Three-body Wear Research Articles

Effect of contact stress on the tribology behaviors of PTFE/316L seal pairs under various abrasive-contained conditions

This study focuses on the tribological characteristics of polytetrafluoroethylene rubbing against 316L stainless steel in the presence of various Al2O3 abrasive particles. The ranges of the contact stresses and abrasive sizes were 2.50–5.01 MPa and 2.0–230 µm, respectively. The evolution of the coefficient of friction, abrasive invasion behavior and damage characteristics on worn surfaces, and the transformation of damage mechanisms under different contact stresses are summarized. Results demonstrate that contact stress exerts a considerable effect on abrasive invasion behavior, the coefficient of friction trends become complicated at low contact stress. With decreasing particle sizes under a contact stress of 2.50 MPa, the wear failure changes from two-body wear to three-body wear, or two wear behaviors exist simultaneously. As contact stress increases, the wear mechanism is gradually simplified. The particle size threshold that causes the change of the wear mechanism is also gradually reduced. The wear rate of polytetrafluoroethylene has no linear relationship with abrasive size, whereas wear increases with contact stress. Under 2.50 MPa conditions, the particles easily invade the tribo-interface in the friction process, thus increasing the wear rate of the metallic counterpart. In addition, with increases contact stress, the polytetrafluoroethylene material transfers to the counterface, and local adhesion occurs. When the contact stress is increased to 5.01 MPa, polytetrafluoroethylene even shows an obvious creep.

Durability of staining and glazing on a hybrid ceramics after the three-body wear

Hybrid ceramic is a promising material for monolithic restorations that could require an individualization through the extrinsic staining to improve aesthetics. Due to the possibilities to treat this ceramic prior to staining, this study evaluated the wear resistance of surface treatments prior to staining and glazing a hybrid ceramic. Thirty-two specimens (Vita Enamic) were divided into 8 groups according to the surface treatment prior to the staining (Polishing: Pol, Acid etching: Ac, Sandblasting with Al2O3: Sd or Self-etching silane: Ses) and glaze application (with: gl or without: gl). The specimens were submitted to the ACTA wear machine simulating the presence of food bolus and antagonist. The wear rate of the stain was determined after 7 intervals of 20,000 cycles, using a profilometer. The surface before and after staining, and after wear were inspected using Scanning Electron Microscopy (SEM). The rates were analyzed using three-way ANOVA and Tukey test. The wear was affected by surface treatment, glaze application and number of cycles (p < 0.001). 100% of the staining was removed after 20,000 cycles for Pol, 40,000 for Pol + gl, 60,000 for Ses + gl, 80,000 for Ac, 100,000 for Sd and Ses, 120,000 for Ac + gl and 140,000 for Sd + gl. SEM showed similar worn surfaces. Sandblasting followed by glaze application was the most durable treatment to maintain the external staining on the hybrid ceramic surface when subjected to three-body wear.

Wear performance and mechanisms of H13 steels sliding against different Rock types

Disc cutters are the main working tools of full-face hard rock tunnel boring machine (TBM). They are in direct contact with rocks, sustaining enormous loads and vibrations in practical constructions. Therefore, The wear of the disc cutters is very severe and would cause huge economic costs. In this study, the abrasive wear performance of disc cutters’ material (H13 steel) was analyzed by pin-on-disc wear tests in contact with three types of rocks (sandstone, granite and gneiss) under different loads (100 N and 200 N). The friction coefficient was recorded during the tests. The wear rate of H13 steel and maximum wear depth of rocks were calculated and measured. The worn surfaces of H13 steel were observed. Results showed that the friction coefficient, the wear rate of H13 steel and the maximum wear depth of rocks under the load of 100 N was lower than those of 200 N. The main wear mechanism of H13 steel in contact with sandstone was three-body wear, while the main wear mechanism of H13 steel in contact with high-strength rocks (granite and gneiss) was abrasive wear. The study of wear performance and mechanisms of H13 steels sliding against different rock types would provide theoretical supports for the construction of TBM under various geological conditions.

Effect of titanium binder addition on the interface structure and three-body abrasive wear behavior of ZTA ceramic particles-reinforced high chromium cast iron

The effects of Ti alloy binder addition on the wettability, interface microstructure, and three-body wear behaviors of ZTA ceramic particle-reinforced composites were investigated systematically. With binder addition from 5% to 15%, molten Cr26 can wet the ZTA ceramic surface, with a wetting angle of only 17.7°. Oxygen and iron atoms diffused into the transition layer to form a metallurgical bonding interface, which enhanced the interface bonding strength and brittleness. A combined supporting effect of the Cr26 matrix on the ZTA ceramic particles and protecting effect of the ZTA ceramic particles on the matrix during wear resulted in an improvement in wear resistance. The brittleness interface harmed the wear resistance at a higher load (2 kg and 3 kg). This indicates the ZTA ceramic particles has positive influence on the wear resistance of composites.

Flexural strength, fracture toughness, three-body wear, and Martens parameters of pressable lithium-X-silicate ceramics

ObjectivesTo test and compare five pressable lithium-X-silicate-ceramics on their mechanical and wear properties. MethodsSpecimens were pressed and prepared from: i. Amber Press (AP), ii. Celtra Press (CP), iii. Initial LiSi Press (IL), iv. Livento Press (LP), and v. IPS e.max Press (IE). Four-point flexural strength (FS), SEVNB fracture toughness (KIC), three-body wear (3BW), Martens hardness (HM) and indentation modulus (EIT) were measured. For CP, FS and HM were measured with and without additional Power Firing. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov–Smirnov, one-way ANOVA followed by Scheffé test, Kruskal–Wallis-H-, Mann–Whitney-U-, and Spearman–Rho-test (p < 0.05). The Weibull modulus was calculated using the maximum likelihood estimation method. ResultsAP and CP presented higher FS than IL. LP presented the highest Weibull modulus. CP showed lower KIC values than AP, and AP was not significant compared to LP and IE. The most 3BW material loss was observed for CP. CP revealed higher HM values than the remaining ceramics. IL presented lower EIT compared to AP and CP. The following correlations were observed between the test parameters: 3BW with FS (r = 0.279, p = 0.015), with HM (r = −0.378, p = 0.001), and with EIT (r = −0.344, p = 0.004); EIT with FS (r = 0.203, p = 0.028); and HM with FT (r = −0.223, p = 0.027) and EIT (r = 0.884, p < 0.001). No correlations were observed between FS and KIC (r = 0.046; p = 0.346). SignificanceAP followed by LP showed the highest and IL followed by CP the lowest properties tested. Power Firing of CP improved the flexural strength. Ceramics with high flexural strength and Martens parameters showed lower wear. Materials with high Martens hardness presented lower fracture toughness values and ones with high indentation modulus showed high flexural strength.

Three-body wear effect on different CAD/CAM ceramics staining durability

Regardless the materials properties, the vast majority of ceramic restorations could require an individualization through the extrinsic staining to improve aesthetics. This study aimed to compare the staining wear durability of different monolithic ceramics. Specimens of high translucent zirconia (YZHT), zirconia reinforced lithium silicate (ZLS), hybrid ceramic (HC) and feldspathic ceramic (FLD) were divided in five groups according to each material staining technique. The ZLS ceramic was tested with stained prior (ZLS1) and after crystallization (ZLS2). All specimens were extrinsically characterized, i.e. stained, and crystallized or sintered in specific ovens, according to the manufacturer's recommendation. The specimens were submitted to three-body wear tests in ACTA wear machine, simulating the presence of food bolus and antagonist (pH 7, 15 N, 1 Hz). The wear rate of the stain surface was determined after 5 intervals of 200,000 cycles, using a profilometer. The ceramic surface before and after staining, and after wear were inspected by Scanning Electron Microscopy (SEM). The wear rates were analyzed using two-way ANOVA and post-hoc Tukey test. The wear rates of the staining were affected by ceramic and the number of cycles (P < 0.001). 100% of staining was removed after 200,000 cycles for HC, and after 600,000 cycles for YZHT and ZLS1. Staining of ZLS2 and FLD remained on ceramic surface even after 1,000,000 cycles. Furthermore, FLD showed a significant higher staining durability than ZLS2. SEM revealed different surface morphologies for each group with and without staining and after the wear test. Ceramics with fired staining showed higher durability compared to the polymerized one. The feldspar ceramic presented superior staining durability, followed by zirconia reinforced lithium silicate and high translucent zirconia. The conventional two steps staining technique showed improved durability for zirconia reinforced lithium silicate.

Three-body wear of 3D printed temporary materials

ObjectiveThe aim of this study was to investigate the three-body wear of different additively manufactured temporary materials, one temporary PMMA material for CAD/CAM milling and one resin-based composite for direct restorations as a control group by using an ACTA machine. MethodsSpecimens (n=8) of the 3D printing materials 3Delta temp, NextDent C&B, Freeprint temp were additively manufactured by DLP 3D printer. Postprocessing was carried out according to the manufacturer's specifications. Telio CAD were cut out of blocks, Tetric EvoCeram was applied directly and light cured. Three-body wear was simulated with an ACTA machine. Data were statistically analysed (ANOVA, post hoc test: Tukey, p<0.05). The worn surfaces of the specimens were examined with a FE-SEM. ResultsThe average mean wear was 50±15μm for Tetric EvoCeram<62±4μm for 3Delta temp<236±31μm for Telio CAD<255±13μm for NextDent C&B<257±24μm for Freeprint temp. After 200,000 cycles, the wear and wear rates for Tetric EvoCeram and 3Delta temp were significantly lower than those for the other materials. SEM revealed that 3Delta temp has a higher filler proportion than the other 3D printing materials but less than Tetric EvoCeram. SignificanceThe filler content influences the wear behaviour of additively manufactured materials as well as dental restorative composite materials. While most 3D printing materials have a low inorganic filler load, which qualifies the materials for temporary use only, one 3D printing material has an optimized composition that would qualify the material for longer clinical service time if wear is considered as the outcome variable.

Interfacial Bonding and Abrasive Wear Behavior of Iron Matrix Composite Reinforced by Ceramic Particles.

Using zirconia toughened alumina (ZTA) particles and Ni–Ti complex powders as raw materials, high-Cr cast iron reinforced by ZTA particles was prepared by an infiltration casting process. A continuous transition layer formed at the interface between ZTA particles and the Cr15 matrix, which proves that there is strong metallurgical interfacial bonding at the interface. The phases in the Ni–Ti layer of the ZTAP/Fe composite were preserved compared with the microstructure of sintered ZTA ceramic preform. The hardness of the Ni3Ti, TiO and AlNi2Ti phases in the interfacial transition layer was measured by the nano-indentation method, which is 12.5 GPa, 16.1 GPa and 9.2 GPa, respectively. The three-body wear resistance of the composite reached 12.6 times that of high-Cr cast iron.

Effect of Synthesized Bis-GMA and UDMA Nanofibers on Cuspal Flexure, Microhardness, Wear, Surface Roughness and Color Stability of Experimental Resin-Composites

Objective: To study the cuspal flexure (CF), Vickers microhardness (HV), three-body wear (W), surface roughness (SR) and color stability (CS) of experimental resin-composites reinforced with Bis-GMA and UDMA nanofibers synthesized by electrospinning technique.Materials and methods: Bis-GMA (Bis-GMA+TEGDMA+PEGDMA) and UDMA (UDMA+PEGDMA) nanofibers were synthesized by wet electrospinning technique and characterized by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). After being ball-milled to a nanoscale size (< 100 nm) in a ball-milling machine (Retsch – PM 400, Haan, Germany), these nanofibers were added to a prepared experimental resin-composite. This study was divided, according to the percent and type of added nanofibers, into eight groups (n=10/group except for color stability n=11): one control group, three groups reinforced with 7, 11 and 15 wt% Bis-GMA nanofibers and four groups reinforced with 7, 11, 15 and 20 wt% UDMA nanofibers. For each of these groups, CF, HV, W, SR and CS were studied. CF was studied by the digital image correlation method which analyzes the displacement of an object using a USB digital microscope with a built-in camera (COMET xS, Steinbichler Optotechnik GmbH, Neubeuern, Germany). HV was measured according to the ASTM E-384:1999 using a Digital Display Vickers Microhardness Tester (ZHVµ Micro Vickers Hardness Tester, Indentec Hardness Testing, Zwick Roell Co., Ltd. Atlanta, USA). W testing was carried out according to ISO/TS 14569:2001 using a custom-made cusp-on-disc sliding machine. Measurement of SR was performed according to ISO 25178-2:2012 and CS testing was carried out according to the regulations of ISO 4049; 2009 using a portable reflective spectrophotometer (X-Rite, model RM200QC, Neu-Isenburg, Germany). Data were collected and submitted to One-way ANOVA and post-hoc Tukey and Dunnett’s T3 tests with the significance level set at (p ≤ 0.05). Results: Pure forms of Bis-GMA (70-100 nm) and UDMA (50-100 nm) nanofibers were confirmed by SEM and FTIR. One-way ANOVA revealed significant differences between studied groups for CF, HV, W and SR (p = 0.001) but not for CS (p = 0.068). For both types of nanofibers, compared to the control group, reinforced groups showed lower CF, HV and SR and greater W results. For CS, there was no consistent trend of results of experimental groups that were comparable to that of control group. Within the range of added nanofibers (7-20 wt%), Bis-GMA nanofibers exhibited more favourable HV and W results than UDMA nanofibers, while the reverse was the case for CF and SR. Both nanofibers exhibited comparable CS results.Clinical Significance: A resin-composite reinforced with such nanofibers showing improved CF and unfavorably lower HV and more W should be used as a base layer and covered with a layer of another resin-composite with enhanced surface properties.

Two-Body and Three-Body Wear Behavior of a Dental Fluorapatite Glass-Ceramic

As a veneering porcelain coating of dental prosthesis, two-body and three-body wear behavior of dental glass-ceramic with the main crystalline phase of fluorapatite has not been comprehensively studied. In this work, a self-made fluorapatite glass-ceramic was synthesized and the mechanical and tribological performances of the glass-ceramic were tested, comparing with a commercial feldspathic glass-ceramic. The friction and wear experiments were performed between disk-shaped glass-ceramics and natural teeth in two-body (dry, water, saliva) and three-body (slurry) modes, respectively. Results showed that good mechanical properties of fluorapatite glass-ceramic can be achieved by the sintering process. In both two-body and three-body modes, the fluorapatite glass-ceramic had a smaller friction coefficient and wear rate and caused less damage on antagonistic teeth than the feldspathic glass-ceramic. The greater mechanical properties give fluorapatite glass-ceramic a better wear resistance and reduce the adhesive wear.

The effect of food medium on the wear behaviour of veneering porcelain: An in vitro study using the three-body abrasion mode

ObjectivesThe present study examined the effect of food medium on the three-body wear behaviour of veneering porcelain derived from porcelain-fused-to-metal crowns. MethodsSeventy-four rectangular metal–ceramic specimens were prepared using Ceramco III as the veneering porcelain. After storage in distilled water at 37 °C for 2 days, the specimens were tested with a custom-designed chewing machine with a stainless steel ball as antagonist (350 N loads, 2.4 × 106 cycles). Testing was performed using water, silica beads, poly(methyl) methacrylate beads, millet seed slurry, chicken slurry or celery slurry as abrasive medium. Wear analysis of the veneering porcelain was performed using a 3D profilometer after every 300,000 wear cycles and analysed with one-way analysis of variance and post-hoc pairwise comparison procedures. Worn surfaces were examined with scanning electron microscopy. ResultsThe wear curves of all experimental groups demonstrated three wear stages (running-in, steady wear and severe wear) with characteristic microstructure of worn surfaces. All the three food items selected in the present study (celery, chicken and millet seeds) had lower hardness compared with the veneering porcelain and produced less abrasion of the porcelain than a two-body wear system (water only). Abrasive wear produced with silica particles was the highest for the veneering porcelain. ConclusionThe wear process of veneering porcelain in porcelain-fused-to-metal restorations is affected by the type of food consumed during mastication. Clinical significanceExcessive abrasion may lead to premature failure of porcelain-fused-to-metal restorations. The importance of the wear behaviour of dental ceramic materials cannot be overstated. Three-body wear is an unavoidable consequence of oral function and occurs daily during eating. Understanding the effect of food particles on the wear behaviour of dental porcelain provides insight into the clinical performance and durability of these restorations.

The response of two-wheeler tires to three-body wear phenomena by experimental simulation of off-road terrains

The operation of two wheelers frequently encounters off-road terrain comprising loose particles of sand and soil, which setup three-body abrasive wear phenomena affecting the tire life. To evaluate the response of two-wheeler tires on such terrains, the dry abrasive wear behavior of two-wheeler tires was experimentally determined using a three-body wear test apparatus. Three different mixtures of sand and granite dust of varying grit size, 100, 200, and 300 µm, were employed to represent the abrasive cluster, typical of the varying roughness on off-road terrains. Taguchi’s L27 (33) orthogonal array was applied to analyze the specific wear rate as a response to three parameters—load, speed, and road roughness—separately for front and rear two-wheeler tires. Variation of hardness and wear pattern observation for the front and rear tires were carried out to oversee the surface deterioration. A numerical model based on abrasive grit-tire surface interaction was developed for comparison with the experimental results.

Wear of direct resin composites and teeth: considerations for oral rehabilitation.

Little is known about the wear rate of enamel and dentin opposing resin composite following restoration of the occlusal surface in patients with tooth wear. Hence, the aim of this invitro study was to evaluate the wear of enamel and dentin surfaces when opposing each of three resin composites in a two-body and three-body wear test. The two-body and three-body wear of dentin, enamel, and three resin composites (Clearfil AP-X, Filtek Z250, and Filtek Supreme) opposing four antagonists (stainless steel and three resin composites) were evaluated using the ACTA wear machine. In addition, all the surfaces were evaluated with scanning electron microscopy. The results showed the lowest wear rate in enamel and the highest in dentine, with the composite showing intermediate wear rates. The three-body wear results were not affected by the antagonist and showed pure wear caused by the abrasive food medium. The invitro enamel/composite wear ratio was 2.5. The results show that tooth wear accelerates as soon as enamel disappears and dentin is exposed to composite resin. Therefore, it is important to protect dentin with a restorative material.

Effect of zirconia polycrystal and stainless steel on the wear of resin composites, dentin and enamel

This study evaluated the effect of two antagonist substrates (Y-TZP/zirconia or stainless steel) on the wear rate and surface alterations of different composite materials and bovine tooth substrates (enamel and dentin). The wear rate of different composite materials (n = 20; two direct composite resins: HelioMolar – HM; Clearfil AP-X – CAP, three indirect composite resins: Estenia C&B – EST; Adoro – ADO; Sinfony – SFY, and one composite resin for direct/indirect restorations: Filtek Z250 – Z250), bovine enamel and dentin against two different antagonist materials (zirconia or stainless steel) into two mediums (two-body and three-body wear) were collected. After wear tests on ACTA wear machine, Scanning Electron Microscopy (SEM) analysis was performed to access the surface alterations. The wear data were evaluated by three-way ANOVA and Tukey post-hoc test (α = 0.05). The factors ‘antagonist’, ‘medium’, ‘restorative materials’, and the interaction of all factors grouped by two and integrated showed statistical significance on the wear rates. A two-body test depicted no difference among all composites and enamel for wear rate, while a three-body test depicted differences among composites directly related to the filler content: EST < Z250 = CAP < ADO = HM < SFY. Dentin always showed the highest wear rates and enamel the lowest rates. The presence of food bolus (three-body test) led to higher wear rates in comparison to an only aqueous medium (two-body test). SEM analysis showed that different materials present specific wear patterns, regardless of the medium and the antagonist considered. Differently from enamel, dentin substrate was intensively prone to wear, regardless of the antagonist/medium. Resin composite substrates presented intermediate wear rates, depending directly on their filler content (% in weight).

Investigations on the mechanical properties and three-body wear behavior of pure Fe2B intermetallic with different chromium additions

The effects of chromium on the mechanical properties and three-body abrasive wear behavior of pure Fe2B intermetallic are investigated in this work. The results show that, with chromium addition from 0 to 4.88 wt%, the fracture toughness of pure Fe2B sample initially increases to the highest value of 7.06 MPa m1/2, and then decreases. The fracture toughness was improved by approximately 161.4% with chromium addition of 4.07 wt%. Simultaneously, with the increment of chromium addition, the wear mass loss decreases and then increases in case of both SiC and SiO2 abrasives. Through systematical analysis of the wear surface and subsurface, it can be found that fracture toughness plays a dominant role in reducing the wear mass loss. Specific wear mechanisms are also explicitly discussed.

Surface degradation mechanisms in precipitation-hardened high-entropy alloys

Design of high-entropy alloys with complex microstructures presents a unique opportunity to combine the best of solid solution strengthening and precipitation hardening. These alloys are potentially disruptive for several high-performance applications including aerospace, oil and gas, nuclear industry, and next-generation tribology. This study presents the thermo-mechanical treatment, microstructural evolution, and surface degradation resistance in precipitation hardenable Al0.3Cu0.3Ti0.2CoCrFeNi high-entropy alloy. The heat-treated alloy consisted of fine precipitates of L12 and L21, strengthening the face-centered cubic solid solution matrix. Potentiodynamic polarization showed nano-galvanic coupling between the intermetallic particles and the matrix. Phase-specific nano-indentation showed that hard intermetallic particles caused three-body wear and higher friction values during sliding wear. The microstructure was correlated with processing conditions and resulting surface degradation resistance using transmission electron microscopy imaging and analysis.

Effect of Simulated Mastication on the Surface Roughness and Wear of Machinable Ceramics and Opposing Dental Enamel.

Computer aided design-computer aided machining (CAD-CAM) ceramic crowns are replacing ceramo-metal ones due to newly developed mechanical properties and esthetics. To obtain knowledge about their interactions due to polishing and occlusal contacts with the opposing dental enamel specimen, including surface roughness and wear, the three-body wear simulation was investigated. The surface roughness (RA) and wear rate (mm) of four CAD-CAM blocks with different compositions including Vita Mark II, e.max, Suprinity, and Enamic, after two surface treatments of glazing and polishing, and their opposing enamel specimens, were investigated using a mastication simulator and atomic force microscope. The roughness of all ceramic and to a greater extent enamel samples, with the exception of enamel opposing polished Enamic samples, was decreased after wear. No significant difference in wear was evident for the ceramic samples between the glazed and polished treatments. Lower wear rates were recorded only for polished Vita Mark II and polished Enamic in comparison to the glazed ones. The newly developed polishing systems for CAD-CAM ceramics can be good alternatives to reglazing, because the roughness and wear rate of both the ceramic and the opposing enamel will either not change or decrease.

Wear and Corrosion Behavior of Tungsten Carbide Based Coating on Carbon Steel

High velocity oxy-fuel (HVOF) coating techniques are employed mainly to improve the service life of engineering components, which is exposed to wear, erosion, corrosion or combination of both; wear and corrosion. The aim of this study is to investigate the wear and corrosion behavior of WC-10Ni and WC-12Co coating deposited onto medium carbon steel (Cast steel BS 3100 GR A3) blade. The blade was used to stir the mixture of sulfuric acid (H2SO4) with ilmenite to produce titanium dioxide (TiO2) pigments. The microstructures of both coatings before and after wear and corrosion testing were evaluated using scanning electron microscope (SEM). Vickers microhardness testing was used to examine the coatings hardness. The three-body wear test with wet condition using silicon carbide (SiC) slurry was used to investigate the wear behavior for both coating. The experiment was based on weight loss of the sample and Archard’s law to determine the wear rate of the coating. In addition, the three-electrode electrochemical test was used to investigate the corrosion behavior of the coatings. The mixture of H2SO4 and ilmenite used as an electrolyte of the test. It is found that the wear rate will increase with increasing of the weight loss. This is consistent with decreases of the volume fraction loss and hardness of the coating. After corrosion test, it can be observed that the existence of the crack and porosity on the coating increasing the corrosion behavior of coating. With high volume fraction and hardness, WC-12Co shows higher wear resistance compared to WC-10Ni. However, the value of corrosion rate for both coating has a slight difference due to better corrosion resistance of Ni binder itself.

Investigation of Two- and Three-Body Wear Resistance on Flowable Bulk-Fill and Resin-Based Composites

The purpose of the present study was to investigate two and three-body wear resistance and hardness of eighth kinds of modern bulk-fill and resin-based composite materials — Grandio, Estelite Flow, Filtek bulk-fill, Charisma, Clearfil, Ultimate, Quadrant, and G-aenial. All samples were kept in distilled water for one week, and their Vickers hardness was determined before two- and three-body wear tests. The mean volume loss of all specimens after the wear tests was determined by the 3D profilometry. In addition, a random specimen was selected from each test group and scanning electron microscope images were taken for an analysis of wear tracks. The surface morphology of the Clearfil and Ultimate composite materials was damaged severely, whereas Grandio and Charisma had a very smooth surface after two-body wear tests. The lowest mean volume loss was measured in micro-fill Grandio two-body and three-body wear tests. The Filtek bulk-fill and resinbased composites showed similar two- and three-body wear behavior. For the composite materials considered, correlations between the filler volume loss, Vickers hardness, and two- and three-body wear resistances were found to be insignificant.

Wear Characteristics and Volume Loss of CAD/CAM Ceramic Materials.

In the field of prosthodontics, patients often require complex and extensive restorative care. This can involve the use of dental restorations to restore teeth on both the maxillary and mandibular arch. Current literature has evaluated the wear properties of different dental ceramics against enamel, but studies regarding dental ceramics opposing one another are limited. The purpose of this study was to assess the wear potential and wear behavior of CAD/CAM zirconia (ZR) and lithium disilicate (LD) materials against a similar ceramic material, and how the surface finish of these dental ceramics might affect patterns of wear. Using a sphere-on-plate tribometer system, different surface finishes (glazed-G and glazed then polished-GP) of ZR and LD were evaluated following wear simulation. Artificial saliva of physiologic pH was used as a lubricant during wear simulation at 37°C. The coefficient of friction (COF) was calculated during the wear simulation. After wear simulation was complete, volume loss, surface roughness, and surface characterization of the specimens were analyzed using white-light interferometry and scanning electron microscopy (SEM). Statistical significance between materials and surface finish was established with two-way ANOVA and Bonferroni post hoc test (α = 0.05). Based on the 2-way ANOVA, material (p = 0.002) significantly affected the COF. LD showed a higher COF (p = 0.002) than ZR. Material (p < 0.001) and surface finish (p = 0.004) significantly affected the surface roughness inside the scar. ZR had significantly lower surface roughness compared to LD (p < 0.001). For outside scar, surface finish (p < 0.001) significantly affected the surface roughness. Polished specimens showed significantly higher roughness compared to glazed specimens for both inside (p = 0.004) and outside scar (p < 0.001). For volume loss, material (p < 0.001) and the interaction between material and surface finish (p < 0.001) were statistically significant. LD had higher volume loss than ZR (p < 0.001). For both glazed and polished finished, LD-G and LD-GP had significantly higher volume loss than ZR-G (p = 0.028), and ZR-GP (p < 0.001), respectively. SEM analysis indicated particle build-up and a grooving mechanism of wear for the LD-GP specimens. This suggested a three-body wear phenomenon occurring for LD-GP specimens, which was not visible in SEM imaging for other specimen types. This study demonstrated the resistance to wear and low abrasiveness of ZR when compared to LD in a simulated masticatory environment. This can be best explained by the increased strength of ZR, and the introduction of three-body wear to LD specimens from the accumulation of embedded wear debris onto its surface. Wear data and comparison of SEM images following wear simulation confirmed this interpretation.