Surface Roughness Of Specimens Research Articles

Effect of airborne-particle abrasion with a novel spherical abrasive on the zirconia surface

Statement of problemA novel zirconia-alumina composite (ZAC) particle has yet to be studied for airborne-particle abrasion in a bonding protocol for the zirconia surface. PurposeThe purpose of this in vitro study was to evaluate the shear bond force of resin cement to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) when using spherical ZAC particles to conduct airborne-particle abrasion and modify the topography of Y-TZP. Material and methodsSpherical 30- to 70-μm ZAC particles were fabricated by using a hybrid gel technique. A total of 160 Ø6.6×4.0-mm zirconia disks were fabricated from 4 commercially available zirconia blanks, e.max ZirCAD zirconia (EM), NexxZr T zirconia (NE), Lava Plus High Translucency zirconia (LP), and Imagine High Translucency Zirconia (IM), by using computer-aided manufacturing technology. As-sintered specimens without further surface treatment were used as controls (ZR0). Surface treatment groups included sharp-edged alumina airborne-particle abrasion (ABC), 50 μm, 0.2 MPa; airborne-particle abrasion with ZAC particle at 0.2 MPa (2ZA); and airborne-particle abrasion with spherical ZAC particle at 0.4 MPa (4ZA). All surface treatment groups were airborne-particle abraded at the specified pressures for 10 seconds at a standardized distance of 10 mm. The surface roughness (Ra) and area roughness (Sa) of specimens from each group were measured. Following the application of an adhesive (Scotchbond Universal), Ø6.6×4.0-mm resin cement (RelyX Ultimate) buttons were fabricated for shear bond testing by using a universal testing machine at a 5-mm/min crosshead speed (n=10). The data were analyzed by using a 2-way ANOVA, Tukey HSD test, and regression analysis (α=0.05). Scanning electron microscopy (SEM) was performed to observe changes of the zirconia surface and the failure modes of each group before and after shear bond testing. ResultsThe mean ±standard deviation shear bond force values ranged from 272.6 ±41.4 N to 686.7 ±152.8 N. Statistically significant higher force values than those of the controls (P<.05) were obtained by using airborne-particle abrasion. No significant differences were found among any of the airborne-particle abrasion treatment groups (P>.05). The mean of Ra values ranged from 0.27 μm to 0.74 μm, and the mean of Sa values, from 0.48 μm to 1.48 μm. SEM observation revealed that the zirconia surface was made jagged by abrasion with sharp-edged alumina particles. The spherical ZAC particles create microcraters on the zirconia surface. Fractographic observation disclosed that failures were adhesive-cohesive failure modes with residual resin cement attached on the zirconia surface. ConclusionsThe surface treatment of zirconia with sharp-edged alumina or the spherical ZAC abrasives improved the bonding force between the zirconia and resin cement. No statistically significant differences in shear bond force values were found between airborne-particle abrasion surface treatment groups.

Optimization of Burnishing process by Taguchi method for surface enhancement of EN31 steel

Surface finish plays important role in service characteristics of an element, such as corrosion resistance, wear resistance and fatigue life. This leads to investigate surface finishing processes like polishing, buffing, lapping, burnishing etc. Burnishing is well known, effective and efficient super finishing technique which involves surface layers plastic deformation by cold working to refine surface texture and improve service life of component. Current work focuses on investigation of ball burnishing process and optimization of it on EN31 steel. Taguchi method is implemented for determination of best possible process parameters combination to decrease surface roughness and increase hardness of EN31 steel specimens. After burnishing surface roughness decreases from 0.446 to 0.089 μm and hardness increases from 179.5 to 266.5 Hv. Burnishing speed and feed are remarkable factors for decreasing surface roughness, whereas no. of tool passes and applied force are crucial for increasing hardness, according to optimization results. Validation tests are carried out with ideal levels of process parameters, confirming that the process of ball burnishing has improved the surface finish and hardness of EN31 steel.

The effect of laser shock peening on surface integrity and high and very high cycle fatigue properties of 2024-T351 aluminum alloy

Laser shock peening (LSP) as an emerging surface peening technology that is widely used in aerospace manufacturing. The effect of laser shock peening on surface integrity and high cycle fatigue (HCF) and very high cycle fatigue (VHCF) properties of 2024-T351 aluminum alloy was investigated in this study. Accordingly, the surface roughness, surface topography, microstructural, microhardness and residual stress of specimens treated with two different LSP pulse energy levels (10 J and 20 J) were analyzed. Additionally, the HCF and VHCF test was performed by ultrasonic fatigue test system. The results showed that surface roughness Ra value and microhardness of LSP treated specimens increased by a maximum of 89.37% and 16.3% comparing to the untreated specimen, respectively. X-ray diffraction analysis also showed that subgrain sizes were refined to the nanoscale. Furthermore, high-level compressive residual stresses (the maximum value about −210 MPa with 700 μm thickness) were introduced to the surface layer of the specimens. The S-N curve results showed that LSP treatment reduced the fatigue life of specimens, and the higher the laser pulse energy, the more obvious the effect of reduction. The fatigue fracture of specimens was analyzed via scanning electron microscope and residual stress distribution map. It is observed that fatigue cracks are predominantly initiated at fractured secondary phase particle locations in a VHCF range for untreated specimens. However, for LSP specimens, surface and internal crack initiation mechanisms were both observed. Under low and intermediate stress levels, the tensile residual stresses (which coexists with the compressive residual stresses) initiated fatigue cracks from the interior of the specimens; under high-stress levels, fatigue cracks were initiated at the material surface.

Evaluation of the effects of different surface modification methods on the bond strength of high-performance polymers and resin matrix ceramics.

The purpose of this in vitro study was to investigate the effects of various surface treatment methods on the shear bond strength of self-adhesive resin cement to polymer-infiltrated materials. One hundred twenty-eight polymer-infiltrated specimens (n = 32) for four different computer aided design-computer-aided manufacturing (CAD-CAM) materials, polyether ether ketone (PEEK) (PE), polyether ketone ketone (PEKK) (PK), composite resin nanoceramic (Cerasmart) (CS), and polymer-infiltrated ceramic network (PICN) (VITA ENAMIC) (VE) were milled from CAD-CAM blocks. They were divided into two groups (n = 16) in terms of surface treatments: airborne-particle abraded (AA) or silica-coated (SC) and two subgroups (n = 8) according to adhesive application or no adhesive. The surface roughness, contact angle, and shear bond strength (SBS) values of specimens were measured. Data were analyzed with Shapiro-Wilk test, the generalized linear models' method, and Bonferroni corrected t test (α ˂ 0.05). No statistically significant differences were found between the groups in terms of surface roughness and SBS values (P > 0.05). A statistically significant effect of the main adhesive interaction on the bond strength was found independent of the material and surface treatments (P < 0.001). While the average bond strength of the non-adhesive was 4.9MPa, the average of the adhesive applied was 9.1MPa. On the other hand, there is a statistically significant difference between the means of the contact angle values (P ˂ 0.001). While the highest mean contact angle value was 117.1 ± 14.8° obtained from the non-adhesive PK in the AA group, the lowest mean contact angle value 22.6 ± 4.3° was obtained from the VE without adhesive in the SC group. Roughness and SBS values were similar between groups after surface treatments. Adhesive application increased the SBS values. Surface treatments were found to have an effect on the contact angle. Since the AA and SC surface treatments used in the study show similar bond strength values, the Cojet system, which is more practical and easier to use, can be preferred as an alternative to AA after restoration production with CAD-CAM as a chairside.

Mechanical Properties and Bond Strength of Additively Manufactured and Milled Dental Zirconia: A Pilot Study.

To evaluate and compare the mechanical properties and ceramic bond of additively manufactured and milled dental zirconia materials. Disc (r = 10mm, h = 2mm) and bar (25 4 × 1. 2mm) shaped milled (M group) (Nacera Pearl; Doceram) and additively manufactured (AM group) (NanoParticle Jetting; XJet, Carmel 1400) zirconia specimens were prepared for 2 experimental groups. Ceramic was applied to the disc specimens (h = 4mm, r = 6mm) (n = 9) and their shear bond strength (SBS) was measured. The surface morphology of disc specimens was analyzed with a scanning electron microscope (SEM). The Vickers microhardness (Vh), surface roughness (Ra), and three-point flexural strength (FS) of bar specimens (n = 9) were measured. Results were statistically analyzed with Mann-Whitney U-test (α = 0.05). Significant differences were found in FS and Vh values of the M and AM groups. M group (1501.4 ± 60.1 HV1) showed a significantly higher Vh value than the AM group (1169.2 ± 48.4 HV1) (p < 0.001). FS of the M group (1287.5 ± 115.2 MPa) exhibited significantly high value than the AM (1030.0 ± 29.2 Mpa) group (p < 0.001). Statistically, no significant differences were seen in SBS and Ra values of the M and AM groups. Within the limitations of this in vitro study, the manufacturing technique affected the mechanical properties of the zirconia materials. AM zirconia material showed lower Vh and FS values than M zirconia. Additionally AM zirconia demonstrated adequate bond strength with dental ceramic.

Comparison of HSS M35 and titanium-nitride coated tool in novel CNC drilling operation of aluminium alloy AA6351-T6 material on surface roughness

The aim of the study is to compare the HSS M35 and TiN coated tool on surface roughness in CNC drilling operation on Aluminium Alloy AA6351-T6. HSS M35 and Titanium Nitride coated tool twist drill bits are employed in this study. The specimen on which the drilling operation performed is Aluminium Alloy AA6351-T6. This study consists of two groups of 20 specimens, each of which is drilled using both drill tools. Controlled variables included speed (rpm), depth of cut (mm) and feed rate (mm3/rev). The input speed, feed and depth of cut were 2200, 200 and 10 respectively. Each specimen's surface roughness was assessed using Mitutoyo Surface Roughness tester SJ-410 equipment with 95% significance level and analyzed using SPSS v.26 software. The mean value for HSS M35 is 0.855 with a standard deviation of 0.02438609 while mean value for TiN is 0.411 and standard deviation is 0.06010208. The obtained significance value for Surface Roughness is 0.01 that is less than 0.05. In this study, observed surface roughness values of TiN coated tool is less when compared with the HSS M35 tool for the same input speed, feed and depth of cut.

Электронно-пучковая обработка поверхности металлических материалов, изготовленных аддитивным способом

A method for finishing the surface of metal materials manufactured by additive technologies with an intense pulsed electron beam, which can be an alternative to traditional processing methods is presented. The optimal irradiation modes for VT6 titanium alloy specimens produced by metal powder fusion and 308LSi stainless steel specimens produced by electron beam welding are determined. It is shown that the presented processing method leads to a visual decrease in porosity and a multiple decrease in the surface layer roughness (by 20 times (Ra)) of VT6 titanium alloy manufactured by an additive method. The surface roughness of 308LSi stainless steel specimens fabricated by electron beam welding decreases to 2.1 times in the longitudinal direction, to 5.2 times in the transverse relative to the surfacing plane. It is shown that the elemental composition, strength and tribological properties of the specimens do not change during irradiation in optimal modes. Tensile testing of irradiated specimens revealed an increase in tensile strength by 12%, ductility by 10% (VT6) and anisotropy of mechanical properties depending on the direction of tension relative to the surfacing plane (308LSi).

Effect of material powder diameter on surface roughness in laser-powder bed fusion

Additive manufacturing (AM) is a technology that enables the molding of complex shapes from 3D data. Laser powder bed fusion (L-PBF) is one of the AM techniques for manufacturing metal parts. The purpose of this study is to investigate how varying the particle diameter of the material powder affects the surface roughness of the side skins of parts produced by L-PBF. Specimens of different materials were incorporated using stainless steel and maraging steel. The specimens were conducted with twice contour passes. The surface roughness of the specimen side skin was measured in the laser energy density on 1.0, 1.5, 2.0 and 2.5 J / mm2 of the second offset contour path. Results showed that average roughness tended to decrease with contour energy density for both specimens of different species. There was no difference in the average surface roughness for both specimens of different species. However, the specimens made of stainless steel had fewer voids observed in the contours of the specimens than the specimens made of maraging steel.

Surface layer porosity and surface quality in dependency of contour scanning strategy of Ti6Al4V parts

Laser based powder bed fusion of metals (PBF-LB/M) grants the potential for the combination of modern design approaches like topology optimization with the production of near-net shape parts suitable for high performance application. But there is not only the need for high relative density of the parts but also a low surface layer porosity to achieve mechanical properties comparable or better than forging or casting. The surface layer porosity depends among other factors on scanning strategy, precisely the contour parameters, filler parameters and hatch offset. This work investigates the influence of the named parameters and energy input on the correlation of surface porosity and surface roughness of Ti6Al4V specimens. To correlate surface roughness and surface layer porosity with the used laser parameters micro computed tomography (µ-CT) measurements are used.

Effect of Peening Process on Corrosion Fatigue Life for TiNi Shape Memory Alloy

The effect of ultrasonic shot peening on corrosion fatigue properties of a TiNi shape memory alloy was investigated. In this study, the surface condition of the peened specimens was optically observed and the arithmetic mean roughness of the specimen surface was measured. The main points of the results obtained in this study are as follows: (1) The surface roughness of as-peened specimen decreases with increasing the peening coverage because of smoothing effect by shot media. (2) Surface roughing derived from adhesion of Fe in the shot media was observed on the as-peened specimen, especially under high coverage conditions. (3) Mechanical polishing after the peening reduces the surface roughness to the level before peening. (4) No change was observed on the specimen surface even if the peened and then polished materials were heated to induce the reverse transformation.

Surface Roughness Evaluation in Turning of Nimonic C263 Super Alloy Using 2D DWT Histogram Equalization

Surface roughness of specimens is an important area of research since it influences the performance of machined parts. Meanwhile, employing a vision system to judge the roughness of the machined surface of specimens via captured images acquired from the specimen is an innovative and extensively used method. In this investigation, a vision system is used to capture the SEM images of the machined surface. The two‐dimensional images of the machined surface of the Nimonic263 alloy are used to approximate the profile of the surface of specimens in finish turning. Surface roughness was detected in simulated images of specimens in a variety of machining conditions using the imaging technology. In this research work, the surface texture is extracted using a technique that combines 2D surface images and wavelet transform approach. The 2D wavelet transform has the capability to disintegrate a machined surface image into multiresolution depiction for several surface characteristics and can be utilized for surface evaluation. The difference in the histogram frequency of an illuminated region of interest (ROI) from turned surface images was analyzed to aid in the evaluation of surface roughness with an average prediction error of less than 3.2%.

Effects of shot peening with different coverage on surface integrity and fatigue crack growth properties of 7B50-T7751 aluminum alloy

Engineering design methods based on the assumption of crack growth and the application of fracture mechanics principles are commonly used in aerospace engineering for the design of aluminum structures. In aerospace manufacturing, surface shot peening is one of the most widely used techniques for improving the fatigue performance of structural components. This work reviews the effect of different shot peening coverage on surface integrity and fatigue crack growth (FCG) properties of 7B50-T7751 aluminum alloy. The shot peening was applied to middle-crack tension (MT) specimens with four kinds of peening coverage: 100%, 300%, 600% and 1000%, respectively. The results showed that shot peening treatment reduced specimen surface roughness, moreover, surface shot peening promoted a maximum microhardness increased by 28.1% and induced compressive residual stresses in order of −412 MPa compared to untreated specimens. FCG experiment results showed that the effect of shot peening coverage on da/dN-ΔK curves was quite limited at constant amplitude loading. With the increase of shot peening coverage from 100% to 1000%, the FCG rate decreases first and then increase. At 300% of surface shot peening coverage, the FCG rate is the lowest, which results in the longest fatigue crack growth life.

Slide-free histological imaging by microscopy with ultraviolet surface excitation using speckle illumination

Microscopy with ultraviolet surface excitation (MUSE) is a promising slide-free imaging technique to improve the time-consuming histopathology workflow. However, since the penetration depth of the excitation light is tissue dependent, the image contrast could be significantly degraded when the depth of field of the imaging system is shallower than the penetration depth. High-resolution cellular imaging normally comes with a shallow depth of field, which also restricts the tolerance of surface roughness in biological specimens. Here we propose the incorporation of MUSE with speckle illumination (termed MUSES), which can achieve sharp imaging on thick and rough specimens. Our experimental results demonstrate the potential of MUSES in providing histological images with ∼ 1 μm spatial resolution and improved contrast, within 10 minutes for a field of view of 1.7 mm × 1.2 mm . With the extended depth of field feature, MUSES also relieves the constraint of tissue flatness. Furthermore, with a color transformation assisted by deep learning, a virtually stained histological image can be generated without manual tuning, improving the applicability of MUSES in clinical settings.

Enhancing Effect of Waste Engine Oil Bottom Incorporation on the Performance of CR+SBS Modified Bitumen: A Sustainable and Environmentally-Friendly Solution for Wastes

Waste engine oil bottom (WEOB) is a hazardous waste whose effect as an additive to CR+SBS modified asphalt is rarely studied. In this study, the CR+SBS asphalt binder was modified with WEOB in different concentrations (3, 6, and 9 wt%). The GC–MS and FTIR were performed to evaluate the chemical compositions of WEOB and WEOBCR+SBS asphalt. The results showed that the main constituents of WEOB were similar to the functional groups of asphalt, along with maleic anhydride (MAH). Pavement performance-related rheological tests such as RV, temperature sweep (TS), FS, MSCR, and BBR were carried out. Results show that WEOBCR+SBS-6 exhibited the best high- and low-temperature property, followed by CR+SBS-3 and CR+SBS-9. Fluorescence microscope (FM) test, bar thin layer chromatograph (BTLC) test, FTIR, and AFM tests were carried out to evaluate the micro-morphologies and modification mechanism. The analysis revealed increased trends in resin fraction as opposed to asphaltene fraction with the increase of WEOB content. FTIR analysis revealed that the amide groups in WEOBCR+SBS asphalt bonded to the free radicals of CR. Moreover, a modification mechanism was elaborated. WEOB strengthens the cross-linked structure of CR+SBS polymers, reacting with SBS to graft onto MAH-g-SBS, and the free radical of CR interacts with the amide group in WEOB to form a bond. In addition, the content of lightweight components and surface roughness of SBS specimens were in good correlation, which contributed to the rutting resistance and adhesion and self-healing performance.

Effect of graphene modified semi‐conductive shielding layer on space charge accumulation in insulation layer for high‐voltage direct current cable

Space charge accumulation in the insulation layer of high-voltage direct current (HVDC) cable is one of the key factors restricting the development of HVDC cable. The inner semi-conductive layer as an important structure of cable will affect the charge accumulation characteristics in the insulation layer. This work intends to explore the method of modifying the semi-conductive layer with graphene, to suppress charge accumulation in the insulation layer. First, the semi-conductive layer with different contents of Graphene (G) and carbon black (CB) are prepared. Second, the morphology and surface roughness of the cross section are analysed. Further, the effects of the semi-conductive layer on space charge accumulation of the insulation layer are studied by pulsed electro-acoustic method and thermal stimulation depolarisation current method. The experimental results show that a moderate amount of graphene replacing CB can effectively reduce charge accumulation in the insulation layer and inhibit positive temperature coefficient (PTC) effect at the same time. The surface roughness of specimens decreases with the increase of G content from 0 to 3 phr (parts per hundreds of resin), when the CB content decreases from 25 to 10 phr, the surface roughness of specimen increases. The resistivity test shows that doping G can significantly inhibit the PTC effect of the semi-conductive layer. The volume resistivity of the semi-conductive layer decreases with the increase of G content and CB content. In addition, charge accumulation of the insulation layer rises and then drops under the action of the semi-conductive layer.

Influence of Specimen Surface Roughness on Hydrogen Embrittlement Induced in Austenitic Steels during In-Situ Small Punch Testing in High-Pressure Hydrogen Environments

An in-situ small punch (SP) test method has recently been developed as a simple screening technique for evaluating the properties of metallic materials used in high-pressure hydrogen environments. With this method, the test conditions including temperature and gas pressure can easily be adjusted to those used in practice. In this study, specimens of STS316L steel and 18 wt% Mn steel were prepared at two different surface roughness, fabricated using wire-cutting and mechanical polishing. Their effects on hydrogen embrittlement (HE) were evaluated using in-situ SP testing at both room temperature and a lower temperature where HE was shown to occur under 10 MPa hydrogen. Both steels were evaluated using two variables obtained from in-situ SP testing, the SP energy, and the relative reduction of thickness (RRT), to quantitatively determine the effect of specimen surface roughness on HE susceptibility. Their fracture characteristics due to HE under 10 MPa hydrogen showed little difference with surface finish. Surface roughness had a negligible influence on these quantitative factors describing HE, indicating that it is not a dominant factor to be considered in in-situ SP testing when it is used to screen for HE compatibility in steels used in high-pressure hydrogen environments.

SLS Process Parameter Optimization to Improve Surface Quality and Accuracy of Polyamide Parts

The contribution of selective laser sintering (SLS) technique in the 4.0 manufacturing industry is undisputedly significant. SLS part quality exhibits high dependence on SLS process parameters and is a major challenge. Therefore, this research aims to investigate the effect of input parameters (i.e., part orientation, bed temperature, and layer thickness) on the surface roughness and accuracy of laser-sintered polyamide specimens. Response surface methodology (RSM) and ANOVA analysis aided the testing and evaluation. Optimal working conditions for minimum shrinkage were 0.17 mm layer thickness, 177.89°C part bed temperature, and part orientation at 88.91 degrees. The surface quality deteriorated with the increment in part bed temperature and layer thickness, and it shows an inverse trend (or improves) with the part orientation in the prescribed range. The optimal surface roughness was at a layer thickness of 0.11 mm, bed temperature at 174.55°C, and part orientation at 86.5 degrees.

Microstructure and tribological behaviour of FeCoCrNiAlCuMn particles alloyed on Inconel-718 substrate using plasma transferred arc technique

Inconel-718 alloy (IN-718) is a nickel-based superalloy that has extensive applications in many industries such as power generation, gas turbine, tubing hangers, safety valves systems, aerospace, nuclear engineering, etc. However, noticeable wear occurs on the IN-718 structure, leading to reduction in service life and failure of components. In the present study, the ball-milled alloy powders FeCoCrNiAlCuMn were preplaced on the IN-718 substrate and the substrate was alloyed through Plasma Transferred Arc (PTA) process. Then, the thickness of the alloyed region, phase formation, microstructural changes, microhardness and influence of alloy powder on the tribological properties were analysed. Further, the mechanism involved during the wear test and surface roughness of worn-out specimens were studied. The result shows that the PTA alloyed region possesses different phases such as BCC, FCC and intermetallic compounds. The alloying elements were well mixed with the substrate material and good metallurgical bonding was formed. The microhardness of 883 HV0.2 was achieved in the alloyed region while the substrate showed 312 HV0.2. The alloyed specimen exhibited superior wear resistance compared to the substrate due to the higher binding force of alloying elements such as Fe, Co, Ni and Co, which restricted the material deformation during the wear test. Moreover, broadening of the BCC phase of the alloyed region and intermetallic phase increased the hardness of the alloyed region, resulting in the improvement of wear resistance. The oxide phases such as Al2O3, CuO, Cr2O3, NiO and FeO were formed in the alloyed region during the wear test due to the formation of frictional heat. These oxide layers acted as a lubricant film to protect the alloyed region as well as diminished the Coefficient of Friction (CoF).

Effect of brushing on surface roughness, fluoride release, and biofilm formation with different tooth-colored materials

Background/purposeTooth brushing, material mechanical ageing procedure, is the most effective way in removing biofilm. The purpose of this study was to investigate the surface roughness, fluoride-release, and S. mutans biofilm formation on various tooth-colored restorative materials before and after brushing. Materials and methodsDiscs of materials, a nanocomposite (Filtek Z350XT; CO), a giomer (Beautifil II; GIOMER), a resin-modified glass-ionomer material (Fuji II LC; RMGI), and a conventional glass-ionomer material (Fuji IX GP Extra; GI), were prepared, polished with abrasive discs (SofLex), and divided into brushed and not brushed groups. The surface roughness of specimens was observed using a contact profilometer, fluoride-release was measured using a fluoride-specific ion electrode, and S. mutans biofilm formation, biovolume and live/dead cells, was observed under a confocal laser scanning microscope. ResultsHigher roughness was observed on GI and RMGI than on CO and GIOMER. Brushing had no effect on the roughness. The fluoride-release of GI and RMGI was higher than that of GIOMER. The fluoride-release decreased after brushing in all materials. The biovolume of S. mutans was not significantly different between GIOMER, RMGI and GI, while CO showed the highest. Brushing resulted in a higher biovolume for all materials, except CO, which showed no change. After brushing, all the tested materials demonstrated identical biovolumes. There were no significant differences in live/dead cells among all groups. ConclusionBrushing demonstrated a negative effect on the fluoride-release and biovolume of S. mutans biofilms for all tested materials except nanocomposites.

Composite surface roughness and color change following airflow usage

BackgroundEsthetic dental restorations have gained increasing popularity. The surface of restorations should be smooth enough to achieve maximum esthetics and prevent the adhesion of microorganisms and food particles. This study aimed to assess the surface roughness and color change of composite specimens following airflow usage.MethodsIn this in vitro, experimental study, 30 Tokuyama composite discs were fabricated and randomly divided into three groups (n = 10) for the use of airflow with calcium carbonate/bicarbonate powder and conventional polishing with FlexiDisc. The surface roughness of the specimens was measured by profilometry while the color change was assessed by measuring the L*, a* and b* color parameters using spectrophotometry before polishing (T1). The composite specimens were then polished for stain removal, and their surface roughness as well as color parameters were remeasured after polishing (T2). Paired t-test and Tukey’s test were applied for within-group and between-group comparisons.ResultsSignificant differences were noted in roughness average (Ra) between airflow with calcium carbonate (0.251 ± 0.014 μm) and airflow with sodium bicarbonate (0.421 ± 0.208 μm), and between airflow with sodium bicarbonate and FlexiDisc (0.207 ± 0.076 μm) groups after polishing (P < 0.05). Regarding the correlation of change in surface roughness and color parameters at T1 and T2, an inverse correlation was noted between the change in surface roughness and all color parameters except for L*. In other words, reduction in surface roughness decreased the a* and b* color parameters.ConclusionsWithin the limitations of this study, the results showed that the airflow device used in this study had no significant difference with conventional polishing in terms of reduction in surface roughness and staining. Considering the cost and maintenance of the airflow device, it is not suggested as a suitable alternative to the conventional polishing procedures.Trial Registration Number: This study does not involve human subjects.