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Htat HL, Takaichi A, Kajima Y, Kittikundecha N, Kamijo S, Hanawa T, Wakabayashi N. Influence of stress-relieving heat treatments on the efficacy of Co-Cr-Mo-W alloy copings fabricated using selective laser melting. J Prosthodont Res 2024; 68:310-318. [PMID: 37438109 DOI: 10.2186/jpr.jpr_d_22_00283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Purpose This study aimed to evaluate the influence of stress-relieving heat treatments on the metal-ceramic bond strength and fitness accuracy of selective laser melting (SLM)-fabricated Co-Cr alloy copings.Methods SLM-manufactured Co-Cr samples were stress-relieved at 750 (Ht-750) and 1150 °C (Ht-1150). The microstructure, surface roughness, metal-ceramic bond strength, marginal and internal fit, Vickers hardness, and residual stress were then compared with those of the non-heat-treated group (As-built). The results were analyzed using one-way ANOVA and post-hoc tests (Tukey's or Student's t test) (P = 0.05).Results The microstructure of the Ht-1150 samples had a brittle oxide layer and lower surface roughness, resulting in significantly lower bond strength values than those of the other groups. The As-built group exhibited significantly lower marginal gap values than the Ht-750 and Ht-1150 groups. Therefore, the post-heat treatments degraded the marginal fitness. The surface residual stress in all sample groups were compressive because of the sandblasting effect. The compressive stresses were larger in Ht-1150 than in As-built and Ht-750 owing to their low hardness values.Conclusions Stress-relief annealing porcelain-fused-to-metal single crowns does not improve bond strength and degrades fitness accuracy because additional post-heat treatments induce thermal distortion. These findings are expected to facilitate the direct application of As-built SLM single crowns in dentistry to minimize post-manufacturing costs and time.
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Affiliation(s)
- Hein Linn Htat
- Department of Advanced Prosthodontics, Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Atsushi Takaichi
- Department of Advanced Prosthodontics, Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yuka Kajima
- Department of Advanced Prosthodontics, Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Nuttaphon Kittikundecha
- Department of Conservative Dentistry and Prosthodontics, Faculty of Dentistry, Srinakharinwirot University, Bangkok, Thailand
| | - Shingo Kamijo
- Basic Oral Health Engineering, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
| | - Takao Hanawa
- Department of Metallic Biomaterials, Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan
| | - Noriyuki Wakabayashi
- Department of Advanced Prosthodontics, Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
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Lekatou AG, Emmanouilidou S, Dimitriadis K, Baikousi M, Karakassides MA, Agathopoulos S. Simulating porcelain firing effect on the structure, corrosion and mechanical properties of Co-Cr-Mo dental alloy fabricated by soft milling. Odontology 2024; 112:372-389. [PMID: 37642767 PMCID: PMC10925571 DOI: 10.1007/s10266-023-00849-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Accepted: 08/18/2023] [Indexed: 08/31/2023]
Abstract
This study aims at evaluating the effect of simulating porcelain firing on the microstructure, corrosion behavior and mechanical properties of a Co-Cr-Mo alloy fabricated by Metal Soft Milling (MSM). Two groups of Co-28Cr-5Mo specimens (25 × 20 × 3 mm) were prepared by MSM: The as-sintered (AS) specimens and the post-fired (PF) specimens that were subjected to 5 simulating porcelain firing cycles without applying the ceramic mass onto their surface. Phase identification by X-ray Diffraction (XRD), microstructure examination by optical microscopy and Scanning Electron Microscopy combined with Energy-Dispersive X-ray Spectroscopy (SEM/EDX), corrosion testing by cyclic polarization and chronoamperometry in simulated body fluid (SBF), the latter test accompanied by Cr3+ and Cr6+ detection in the electrolyte through the 1.5-diphenylcarbazide (DPC) method and UV/visible spectrophotometry, and mechanical testing by micro-/nano-indentation were conducted to evaluate the effect of the post-firing cycles on the properties of Co-Cr-Mo. The results were statistically analyzed by the t test (p < 0.05: statistically significant). All specimens had a mixed γ-fcc and ε-hcp cobalt-based microstructure with a dispersion of pores filled with SiO2 and a fine M23C6 intergranular presence. PF led to an increase in the ε-Co content and slight grain coarsening. Both AS and PF alloys showed high resistance to general and localized corrosion, whereas neither Cr6+ nor Cr3+ were detected during the passivity-breakdown stage. PF improved the mechanical properties of the AS-alloy, especially the indentation modulus and true hardness (statistically significant differences: p = 0.0009 and 0.006, respectively). MSM and MSM/simulating-porcelain firing have been proven trustworthy fabrication methods of Co-Cr-Mo substrates for metal-ceramic prostheses. Moreover, the post-firing cycles improve the mechanical behavior of Co-Cr-Mo, which is vital under the dynamically changing loads in the oral cavity, whereas they do not degrade the corrosion performance.
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Affiliation(s)
- Angeliki G Lekatou
- Department of Materials Science and Engineering, School of Engineering, University of Ioannina, 451 10, Ioannina, Greece
- Institute of Materials Science and Computing, University Research Center of Ioannina (URCI), 451 10, Ioannina, Greece
| | - Sevasti Emmanouilidou
- Department of Materials Science and Engineering, School of Engineering, University of Ioannina, 451 10, Ioannina, Greece
| | - Konstantinos Dimitriadis
- Department of Materials Science and Engineering, School of Engineering, University of Ioannina, 451 10, Ioannina, Greece.
- Division of Dental Technology, Department of Biomedical Sciences, University of West Attica, 122 43, Athens, Greece.
| | - Maria Baikousi
- Department of Materials Science and Engineering, School of Engineering, University of Ioannina, 451 10, Ioannina, Greece
| | - Michael A Karakassides
- Department of Materials Science and Engineering, School of Engineering, University of Ioannina, 451 10, Ioannina, Greece
| | - Simeon Agathopoulos
- Department of Materials Science and Engineering, School of Engineering, University of Ioannina, 451 10, Ioannina, Greece
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Mushtaq Alam M, Sugail M, Kannan S. Development, Physiochemical characterization, Mechanical and Finite element analysis of 3D printed Polylactide-β-TCP/α-Al 2O 3 composite. J Mech Behav Biomed Mater 2023; 147:106161. [PMID: 37801964 DOI: 10.1016/j.jmbbm.2023.106161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Revised: 09/29/2023] [Accepted: 10/02/2023] [Indexed: 10/08/2023]
Abstract
Herein, material extrusion (MEX) technique is utilized to develop 3D printed models based on reinforcing β-Ca3(PO4)2/α-Al2O3 composite in polylactide (PLA) matrix. β-Ca3(PO4)2/α-Al2O3 composite has been synthesized through co-precipitation method and the phase content of β-Ca3(PO4)2 and α-Al2O3 components are respectively determined as 64 and 36 wt%. The resultant β-Ca3(PO4)2/α-Al2O3 composite mixed with PLA at various weight ratios were extruded as filaments and subsequently 3D printed into definite shapes for the physiochemical, morphological and mechanical evaluation. 3D printed bodies that comprise 5 wt % β-Ca3(PO4)2/α-Al2O3 composite yielded an increasing tensile, compressive and flexural strength in the corresponding order of ∼15, ∼15 and 22% than 3D printed pure PLA. Further, the Representative volume element (RVE) unit cells developed based on the various investigated compositions of PLA-β-Ca3(PO4)2/α-Al2O3 were subjected to mechanical evaluation through Finite element analysis (FEA) under both static and dynamic loading conditions on ASTM standard specimens. The results from experimental and FEA analysis demonstrated good uniformity that confirmed the reinforcement of 5 wt % β-Ca3(PO4)2/α-Al2O3 in PLA matrix as an optimum combination to yield better mechanical strength.
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Affiliation(s)
- M Mushtaq Alam
- Centre for Nanoscience and Technology, Pondicherry University, Puducherry, 605 014, India
| | - Mohamed Sugail
- Centre for Nanoscience and Technology, Pondicherry University, Puducherry, 605 014, India
| | - S Kannan
- Centre for Nanoscience and Technology, Pondicherry University, Puducherry, 605 014, India.
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Zhou Y, Dong X, Li N, Yan J. Effects of posttreatment on metal-ceramic bond properties of selective laser melted Co-Cr dental alloy. Part 1: Annealing temperature. J Prosthet Dent 2023; 129:657.e1-657.e9. [PMID: 36842952 DOI: 10.1016/j.prosdent.2022.11.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 11/07/2022] [Accepted: 11/07/2022] [Indexed: 02/28/2023]
Abstract
STATEMENT OF PROBLEM Dental cobalt-chromium (Co-Cr) alloy manufactured by selective laser melting (SLM) is not recommended for clinical applications before annealing because of excessive residual stress. However, limited information is available regarding the relationship between annealing temperature and the metal-ceramic bond properties of SLM Co-Cr alloys. PURPOSE The purpose of this in vitro study was to investigate the effects of annealing temperature on the metal-ceramic bond properties of SLM Co-Cr alloys. MATERIAL AND METHODS Four groups with different annealing temperatures (850 °C; 950 °C; 1050 °C; 1150 °C) were prepared by using SLM techniques. Bond strengths were measured by using a 3-point bend test; subsequently, debonded surface morphologies and elements were assessed by using a scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS). The area fraction of adherence porcelain (AFAP) value was introduced to analyze fracture characteristics. Microstructural and interfacial characteristics were characterized by SEM/EDS and X-ray diffraction analysis. The coefficient of thermal expansion (CTE) test was used to analyze thermal matching. A 1-way ANOVA and the Tukey honestly significant difference tests were used to analyze bond strengths and AFAP values statistically (α=.05). RESULTS The mean ±standard deviation values of the metal-ceramic bond strengths were 40.68 ±4.34 MPa for the 850 °C group, 37.54 ±5.34 MPa for the 950 °C group, 45.97 ±2.18 MPa for the 1050 °C group, and 50.79 ±1.79 MPa for the 1150 °C group. Significant differences (P<.05) were observed among all groups. Debonded surfaces and AFAP analysis displayed a mixed fracture mode of adhesive and cohesive fracture, and 1150 °C-annealing specimens exhibited better fracture characteristics close to cohesive fractures. As the temperature increased, native oxide film thicknesses remained unchanged; the 850 °C group had the thinnest diffusion layer, while the other 3 groups had similar thicknesses. Although the 1050 °C and 1150 °C groups displayed higher CTE values, their microstructures were more conducive to atomic diffusion and improved chemical bonding. Microstructure analysis found that ε phase and second-phase precipitates jointly affected metal-ceramic bond strength. CONCLUSIONS Annealing temperatures affected the metal-ceramic bond strengths of SLM Co-Cr porcelain specimens. 1150 °C annealing SLM Co-Cr specimens displayed higher bond strengths and improved fracture and interface characteristics among the 4 groups.
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Affiliation(s)
- Yanan Zhou
- Lecturer, School of Mechanical Engineering, Shandong University of Technology, Zibo, PR China
| | - Xin Dong
- Graduate student, School of Mechanical Engineering, Sichuan University, Chengdu, PR China
| | - Ning Li
- Professor, School of Mechanical Engineering, Sichuan University, Chengdu, PR China
| | - Jiazhen Yan
- Associate Professor, School of Mechanical Engineering, Sichuan University, Chengdu, PR China.
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Analysis of microstructure and fatigue of cast versus selective laser-melted dental Co-Cr alloy. J Prosthet Dent 2022; 128:218.e1-218.e7. [PMID: 35786348 DOI: 10.1016/j.prosdent.2022.05.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 05/24/2022] [Accepted: 05/24/2022] [Indexed: 11/22/2022]
Abstract
STATEMENT OF PROBLEM The forces exerted on teeth and prostheses during mastication are repeated and dynamic, resulting in fatigue damage to dental prostheses. Most fractures of dental restorations are fatigue failure. The 4-point bend fatigue behavior of Co-Cr-Mo-W alloys manufactured by investment casting (CAST) and selective laser melting (SLM) has received little attention. PURPOSE The purpose of this in vitro study was to evaluate the 4-point bend fatigue property of dental Co-Cr alloys and determine the relationship between microstructure and the 4-point bend fatigue property of Co-Cr alloys created by traditional casting and SLM. These can guide the use of Co-Cr alloy in dentistry. MATERIAL AND METHODS Co-Cr-Mo-W alloys were fabricated with a dimension of 45×2×2 mm by investment casting and SLM. The 3-point bend test measured the ultimate bend strength with 3 specimens in each group. The 4-point bend fatigue test evaluated the fatigue life under various stresses, with 6 specimens in each group. The specimens were mechanically ground, polished, and electrochemically etched. Scanning electron microscopy was used to identify the microstructures of both etched specimens and fracture surfaces. X-ray diffraction investigations were used to determine the phases. Significant differences in the bend strength were analyzed by using the independent samples t test (α=.05), and the fatigue test was analyzed with ANCOVA (α=.05). RESULTS The mean ±standard deviation bend strength of SLM specimens was 1837 ±3 MPa, higher than the 1200 ±6 MPa for CAST specimens (P<.05). The maximum bend stress of the SLM specimens without fatigue failure was 735 MPa, which was statistically higher than the 394 MPa for CAST specimens (P<.05). The microstructure characteristics of the SLM alloy contributed to its excellent fatigue performance. In SLM alloy, the γ phase constituted the majority with some ε and Laves phases, while the cast alloy possessed higher ε and Laves phases. The grains of SLM alloy were equiaxed and fine, and the second phases were fine and dispersive. In contrast, the cast alloy possessed clear dendrites, and the second phases were sizable. CONCLUSIONS The SLM dental Co-Cr-Mo-W alloy had statistically better 4-point bend fatigue properties than cast alloy, which was associated with an improved microstructure.
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Effects of heat treatment on the microstructure, residual stress, and mechanical properties of Co-Cr alloy fabricated by selective laser melting. J Mech Behav Biomed Mater 2021; 126:105051. [PMID: 34959095 DOI: 10.1016/j.jmbbm.2021.105051] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 12/10/2021] [Accepted: 12/14/2021] [Indexed: 11/24/2022]
Abstract
The mechanical properties and residual stress of dental Co-Cr-Mo (CCM) alloy depend on the manufacturing and post-processing methods, which affect the prognosis of dental prostheses. Two CCM alloys manufactured by casting and selective laser melting (SLM) were compared, and the effect of heat treatment temperature for CCM alloys manufactured by SLM method was evaluated. Specimens were fabricated by casting (Cast Co-Cr) and SLM (SLM Co-Cr). SLM Co-Cr specimens were heat treated at 750, 950, and 1150 °C to compare their properties. Microstructures were analyzed via scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and electron backscattered diffraction (EBSD), and the residual stress was measured via x-ray diffraction (XRD). Mechanical properties were evaluated by a Vickers hardness test and a tensile test; fractography was performed after this. The SLM Co-Cr group exhibited a decrease in porosity, grain size, increase in solid solution limit, and high residual stress compared to Cast Co-Cr; the ultimate tensile strength, yield strength, and hardness were also higher. The microstructures, residual stresses, and mechanical properties differed significantly depending on the heat treatment, and the strength and hardness showed a tendency inverse to that of the elongation. Type I residual stresses mostly decreased after 750 °C heat treatment, however type II and III residual stresses remained even after 1150 °C heat treatment. SLM presented superior mechanical properties to casting. Considering the reduction of tensile residual stress and increased ductility, CCM alloys should be heat treated at a temperature of 950 °C or higher.
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Rylska D, Sokolowski G, Lukomska-Szymanska M. Does Simulated Porcelain Firing Influence Corrosion Properties of Casted and Sintered CoCr Alloys? MATERIALS 2021; 14:ma14154147. [PMID: 34361344 PMCID: PMC8348942 DOI: 10.3390/ma14154147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 07/22/2021] [Accepted: 07/22/2021] [Indexed: 11/16/2022]
Abstract
The aim of the study was to evaluate how heat processing used for dental porcelain firing influences the surface properties of sintered and casted CoCr alloy. Two CoCr alloys, Soft Metal LHK (milling in soft material and sintering) and MoguCera C (casting), were used for the study. The samples were examined using SEM-EDS before and after heat treatment. Next, corrosion examinations (Ecorr, jcorr, polarization curve, Ebr) were performed. Finally, the samples were evaluated under SEM. Based on the results, the following conclusions might be drawn: 1. Thermal treatment (porcelain firing) did not cause chemical impurities formation on the surface of CoCr alloy; 2. The sintered metal exhibited significantly higher corrosion resistance than the casted one due to its homogeneity of structure and chemical composition; 3. Heat treatment (porcelain firing) decreased the resistance of casted and sintered CoCr alloy to electrochemical corrosion. The reduction in corrosion resistance was significantly higher for the casted alloy than for the sintered alloy; 4. The corrosion resistance decrease might be due to an increased thickness and heterogeneity of oxide layers on the surface (especially for the casted alloy). The development of corrosion process started in the low-density areas of the oxide layers; 5. The sintered metal seems to be a favourable framework material for porcelain fused to metal crowns.
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Affiliation(s)
- Dorota Rylska
- Institute of Materials Science and Engineering, Lodz University of Technology, 1/15 Stefanowskiego St., 90-924 Lodz, Poland;
| | - Grzegorz Sokolowski
- Department of Prosthetics, Medical University of Lodz, 251 Pomorska St., 92-213 Lodz, Poland;
| | - Monika Lukomska-Szymanska
- Department of General Dentistry, Medical University of Lodz, 251 Pomorska St., 92-213 Lodz, Poland
- Correspondence: ; Tel.: +48-42-675-74-61
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Topological, Mechanical and Biological Properties of Ti6Al4V Scaffolds for Bone Tissue Regeneration Fabricated with Reused Powders via Electron Beam Melting. MATERIALS 2021; 14:ma14010224. [PMID: 33466387 PMCID: PMC7794945 DOI: 10.3390/ma14010224] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 12/19/2020] [Accepted: 12/29/2020] [Indexed: 12/11/2022]
Abstract
Cellularized scaffold is emerging as the preferred solution for tissue regeneration and restoration of damaged functionalities. However, the high cost of preclinical studies creates a gap between investigation and the device market for the biomedical industry. In this work, bone-tailored scaffolds based on the Ti6Al4V alloy manufactured by electron beam melting (EBM) technology with reused powder were investigated, aiming to overcome issues connected to the high cost of preclinical studies. Two different elementary unit cell scaffold geometries, namely diamond (DO) and rhombic dodecahedron (RD), were adopted, while surface functionalization was performed by coating scaffolds with single layers of polycaprolactone (PCL) or with mixture of polycaprolactone and 20 wt.% hydroxyapatite (PCL/HA). The mechanical and biological performances of the produced scaffolds were investigated, and the results were compared to software simulation and experimental evidence available in literature. Good mechanical properties and a favorable environment for cell growth were obtained for all combinations of scaffold geometry and surface functionalization. In conclusion, powder recycling provides a viable practice for the biomedical industry to strongly reduce preclinical costs without altering biomechanical performance.
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Lee WF, Wang JC, Hsu CY, Peng PW. Microstructure, mechanical properties, and retentive forces of cobalt-chromium removable partial denture frameworks fabricated by selective laser melting followed by heat treatment. J Prosthet Dent 2020; 127:115-121. [PMID: 33234303 DOI: 10.1016/j.prosdent.2020.06.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/22/2020] [Accepted: 06/23/2020] [Indexed: 10/22/2022]
Abstract
STATEMENT OF PROBLEM The effect of heat treatment on the microstructure and mechanical properties of cobalt-chromium (Co-Cr) removable partial denture (RPD) frameworks fabricated by selective laser melting (SLM) is not well understood. PURPOSE The purpose of this in vitro study was to evaluate the suitability of SLM-fabricated Co-Cr alloys followed by heat treatment as a framework for RPDs by determining the microstructure and mechanical properties. MATERIAL AND METHODS Dumbbell specimens and RPD frameworks were fabricated by using SLM followed by heat treatment. The effects of the heat treatment on the microstructure were studied by using optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Tensile and insertion and removal tests were performed to study the mechanical responses of selective laser melting followed by heat treatment specimens, including the ultimate tensile strength (UTS), 0.2% yield strength (0.2% YS), elongation (E), and retentive forces. Specimens fabricated by using the traditional lost-wax process were used as a control (casting) group. RESULTS X-ray diffraction indicated that the γ-face-centered cubic phase dominated SLM and selective laser melting followed by heat treatment specimens. Results from optical microscopy and SEM showed microstructural changes under different fabrication and postprocessing heat treatments; it was difficult to observe the grain boundary in the SLM group, whereas submicrometer-scale grains had formed in the selective laser melting followed by heat treatment group. The selective laser melting followed by heat treatment group exhibited the highest elongation and retentive forces compared with the casting and SLM groups. CONCLUSIONS SLM increased the mechanical properties of Co-Cr alloys. Postprocessing heat treatment further enhanced the tensile ductility. It is suggested that SLM followed by heat treatment is an efficient strategy for fabricating RPD frameworks.
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Affiliation(s)
- Wei-Fang Lee
- Assistant Professor, School of Dental Technology, Taipei Medical University, Taipei, Taiwan, Republic of China
| | - Jia-Chang Wang
- Professor, Department of Mechanical Engineering, National Taipei University of Technology, Taipei, Taiwan, Republic of China
| | - Ching-Ying Hsu
- Dental Technician, Department of Dentistry, Taipei Medical University Hospital, Taipei, Taiwan, Republic of China
| | - Pei-Wen Peng
- Associate Professor, School of Dental Technology, Taipei Medical University, Taipei, Taiwan, Republic of China.
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Shaw KA, Devito DP, Schmitz ML, Murphy JS. Are precontoured cobalt-chromium spinal rods mechanically superior to manually contoured rods? Spine Deform 2020; 8:871-877. [PMID: 32424695 DOI: 10.1007/s43390-020-00133-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 05/04/2020] [Indexed: 11/29/2022]
Abstract
STUDY DESIGN Laboratory based study. OBJECTIVE To compare reduction force and plastic deformation of cobalt-chromium (Co-Cr) spinal rods using a rigid, thoracolumbar spinal deformity model. Pre-contoured spinal rods are growing in their utilization for spinal deformity. Although there are theoretical advantages to pre-contouring rods, no previous studies have compared pre-contoured and manually contoured rods for their ability to maintain sagittal contour and resist mechanical load. METHODS A spinal deformity model was utilized, simulating a rigid, thoracolumbar spinal deformity fixated with pedicle screws. Roll-formed pre-contoured and manually contoured 5.5 mm and 6.0 mm Co-Cr rods were reduced to the model with a load cell attached to the apical screw to measure corrective force. Rods remained reduced in the model for 20 min and change in contour was assessed to characterize plastic deformation. RESULTS Twenty-four rods were tested with six rods per group (Table 1). The load to reduction was significantly lower in the 5.5 mm rods compared to the 6.0 mm rods (95% CI -254.0 to -61.42; p = 0.008). Although there was no difference in the corrective forces for manual and pre-contoured 5.5 mm rods (p = 0.722), the 6.0 mm rod produced significantly less corrective force compared to the manually contoured 6.0 mm rods (95% CI -134.42 to -5.317; p = 0.039). Additionally, rod contour for the manual group showed significantly less plastic deformation than the pre-contoured group in both 5.5 mm and 6.0 mm rods (5.5 mm: 57.1% vs. 61.6%, p = 0.006; 6.0 mm: 54.3% vs. 62.28%, p = 0.003). CONCLUSIONS Roll formed, pre-contoured Co-Cr rods demonstrated significantly greater plastic deformation when compared with manually contoured rods of the same diameter. Furthermore, 6.0 mm pre-contoured rods required significantly lower load for rod reduction, the equivalent of 15 lb-force. Post-manufacturing, roll-formed pre-contouring of larger diameter Co-Cr may impair the rods mechanical properties.
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Affiliation(s)
- K Aaron Shaw
- Department of Orthopedic Surgery, Dwight D. Eisenhower Army Medical Center, 300 East Hospital Road, Fort Gordon, GA, 30905, USA.
| | - Dennis P Devito
- Department of Pediatric Orthopedic Surgery, Children's Healthcare of Atlanta, Scottish Rite Campus, Atlanta, GA, USA
| | - Michael L Schmitz
- Department of Pediatric Orthopedic Surgery, Children's Healthcare of Atlanta, Scottish Rite Campus, Atlanta, GA, USA
| | - Joshua S Murphy
- Department of Pediatric Orthopedic Surgery, Children's Healthcare of Atlanta, Scottish Rite Campus, Atlanta, GA, USA
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Nkonta DT, Drevet R, Fauré J, Benhayoune H. Effect of surface mechanical attrition treatment on the microstructure of cobalt-chromium-molybdenum biomedical alloy. Microsc Res Tech 2020; 84:238-245. [PMID: 32914521 DOI: 10.1002/jemt.23580] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 07/15/2020] [Accepted: 08/11/2020] [Indexed: 11/09/2022]
Abstract
This research work describes the impact of the surface mechanical attrition treatment (SMAT) on the microstructure of cobalt-chromium-molybdenum (CoCrMo), a biomedical alloy commonly used for orthopedic applications. This surface treatment induces crystalline phases transformations characterized by X-ray diffraction (XRD) and selected area electron diffraction (SAED). The corresponding structural changes are observed from cross-section images obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the SMAT process induces the martensitic transformation of the CoCrMo alloy (from γ-fcc phase to ε-hcp phase) related to an important grain refinement due to twinning and sliding.
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Affiliation(s)
| | - Richard Drevet
- CeRTEV, Universidade Federal de São Carlos (UFSCar), São Carlos, Brazil
| | - Joël Fauré
- ITheMM, Université de Reims Champagne-Ardenne (URCA), Reims, France
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Zuchuat J, Maldonado Y, Botteri J, Decco O. In vivo effect of UV-photofunctionalization of CoCrMo in processes of guided bone regeneration and tissue engineering. J Biomed Mater Res A 2020; 109:31-41. [PMID: 32418271 DOI: 10.1002/jbm.a.37004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 04/08/2020] [Accepted: 04/19/2020] [Indexed: 12/20/2022]
Abstract
Photofunctionalization of implant materials with ultraviolet (UV) radiation have been subject of study in the last two decades, and previous research on CoCrMo discs have showed good results in terms of bioactivity and the findings of apatite-like crystals in vitro. In the current study, CoCrMo domes were photofunctionalized with UV radiation of 254 nm on their internal faces during 24 hr; they were implanted in rabbit tibia and remained for 3, 4, and 6 weeks. The potential to induce bone formation beneath the dome-shaped membranes was evaluated through morphometric, histologic, and density measurements; and the results were compared with those obtained under control untreated domes. Higher density values were observed for irradiated domes at 3 weeks, whereas higher volumes were obtained under photofunctionalized domes for longer periods (4 and 6 weeks). Histologically, woven bone was formed by endochondral ossification in all cases; differences in the architecture and size of the trabeculae and in the number of osteoblasts were noted between irradiated and non-irradiated samples. The UV radiation of 254 nm generated a larger bone volume fraction compared to that found in the absence of UVC radiation and induced an increase of density in the early stages of healing, leading to a better initial bone quality and improved osseointegration.
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Affiliation(s)
- Jésica Zuchuat
- Bioimplants Laboratory, Faculty of Engineering, National University of Entre Rios, Oro Verde, Entre Rios, Argentina.,National Scientific and Technical Research Council-CONICET, Buenos Aires, Argentina
| | - Ysaí Maldonado
- Imaging Service, Sanatorio Adventista Del Plata, 25 De Mayo 255, Villa Libertador General San Martín, Entre Ríos, Argentina
| | - Julián Botteri
- Bioimplants Laboratory, Faculty of Engineering, National University of Entre Rios, Oro Verde, Entre Rios, Argentina
| | - Oscar Decco
- Bioimplants Laboratory, Faculty of Engineering, National University of Entre Rios, Oro Verde, Entre Rios, Argentina
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Comparison of the Crystal Structure and Wear Resistance of Co-Based Alloys with Low Carbon Content Manufactured by Selective Laser Sintering and Powder Injection Molding. CRYSTALS 2020. [DOI: 10.3390/cryst10030197] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cobalt alloys are widely used in biomedicine, implantology, and dentistry due to their high corrosion resistance and good mechanical properties. The high carbon improves the wear properties, but causes fragility and dangerous cracking of elements during use. The aim of the present work was to analyze and compare the structure and wear resistance of Co-based alloy samples with low carbon content, produced by Selective Laser Sintering (SLS) and Powder Injection Molding (PIM). Structure characterization, mainly with the use of transmission electron microscopy, was applied to investigate the differences in tribological properties. The better resistance to abrasive wear for SLS was explained by the presence of a hard, intermetallic phase, present as precipitates limited in size and evenly distributed in the cobalt matrix. The second factor was the structure of the cobalt matrix, with dominant content of the hexagonal phase. By combining the characteristic features of the matrix and the reinforcing phase, the analyzed material gains an additional advantage, namely a higher resistance to abrasive wear.
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14
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Design, Optimization, and Evaluation of Additively Manufactured Vintiles Cellular Structure for Acetabular Cup Implant. Processes (Basel) 2019. [DOI: 10.3390/pr8010025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Cellular materials with very highly regulated micro-architectures are promising applicant materials for orthopedic medical uses while requiring implants or substituting for bone due to their ability to promote increased cell proliferation and osseointegration. This study focuses on the design of an acetabular cup (AC) cellular implant which was built using a vintiles cellular structure with an internal porosity of 56–87.9% and internal pore dimensions in the range of 600–1200 μm. The AC implant was then optimized for improving mechanical performance to reduce stress shielding by adjusting the porosity to produce stiffness (elastic modulus) to match with the bone, and allowing for bone cell ingrowth. The optimized and non-optimized AC cellular implant was fabricated using the SLM additive manufacturing process. Simulation (finite element analysis, FEA) was carried out and all cellular implants are finally tested under static loading conditions. The result showed that on the finite element model of an optimized implant, cellular has shown 69% higher stiffness than non-optimized. It has been confirmed by experimental work shown that the optimized cellular implant has a 71% higher ultimate compressive strength than the non-optimized counterpart. Finally, we developed an AC implant with mechanical performance adequately close to that of human bone.
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Solid-State Phase Transformations in Thermally Treated Ti-6Al-4V Alloy Fabricated via Laser Powder Bed Fusion. MATERIALS 2019; 12:ma12182876. [PMID: 31489893 PMCID: PMC6765979 DOI: 10.3390/ma12182876] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 07/30/2019] [Accepted: 09/04/2019] [Indexed: 11/28/2022]
Abstract
Laser Powder Bed Fusion (LPBF) technology was used to produce samples based on the Ti–6Al–4V alloy for biomedical applications. Solid-state phase transformations induced by thermal treatments were studied by neutron diffraction (ND), X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). Although, ND analysis is rather uncommon in such studies, this technique allowed evidencing the presence of retained β in α’ martensite of the as-produced (#AP) sample. The retained β was not detectable by XRD analysis, nor by STEM observations. Martensite contains a high number of defects, mainly dislocations, that anneal during the thermal treatment. Element diffusion and partitioning are the main mechanisms in the α ↔ β transformation that causes lattice expansion during heating and determines the final shape and size of phases. The retained β phase plays a key role in the α’ → β transformation kinetics.
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Microstructural evolution and resulting properties of differently sintered and heat-treated binder-jet 3D-printed Stellite 6. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2019; 102:276-288. [PMID: 31147000 DOI: 10.1016/j.msec.2019.04.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 04/04/2019] [Accepted: 04/04/2019] [Indexed: 01/01/2023]
Abstract
Stellite 6 components are manufactured from gas-atomized powder using binder-jet 3D-printing (BJ3DP) followed by curing and sintering steps for densification. Green parts are sintered at temperatures ranging from 1260 °C to 1310 °C for 1 h. Microstructural evolution and phase formation during sintering and aging are studied by optical and scanning electron microscopy, elemental analysis and X-ray diffraction. It was found that solid-state sintering was present at temperatures below 1280 °C with Cr-rich carbides present within grains; while supersolidus liquid phase sintering was the dominant sintering mechanism during sintering at 1290 °C and higher in which the Co-rich solid solution regions are surrounded by eutectic carbides. Sintering at 1300 °C resulted in the maximum density of ~99.8%, mean grain size of ~98 ± 6 μm with an average hardness of 307 ± 15 HV0.1 and 484 ± 30 HV0.1 within grain and at the boundaries, respectively. Aging was performed at 900 °C for 10 h leading to the martensitic transformation (fcc → hcp) as well as an increase in eutectic carbides at boundaries and nano-sized carbides within grains where the average hardness within grains and boundaries was enhanced to 322 ± 29 HV0.1 and 491 ± 58 HV0.1, respectively. Fibroblasts seeded on top of 3D-printed Stellite 6 discs displayed a cell viability of 98.8% ± 0.2% after 48 h, which confirmed that these materials are non-cytotoxic. Presented results demonstrate that binder jetting can produce mechanically sound complex-shaped structures as shown here on a denture metal framework and small-scale knee model.
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Al Jabbari YS, Barmpagadaki X, Psarris I, Zinelis S. Microstructural, mechanical, ionic release and tarnish resistance characterization of porcelain fused to metal Co-Cr alloys manufactured via casting and three different CAD/CAM techniques. J Prosthodont Res 2019; 63:150-156. [PMID: 30642700 DOI: 10.1016/j.jpor.2018.10.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 10/30/2018] [Accepted: 10/31/2018] [Indexed: 12/01/2022]
Abstract
PURPOSE To perform a comparative analysis of the microstructure, porosity, mechanical properties, corrosion, and tarnish resistance of Co-Cr alloys prepared by casting and three different computer aided designed/computer aided manufacturing (CAD/CAM) techniques. METHODS Four groups of metallic specimens were prepared, one each by conventional casting (CST), milling (MIL), selective laser melting (SLM), and milling soft metal (MSM). Ten samples were tested by X-rays, after which their microstructure and elemental composition were tested by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) analysis. Martens hardness (HM) and elastic index (ηIT) were determined by instrumented indentation testing (IIT), while modulus of elasticity (E) was determined by three-point bending. Corrosion measurements were tested according to International Organization for Standardization (ISO) 10271. The electrolytes were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The results were analyzed by one-way ANOVA and Holm-Sidak's multiple-comparison test (α=0.05). RESULTS The CST group illustrated internal flaws while all CAD/CAM group samples were found to be free of them. No statistically significant differences were identified among groups in their elemental composition. SLM showed the highest HM, followed by the MIL, CST, and MSM. Elastic index showed significant differences among all groups, with CST showing the lowest and SLM the highest values. SLM showed the highest elastic modulus values, followed by MSM, MIL, and CST. No significant differences were found in ionic release among groups. No surface deterioration after static and cyclic tarnish testing was determined. CONCLUSIONS The manufacturing procedure significantly affects the microstructure, porosity, and mechanical properties of Co-Cr alloys. In contrast, ionic release and tarnish resistance are independent of the manufacturing technique used.
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Affiliation(s)
- Youssef S Al Jabbari
- Dental Biomaterials Research and Development Chair, College of Dentistry, King Saud University, Riyadh, Saudi Arabia; Prosthetic Dental Sciences Department, College of Dentistry, King Saud University, Riyadh, Saudi Arabia.
| | | | | | - Spiros Zinelis
- Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece; Dental Biomaterials Research and Development Chair, College of Dentistry, King Saud University, Riyadh, Saudi Arabia
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Ucar Y, Ekren O. Effect of layered manufacturing techniques, alloy powders, and layer thickness on mechanical properties of Co-Cr dental alloys. J Prosthet Dent 2018; 120:762-770. [DOI: 10.1016/j.prosdent.2017.11.032] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2017] [Revised: 11/29/2017] [Accepted: 11/29/2017] [Indexed: 11/26/2022]
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Dan ML, Costea LV, Savencu CE, Porojan L. Influence of pH on the Corrosion Behaviour of Laser-Processed Co-Cr Dental Alloys in Artificial Saliva. ACTA ACUST UNITED AC 2018. [DOI: 10.1088/1757-899x/416/1/012036] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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20
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Harun W, Kamariah M, Muhamad N, Ghani S, Ahmad F, Mohamed Z. A review of powder additive manufacturing processes for metallic biomaterials. POWDER TECHNOL 2018. [DOI: 10.1016/j.powtec.2017.12.058] [Citation(s) in RCA: 110] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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21
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Torii M, Nakata T, Takahashi K, Kawamura N, Shimpo H, Ohkubo C. Fitness and retentive force of cobalt-chromium alloy clasps fabricated with repeated laser sintering and milling. J Prosthodont Res 2018; 62:342-346. [PMID: 29428170 DOI: 10.1016/j.jpor.2018.01.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 12/28/2017] [Accepted: 01/03/2018] [Indexed: 10/18/2022]
Abstract
PURPOSE With computer-aided design and computer-aided manufacturing (CAD/CAM), the study was conducted to create a removable partial denture (RPD) framework using repeated laser sintering rather than milling and casting techniques. This study experimentally evaluated the CAM clasp and compared it to a conventional cast clasp. METHODS After the tooth die was scanned, an Akers clasp was designed using CAD with and without 50μm of digital relief on the occlusal surface of the tooth die. Cobalt-chromium (Co-Cr) alloy clasps were fabricated using repeated laser sintering (RLS) and milling as one process simultaneously (hybrid manufacturing; HM). The surface roughness of the rest region, gap distances between clasp and tooth die, initial retentive forces, and changes of retentive forces up to 10,000 insertion/removal cycles were measured before and after heat treatment. The HM clasp was compared to the cast clasp and the clasp made by repeated laser sintering only without a milling process. RESULTS The HM clasp surface was smoother than those of cast and RLS clasps. With the digital relief, the fitness accuracy of the HM clasp improved. The retentive forces of the HM clasps with relief and after heat treatment were significantly greater than for the cast clasp. HM clasps demonstrated a constant or slight decrease of retention up to 10,000 cycles. CONCLUSIONS HM clasp exhibited better fitness accuracy and retentive forces. The possibility of clinically using HM clasps as well as conventional cast clasps can be suggested.
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Affiliation(s)
- Mana Torii
- Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan.
| | - Toyoki Nakata
- Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan
| | - Kazuya Takahashi
- Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan
| | - Noboru Kawamura
- Department of Technician Training Institute, Tsurumi University Dental Hospital, Yokohama, Japan
| | - Hidemasa Shimpo
- Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan
| | - Chikahiro Ohkubo
- Department of Removable Prosthodontics, Tsurumi University School of Dental Medicine, Yokohama, Japan
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22
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Bending fracture of Co-Cr dental bridges, produced by additive technologies: experimental investigation. ACTA ACUST UNITED AC 2018. [DOI: 10.1016/j.prostr.2018.12.077] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Improvement of Cr-Co-Mo Membrane Surface Used as Barrier for Bone Regeneration through UV Photofunctionalization: An In Vitro Study. MATERIALS 2017; 10:ma10070825. [PMID: 28773195 PMCID: PMC5551868 DOI: 10.3390/ma10070825] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 07/05/2017] [Accepted: 07/11/2017] [Indexed: 12/14/2022]
Abstract
Although there are several studies of the ultraviolet (UV) light-mediated photofunctionalization of titanium for use as implant material, the underlying mechanism is not fully understood. However, the results of in vitro and in vivo studies are very encouraging. The use of UV photofunctionalization as a surface treatment on other implant materials, as the Cr-Co-Mo alloy, has not been explored in depth. Using sandblasted Cr-Co-Mo discs, the surface photofunctionalization was studied for ultraviolet A (UVA, 365 nm) and ultraviolet C (UVC, 254 nm), and the surfaces were evaluated for their ability to sustain hydroxyapatite crystal growth through incubation in simulated body fluid for a seven-day period. The variation of the pre- and post-irradiation contact angle and surface composition was determined through the quantification of the weight percentage of Ca and P crystals by the EDAX ZAF method (EDS). Statistically significant differences (p < 0.05) were found for samples irradiated with UVA over 48 h, corresponding with hydrophilic surfaces, and the same result was found for samples exposed to 3 h of UVC. Superhydrophilic surfaces were found in samples irradiated for 12, 24 and 48 h with UVC. The decrease in the carbon content is related with the increase in the surface content of Ca and P, and vice versa over the Cr-Co-Mo surfaces.
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Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings. MATERIALS 2017; 10:ma10010093. [PMID: 28772451 PMCID: PMC5344574 DOI: 10.3390/ma10010093] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 01/17/2017] [Accepted: 01/18/2017] [Indexed: 12/04/2022]
Abstract
Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture) milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance), a Scheffe’s test, and Pearson’s correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps (p < 0.05). The CAD/CAM milled group revealed a significantly high axial internal gap. There are moderate correlations between the vertical marginal discrepancy and the internal gap variables (r = 0.654), except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit.
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Development of microstructure and mechanical properties during annealing of a cold-swaged Co–Cr–Mo alloy rod. J Mech Behav Biomed Mater 2016; 64:187-98. [DOI: 10.1016/j.jmbbm.2016.07.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2016] [Revised: 06/18/2016] [Accepted: 07/08/2016] [Indexed: 11/24/2022]
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Clasp fabrication using one-process molding by repeated laser sintering and high-speed milling. J Prosthodont Res 2016; 61:276-282. [PMID: 27825561 DOI: 10.1016/j.jpor.2016.10.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/03/2016] [Accepted: 10/14/2016] [Indexed: 11/22/2022]
Abstract
PURPOSE A single machine platform that integrates repeated laser sintering and high-speed milling for one-process molding has been developed. METHODS The Akers clasp was designed using the CAD system (DWOS Partial Frameworks, Dental Wings) and fabricated using repeated laser sintering and a high-speed milling machine (LUMEX Advance-25, Matsuura) with 50-μm Co-Cr particles (CAM clasp). As controls, cast clasps of the same forms were also prepared using conventional casting methods with a Co-Cr alloy and CP titanium Grade 3. After the surface roughness was measured, the gap distance between the clasps and the tooth die was assessed using the silicone film method. The initial retentive force and changes in retention up to 10,000 cycles were also measured. The data were analyzed using two-way ANOVA and Tukey's multiple comparison test (α=0.05). RESULTS CAM clasps exhibited significantly smoother surfaces than those of cast Co-Cr and CP Ti clasps (p<0.05). However, the gap distances of the CAM clasps were significantly greater than those of the cast clasps (p<0.05). The retentive forces of both CAM and cast Co-Cr clasps were significantly higher than those of CP Ti clasps. (p<0.05). The retention of CAM clasps demonstrated a constant or slight decrease from 1000 up to 10,000 cycles. CONCLUSIONS The CAM clasp made by repeated laser sintering and high-speed milling can be used effectively as an RPD component.
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Microstructures and Mechanical Properties of Co-Cr Dental Alloys Fabricated by Three CAD/CAM-Based Processing Techniques. MATERIALS 2016; 9:ma9070596. [PMID: 28773718 PMCID: PMC5456947 DOI: 10.3390/ma9070596] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/25/2016] [Revised: 07/12/2016] [Accepted: 07/15/2016] [Indexed: 11/29/2022]
Abstract
The microstructures and mechanical properties of cobalt-chromium (Co-Cr) alloys produced by three CAD/CAM-based processing techniques were investigated in comparison with those produced by the traditional casting technique. Four groups of disc- (microstructures) or dumbbell- (mechanical properties) specimens made of Co-Cr alloys were prepared using casting (CS), milling (ML), selective laser melting (SLM), and milling/post-sintering (ML/PS). For each technique, the corresponding commercial alloy material was used. The microstructures of the specimens were evaluated via X-ray diffractometry, optical and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and electron backscattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test according to ISO 22674 (n = 6). The microstructure of the alloys was strongly influenced by the manufacturing processes. Overall, the SLM group showed superior mechanical properties, the ML/PS group being nearly comparable. The mechanical properties of the ML group were inferior to those of the CS group. The microstructures and mechanical properties of Co-Cr alloys were greatly dependent on the manufacturing technique as well as the chemical composition. The SLM and ML/PS techniques may be considered promising alternatives to the Co-Cr alloy casting process.
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