stem surface when the component loosens and abrades against fragmented cement. In selected cases in which the titanium metallic debris is copious, premature failure and severe progressive bone loss occurs. Electron microscopy demonstrates that the particles of metallic debris can be extremely small (a few hundredths of 1 micron). They are phagocytized by the macrophages and transported to the phagolysosomes. In this highly corrosive environment, the very high surface area of the particles may release toxic concentrations of the constituents of the alloy intracellularly, probably leading to progressive cell degeneration and death, with subsequent release of intracellular enzymes and ingested metallic debris. This cycle most likely repeats itself, leading to tissue necrosis. The results presented do not support the use of titanium alloy femoral components for cemented THA, particularly for the articulating surface.

Laboratory simulation of the wear process of belt conveyor rollers

Rollers used to support belt conveyors deteriorate as the result of a three-body wear process in which ore particles become trapped between the belt and roller to create abrasive wear under slight stress. Therefore, when a roller blocks as the result of a change in rolling motion, the combined action of the belt and abrasive particles transforms the steel roller into a sharp instrument that can cut the belt. New composite materials that prevent this from happening are currently the subject of experiments in plants and laboratories. The rubber wheel test simulates the type of wear that occurs when the roller is blocked. To correctly simulate the wear of rollers under normal conditions, the rubber wheel test apparatus was modified to allow the sample to turn and thus, more accurately duplicate in situ conditions. In this paper, we compare the wear resistance of a low carbon steel and polyester matrix composites containing hard particles. For all tests, the loss of weight converted into loss of volume was used to determine wear resistance.

Influence of shearing action of food on contact stress and subsequent wear of stress-bearing composites.

The influence of sliding action of the antagonist on occlusal three-body wear of composites and an amalgam was investigated in vitro by gradual change in the distance between the opposing substrates. When the distance was decreased from 10 microns to approximately 3 microns, wear increased significantly by a factor of two to three and was exclusively of erosive nature. At a slurry-film thickness of approximately 1 micron, direct contacts between the antagonist and protruding composite filler particles started to occur. This consequently slowed the erosive wear. Ultimately, direct contact phenomena predominated, decreasing the wear rate of the various materials to different degrees. Loss of material due to subsurface fatigue could not be demonstrated with a contact pressure of 45 MPa at which the experiments were performed. From this study, it can be concluded that minor alterations of the food-film thickness at the contact areas result in considerable changes in wear rates and wear-rate ranking of composite materials, which may partly explain inconsistencies among clinical trials.

SURFACE MODIFICATION ISSUES FOR ORTHOPAEDIC IMPLANT BEARING SURFACES

ABSTRACT In total joint replacement, generally a polished metal surface articulates against an ultra high molecular weight polyethylene (UHMWPE) counter bearing surface. Metals used include 316L stainless steel, Co-Cr-Mo alloy, and Ti-6AI-4V alloy (particularly with a hardened N+ ion implanted surface). Minimizing friction and UHMWPE wear is of prime concern for long-term performance. Additionally, it is desirable to minimize metal ion release which results from constant removal and reformation of passive surface oxides and oxyhydroxides during articulation. Long term effects from the presence of potentially toxic or carcinogenic ions of Cr, Co, Mo, Ni, V, and Al are not well known. Inert ceramic bearing surfaces eliminate this issue and are also resistant to potential three-body wear from bone cement debris or potential stray porous metal coating material. However ceramic (Al2O3 and ZrO2) materials are only available for total hip replacement. For total knee replacement, ft is too difficult and expensive...

Water and Abrasive Effects on Three-body Wear of Composites

The degrees of in vitro three-body wear resistance of a hybrid, a small-particle, and a microfilled composite were determined after water storage for up to 24 months. The hybrid composite was the most wear-resistant, while the microfilled composite showed the most wear. The hybrid composite showed no loss of wear resistance as a result of water storage. The small-particle composite showed a decrease in wear resistance after water storage only when tested with silicon carbide abrasive. The wear resistance of the microfilled composite decreased following water storage when tested with either a soft (CaCO3) or a hard (SiC) abrasive. For all composites, the soft abrasive was not capable of causing preferential wear of the polymer matrix, as observed on in vivo specimens. Instead, the filler particles became flattened, with minimal loss of interparticle substance. The hard abrasive did cause preferential wear of the matrix. All composites absorbed water and leached silicon during water storage, indicating that the filler-polymer bond was attacked by hydrolytic degradation. Scanning electron microscopic evaluation of the three-body wear specimens indicated that the in vitro wear method did not duplicate in vivo wear conditions (e.g., the hard abrasive caused excessive wear and chipping of the filler particles in vitro, a pattern that was not usually observed in vivo). Filler-polymer de-bonding was observed on in vivo specimens of all the composites, while it was found only on the in vitro microfilled composite specimens. These findings suggest that filler dislodging is a complex process that cannot be simulated with the in vitro wear method used in this study, not even after prolonged water storage.

Measurements of the wear of a thin film disk

A test designed to simulate worst-case start-stop contacts is described. It combines controlled contact stresses with well-defined flying. Magnetic readback and optical methods are used to characterize the damage. Two failure modes are observed: in one, the disk is overstressed and it fails rapidly; the other mode of failure occurs for lower stresses. Contacts induce changes which increase with repeated contacts until failure occurs. Changes in the magnetic signal and in the reflected light intensity and ellipticity are reported. The optical phenomena are attributed to the overcoat being worn thin. The average depth of the trough is found to be similar to the loss of overcoat thickness. Failure is similar to that observed with higher stresses. It is characterized by an increase in light scattering, by a nonlinear and irregular increase in wear with increasing number of contacts, and by spreading of the damage to other areas. These phenomena are shown to be delamination and three-body wear. The magnetic measurements prove to be a sensitive detector of mechanical head/disk interaction, showing changes before overcoat thinning could be detected.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A comparison of microstructural effects on two-body and three-body abrasive wear

The two-body abrasive wear resistance of steels can be altered by microstructural variations which have little effect on the bulk hardness. Three microstructural features which can improve the two-body abrasive wear resistance of steels are strengthening by the precipitation of alloy carbides (secondary hardening), undissolved carbides and large volume fractions of retained austenite. This work compares the effects of these microstructural constituents on the two-body and three-body abrasive wear resistances. The results indicate that microstructural features which improve the two-body wear resistance have a similar influence on the three-body wear resistance.

Investigation of abrasive wear resistance and wear mechanism of composite alloys

The abrasive wear resistance of composite alloys comprising hard tungsten carbide and soft CuNiMn matrix under different wear conditions has been investigated and compared with CrMo cast iron. It was found that Yz-composite alloy with hard cast angular tungsten carbide has greater wear resistance than CrMo cast iron under two-body wear conditions, but lower resistance than Cr-Mo cast iron under three-body wear conditions. It was found that under three-body wear conditions selective wear of the matrix and digging or fragmentation of tungsten carbide particles dominate in Yz-composite alloy, and microcutting and deformed ploughing is dominant under two-body wear conditions. The abrasive wear resistance of composite alloys under two-body wear condition is independent of bulk hardness, but is closely related to the microhardness of tungsten carbide.

Use of primates for wear testing of dental restorative materials

The mechanical loss of substance, both of teeth and man-made materials used to fill or replace teeth, principally occurs by attrition (the grinding of one tooth against another) or abrasion due to coarse particles present in the diet, dentifrices, or as products of the grinding itself. Nonhuman primates often have pronounced grinding or bruxing habits that serve to sharpen the teeth. Papio anubis baboons were used as a model to study the ability of teeth and restorative materials to withstand continual two- or three-body wear. One test site used the mandibular first premolars, occluding with the maxillary canines. For other studies, fixed appliances were cemented to the upper and lower incisors allowing placement of materials. Periodically, replica models of the surfaces were made for examination in a scanning electron microscope. Detailed descriptions of the morphological changes and/or failure of the materials appear elsewhere. It was found that the nonhuman primate model provides a rapid test of physiologic and pathologic wear of dental materials. It differs from the human situation only in the lack of good oral hygiene and the absence of extremes of thermal variations.

A classification of three-body abrasive wear and design of a new tester

Abstract A study of the literature reveals that while a considerable amount of work has been conducted on two-body abrasive wear, relatively little has been done about the equally important problem of three-body abrasive wear. A classification of the various types of three-body abrasive wear is presented. Following an examination of existing three-body abrasive wear testers and their limitations a novel tester to simulate a certain type of three-body wear has been designed. With simple modifications the tester can also simulate two-body wear. The paper describes the new tester and some preliminary results.