Volumetric Wear Rate Research Articles

Wear debris in metal-on-metal bearings and modular junctions : What have we learned from the last decades?

Metal-on-metal (MoM) bearing hip arthroplasty saw increasing utilization and peaked in the 1990s and early 2000s. Although the linear and volumetric wear rate for aMoM bearings was lower than its polyethylene counterpart, metal ion particles were found to be approximately 10 × smaller and 500 × higher in quantity compared to polyethylene wear debris. Research into these articulations have demonstrated their relationship to the formation of lymphocyte-mediated adverse local tissue reactions. The work-up for metal particle-associated conditions (metallosis) includes athorough patient history and physical examination, blood laboratory studies for metal ion concentrations, and advanced imaging studies including magnetic resonance imaging (MRI). The treatment of metallosis and adverse local tissue reactions ranges from close serial observation to extensive debridement and full revision of arthroplasty components, when indicated.

Effect of different molding pressures on the properties of glass fiber / molybdenum disulfide / Polytetrafluoroethylene composites

Both glass fiber (GF) and molybdenum disulfide (MoS2) can enhance the comprehensive properties of PTFE (polytetrafluoroethylene)-based composites, however the properties of the composites are significantly influenced by the molding pressure utilized. In this study, GF/MoS2/PTFE composites were produced under varied molding pressures (50–70 MPa), and the composites’ mechanical and tribological properties were evaluated. The results showed that the tribological parameters (such as friction coefficient and volumetric wear rate) and mechanical parameters (such as density, hardness, tensile strength, and elongation at break) varied depending on the molding pressure. When the molding pressure was 50 MPa, the GF/MoS2/PTFE composites displayed their finest mechanical properties. The composite had the best wear resistance with the lowest wear rate of only of 2.135 × 10−6 mm3/Nm at a molding pressure of 60 MPa and the lowest friction coefficient of 0.166 at a molding pressure of 70 MPa. The increased molding pressure that was employed to make the samples, as predicted by SEM analysis, would lead to greater residual stresses inside the specimens, which would ultimately result in cracking and peeling. In the friction test, specimens with a lower forming pressure are more likely to have surface furrows that are deeper and wider, as well as to shed their filler. Due to the increased molding pressure, the depth of furrows and filler shedding on the composite surface are also more apparent.

Application of ceramic nanoparticles in microstructure manipulation and simultaneously strengthening toughness and wear resistance of tool and die steels

Simultaneously improving the wear resistance and toughness can extend the service life of steel. In this study, nano-TiC-H13 steel was successfully fabricated by pre-dispersion nano-TiC/Al master alloy in conventional casting to simultaneously improve the wear resistance and toughness. The influence of nano-TiC ceramic particles on the microstructure, tensile properties, impact toughness, and wear behavior under the synergistic effect of high load and temperature was explored. Results indicated that nano-TiC ceramic particles can effectively refine the microstructure and promote the precipitation of the finer carbides, which significantly improved the properties of steel. The no-notch impact toughness (380.2 J/cm2), U-shaped notch impact toughness (36.6 J/cm2), and yield strength (1440 MPa) of nano-TiC-H13 increased by 12.7%, 31.2%, and 8.2%, respectively, compared with that of H13. Furthermore, the volumetric wear rate (8.2 × 10−10 m3/m) of nano-TiC-H13 under 450 °C and 30 N is decreased by 28.6% in contrast with H13. The high strength and plasticity in nano-TiC-H13 can resist the intrusion of debris and reduce plastic deformation. This work provides an innovative approach for the simultaneous improvement of the wear resistance and toughness of steel.

CARBON FIBRE-REINFORCED PEEK AS BIOMATERIAL IN A ROTATING HINGE KNEE DESIGN: BIOTRIBOLOGICAL TESTING IN COMPARISON WITH RETRIEVAL FINDINGS

Total knee arthroplasty with a rotating hinge knee with carbon-fibre-reinforced (CFR)-PEEK as an alternative bushing material with enhanced creep, wear and fatigue behaviour has been clinically established [1–4]. The objective of our study was to compare results from in vitro biotribological characterisation to ex vivo findings on a retrievals.A modified in vitro wear simulation based on ISO 14243-1 was performed for 5 million cycles on rotating hinge knee (RHK) designs (EnduRo®) out of cobalt-chromium and ZrN-multilayer ceramic coating. The rotational & flexion axles-bushings and the flanges are made of CFR-PEEK with 30% polyacrylonitrile fibre content.Analysis of 12 retrieved EnduRo® RHK systems in cobalt-chromium and ZrN-multilayer in regard to loosening torques, microscopic surface analysis, distinction between different wear modes and classification with a modified HOOD-score has been performed.For the RHK design with the polyethylene gliding surface and bushings and flanges made out of CFR-PEEK, a cumulative volumetric wear was measured to be 12.9±3.95 mm3 in articulation to cobalt-chromium and 1.3±0.21 mm3 to ZrN-multilayer coating - a significant 9.9-fold decrease (p=0.0072).For the CFR-PEEK flexion bushing and flanges the volumetric wear rates were 2.3±0.48 mm3/million cycles (cobalt-chromium) and 0.21±0.02 mm3/million cycles (ZrN-multilayer) (p=0.0016). The 5 million cycles of in vitro wear testing reflect a mean in vivo service life of 2.9 years, which is in accordance to the time in vivo of 12-60 months of the retrieved RHK components [5]. The main wear modes were comparable between retrievals and in vitro specimens, whereby the size of affected area on the retrieved components showed a higher variation.For the EnduRo® RHK design the findings on retrieved implants demonstrate the high suitability of CFR-PEEK as a biomaterial for highly loaded bearings, such as RHK bushings and flanges in articulation to cobalt-chromium and to a ZrN-multilayer coating.

How does bicycling affect the longevity of Total Hip Arthroplasty? A finite element wear analysis

As the number of young and active individuals undergoing Total Hip Arthroplasty (THA) are increasing yearly, there is a need for hip prostheses to have increased longevity. Current investigations into the longevity of these prostheses only include walking as the patient's activity as there is limited data on the amount and intensity of other activity performed by the patient. To further understand the evolution of wear and increase the longevity of these implants, the impact of different activities on the hip prosthesis needs to be investigated. In this study, a finite element model and wear algorithm was developed to simulate both walking and bicycling over a 5-year period. The XLPE acetabular cup volumetric wear rate was found to be 33 mm3/yr while the femoral head taper wear rates were between 0.01 – 0.39 mm3/yr. The results showed that by adding bicycling of up to 80 km per week with normal walking activity, the XLPE mean volumetric wear rate increased by 67% and the metallic mean volumetric wear rate by 11%. However, the patient may gain further health benefits from this additional activity. Assistive electric bikes may also be used to further reduce the loads on the hip joint, allowing for lower amounts of wear.

Thin highly cross-linked polyethylene liners combined with large femoral heads in primary total hip arthroplasty show excellent survival and low wear rates at a mean follow-up of 12.8 years.

Several short- and mid-term studies have shown minimal liner wear of highly cross-linked polyethylene (HXLPE) in total hip arthroplasty (THA), but the safety of using thinner HXLPE liners to maximize femoral head size remains uncertain. The objective of this study was to analyze clinical survival and radiological wear rates of patients with HXLPE liners, a 36 mm femoral head, and a small acetabular component with a minimum of ten years' follow-up. We retrospectively identified 55 patients who underwent primary THA performed at a single centre, using HXLPE liners with 36 mm cobalt-chrome heads in acetabular components with an outer diameter of 52 mm or smaller. Patient demographic details, implant details, death, and all-cause revisions were recorded. Cox regression and Kaplan-Meier survival was used to determine all-cause and liner-specific revision. Of these 55 patients, 22 had a minimum radiological follow-up of seven years and were assessed radiologically for linear and volumetric wear. Overall survival rate for all-cause revision was 94.5% (95% confidence interval (CI) 81.7% to 97.2%) at a mean follow-up of 12.8 years (10.9 to 18.7). Three patients were revised, none for liner wear, fracture, or dissociation. A total of 22 patients were included in the radiological analysis (mean follow-up 9.9 years (7.5 to 13.7)). Mean linear liner wear was 0.085 mm (95% CI -0.086 to 0.257) and the volumetric wear rate was 11.097 mm3/year (95% CI -6.5 to 28.7). Using HXLPE liners with 36 mm heads in 52 mm acetabular components or smaller is safe, with excellent survival and low rates of linear and volumetric wear at medium-term follow-up. Patients did not require revision surgery for liner complications such as fracture, dissociation, or wear. Our results suggest that the advantages of using larger heads outweigh the potential risks of using thin HXLPE liners.Cite this article: Bone Joint J2023;105-B(1):29-34.

A novel CoCrNi/W/Agx medium-entropy alloy matrix composite reinforced by Ag nanoparticle and self-lubricating mechanism under ambient air and high vacuum conditions

The present work aims to synthesize the CoCrNi/W/Agx composites with the high wear-resistance under ambient air and vacuum conditions. The friction and wear properties of the CoCrNi/W/Agx composites and CoCrNi medium entropy alloy were fully evaluated, and the chemical components and microstructural evolution of the tribo-films were observed and analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. The self-lubricating mechanism of the CoCrNi/W/Agx composites under ambient air and vacuum conditions was investigated. Increasing the Ag content increased the thickness of the tribo-films improving the friction and wear properties of the alloys, and the thickness of the tribo-films formed on the worn surface of the CoCrNi/W/Ag1.0 composite was about 150 nm. The CoCrNi/W/Ag1.0 composite exhibited an evident improvement in tribological performance, with a high wear-resistance of 2.79 × 10−5 mm3/N·m under vacuum condition and a volumetric wear rate as low as 1.35 × 10−5 mm3/N·m under ambient air condition.

The Computational Approach to Predicting Wear: Comparison of Wear Performance of CFR-PEEK and XLPE Liners in Total Hip Replacement

Wear on articulating bearing surfaces is a key factor causing revision in total hip replacement (THR). Wear debris that releases particles from bearing surfaces might result in adverse soft tissue reactions requiring revision surgeries. In this study, a comprehensive computational wear model based on the Archard wear equation was performed to investigate the wear performance under a three-dimensional (3D) physiological gait cycle, mimicking a normal walking condition (5 million cycles). The study shows that the accuracy of the model is highly dependent on the mesh convergence, the wear fraction, and the scaling factor. The simulations were run to provide a vast amount of detail for the reproducibility of the work. Cobalt chromium (CoCr) on cross-linked polyethylene (XLPE) and CoCr on carbon-fiber-reinforced polyether ether ketone (CFR-PEEK) prototype models were created in silico. The volumetric wear rates for CoCr-on-XLPE were calculated as 0.2989 for CoCr head and 21.0271 for XLPE liner, while for CoCr-on-CFR-PEEK they were 0.3484 for CoCr head and 1.8476 for CFR-PEEK liner. When compared to in vivo and in vitro studies, the wear patterns of these two prototypes are consistent with those of the conventional polyethylene liners in the literature. Although the volumetric wear rate of the CFR-PEEK liner is about 11 times lower than the counterpart of XLPE in MoP implants, the wear rate of CoCr was higher when compared to its use with XLPE. Therefore, CFR-PEEK articulating against orthopa\\edic metals may not be as good an alternative as XLPE, due to higher indicative metallic wear. This detailed computational wear modeling methodology could be utilized in design improvements of implants.

Tribological analysis of jute reinforced composites with different nano-fillers

This study investigates the carbon nanoparticle effects on the bulk and surface of jute-epoxy composites. Nano-fillers Graphene Oxide (GO) and Functionalized Graphene (FG) were used for Jute composite preparation. Tests like density, hardness, wear rate, specific wear rate, volumetric wear rate, are and wear resistance done to evaluate the tribological properties. Graphene Oxide and Functionalized Graphene as nano-fillers enhanced the tribological properties. The tribological test is carried by a pin on disc apparatus operating in dry atmospheric conditions and with different sliding speeds of (5 m/s), applied load (50 N), and distance of slide (10,000 m). The weight of fillers taken is (0.50,0.75, 1.0) weight percentage of Graphene Oxide and Functionalized Graphene nano-fillers. Test results showed that jute composite with 0.50 wt% of Functionalized Graphene and Graphene Oxide displayed improved performance at properties like hardness, wear resistance and volumetric wear loss in comparison to samples without any nano-fillers. After the addition of 0.50 wt.%, further addition of nano-fillers degrades the tribological properties of the sample.

Low Wear at 10-Year Follow-Up of a Second-Generation Highly Cross-Linked Polyethylene in Total Hip Arthroplasty.

Characterizations and factors influencing longer term performance of second-generation sequentially irradiated and annealed highly cross-linked polyethylene (HXLPE) are lacking. We evaluated patients who underwent total hip arthroplasty with HXLPE at mean 10-year follow-up for (1) linear and volumetric wear rates, (2) patient and implant characteristics, (3) implant survivorships, and (4) functional scores. We evaluated 130 hips (110 patients) that received HXLPE acetabular liners at a single center. The mean age was 56 years (range, 20-79 years), with a mean follow-up of 10 years (range, 8-15). Radiographic linear (millimeters/year) and volumetric (cubic millimeters/year) wear rates were quantified using radiographic analysis. Survivorship was assessed by all-cause and wear-related revision rates. Functional outcomes were assessed by Short Form 12 and modified Harris Hip Scores. The mean linear wear rate was 0.02 ± 0.03 mm/y, and the mean volumetric wear rate was 12.6 ± 5.3 mm3/y. Younger age had higher volumetric wear (total and yearly, P= .01). Increasing body mass index trended toward higher total and yearly linear (both, P ≤ .09) and volumetric wear (both, P ≤ .07). Ten patients required revisions, with an all-cause survivorship of 92% and a wear survivorship of 100%. The mean modified Harris Hip Scores was 84, and the mean Short Form 12 scores were 46 (physical) and 55 (mental). We observed low linear and volumetric wear rates for HXLPE at 10-year mean follow-up. Younger age and higher body mass index at the time of surgery may be important patient characteristics influencing long-term wear. These results illustrate the potential for this second-generation HXLPE to be an appropriate long-term total hip arthroplasty interface.

Pairing 40-mm Femoral Heads With the Smallest Compatible Acetabular Components in Total Hip Arthroplasty: Mid-Term Outcomes in 177 Cases.

Contemporary total hip arthroplasty (THA) often employs larger femoral heads to optimize hip stability. However, pairing 40-mm femoral heads with the smallest compatible acetabular components poses a potential risk for implant failure. The purpose of this study is to evaluate the outcomes of primary THAs using 40-mm femoral heads and the smallest compatible acetabular components. Between 2007 and 2018, 177 primary THAs involving 40-mm femoral heads and acetabular components ≤56 mm with highly cross-linked polyethylene liners were identified. Mean age was 61 years, 56% were females, and mean body mass index was 32 kg/m2. Cumulative incidences of dislocation, any revision, and any reoperation were determined utilizing a competing risk model. Osteolysis and femoral head penetration were assessed at minimum 8-year follow-up (n= 16). Mean follow-up was 6 years. There were no cases of liner fractures or dissociations. The 10-year cumulative incidences of dislocation, any revision, and any reoperation were 3.6%, 4.2%, and 6.8%, respectively. Mean linear femoral head penetration was 0.01 mm/y and mean volumetric wear rate was 50 mm3/y. One THA demonstrated stable, asymptomatic periacetabular radiolucent lines at most recent follow-up. In 177 primary THAs pairing 40-mm femoral heads with the smallest compatible acetabular components, there were no liner fractures or dissociations. The cumulative incidence of dislocation was modest at 10 years. The cumulative incidences of any revision and any reoperation were low at mid-term. IV.

The Wear Rate and Survivorship in Total Hip Arthroplasty Using a Third-generation Ceramic Head on a Conventional Polyethylene Liner: A Minimum of 15-year Follow-up.

PurposeThe purpose of this study was to evaluate the wear and survival rates of third-generation ceramic heads on a conventional ultra-high molecular weight polyethylene liner.Materials and MethodsA total of 160 hips (147 patients with a mean age of 55.9 years) who underwent total hip arthroplasty using the third-generation ceramic head on a conventional polyethylene liner from March 1998 to August 2003 were reviewed retrospectively. Evaluation of the wear rate for 56 hips (49 patients) followed-up for at least 15 years was performed using the PolyWare program version 8 (Draftware Developers, USA). The Kaplan–Meier survivorship was also evaluated.ResultsLinear wear and volumetric wear rates were 0.11±0.47 mm/year and 32.75±24.50 mm3/year, respectively. Nine revisions were performed during the follow-up period because of cup or stem loosening. The Kaplan–Meier survival rate, using cup revision or total revision total hip arthroplasty (THA) as the endpoint of analysis, was 93.7% at 15 years and 73.6% at 20 years.ConclusionBecause all revisions were performed between 15 and 20 years in our study, surgeons should pay greater attention to patients who underwent THA with ceramic-on-polyethylene bearing from 15 years postoperatively. Contemporary alumina ceramic on highly cross-linked polyethylene could certainly be a good alternative bearing couple providing better longevity.

Оценка надежности трибосистем на неустановившихся режимах работы

The issue of determining the wear rate in unsteady operating modes (during running-in period) and in stationary modes (after running-in is completed) during bench tests of vessel technical equipment is considered. The availability of such information will reduce the time for finishing prototypes. Moreover, it will help to identify ways to improve the reliability of technical equipment during operation. There have been carried out the experimental studies that showed the reliability of the kinetics of the surface destruction processes at the stage of tribosystems running-in. Experimental studies were carried out in two stages and determined the correlation between the rate of volumetric wear and acoustic emission parameters: the variance of signal amplitudes and the spectral power of radiation. The presented graphic dependences demonstrate that the spectral power has the optimal functional relationship with the friction parameters: friction torque and temperature. The analysis of the dependences obtained showed that the variance of the amplitudes and the spectral power of the acoustic emission signals reflects sufficiently complete the wear process. Thus, it is in a functional relationship with the rate of volumetric wear. It has been experimentally confirmed on various tribosystems that the spectral power of acoustic emission signals has a better correlation coefficient with the wear rate than variance. Therefore, it can serve as a parameter for estimating the wear rate in unsteady operating modes. A technique for evaluating the tribosystems wear rate during running-in is proposed. The technique is based on the recording of acoustic radiation from the friction zone. The spectral power of acoustic radiation correlates with the wear rate with a correlation coefficient R = 0.82.

A Fractional Time-Derivative Model for Severe Wear: Hypothesis and Implications

Based on the example of wear of polymers, which exhibit a power-law time variation of the wear loss under constant loading conditions, a fractional time-derivative wear equation has been introduced. The wear contact problem with a fixed contact zone is solved using the known method of separation of spatial and time variables. It is shown that during the wear process, the contact pressure approaches a uniform distribution over the contact area, which is termed as a quasi-steady-state solution, since the mean volumetric wear rate does not tend to become constant. It is of interest that the contact pressure variation displays a decaying oscillatory nature in the case of severe wear, when the mean volumetric wear rate increases with time.

Long-Term Follow-Up of Conventional Polyethylene in Total Hip Arthroplasty in Young Patients: Heightened Wear-Related Complications Are Observed at the Beginning of the Third Decade

BackgroundConventional polyethylene (CPE) was used widely in the past as a bearing surface in total hip arthroplasty (THA). As CPE THAs age and the revision burden continues to grow, it is increasingly important to understand the durability and failure mechanisms of this bearing material. Currently, such long-term data remain limited, particularly in younger, more active patients in whom wear issues are of greater concern. MethodsWe retrospectively reviewed 90 hips (77 patients) that underwent primary THA with CPE bearings on cobalt chrome femoral heads at age ≤50 years at 20-year minimum follow-up (mean 21.6 [20-23]). We analyzed polyethylene wear rates, clinical outcomes (modified Harris Hip Score, University of California, Los Angeles Activity Score), and implant survivorship. ResultsWear analysis revealed a median linear wear rate of 0.113 mm/y (95% CI 0.102-0.148) and a median volumetric wear rate of 41.20 mm3/y (95% CI 43.5-61.0). Modified Harris Hip Scores remained 37 points above preoperative baseline (P < .001) and University of California, Los Angeles scores 1.4 points above baseline (P = .018) at 21.6-year mean follow-up. Twenty-nine hips (32.2%) were revised, 20 of which (22.2%) were wear-related at a median of 15.4 years (interquartile range 11.4-19.5). Survivorship free from wear-related revision was 95.6% (95% CI 88.7-98.3), 87.9% (78.6-93.3), 78.1% (49.6-66.5), and 61.1% (41.3-67.0) at 10, 15, 20, and 25 years. ConclusionWear-related issues developed at increasingly high rates after 15 years, suggesting the need for surveillance after this time. The long-term wear and survivorship data of this study may be used as a benchmark when evaluating the performance of contemporary bearings in young, active THA patients.

Assessing the Mechanical Properties of a New High Strength Aluminum Hybrid MMC Based on the ANN Approach for Automotive Application.

Aluminum-based composites with characteristics such as low density and high strength to weight ratio have been identified to be one of the best-emerging alternatives. The lightweight composite is gaining popularity, particularly in the automotive industry. The composite’s qualities make it a prospective material to replace significant materials that are now used in the automobile industry. For lightweight products, various weight reduction solutions were proposed. In the present work, one such lightweight composite was fabricated by using a stir casting process, which includes reinforcement powders viz. carbon nanotube and fly ash to pure aluminum. The use of fly ash helps in reducing the overall associated cost of the material as well as provides low density. The work aims to identify the amount of fly ash (by weight %) suitable to avail good mechanical properties. In concern with the mechanical properties, density, yield strength, ultimate tensile strength, and wear resistance of the composite specimen were examined. Moreover, the artificial neural network was adopted to identify minimum volumetric wear for a given set of conditions. From the results, it was perceived that with the increase in fly ash content, the volumetric wear of the fabricated composite decreases. However, with the increase in load and speed, the volumetric wear rate increases.

An evaluation of corrosion & wear properties of AL6082 reinforced with graphite particles

The lineage of applied materials science is always in demand for light weight and highly performing materials. Such materials would find their applications in aircraft, structural, non-structural and automobile industries, etc. The present study aims at investigating the wear and corrosion behavior of Al-Based 6082 metal matrix composites (AMMCs) reinforced with graphite particles by pin-on-disc configuration. AMMCs were fabricated with three different weight fractions of graphite particles ranging from 5 to10% by using this stir-casting method. The friction coefficients and volumetric wear rates were continuously evaluated under uniform load of 10 N and sliding velocity of 0.5 m/s for the constant sliding distance of 300 m. Micro structural characterization was carried out by using trinocular microscope. Prepared composite was evaluated for wear, corrosion and hardness test as per ASTM standards 6082 aluminium alloy is an alloy in the wrought aluminium –magnesium –silicon family. It is one of the more popular alloys in its series, although it is not strongly feature in ASTM. This investigation reveals that wear, corrosion, micro-structural and hardness analysis of base alloy aluminium 6082 reinforced with different compositions of 5, 10 and 15 %.

The relation between body weight and wear in total hip prosthesis: A finite element study

As the current obesity epidemic grows, an increased number of obese patients undergoing Total Hip Arthroplasty (THA) can be expected in the coming years. The National Health Service of the UK (NHS) recommends that an obese patient should undergo weight loss before THA. It is understood that an increased body weight would increase the wear rates on the prostheses, however, the extent of increased wear and the impact on the longevity of the prosthesis is unclear. The NHS found that 45% of THA failures in 2019 were caused by wear which led to a multitude of failures such as infection, aseptic loosening and dislocation such that a revision surgery is then needed. In this study, a finite element model was created to model a walking cycle and a newly developed wear algorithm was used to perform a series of computational wear analyses to investigate the effect of different patient weights on the evolution of wear in THAs up to 5 million cycles. The wear rates shown in this study are closely comparable to previous literature. The XLPE volumetric wear rates were found to be between 15 and 35 mm3/yr (range: 1.5–57 .6mm3/yr) and femoral head taper surface volumetric wear rates were between 0.174 and 0.225 mm3/yr (range: 0.01–3.15 mm3/yr). The results also showed that an increased weight of 140 kg can increase the metallic wear by 26% and polyethylene wear by 30% when compared to 100 kg body weight. As increased wear can lead to a multitude of failure such as aseptic loosening, dislocation and metallosis, from this study, it is recommended that obese patients undergo recommended weight loss and maintain this lesser weight to reduce wear and prolong the life of the THA.

Structure Integrity Analysis on Nickel–Diamond Blade in Dicing of Hard-brittle Ceramic Die

Dicing operation in cutting hard-brittle ceramic die using nickel–diamond blade causes cracked or chipped die, accelerated tool wear and, ultimately, shortage of blade lifetime. This study aims to analyse the structural integrity of dicing blade in terms of tool wear, surface roughness, microstructure and elements during dicing. The measurements of wear blade on the blade are made by confocal microscope, whereas surface and elemental analyses are carried out with EDX SEM. Results show that the volumetric wear rate of blade is 20%, similar to roughness. The microstructure of the blade changes with occurrence of Aluminium owing to abrasive wear mechanism during cutting.

The use of an elastomeric methacrylate monomer (Exothane 24) to reduce the polymerization shrinkage stress and improve the two-body wear resistance of bulk fill composites

ObjectivesCharacterize the chemical structure of an elastomeric monomer (Exothane 24) and evaluate the degree of conversion (DC), polymerization shrinkage stress (PSS), rate of polymerization (Rp), flexural strength (FStrenght), flexural modulus (FModulus), Vickers hardness (VHardness) and two-body wear resistance of dental bulk fill composites (BFCs) containing Exothane 24. MethodsThe Exothane 24 was characterized using mass spectroscopy, elemental analysis, 13C- and 1H NMR. BFCs were formulated containing Exothane 24 (E10, E25, and E50). Similar BFCs containing regular UDMA (U10, U25, and U50), commercial conventional, and BFCs were used as control groups. ATR-FTIR spectroscopy was used to measure DC and the Rp of the composites. The PSS was measured using the universal testing machine method. Specimen bars were used to assess the FStrenght, FModulus, and VHardness. RBCs were submitted to a two-body wear test using a chewing simulator machine; the rate and volumetric wear loss were evaluated using an optical scanner. Data were analyzed statistically with α = 0.05 and β = 0.2. ResultsExothane 24 is a urethane isophorone tetramethyl methacrylate monomer with polymerization stress-relieving properties. No differences were found in the DC up to 4 mm in depth for E25. All BFCs had similar FStrenght, except for E50. E25 had the lowest volumetric wear loss and wear rate. E25 had approximately 30% lower PSS and slower Rp than commercial BFCs with similar wear resistance to conventional commercial composites. SignificanceThe Exothane 24 reduced the PSS and increased the wear resistance of BFCs; however, the formulation is important to optimize the properties of the BFCs.