Surface Roughness Parameters Research Articles

Retrieval of soil moisture in salinized farmland soil by multi-polarization SAR

ABSTRACT Synthetic Aperture Radar (SAR) is a potent instrument for estimating soil moisture across vast farmland areas. However, when soil salinity rises, existing SAR retrieval models for soil moisture become less accurate. Soluble salts in soil water alter the inherent correlation between the SAR backscattering coefficients and soil water, thus compromising the performance of retrieval models. The need to get surface roughness parameters from the field also limits the widespread application of the model. To address these issues, we developed a retrieval model for salty soil moisture assessment under small-scale roughness surfaces. First, we found a method to distinguish between slightly rough and rough surfaces using scattering entropy obtained from full-polarization decomposition. Then, we harnessed the co-polarization ratio to mitigate the effect of surface roughness in slightly rough conditions. Later, we developed a soil moisture retrieval model based on the co-polarization ratio, considering incidence angle, residual roughness, and soluble salt content. The validation of the model was verified using field surveying data, yielding an RMSE of 0.026 cm3 ·cm− 3 for the estimated soil moisture. This accuracy is comparable to or surpasses the level achieved by SAR for non-salinized soil moisture retrieval. Our findings showed that Scattering entropy is an effective parameter for distinguishing scattering mechanisms on farmland surfaces effectively. Specifically, when the scattering entropy of farmland is less than 0.5, the co-polarization ratio can mitigate some surface roughness effects. Additionally, when the soil-soluble salt content is incorporated, our model can accurately estimate the soil moisture of salty soil.

Investigation of the influence of packaging cardboard surface topography on the quality of printed products

The article investigates the impact of surface topography of various types of packaging cardboard on the quality of offset printed impressions. It analyzes the morphological structure of coated (GD2) and uncoated (UD3) cardboard, their microstructure, as well as surface roughness parameters such as Ra, peak, and valley areas. The article also provides a comparative analysis of the morphological indicators of unprinted cardboard surfaces and their printed impressions. Recommendations are proposed for selecting packaging materials to ensure optimal print quality.

Influence of material orientation, loading angle, and single-shot repetition of laser shock peening on surface roughness properties

Titanium alloy Ti6Al4V is extensively utilized in biomedical applications due to its excellent biocompatibility, corrosion resistance, and mechanical properties. The design of dental implant surface textures has changed throughout time to address issues with oral rehabilitation in both healthy and damaged bones. The longevity of an implant is significantly impacted by surface roughness. This study examines the use of laser shock peening (LSP) as a surface modification technique to improve the mechanical properties of implants. A numerical model is developed using the commercial finite elements software in ABAQUS/Explicit for simulating dynamic conditions. The aim of the study is to develop surface roughness parameters using computational methods such as studies have not yet been contemplated. The single shot angle, shot repeat, time, material orientation, and laser power are applied for the first time simultaneously to evaluate the impact of material orientation and loading angles on surface roughness parameters. The study showed that the developed computational model’s compressive residual stress was −578.45 MPa, while the experimental samples were −592.18 MPa. Consequently, the difference between the computational and experimental results was 2.32%. Without regard to material orientation or angle, the compressive residual stress of the samples under examination was found to be −578.450 MPa after three repetitions and to decreased to −1.620 MPa after four. These results demonstrate that by varying the material orientation and loading angle, the Ra value may be increased four times.

Low-Cost and Contactless Survey Technique for Rapid Pavement Texture Assessment Using Mobile Phone Imagery

Collecting pavement texture information is crucial to understand the characteristics of a road surface and to have essential data to support road maintenance. Traditional texture assessment techniques often require expensive equipment and complex operations. To ensure cost sustainability and reduce traffic closure times, this study proposes a rapid, cost-effective, and non-invasive surface texture assessment technique. This technology consists of capturing a set of images of a road surface with a mobile phone; then, the images are used to reconstruct the 3D surface with photogrammetric processing and derive the roughness parameters to assess the pavement texture. The results indicate that pavement images taken by a mobile phone can reconstruct the 3D surface and extract texture features with accuracy, meeting the requirements of a time-effective documentation. To validate the effectiveness of this technique, the surface structure of the pavement was analyzed in situ using a 3D structured light projection scanner and rigorous photogrammetry with a high-end reflex camera. The results demonstrated that increasing the point cloud density can enhance the detail level of the real surface 3D representation, but it leads to variations in road surface roughness parameters. Therefore, appropriate density should be chosen when performing three-dimensional reconstruction using mobile phone images. Mobile phone photogrammetry technology performs well in detecting shallow road surface textures but has certain limitations in capturing deeper textures. The texture parameters and the Abbott curve obtained using all three methods are comparable and fall within the same range of acceptability. This finding demonstrates the feasibility of using a mobile phone for pavement texture assessments with appropriate settings.

Optical and surface properties of Schiff base ligands and Cu(II) and Co(II) complexes

Objectives. To study the transition of electrons in 1,2-phenyl(4’-carboxy)benzylidene Schiff base ligand and transition metal ions, optical properties, as well as the surface chemistry of supported transition metals using diffuse reflectance spectroscopy (DRS); to study the roughness and morphology of the Schiff base ligand and its complexes using atomic force microscopy (AFM).Methods. DRS, AFM, and Fourier-transform infrared spectroscopy instruments were used to identify electron transitions, optical properties, and surface morphology in Schiff base ligands and their complexes.Results. The DRS revealed the d–d transitions and charge transfer shifts of all compounds, and helped identify the structure of the ligand. One of the optical properties studied was the energy gap calculation of the ligand and its complexes. The copper complex exhibited more semiconducting behavior with surface morphology properties such as surface roughness parameters lower than those of the ligand and the cobalt complex. This can be attributed to the smaller size of the copper atom, as well as lower electron transitions compared to the cobalt complex and the square planar bonding shape.Conclusions. In Schiff base ligands, the reflectance spectrum bands reveal three electron transitions: n→π*, π→π*, and σ→σ* transitions. In cobalt complexes, four transitions are indicated: 4A2(F)→4T1(F), 4A2(F)→4T1(P), charge transfer bands, and tetrahedral geometry. Copper complexes exhibit three transitions: 2B1g→2A1g, 2B1g→2Eg, and charge transfer bands, with a square planar geometry for their structure. The energy gap calculations were 2.42, 2.29, and 2.30 eV, respectively. In the case of the SH ligands, copper complexes, and cobalt complexes, all compounds exhibited semiconductor properties. However, the complexes displayed increased conductivity due to the influence of the metal and coordination structure.

Heat transfer analysis of hybrid nanofluid under the effects of surface roughness along with velocity and thermal slips

AbstractSurface roughness has a great impact on the peristaltic motion of nanofluid flow and plays an important role in engineering, manufacturing, and material sciences. During tissue engineering, imaging techniques, implant surface finish, surgical instrument texture, and tissue engineering, and so forth. This study explores the effects of electrical double layers, surface roughness, velocity slip, and thermal slip to investigate the heat transfer rate of cobalt and alumina nanoparticles with water through uniform and nonuniform horizontal tubes. In the present study, the Jeffrey nanofluid flow model is chosen to investigate the heat transfer phenomenon of hybrid nanofluids based on alumina and cobalt nanoparticles suspension in water. The effects of electroosmosis, surface roughness, viscous dissipation, heat source/sink parameter, velocity, and thermal slips are also under consideration during the peristaltic motion of hybrid nanofluid in uniform and nonuniform tubes. The mathematical software MATHEMATICA 13.3 is utilized to find the exact solution and graphical results to investigate the complicated flow behavior. It is noticed that the velocity near the walls of the tube is lower for the surface roughness parameter and higher in the core part. The behavior of velocity for the remaining parameter is the opposite. The temperature of the current fluid flow increases for all parameters except the surface roughness parameter. The effects of velocity for hybrid nanofluid are prominent as compared with nanofluid in the core part. The temperature profile and heat transfer rate for hybrid nanofluids are lower as compared with nanofluids, which shows the cooling effects. This study is beneficial for hyperthermia, gene therapy, drug delivery, and tissue engineering.

Experimental Investigation on the Important Factors on Structural Adhesive Joint Strength of Fiber-Reinforced Epoxy Composites

The static strength of fiber-reinforced epoxy composite structural adhesive lap joints was examined experimentally. Surface roughness and geometrical control parameters (adherent and adhesive kinds) were assessed for their effects. To examine load, elongation, and strength at failure, tensile tests were conducted. Cyanoacrylate glue outperformed SHCP 268 resin, and glass fiber-reinforced epoxy composites outperformed sisal fiber-reinforced epoxy composites. The study offers information on how to maximize adhesive bonding for lightweight multi-material design construction.

Surface Treatment of Oak Wood with Silica Dioxide Nanoparticles and Paraloid B72

Wood is a valuable material with incomparable advantages, though it is susceptible to biotic and abiotic factors action that affect it adversely and shorten its service life. In the current study, the surface modification of oak wood is carried out through brief immersion in a solution of acrylic polymer Paraloid B72, in which silica dioxide nanoparticles in the form of nanopowder were dissolved at different contents (1, 2, 3, and 4% w/v of the solution) aiming at the elimination of wood material hygroscopicity, and the protection and improvement of other properties. Specifically, the modified and unmodified wood specimens were characterized in terms of physical characteristics (density, equilibrium moisture content, colour, and surface roughness), hygroscopic properties (swelling and absorption percentage) and accelerated weathering performance using xenon light and cycles of moisturizing and drying. The results revealed the dimensional stability of the samples and a significant increase in the hydrophobicity of the modified wood, as well as a significant increase in the resistance to the ageing/weathering factors of oak wood, which was proportional to the increase in the presence of nanoparticles in the Paraloid B72 solution. The colour of the treated samples slightly changed towards darker shades, more reddish and yellowish (with L* to decrease, while a* and b* to slightly increase), though the treated wood revealed higher colour stability. The surface roughness parameters (Ra, Rq, and Rz) increased significantly, restricting the wide application of the treated wood in indoor or outdoor applications where surface roughness constitutes a critical factor. The findings of the current work contribute not only to the production of longer-lasting wood and timber structures, but also to the conservation of the existing weathered heritage timber structures.

Synergistic effects of deep eutectic solvents on the morphology and performance of polysulfone ultrafiltration membranes

This study investigates the synthesis of flat sheet asymmetric Polysulfone (PSF) membranes using the Non-Solvent Induced Phase Separation (NIPS) method, enhanced by incorporating Deep Eutectic Solvents (DES) composed of Choline Chloride (ChCl) and DL-Malic Acid (MA). The research explores the individual and combined effects of ChCl and MA on membrane morphology and performance. Comprehensive characterization techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy-Universal Attenuated Total Reflectance (FTIR-UATR), and Atomic Force Microscopy (AFM), were employed to analyze the structural and surface properties of the membranes. Key performance metrics such as Pure Water Permeability (PWP), protein and dye rejection, fouling behavior, porosity, surface hydrophilicity, and mechanical strength were evaluated. Results demonstrated that integrating DES into the PSF matrix significantly improved membrane properties. The 3% DES membrane exhibited the highest Pure Water Permeability (PWP) of 186.82 L/m2h/bar, the lowest water contact angle of 68.8°, and optimal balance in surface roughness parameters, leading to superior antifouling properties with high flux recovery ratio (FRR) and balanced reversible (Rr) and irreversible fouling (Rir) components. The ChCl (HBA) membrane displayed a notable PWP of 121.62 L/m2h/bar, large pore sizes (42.72 nm), and moderate surface roughness (Ra of 3.32 nm). In contrast, the MA (HBD) membrane demonstrated the highest hydrophilicity with the lowest contact angle (70.7°) and a compact, robust structure, despite its smallest pore sizes and lack of permeability. The findings underscore the synergistic effect of DES formation in the membrane, improving overall performance for ultrafiltration applications. This study provides valuable insights into the distinct roles of ChCl as an HBA and MA as an HBD in DES-modified PSF membranes, revealing their individual contributions and the importance of optimizing DES components and concentrations for specific filtration applications.

Experimental study of the surface finishing of CNC magnetic abrasive finishing based on ANN

ABSTRACT CNC Magnetic Abrasive Finishing (CNC MAF) is famous for aluminium sheet processing. This study used an artificial neural network (ANN) analytical model with a Bayesian regularisation algorithm (BR) to examine how machine parameters (rotation speed, feed rate, depth of cut, and several passes) affect surface roughness during CNC MAF of aluminium sheet. Experimental and quantitative data proved its prediction ability. ANN model to select the best machine parameters for low surface roughness. The perfect numerical solution was experimentally tested, and surface morphology and roughness were used to evaluate processing quality under optimal machine parameters. The ANN model is also compared to Taguchi L16 for prediction and optimisation. Compared to ANN, prediction and optimal surface finishing mean absolute error are 96% lower. The results show that the ANN model is better at studying machine configuration during CNC MAF of Al sheet. SEM and 3D Optical profilometer were also used to analyze the Al sheet. The UV-VIS Spectrophotometer measures Al polished sample reflectance at 200–700 nm.

A Novel Normal Contact Stiffness Model of Bi-Fractal Surface Joints

The contact stiffness of the mechanical joint usually becomes the weakest part of the stiffness for the whole machinery equipment, which is one of the important parameters affecting the dynamic characteristics of the engineering machinery. Based on the three-dimensional Weierstrass–Mandelbrot (WM) function, the novel normal contact stiffness model of the joint with the bi-fractal surface is proposed, which comprehensively considers the effects of elastoplastic deformation of asperity and friction factor. The effect of various parameters (fractal dimension, scaling parameter, material parameter, friction factor) on the normal contact stiffness of the joint is analyzed by numerical simulation. The normal contact stiffness of the joint increases with an increase in the fractal dimension, normal load, and material properties and decreases with an increase in the scaling parameter. Meanwhile, the fractal parameters of the equivalent rough surface of the joint are calculated by the structural function method. The experimental results show that when the load is between 14 and 38 N∙m, the error of the model is within 20%. The normal contact stiffness model of the bi-fractal surface joint can provide a theoretical basis for the analysis of the dynamic characteristics of the whole machine at the design stage.

An assessment of PLA/wood with PLA core sandwich multilayer component tensile strength under different 3D printing conditions

Material extrusion is increasingly used to make functional parts in small batches that are challenging to produce with traditional machining. Also, intensive efforts are being made to develop new eco–friendly materials. This work investigates the strength of multilayer samples made in sandwich form with 4–5–4 layers of 0.3 mm layer thickness, externally with polylacticacid wood (PLA/wood, 61.5 % of specimens' material) and internally with pure PLA (38.5 % of specimens' material), under tensile loads. The intent is to investigate the possibility of manufacturing biocompatible components that take advantage of the excellent surface properties of wood externally and the durability properties of PLA internally. For this purpose, a designed experiment following the Taguchi L9 orthogonal array was prepared, and nine samples were fabricated: three with pure PLA, three with a sandwich PLA/wood–PLA–PLA/wood form, and three with composite PLA/wood form. Printing speed and temperature were varied during the experiment, and the results were examined using the analysis of means and residuals. Sandwich specimens improve tensile strength and elastic modulus by 100 % and 50 % compared to PLA/wood components while exhibiting slightly better surface roughness parameters, i.e., Ra and Rz, about ∼10 % lower values. Additionally, even if PLA parts showed better strength and surface texture than sandwich parts (∼100 % and ∼56 % higher tensile strength and elastic modulus), they had lower performance in terms of PLA–PLA/wood material ratio, i.e., 160 % more PLA than sandwich parts. The findings of this research, with the potential to design functional and sustainable new products with optimal performance, are significant and can be exploited in various industries.

EFFECT OF BUILD POSITION ON SURFACE ROUGHNESS OF SLM PRINTED INCONEL 718

The present work investigates the variation of the surface roughness due to the build position of specimens with respect to the inert gas flow direction and re-coater movement direction. Selective laser melting (SLM) method was used to study this effect using Inconel 718 as workpiece material. A total of 21 samples were placed equidistant from each other on the built plate to observe the effect of gas flow and re-coater movement. The effect of these parameters on the printed samples was analyzed in terms of the profile surface roughness parameter such as Ra and Rz in the build direction. The result showed that samples placed near the gas inlet and the re-coater starting position had larger roughness as compared to the samples placed further from the gas inlet and re-coater end position. The result showed that the profile average roughness parameter values varied from Ra = 5.02 µm to 14.7 µm and profile maximum height surface parameter varied from Rz = 47.61 µm to 118.3 µm for all the printed samples. Surface topography of the samples was also studied which showed common printing defects such as cracks, micropores, local solidified melt pools, and dimples. The study opens an avenue to explore and optimize the placement of the printing sample on the build plate with respect to the inlet gas flow and re-coater movement directions for better surface roughness.

Using bearing ratio curves to quantify the surface roughness parameters of fly ash-teff straw ash-based geopolymer mortars

Considering the prominent attributes of surface roughness parameters, the closer their solutions are to real surfaces, the more appropriate they are for civil engineering applications. One of the steps that can be considered for such applications is to incorporate the bearing ratio curve (BRC) parameters in the study of civil engineering materials. In this research, the bearing ratio curves have been used for the first time to quantify the surface roughness attributes of fly ash-teff straw ash-based geopolymer mortars. For various cases, the roughness parameters in the V-group are compared with the roughness parameters in the Rk group, which contributes to the attractiveness of this research. The fly ash-teff straw ash-based geopolymer mortar specimens in this study are dominated by smooth surfaces, as evidenced by the Rvk and Rpk values of less than 0.21 μm for all specimens. The study highlights that if such surfaces are to be used in mortar-to-mortar bonding, imposed surface roughness could be required to enhance the bond strength of the layers. In addition, the results indicate that critical roughness parameters can be identified from the bearing ratio curves when a surface is undergoing roughness transformations. These findings provide a step towards the understanding of BRC parameters for fly ash-teff straw ash-based geopolymer mortar surfaces. Overall, the approach demonstrated in this study could also accelerate and promote the surface roughness characterisation for geopolymer mortars and could be extended to unlock peculiar surface roughness properties for other civil engineering materials.

Optimization of abrasive slurry assisted rotating ultrasonic machining for enhanced micro-channel fabrication on ceramic silicon wafer (111)

This study examined the impact of abrasive slurry assisted Rotating Ultrasonic Machining (RUM) using Boron Carbide (B4C) powder of three mesh sizes: 400 Mesh, 600 Mesh, and 800 Mesh. The effects of abrasive size, feed rate, and tool rotation on Material Removal Rate (MRR) and Surface Roughness (SR) were investigated. The highest MRR of 3.454 mm³/min was achieved with 400 mesh, 30 mm/min feed rate, and 1250 rpm due to larger abrasive size, medium feed rate, and medium tool rotation velocity, while the lowest MRR of 0.284 mm³/min was noted with 600 mesh, 30 mm/min feed rate, and 1500 rpm, attributed to intermediate abrasive size and high tool rotation. The lowest SR of 1.16 μm was observed at 800 mesh, 15 mm/min feed rate, and 1500 rpm, resulting from smaller abrasive size and higher tool rotation facilitating polishing action and vibrational dampening. The highest SR of 3.71 μm occurred at 400 mesh, 45 mm/min feed rate, and 1500 rpm, due to larger abrasive size, higher feed rate, and tool rotation, increasing surface corrosion. ANOVA and regression analyses highlighted mesh size as the most significant parameter for both MRR and SR, with strong model-experimental value correlations. The findings demonstrate the suitability of abrasive slurry assisted RUM for fabricating micro-channels in X-Ray, optoelectronic, and semiconductor applications.

Effects of Time-Elapsed Bleaching on the Surface and Mechanical Properties of Dentin Substrate Using Hydrogen Peroxide-Free Nanohydroxyapatite Gel.

There is a critical need to address concerns surrounding the potential impact of bleaching gels specifically on the tooth substrate. Therefore, this laboratory investigation aimed to assess the impact of a hydrogen peroxide (HP)-free bleaching (HiSmileTM) in comparison to an HP-based bleaching (Opalescence RegularTM) on the surface and mechanical characteristics of tooth substrate. Sixty sound human premolar teeth were sectioned to produce dentin fragments and divided into two primary groups based on the bleaching agent used. Each group was subdivided into three subgroups (n = 10) per distinct bleaching regimens: (T1) fragments underwent a 7-day immersion in distilled water at 37°C without any bleaching treatment, (T2) fragments underwent a 7-day immersion in distilled water at 37°C, with the application of bleaching gel occurring on the seventh day for 10minutes, and (T3) fragments underwent a bleaching regimen for seven consecutive days, each session lasting for 10minutes. The initial and final evaluations of surface roughness, nano-hardness, and elastic modulus were performed. Following the bleaching regimens of T3, a composite stub was fabricated on the dentin fragments for the shear bond strength (SBS) test. Statistical testing was accomplished using the analysis of variance (P < 0.05). HP-based bleaching gel showed significant differences between measurement intervals in surface roughness, elastic modulus, and SBS parameters (P < 0.05). In contrast, HP-free bleaching gel showed insignificant differences within the group (P > 0.05). The SBS between dentin-composite was significantly affected with the use of HP-based bleaching gel, while HP-free bleaching gel showed insignificant difference between measurement intervals. The qualitative validation of the treatment's impact was further demonstrated using the scanning electron microscopy. The findings suggest that the bonding stability of composite restorations to dentin may be compromised after bleaching with an HP-based gel, whereas immediate bonding procedures can be safely conducted following the application of an HP-free bleaching gel.

Piezoelectric Ultrasonic Local Resonant Ultra-Precision Grinding for Hard-Brittle Materials.

Hard-brittle materials are widely used in the optics, electronics, and aviation industries, but their high hardness and brittleness make it challenging for traditional processing methods to achieve high efficiency and superior surface quality. This study aims to investigate the application of ultrasonic local resonant grinding to sapphire to improve the efficiency and meet the requirements for the optical window in the surface roughness of the material. The resonant frequency of a piezoelectric ultrasonic vibration system and the vibration amplitude of a grinding head's working face were simulated and tested, respectively. The results of ultrasonic grinding experiments showed that the local resonant system reduced the surface roughness parameter (Ra) of sapphire to 14 nm and improved its surface flatness to 44.2 nm, thus meeting the requirements for the ultra-precision grinding of sapphire. Compared with a conventional resonant system, the surface roughness of the sapphire ground with the local resonant system was reduced by 90.79%, its surface flatness was improved by 81.58%, and the material removal rate was increased by 31.35%. These experimental results showed that ultrasonic local resonant grinding has better effects than those of conventional ultrasonic grinding in improving surface quality and increasing the material removal rate.

Grinding of C/SiC ceramic matrix composites: Influence of grinding parameters on tool wear

C/SiC Ceramic Matrix Composites (CMCs) have been identified as a key material for improving high-speed braking systems and aerospace components as they offer low density, and high specific strength at high temperatures. Grinding is often used for the machining stage due to the high hardness, heterogeneity, and brittle nature of CMSs. Previous studies have explored the effect of grinding parameters, but most of them do not indicate whether they have used the same grinding wheel for all tests. In fact, there is limited understanding of how wear impacts process performance over the grinding wheel's lifespan. In this work, the effect of grinding wheel wear on cutting forces is addressed and grinding wheel topography is analyzed with the objective of identifying a parameter that allows to quantify grinding wheel wear in a non-destructive way. Results have shown that, after a short conditioning stage, cutting forces increase approximately linearly with the machined length. For the machining conditions analyzed, normal forces increase 200 % in the first machined meter (first stage), then rise 17 % per meter thereafter (second stage). Tangential forces rise 300 % in first meter and then climb 27 % per meter subsequently. In this second stage, force ratio approaches a constant value and the generation of flat surfaces on the diamond grains is the dominating wear mechanism. Under such conditions, 3D surface roughness parameters Sa, Sq, Spk and Sku have been proven to be useful for monitoring wheel wear.

Assessment of concrete-to-concrete shear bond behavior using 3-D direct shear testing

The interfaces that develop when fresh concrete is poured onto existing substrates are noted for their vulnerability and influence on the durability and integrity of the composite structure. Studies on the shear bond properties and failure mechanisms of such composite concrete-to-concrete joints under normal stress are essential for developing predictive and numerical models that accommodate various levels of joint substrate roughness. This study aims to use an innovative 3D shearing box, BCR3D, to analyze the shear behavior of concrete-to-concrete joints under direct shear tests at a constant normal stress. The influence of the degree of surface roughness on the pure shear behavior of these joints was assessed at a normal stress level of 1 MPa. The substrate post-hardening surface morphology was evaluated using a high-resolution laser profilometer. Statistical surface roughness parameters were computed using MATLAB. A parametric study was carried out involving bond strength, residual shear stress, contractive-dilative behaviors, and total fracture energy. Results showed that bond strength, dilative normal displacement, and total fracture energy were proportional to the substrate surface roughness. Residual shear stress was not affected by the initial surface roughness. Dilative normal displacements were more significant for specimens with higher surface substrate roughness due to interlocking, with values reaching up to 1.77 mm. Joints with high substrate surface roughness exhibited similar bond strength and fracture energy to those obtained from the monolithic specimens, underscoring the significance of substrate preparation before casting new concrete layers.

Comparative Strength Study of Indirect Permanent Restorations: 3D-Printed, Milled, and Conventional Dental Composites.

Background/Objectives: Limited research has been performed to assess the strength of resin-bonded 3D-printed restorations. Based on that, this study investigates the impact of different manufacturing methods on the fracture load of indirect composite restorations (ICRs) following an aging process. Methods: Three manufacturing techniques-conventional (CRC), milled (MRC), and printed (PRC)-were evaluated using 60 specimens, each with a diameter of 10 mm and a thickness of 1.0 mm. Sandblasting with Al2O3 particles was employed to optimize the bonding process, significantly influencing surface roughness parameters (Ra, Rz, RSm). All specimens were bonded to the dentin analog using composite resin cement and subjected to either 10,000 thermocycles (TC) or storage (ST) at 37 °C in distilled water. Fracture load assessments were performed using a universal testing machine. A finite element analysis was conducted to assess stress distribution. Results: Two-way ANOVA results indicated that the manufacturing method significantly affected mean fracture load values (p < 0.001), with PRC showing the highest mean fracture load (4185 ± 914 N), followed by MRC (2495 ± 941 N) and CRC (599 ± 292 N). The aging protocol did not have a significant impact on fracture load. Conclusions: This study revealed that 3D-printed resin composite exhibited comparable strength to milled resin composite when adhesively cemented, suggesting it is a promising option for indirect composite restorations based on its mechanical performance. However, further research is needed to evaluate its bond strength and optimal surface treatment methods to prevent early debonding.