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Purpose: To compare the precision of adaptation of cobalt-chromium (Co-Cr) three-unit fixed dental prostheses (FDPs) fabricated using different techniques. Materials and Methods: A master model was prepared to receive a three-unit FDP. This model was duplicated 60 times from a silicone mold. The dies (N = 60) were scanned and divided into three groups (n = 20 each) to receive the FDPs made of pre-sintered Co-Cr (CS), laser-sintered Co-Cr (LS), or cast Co-Cr (Gi). Frameworks were layered with ceramic, and each framework was seated on its specific model. The replica technique was used to measure the marginal and internal discrepancies in the mesiodistal and buccolingual planes. Prepared silicone samples were examined with scanning electron microscopy. Obtained data were analyzed using Levene test, t test, and analysis of variance (α = .05). Results: When overall mean discrepancy values were compared, in mesiodistal planes, LS showed better adaptation than Gi (P = .025). Similar adaptation was found for CS and Gi, and for CS and LS (P = .169 and P = 1.000, respectively). In buccolingual planes, the difference in fit was not significant among the three tested groups (P > .05). In a pairwise comparison between materials, a net increase in values between points 1 and 5 was noted (P = .57). Difference in discrepancy values within points was significant. This was confirmed at abutment level on some measurement points. Within each material, at abutment level, differences were significant at several measurement locations in both the mesiodistal and buccolingual planes. Conclusion: Within the limitations of this study, three-unit Co-Cr FDPs showed similar marginal and internal discrepancy values. Presintered and laser-sintered Co-Cr alloys can be considered for three-unit FDP fabrication. [ABSTRACT FROM AUTHOR]

Six alloys (25 wt% Cr, 0.4 C, 1.6 Ti, Co and Ni (bal.)) were prepared by casting for evaluating their oxidation and creep properties at 1200°C. Their microstructures consist of a dendritic matrix with eutectic carbides in the interdendritic spaces. Carbides are TiC for the alloys richer in Co than in Ni, and chromium carbides in the alloys richer in Ni than in Co. Differential thermal analysis shows that all alloys start melting above 1250°C. The oxidation tests in air at 1200°C allow observing a chromia–forming behavior of the alloys rich in nickel better than the cobalt alloys. In contrast, the creep resistance tests at 1200°C demonstrate an undeniable superiority of the alloys rich in cobalt. Good compromise for both types of high temperature behavior appears to be obtained by a Co-base alloy containing nickel as minor element but with significant proportion in nickel (15–30 wt% Ni). [ABSTRACT FROM AUTHOR]

Abstract The performance of CoCrMo alloy in orthopaedic implants may be unfavourably affected by hyaluronic acid (HA) in synovial fluid. In this study, the authors aimed to understand the interactions between HA and CoCrMo using dedicated electrochemical experiments and surface analyses. A sequence of electrochemical measurements (open‐circuit potential, linear polarization resistance, potentiodynamic and potentiostatic polarizations) was run on LC‐CoCrMo (ASTM F1537) in Dulbecco's phosphate‐buffered saline (DPBS) solution with and without HA and in DPBS mixed with newborn calf serum (NCS) and HA, partially under simultaneous recording of surface pH using custom‐made microelectrodes. Samples were analysed by optical and electron microscopy. HA had no significant impact on the corrosion potential of CoCrMo alloy (ECORR = −173 ± 8, −211 ± 16, and −254 ± 30 mVAg/AgCl, in DPBS, DPBS + HA, and DPBS + NCS + HA, respectively). Average current density values at the transpassive domain were double in DPBS compared to DPBS + HA and DPBS + NCS + HA. At potentials above +0.6 VAg/AgCl, surface pH values decreased from 7.5 to 6.5 in DPBS and from 7.5 to below 4 in DPBS + HA. In conclusion, the presence of HA did not compromise the corrosion resistance of CoCrMo alloy at free potential, but it enhanced acidic conditions at the near surface under anodic‐applied potential in the transpassive domain.

Purpose: This study aimed to assess dentists' views of the utility of an unrestored shortened dental arch (SDA) compared to the utility of various prosthetic treatment options.Materials and Methods: A total of 142 dentists working at four sites in Riyadh, Saudi Arabia, were interviewed and presented with 18 scenarios for patients of different ages with SDAs that lost molar teeth. Participants were asked to indicate on a standardized visual analog scale (VAS) how they would value the health of the patient's mouth if the SDAs were left unrestored or restored with five prosthetic dental restorations.Results: With a utility value of 0.0 representing the worst possible health state for a mouth and 1.0 representing the best, dentists' mean utility value for unrestored SDAs was 0.43 (standard deviation [SD] = 0.28). For implant-supported fixed dental prostheses (ISFDPs), cobalt-chromium removable partial dentures (RPDs), acrylic RPDs, cantilever conventional fixed dental prostheses (CFDPs), and cantilever resin-bonded fixed dental prostheses (RBFDPs), the mean utility values were 0.64 (SD = 0.27), 0.54 (SD = 0.20), 0.48 (SD = 0.20), 0.42 (SD = 0.28), and 0.39 (SD = 0.27), respectively. Neither patient age nor dentists' clinical experience had an impact on dentists' perceptions of the utility of unrestored SDAs and outcomes of this treatment concept (P > .01).Conclusion: Restoration of SDAs by ISFDPs received the highest utility value among the surveyed group of dentists. Although the assigned value for unrestored SDAs was low, this value was comparable to the value of SDAs that were restored by acrylic RPDs or cantilever FDPs of either type. [ABSTRACT FROM AUTHOR]

Due to the special manufacturing process of cobalt–chromium alloy cardiovascular stent tubes, there are serious surface defects in their inner walls, which affects the therapeutic effect after implantation. At the same time, the traditional processing technology cannot finish the inner wall of a cardiovascular stent tube. In light of the above problems, magnetic abrasive finishing (MAF) equipment for the inner wall of an ultra-fine and ultra-long cardiovascular stent tube is proposed, and MAF technology is used to improve the surface quality of its inner wall. High-performance spherical magnetic abrasive powders are used to finish the inner wall of a cobalt–chromium alloy cardiovascular stent tube with an inner diameter of 1.6 mm and an outer diameter of 1.8 mm. The effects of finishing time, tube rotational speed, feed speed of the magnetic pole, MAPs filling quantity, and MAP abrasive size on the surface roughness and material removal thickness of cobalt–chromium alloy cardiovascular stent tube are investigated. The results show that the surface roughness of the inner wall of the cobalt–chromium alloy cardiovascular stent decreases from 0.485 μm to 0.101 μm, and the material removal thickness of the defect layer is 4.3 μm. MAF technology is used to solve the problem of the poor surface quality of the inner walls of ultra-fine and ultra-long cobalt–chromium alloy cardiovascular stent tubes. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is being applied to metallic biomaterials and dental alloys, including CoCrMo. CoCrMo mechanical properties and corrosion resistance are vital to the structural integrity of implants and dental appliances. The goal of this work is to assess the resistivity of AM cobalt chromium alloys by comparing them with traditional CoCrMo, regarding electrochemical properties resulting from microstructural and oxide film differences. In this work, selective laser melting (SLM), was used to manufacture CoCrMoW. The corrosion characteristics of AM alloy were compared to that of wrought LC CoCrMo (ASTM F-1537) in both phosphate buffered saline (PBS) and PBS with 10 mM H 2 O 2 to simulate increased inflammatory conditions. Anodic polarization and electrochemical impedance spectroscopy (EIS) were performed. Both alloys were substantially similar in corrosion behavior in both solutions. They exhibited changes with the different solutions. Polarization resistances were statistically lower (R p AM = 1.4 MΩcm2 (PBS) vs. 0.72 MΩcm2 (H 2 O 2), R p LC = 1.86 MΩcm2 (PBS) vs. 0.55 MΩcm2 (H 2 O 2)), and open circuit potentials (OCP's) were statistically higher in 10 mM H 2 O 2 for both alloys (0.20 V (in H 2 O 2) vs. − 0.09 V in PBS). Chemistry variations were revealed by the corrosion tests indicating that wrought LC CoCrMo retained its casting-based chemical heterogeneity, while AM CoCrMoW had sub-cell structures within the solidified grains. As novel production methods like AM arise, it is necessary to understand any microstructural differences that may diminish the corrosion resistance properties. AM CoCrMoW alloys hold significant promise for use in dentistry where complex geometries are required. • Production (additive vs. wrought) results in significant microstructural variations. • Additively manufactured alloy has less uniform, larger grains. • Additively manufactured CoCrMoW has a distinct columnar subgranular microstructure. • Additively manufactured and wrought alloy had similar electrochemical behavior. • Impedance, corrosion potential and current, and breakdown potential were comparable. [ABSTRACT FROM AUTHOR]

Background. To evaluate and compare the shear bond strength of feldspathic porcelain to four distinctively surface-treated Ni-Cr and Co-Cr alloys and to assess the impact of oxidation-heat treatment on porcelain to base metal alloy bond strength. Methods. 40 specimens each of nickel-chromium alloy and cobalt-chromium alloy were cast. A total of four groups of specimens were created. Group I was surface-treated by sandblasting with 50 μm alumina particles, Group II was surface-treated by sandblasting with 110 μm alumina particles, Group III and Group IV were surface-treated with 250 μm alumina particles. In Group IV, after sandblasting initially with 250 μm alumina particles, the alloys were subjected to oxidation and resandblasting with 250 μm alumina particles. Each of the specimen was coated with opaque and body porcelain and fired to a total thickness of 2 mm porcelain. A universal measuring machine was used to assess shear bond strength at a crosshead speed of 0.5 mm/min. Results. Two-way ANOVA followed by Tukey's post hoc test was used to assess the significant difference within the groups. Unpaired t-test was used for the intergroup comparison of the obtained data. The study showed that the size of the air abrasion particles used for sandblasting significantly influenced the porcelain to metal surface bond strength, with p value <0.001. The bond strength values of the two alloys tested showed no major variations. Result also showed that oxidation influences the metal-ceramic bond strength. Conclusions. The bond strength of the metal-ceramic interface is influenced by the alloy's surface treatment. The oxidation process impacts the bond strength of the metal-ceramic system. [ABSTRACT FROM AUTHOR]

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Purpose: To evaluate the influence of cobalt-chromium (Co-Cr) casting alloys' melting temperatures on the cast-to Co-Cr implant cylinders' marginal fit.Materials and Methods: Co-Cr alloys with different melting ranges were cast into 20 Co-Cr cylinders: 10 in a high-melting temperature (HMT) group and 10 in a low-melting temperature (LMT) group. Ten cylinders were used as received as a control group. Cylinders' marginal misfit and dimensional stability were evaluated using scanning electron microscopy (×500).Results and Conclusion: HMT cylinders showed significant differences in marginal misfit (2.48 ± 1.07 μm2) compared to LMT (1.53 ± 0.37 μm2) and control (1.27 ± 0.57 μm2) cylinders, but there were no differences in dimensional stability. HMT Co-Cr alloys produce implant-supported prostheses with poor marginal fit. [ABSTRACT FROM AUTHOR]

Background: Bite marks attributed to adult Tyrannosaurus rex have been subject to numerous studies. However, few bite marks attributed to T. rex have been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous. Methods: Here we present bite force estimates for a juvenile Tyrannosaurus rex based on mechanical tests designed to replicate bite marks previously attributed to a T. rex of approximately 13 years old. A maxillary tooth of the juvenile Tyrannosaurus specimen BMR P2002.4.1 was digitized, replicated in dental grade cobalt chromium alloy, and mounted to an electromechanical testing system. The tooth was then pressed into bovine long bones in various locations with differing cortical bone thicknesses at varying speeds for a total of 17 trials. Forces required to replicate punctures were recorded and puncture dimensions were measured. Results: Our experimentally derived linear models suggest bite forces up to 5,641.19 N from cortical bone thickness estimated from puncture marks on an Edmontosaurus and a juvenile Tyrannosaurus. These findings are slightly higher than previously estimated bite forces for a juvenile Tyrannosaurus rex of approximately the same size as BMR P2002.4.1 but fall within the expected range when compared to estimates of adult T. rex. Discussion: The results of this study offer further insight into the role of juvenile tyrannosaurs in late Cretaceous ecosystems. Furthermore, we discuss the implications for feeding mechanisms, feeding behaviors, and ontogenetic niche partitioning. [ABSTRACT FROM AUTHOR]

Abstract: Adverse local tissue reactions (ALTRs) were initially reported as complications associated with metal-on-metal (MoM) bearings; however, there is increasing concern regarding the occurrence of adverse local tissue reactions from mechanically assisted crevice corrosion (MACC) at the femoral head-neck junction or between other modular junctions of the implant containing cobalt chromium parts in patients with metal-on-polyethylene (MoP) bearings. ALTR due to MACC at the head-neck junction has primarily been reported in association with cobalt chromium alloy femoral heads. As pain following total hip arthroplasty may have various intrinsic and extrinsic causes, a systematic approach to evaluation (risk stratification algorithm) based on the currently available data is recommended to optimize patient management. Evaluation should begin by ruling out common causes of pain, including component loosening and periprosthetic joint infection. While specialized tests such as blood metal analysis and metal artifact reduction sequence magnetic resonance imaging (MARS MRI) are useful modalities in evaluating for ALTRs, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. There should be a low threshold to perform a systematic evaluation for ALTR due to MACC in patients with metal-on-polyethylene total hip arthroplasty as early recognition and diagnosis is critical, as delays in appropriate treatment initiation may result in soft-tissue damage, which complicates surgical treatment and is associated with a higher risk of complications and poorer patient outcomes. [ABSTRACT FROM AUTHOR]

Background: There are concerns regarding glenoid erosion with metal shoulder hemiarthroplasty. PyroCarbon may offer an alternative because of favorable wear characteristics and preservation of the glenoid. The purpose of this study was to assess in vitro bone wear characteristics of PyroCarbon relative to cobalt chromium alloy hemiarthroplasty in a shoulder wear simulator. Methods: Wear of PyroCarbon and cobalt chromium prostheses articulating with bone were characterized by means of bone wear penetration rate, changes to surface roughness, and wear particle analysis. Results: PyroCarbon prostheses produced significantly less damage to bone and were less damaged by the bone than cobalt chromium prostheses. Cobalt chromium testing was halted at approximately 320,000 cycles because the bone was consumed. Wear testing of PyroCarbon specimens continued through five million cycles. Linearized bone penetration rate, bone volume loss rate, and surface roughness for cobalt chromium test specimens were 30 times greater than for PyroCarbon. Conclusions: Results demonstrate significantly less damage to bone in simulated shoulder function testing for PyroCarbon hemiarthroplasty implants relative to conventional cobalt chromium implants. Our study supports use of PyroCarbon in humeral head hemiarthroplasty as a viable alternative to conventional metal hemiarthroplasty. Further investigation of PyroCarbon performance in clinical settings is warranted. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the strain of complete dentures with and without full palatal coverage and to determine the effect of reinforcement. Three types of maxillary complete dentures (with palate, without palate, and without palate but with reinforcement) were fabricated, and reinforcements were made from a cobalt-chromium alloy. Strain gauges were attached to the polished surface, and a vertical load was applied in the region of the first premolar and first molar. The strains were statistically compared. The greatest strain occurred on the anterior palatal surface and was tensile in the denture with palatal coverage and compressive in the denture without palatal coverage. Significantly less strain occurred in dentures with reinforcement than without reinforcement. Int J Prosthodont 2013;26:419-422. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this retrospective study was to evaluate the 5-year clinical outcome for ceramic veneered cobalt-chromium (Co-Cr) fixed dental prostheses (FDPs) fitted in a private clinical setting. Materials and Methods: All patients treated consecutively with Co-Cr FDPs from January 2000 to November 2005 were included, and complications were registered. Patient records were examined for details on the restorations and abutment teeth. A total of 149 patients with 201 FDPs, 1,135 units, and 743 abutment teeth were recorded. Results: Of the 149 patients, 122 (82%) were followed for 5 years. Complications occurred in 34 patients (23%) and 38 FDPs (19%). The most frequent were caries (6.7% of patients, 5% of FDPs, 2.2% of abutments) and cement failure (6.7% of patients, 5% of FDPs, 3.1% of abutments). Cohesive ceramic fractures occurred in only 7 FDPs (3.5% of FDPs, 0.7% of units). No adhesive ceramic fractures were recorded. The 5-year cumulative rates for success and survival were 83.8% and 92.8%, respectively. Conclusions: Co-Cr FDPs appear to be a promising prosthodontic treatment modality, presenting low incidence of complications and a high survival rate during the first 5 years of function. However, long-term randomized controlled studies are necessary to confirm these findings. [ABSTRACT FROM AUTHOR]

The possibility of fabrication of granulate based on an alloy of the Fe – Cr – Co system with reduced (7 – 10%) cobalt content for synthesizing permanent magnets by the MIM process is considered. A multicomponent granulate composition (polyformaldehyde, high-pressure polyethylene, stearic acid, beeswax) of spherical powders of the Fe – Cr – Co alloy with reduced cobalt content is produced by gas sputtering (average particle diameter 4.2 μm, degree of polydispersity 0.75). The microstructure of the granulate and its granulometric composition are studied. The characteristics of the granulate (the mean diameter of the particles, their morphology and degree of polydispersity) exceed qualitatively the characteristics of the Catamold 42CrMo4 high-quality granulate produced by the BAFS Company. [ABSTRACT FROM AUTHOR]

Purpose Of the Study: To comparatively evaluate the wear resistance of two different posterior indirect restorative materials against human enamel.Materials and Methods: Two different posterior indirect restorative materials of ten in each Group-I (Monolithic zirconia) (n = 10) and Group-II (Cast cobalt chromium) (n = 10) were formed into disc and used as a substrate for the wear test. Freshly extracted mandibular first premolars were used as a pin (antagonist) (n = 20). Pin-on-disc wear testing machine was used to simulate the masticatory parameters and evaluation of the wear parameters was done after 1,20,000 cycles, with load of 40N for specific duration. Data related to wear testing procedure were tabulated and evaluated. Results were statistically analyzed using Mann-Whitney test and Wilcoxon signed rank test.Results: Mean surface roughness value (Ra value) obtained for Group-I disc test samples showed no statistical significance (P value < 0.05). Mean wear rate value of test disc samples was statistically significant between Group-I and Group-II (P value < 0.05). Mean surface roughness value was statistically significant between Groups-I and II before and after wear test (P value < 0.05).Conclusion: From the results obtained, it was found that the Group-I (Monolithic zirconia) exhibited higher wear resistance than Group-II (cast cobalt chromium) and causes less wear to the opposing enamel antagonist. [ABSTRACT FROM AUTHOR]

Study Design: Experimental study of spinal rod as per the American Society for Testing Materials (ASTM) F2193 methodology for static and dynamic four-point bending.Objective: The hypotheses underlying this study were that the notch-free, curved rod would have a significantly higher ultimate load and fatigue strength compared with conventional notched curved rods. This study aimed to analyze the mechanical properties of notch-free curved rods compared with conventional notched rods.Summary Of Background Data: The goal of instrumented spinal fusion in the management of spinal deformities is to realign the spine and maintain the correction and stability in order to obtain arthrodesis. Although rod curvature could play an important role, intraoperative contouring of the straight rod induces notches into the rod, leading to decreased fatigue strength.Methods: Commercially produced titanium alloy (ϕ6.0 mm) and cobalt chromium alloy (ϕ5.5 mm) spinal rods were assessed by four-point bending tests in accordance with the ASTM F2193.Results: Static four-point bending tests for the curved spinal rods showed that cobalt chromium alloy rods had significantly higher stiffness compared with titanium alloy rods. Notch-free cobalt chromium alloy rods had a significantly higher ultimate load than the conventional notched cobalt chromium alloy and titanium alloy rods. The dynamic four-point bending test showed that force/displacement at a minimum force at 2,500,000 cycles was larger in the notch-free cobalt chromium alloy rod than in the notched cobalt chromium alloy rod.Conclusion: The notch-free curved cobalt chromium alloy rod is likely to maintain its curvature after spinal deformity surgery with a decreased risk of breakage and could overcome the problems of the conventional notched rod such as breakage and spring-back.Level Of Evidence: N/A. [ABSTRACT FROM AUTHOR]

Purpose: Evaluation of reendothelialization with a new thin struts cobalt chromium alloy stent coated with a nano-layer of Polyzene™-F (PzF) in a rabbit iliac artery model.Methods: Fifteen stented external rabbit iliac arteries were harvested at Day 7 for electron microscopy analysis following Cobra PzF stents implantation to assess reendothelialization and compare to historical data. Ten additional rabbits were used to assess time course of reendothelialization at 3 and 5 days.Results: At Day 7, almost complete coverage of endothelial cells was observed with a coverage of 99.54 ± 0.25% of the stented area. No thrombus area was noted. At Day 3, more than half of examined pieces was reendothelialized and reached 78.30 ± 3.7% at Day 5 (p < .01 between each group). All stents were well expanded against the arterial wall and no struts were mal-apposed.Conclusions: Reendothelialization was rapid and complete at Day 7. This is the fastest reendothelization process after stenting in this model. No stent occlusion was observed. [ABSTRACT FROM AUTHOR]

Purpose: This retrospective study investigated the survival rate of 174 clasp-retained removable partial dentures (CR-RPDs) made at the Department of Prosthodontics of the Regensburg University Medical Center over a 25-year period (1984 to 2009). Materials and Methods: The study analyzed the frequency of and time to the fracture of clasps, connectors, or denture bases; the occurrence of caries or periodontal lesions; the loss of abutment teeth; and the necessity of maintenance procedures such as relining or treatment of pressure areas. Results: The median follow-up time of 3 years was calculated using the inverse Kaplan-Meier method. The 5-year survival rate (time to renewal) of all CR-RPDs was 96.4%; the 10-year survival rate was 89.8%. Fractures most frequently occurred in clasps (n = 28, 16.1%) followed by major connectors (n = 9, 5.1%) and minor connectors (n = 6, 3.4%). The 5-year event-free rate for clasp fracture was 80.4%; the 10-year event-free rate was 76.9%. Caries lesions on abutment teeth were seen in 31.6% of patients, and 35.6% showed inflammation of the periodontal tissue surrounding the abutment teeth. The 5-year event-free rate for caries was 58.4%; the 10-year rate was 39.6%. A frequent complication was loss of abutment teeth (n = 15), but this complication was not age-dependent. After insertion of their prostheses, one-third of patients (n = 53, 30.5%) showed pressure areas of the mucosa. Significantly more (P < .001) pressure areas were caused by prostheses of the mandible (39.6%) than by those of the maxilla (12.5%). Conclusions: CR-RPDs showed a survival rate of approximately 90% after 10 years of oral service. The predominant complications during oral service were caries lesions, loss of abutment teeth, and fracture of clasps. [ABSTRACT FROM AUTHOR]

The purpose of this study was to test intraorally the effect of a cobalt-chromium cast reinforcement embedded in the denture base of a maxillary complete denture on the distribution of stress. Eight subjects were selected randomly, and three designs of a cobalt-chromium alloy bar were embedded in the dentures. A strain gauge was attached at three positions around the midline of the polished surface of each denture. Strain in the reinforced dentures was significantly less than strain in dentures without reinforcement. These observations suggest that a cast cobalt-chromium reinforcement reduces strain and could contribute to fracture avoidance deformation in maxillary complete dentures. [ABSTRACT FROM AUTHOR]

Purpose: Long-term comparisons of frameworks at the implant or abutment level are not available, and knowledge of the clinical function of cobalt-chromium (Co-Cr) alloy frameworks is limited. Primarily, the aim of this study was to compare the 5-year clinical performance of frameworks with or without abutment connections to implants. Secondly, the outcomes of prostheses made from Co-Cr alloy with porcelain veneers to those made of commercially pure titanium (CP Ti) with acrylic veneers were compared. Materials and Methods: The test groups comprised patients treated with screw-retained fixed prostheses made at the implant level according to the Cresco method in either dental porcelain-veneered Co-Cr alloy (n = 15) or acrylic-veneered CP Ti (n = 25). A control group of 40 randomly selected patients were provided with prostheses made at the standard abutment level in CP Ti with acrylic veneers. For all patients, clinical and radiologic 5-year data were retrospectively collected and evaluated. Results: Five-year implant cumulative survival rates (CSRs) were 98.6% and 97.6% for test and control groups, respectively (P > .05). No major differences in bone level were demonstrated between the groups after 5 years (P > .05). Significantly more complications occurred in the test groups compared to the control group (P < .01), with the most common complications being mucositis and fracture of veneers. Conclusions: After 5 years, the clinical outcomes of implant-level prostheses made of porcelain-veneered Co-Cr or acrylic-veneered CP Ti seem comparable to acrylic-veneered titanium prostheses made at the standard abutment level regarding implant CSR and bone levels. However, more complications were registered in implant-level prostheses compared to the standard abutment-level prostheses. [ABSTRACT FROM AUTHOR]

Purpose: The shear bond strength of an auto-polymerizing poly(methyl methacrylate) denture base resin material to cast titanium and cobalt-chromium alloy treated with six conditioning methods was investigated. Materials and Methods: Disk specimens (10 mm in diameter and 2.5 mm in thickness) were cast from pure titanium and cobalt-chromium alloy. The specimens were wet ground to a final surface finish of 600 grit, air dried, and treated with the following bonding systems: 1) air abraded with 50-70-μm-grain alumina (SAN); 2) air abraded with 50-70-μm-grain alumina + conditioned with Alloy Primer (ALP); 3) air abraded with 50-70-μm-grain alumina + conditioned with AZ Primer (AZP); 4) air abraded with 50-70-μm-grain alumina + conditioned with Estenia Opaque Primer (EOP); 5) air abraded with 50-70-μm-grain alumina + conditioned with Metal Link Primer (MLP), and 6) treated with ROCATEC system (ROC). A denture base material (Palapress Vario) was then applied to each metal specimen. Shear bond strengths were determined before and after 10,000 thermocycles. Results: The strengths decreased after thermocycling in all combinations. Among the treatment methods assessed, groups 2 and 4 showed significantly (p < 0.05) enhanced shear bond strengths for both metals. In group 4, the strength in MPa (n = 7) after thermocycling for cobalt-chromium alloy was 38.3, which was statistically (p < 0.05) higher than that for cast titanium (34.7). Conclusion: Air abrasion followed by the application of two primers containing a hydrophobic phosphate monomer (MDP) effectively improved the strength of the bond of denture base material to cast titanium and cobalt-chromium alloy. [ABSTRACT FROM AUTHOR]

The retentive force of a wire clasp composed of a β-type Ti-6Mo-4Sn alloy (β-Ti alloy) with a low Young modulus was evaluated using a piezoelectric transducer to determine the appropriate undercut for removable partial dentures. There were no significant differences in retentive force between a β-Ti alloy wire with a 0.50-mm undercut and a cobalt-chromium alloy (Co-Cr alloy) wire with a 0.25-mm undercut, or between a β-Ti alloy wire with a 0.75-mm undercut and a Co-Cr alloy wire with a 0.50-mm undercut. The β-Ti alloy wire may be applicable for abutment teeth with a large number of undercuts. [ABSTRACT FROM AUTHOR]

Purpose: This study evaluated the vertical misfit of implant-supported frameworks made using different techniques to obtain passive fit.Materials and Methods: Thirty three-unit fixed partial dentures were fabricated in cobalt-chromium alloy (n = 10) using three fabrication methods: one-piece casting, framework cemented on prepared abutments, and laser welding. The vertical misfit between the frameworks and the abutments was evaluated with an optical microscope using the single-screw test. Data were analyzed using one-way analysis of variance and Tukey test (α = .05).Results: The one-piece casted frameworks presented significantly higher vertical misfit values than those found for framework cemented on prepared abutments and laser welding techniques (P < .001 and P < .003, respectively).Conclusion: Laser welding and framework cemented on prepared abutments are effective techniques to improve the adaptation of three-unit implant-supported prostheses. These techniques presented similar fit. [ABSTRACT FROM AUTHOR]

A study by transmission electron microscopy of the influence of the In and N contents in the ranges of 20%–35% and 1.1%–3%, respectively, on the microstructure of Ga1-xInxNyAs1-y quantum wells is presented. Frank dislocation loops characterized as extrinsic have been found in the samples with x>=0.25. In these structures, threading dislocations appear as a consequence of the unfaulting of the loops for y>=0.014. An analysis of the density and size of the dislocation loops has provided an estimation of the critical radius for the unfaulting process. A model for this critical radius of the unfaulting process of extrinsic Frank loops is proposed. From this model and experimental values of critical radius, an estimation of the stacking fault energy of the GaInNAs alloy has been made. We have found a reduction in the stacking fault energy of the GaInNAs alloys when increasing the N content from 1.4% to 2.3% in good agreement with the theoretical estimation of the stacking fault energies of zinc-blende GaN and InN. [ABSTRACT FROM AUTHOR]

Objective: This study investigated The cervical microleakage between a cobalt-chromium (Co-Cr) alloy and four indirect polymeric veneering materials using different adhesive systems. Method and materials: The Co-Cr-based alloy for fixed prosthesis used in this study (Biosil F, Degussa) was veneered with four different polymeric materials: Artglass, Chromasit, Solidex, and Superacryl. Results: Superacryl produced the highest microleakage score (4 ± 0.0). The least microleakage at the interface was produced by Artglass (1 ± 0.816), fallowed by Chromasit (2 ± 1.414) and Solidex (23 ± 1.0) Only the differences between Artglass and Superacryl were significant. Conclusion: Within the limitations of this in vitro study, cervical microleakage between the coping and the veneer depended on the particular polymeric material used for veneering. Leakage was significantly lower when resin materials were used together with a chemical conditioning system (ie, Artglass/Siloc). [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to compare 3 different electrobrightening techniques and 3 electrolytic solutions in their effects upon the fit surface of cast cobaltchromium frameworks. Materials and Methods: Fifty cast cobalt-chromium frameworks, which were subsequently divided into batches of 10, were prepared according to a standard protocol. Three electrobrightening techniques were tested initially using a single brand of electrolyte (Croform) and a batch of 10 frameworks per technique. The loss of metal by weight was determined from the fit surface of each casting. The least corrosive technique of these 3 was used again with 2 other brands of electrolyte (Nobilium and E501) in a repetition of the protocol. The fit surfaces of 8 random samples cut from each batch of electrobrightened castings were viewed by scanning electron microscope (SEM). Results: Statistical analysis applying a one-way analysis of variance and Bonferroni's multiple comparison of means test demonstrated that one immersion of the framework for 10 minutes at 1 amp when used in conjunction with Nobilium electrolyte removed the least metal ( P= 0.001). The SEM study suggested that the Nobilium electrolyte also produced the smoothest surface. Conclusion: Electrobrightening techniques affect the amount of metal removed, and the electrolytic solution used influences the resultant surface. [ABSTRACT FROM AUTHOR]

Purpose: Ceramic defects in porcelain-fused-to-metal (PFM) restorations may depend on framework alloy type. This study assessed ceramic defects on cobalt-chromium- (Co-Cr-) and gold-platinum- (Au-Pt-) based PFM restorations.Materials and Methods: In this study, 147 Co-Cr-based and 168 Au-Pt-based PFM restorations inserted between 1998 and 2010 (139 patients) were examined for ceramic defects. Detected defects were assigned to three groups according to clinical defect relevance.Results: Ceramic defect rates (Co-Cr-based: 12.9%; Au-Pt-based: 7.2%) revealed no significant difference but a strong statistical trend (U test, P = .082). Most defects were of little clinical relevance.Conclusions: Co-Cr PFM restorations may be at higher risk for ceramic defects compared to Au-Pt-based restorations. [ABSTRACT FROM AUTHOR]

A preliminary tensile test was performed to evaluate the mechanical properties of cobalt-chromium (Co-Cr) alloys fabricated by three new manufacturing processes: metal milling, milling for soft metal, and rapid prototyping (n = 6). For comparison, the three alloy materials were also used to fabricate specimens by a casting procedure. In all groups tested, the proof strength and elongation were over 500 MPa and 2%, respectively. The milled soft alloy in particular showed a substantially greater elongation, whereas the alloy fabricated by rapid prototyping exhibited a higher proof strength. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) metal printing is an attractive technique for fabricating biomedical devices. The microstructures and mechanical properties of the fabricated 3D metal printed products show anisotropy because the grains grow along the z-axis direction. However, the effects of different printing directions on the cytocompatibility of the products are unknown. In the present study, cobalt–chromium–molybdenum (Co–Cr–Mo) alloy cylinders were fabricated along the z-axis (vertical) and x-axis (horizontal), respectively, and the effect of build direction on the cytocompatibility was evaluated. The build direction of 3D printed Co–Cr–Mo alloy changed grain anisotropy; however, there was no statistical difference in grain size. The wettability, protein adsorption, cell attachment, and cell proliferation on the disks of vertical and horizontal products were similar to those on cast alloy; they were significantly lower than those of commercially pure titanium and tissue culture polystyrene. The build direction of 3D printed Co–Cr–Mo alloy does not affect osteoblast compatibility.

The relationship between the wear behaviour of an ultra-high-molecular-weight polyethylene (GUR1050) pin and surface profile of a Co-28Cr-6Mo alloy (ASTM F-75) disc was investigated. Tribological tests have been performed by pin-on-disc wear testing machine with multi-directional pathways, obtaining the influence of micro slurry-jet erosion (MSE) processed Co–Cr–Mo alloy. The specific wear and the wear particles have been investigated. It was elucidated that the Co–Cr–Mo alloy surface processed by MSE influenced the specific wear rate of polyethylene; however, the morphological aspect of polyethylene wear particles was not drastically changed. The wear particles isolated from the lubricating liquid were added to a culture medium, and human monocyte-derived macrophages were incubated by using an upright/inverted method. The production of TNF-α and IL-6 seemed to have a correlation with the amount of wear particles added, however, the influence of particle size on the production of TNF-α and IL-6 was not obvious. This means that the improvements for the incubation method, i.e. upright/inverted method, need further investigation for the accurate analysis.

In order to improve the efficiency of drilling hard rock formation, the matrix structure of diamond-impregnated bit is designed as grid shape, and the basic parameters of this diamond-impregnated bit with grid-shaped matrix is theoretical analyzed. Two kinds of test samples, made by two selected 3D printing materials (Inconel 718 and CoCrMo alloy), are prepared by using powder metallurgy, and the optimum sintering parameter is determined by studying the effect of sintering temperature on three-main mechanical properties, hardness, abrasive resistance and bending strength. Also the mechanical properties of Inconel 718 and cobalt chromium alloy fetal bodies sintered at the optimum sintering temperature are compared with traditional WC matrix composite. It shows that the Inconel718 and the CoCrMo alloy can possess the optimal mechanical properties when the sintering temperature is 1050 °C. Meanwhile, CoCrMo alloy indicates to be more suitable for the matrix material of DIBGM due to its similar mechanical properties with WC matrix. The 3D printing working layer test and the rock cutting test confirmed the feasibility of the CoCrMo alloy acting as a matrix material, and the 3D-printed grid pieces that suitable for the hard rock with different strength are summarized as well. • A new designed impregnated diamond bit with grid-shaped matrix (IDBGM) was proposed. • The 3D printing technology was used to manufacture a diamond bit. • The matrix material for the IDBGM was optimized. • The 3D printing test and rock cutting test were used to verify the feasibility of CoCrMo alloy acting as a matrix material. • 3D-printed grid pieces that suitable for the hard rock with different strength are summarized. [ABSTRACT FROM AUTHOR]

The wear behavior of a non-standard cast cobalt chromium alloy (Co30Cr19Fe), during vibratory cavitation test, was investigated. Low stacking fault energies (SFE) cobalt alloys deform by complex plastic deformation mechanisms, which enhance the cavitation erosion (CE) resistance, since the onset of localized stress, leading to fatigue failure and material removal, is delayed. The purpose of this work is to characterize the main operating deformation mechanisms during cavitation erosion testing of the non-standard Co30Cr19Fe alloy. As cast, solution treated, and 15% and 30% cold rolled specimens were tested. The as cast microstructure consisted of ~2 mm fcc alpha grains and hcp epsilon-martensite. The 1473 K solubilization treatment led to primary recrystallization and formation of 250 µm new grains. The 15% cold worked microstructure consisted of heavily deformed fcc phase containing deformation twins and epsilon-martensite. Ultrasonic cavitation testing was carried out, during 40 h, according to ASTM G32-09. The solubilized specimens presented the worst behavior, whereas, the 30% cold worked specimens were the most CE resistant. The CE results are discussed based on the microstructural parameters: amount of alpha fcc and epsilon-hcp phases, grain sizes, relative amounts of twinning, slip lines and strain induced martensite formation. • Cavitation erosion resistance of Co30Cr19Fe alloy was determined. • Cold working was the most important mechanism improving wear resistance. • Wear mechanisms of Co30Cr19Fe alloy are dominated by plastic deformation. • Strain induced martensite also contributes to improve CE wear resistance. [ABSTRACT FROM AUTHOR]

Abstract Medical grade cobalt chromium alloys are one of a select number of material types approved for use in the components of orthopaedic implants. However, there has been minimal published research into the fundamental mechanisms in the cutting processes used in their manufacture. These processes affect the form accuracy, surface finish and integrity of these safety critical devices. The present work reports on a scientific investigation into the fundamental mechanisms of tool wear in continuous cutting of the biomedical grade Co-Cr-Mo ASTM F75 alloy using uncoated tungsten carbide tools. Confocal and scanning electron microscopy (SEM) is used to examine and characterise the progression of tool wear at intervals up to a defined "end of life limit" for each combination of speed (v c) and feed rate (f) in experiments where the range of these parameters vary from 20 to 60 m/min and 20–60 μm/rev respectively to reflect the ranges used in industry. An empirical model is then established for progressive tool wear which demonstrates that the wear rates vary by over an order of magnitude. The parameters for the Taylor equation are also determined for this material for the first time. Microscopic examination shows the presence of characteristic tool wear "zones" with consistent size, shape and composition. These zones evolve depending on combination of speeds and feeds as determined in the full factorial experiment. Detailed characterisation of the wear surfaces and cross sections provide a number of insights into the possible mechanisms of wear. It is hypothesised that micron thick layers of Co-Cr-Mo, found on the rake and flank wear surfaces, indicate primary wear mechanism involving adhesion of the work material and subsequent removal of WC hard particles by entrainment in the work material flow. Highlights • Authors investigated wear mechanisms in cutting of medical Co-Cr-Mo alloy. • Two modes of deterioration were identified: progressive wear and fracture. • Results were used to calibrate an empirical tool life model for progressive wear. • Layers of work material adhered to wear zones were found using SEM and EDX. • Authors hypothesize on dissolution of Co-binder and adhesive removal of WC particles. [ABSTRACT FROM AUTHOR]

Plasma transferred arc welding (PTAW) is one of the outstanding overlay coating technique used in numerous industries including pressure vessel, automotive, chemical, nuclear, etc. owing to its superior characteristics, low dilution and high efficiency in the coating. In the present investigations, an effort is made to investigate the multitrack overlay deposition by PTAW on 16 mm thick 316 L plate by CO-Cr alloy. Samples are produced under different processing conditions, as per full factorial central composite design of experiment with preheating of 200°C by maintaining the interpass temperature 250 °C. Effects of transferred arc current, welding travel speed, powder feed rate, welding oscillation speed and stand-off distance on weld bead shape parameters comprising of width of deposition and reinforcement are presented and discussed based on experimental observations and fitted model. Relationship between the input process parameters with deposition characteristics is also presented in the form of regression equation. Lower current (100–120 A), intermediate travel speed (120–140 mm/min), intermediate powder feed rate (12–14 gms/min), lower oscillating speed (450–550 mm/min) and lower stand-off distance (6–8 mm) would give better deposition characteristics with minimum distortion, less residual stresses, no surface defects with strong metallurgical bond. [ABSTRACT FROM AUTHOR]

Presents information on a study which measured the rate at which recorded signals decay in perpendicular cobalt (Co) [sub78] chromium (Cr) [sub17] tantalum (Ta) [sub5] alloys, Co[sub70] Cr[sub15] Ta[sub5] platinum[sub10] alloys and palladium/cobalt multilayers. Importance of time relaxation in information storage; Experimental procedure; Results.

Presents a study that investigated the properties of cobalt-chromium alloy double-layered thin films. Analysis of the magnetic properties of the thin films; Examination of the structural properties of the thin films; Evaluation of the recording properties of the thin films.