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1.
Indian J Dent Res ; 31(4): 537-545, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33107453

RESUMEN

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.


Asunto(s)
Aleaciones de Cromo , Porcelana Dental , Diseño Asistido por Computadora , Esmalte Dental , Humanos , Ensayo de Materiales , Propiedades de Superficie , Circonio
2.
Niger J Clin Pract ; 23(9): 1274-1280, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32913168

RESUMEN

Background: Poor marginal adaptation may give rise to a series of biological complications. Despite its importance, comparative studies on marginal adaptation of metal-ceramic fixed restorations fabricated with newer methods are limited. Aim: Therefore, it was aimed to assess the marginal accuracy of copings fabricated with subtractive and additive manners used in contemporary dentistry. Materials and Methods: For a typodont model, 60 three-unit cobalt-chrome metal copings were fabricated by selective laser sintering (SLS), hard alloy milling (HAM), and soft alloy milling (SAM) in comparison to casting (C). Marginal discrepancy assessment was performed by using replication technique. Mesiodistal and buccopalatal cross-sections of silicone replicas were investigated under a stereomicroscope at × 80 magnification. A total of 960 measurements were subsequently made by means of corresponding image-review software on captured images after calibration of the software to µm scale. Obtained data were subjected to nonparametric Kruskal Wallis and Tamhane post-hoc tests (α =0.05). Results: Marginal adaptation of C group was significantly inferior to test groups in both canine- and premolar-teeth measurements (P < 0.05). Marginal fit was found to be tooth dependent (P < 0.001). HAM, SAM, and SLS groups exhibited analogous marginal discrepancy values on canine-tooth measurements. Differences among these groups were not statistically significant (P > 0.05). SAM and SLS groups demonstrated better marginal adaptation than others on premolar-tooth measurements. Also, no statistically significant difference was detected between SAM and SLS groups (P > 0.05). Conclusions: SAM group demonstrated superior marginal accuracy. All groups had clinically acceptable marginal discrepancy values (<120 µm), except cast group.


Asunto(s)
Aleaciones de Cromo/química , Diseño Asistido por Computadora , Técnica de Colado Dental , Adaptación Marginal Dental , Aleaciones de Cerámica y Metal/química , Adaptación Psicológica , Calor , Humanos , Rayos Láser
3.
Bone Joint J ; 102-B(7_Supple_B): 33-40, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32600210

RESUMEN

AIMS: The aim of this study was to develop a novel computational model for estimating head/stem taper mechanics during different simulated assembly conditions. METHODS: Finite element models of generic cobalt-chromium (CoCr) heads on a titanium stem taper were developed and driven using dynamic assembly loads collected from clinicians. To verify contact mechanics at the taper interface, comparisons of deformed microgroove characteristics (height and width of microgrooves) were made between model estimates with those measured from five retrieved implants. Additionally, these models were used to assess the role of assembly technique-one-hit versus three-hits-on the taper interlock mechanical behaviour. RESULTS: The model compared well to deformed microgrooves from the retrieved implants, predicting changes in microgroove height (mean 1.1 µm (0.2 to 1.3)) and width (mean 7.5 µm (1.0 to 18.5)) within the range of measured changes in height (mean 1.4 µm (0.4 to 2.3); p = 0.109) and width (mean 12.0 µm (1.5 to 25.4); p = 0.470). Consistent with benchtop studies, our model found that increasing assembly load magnitude led to increased taper engagement, contact pressure, and permanent deformation of the stem taper microgrooves. Interestingly, our model found assemblies using three hits at low loads (4 kN) led to decreased taper engagement, contact pressures and microgroove deformations throughout the stem taper compared with tapers assembled with one hit at the same magnitude. CONCLUSION: These findings suggest additional assembly hits at low loads lead to inferior taper interlock strength compared with one firm hit, which may be influenced by loading rate or material strain hardening. These unique models can estimate microgroove deformations representative of real contact mechanics seen on retrievals, which will enable us to better understand how both surgeon assembly techniques and implant design affect taper interlock strength. Cite this article: Bone Joint J 2020;102-B(7 Supple B):33-40.


Asunto(s)
Artroplastia de Reemplazo de Cadera/instrumentación , Simulación por Computador , Prótesis de Cadera , Ajuste de Prótesis , Aleaciones de Cromo , Análisis de Elementos Finitos , Humanos , Diseño de Prótesis , Estrés Mecánico , Propiedades de Superficie , Titanio
4.
Bone Joint J ; 102-B(7_Supple_B): 105-111, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32600211

RESUMEN

AIMS: The purpose of this study is to examine six types of bearing surfaces implanted at a single institution over three decades to determine whether the reasons for revision vary among the groups and how long it takes to identify differences in survival. METHODS: We considered six cohorts that included a total of 1,707 primary hips done between 1982 and 2010. These included 223 conventional polyethylene sterilized with γ irradiation in air (CPE-GA), 114 conventional polyethylene sterilized with gas plasma (CPE-GP), 116 crosslinked polyethylene (XLPE), 1,083 metal-on-metal (MOM), 90 ceramic-on-ceramic (COC), and 81 surface arthroplasties (SAs). With the exception of the COC, all other groups used cobalt-chromium (CoCr) femoral heads. The mean follow-up was 10 (0.008 to 35) years. Descriptive statistics with revisions per 100 component years (re/100 yr) and survival analysis with revision for any reason as the endpoint were used to compare bearing surfaces. RESULTS: XLPE liners demonstrated a lower cumulative incidence of revision at 15 years compared to the CPE-GA and CPE-GP groups owing to the absence of wear-related revisions (4% for XLPE vs 18%, p = 0.02, and 15%, p = 0.003, respectively). Revisions for adverse local tissue reactions occurred exclusively among the MOM (0.8 re/100 year) and SA groups (0.1 re/100 year). The revision rate for instability was lower among hips with 36 mm and larger head sizes compared to smaller head sizes (0.2% vs 2%, p < 0.001). CONCLUSION: The introduction of XLPE has eliminated wear-related revisions through 15-year follow-up compared to CPE-GP and CPE-GA. Dislocation incidence has been reduced with the introduction of larger diameter heads but remains a persistent concern. The potential for adverse local tissue reactions with MOM requires continued follow-up. Cite this article: Bone Joint J 2020;102-B(7 Supple B):105-111.


Asunto(s)
Artroplastia de Reemplazo de Cadera/instrumentación , Prótesis de Cadera , Diseño de Prótesis , Falla de Prótesis/tendencias , Adulto , Anciano , Cerámica , Aleaciones de Cromo , Estudios de Cohortes , Estudios de Seguimiento , Humanos , Inestabilidad de la Articulación/cirugía , Masculino , Prótesis Articulares de Metal sobre Metal , Persona de Mediana Edad , Polietileno , Reoperación/estadística & datos numéricos , Virginia
5.
Ann Vasc Surg ; 69: 453.e5-453.e10, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-32653615

RESUMEN

To report a case of acute arm ischemia and prosthetic shoulder infection treated by extra-anatomical great saphenous vein graft with external vascular scaffolding. A 65 year-old man with multiple surgical interventions for soft tissue sarcoma of the right shoulder, local radiotherapy with residual brachial plexus neuropraxia, was referred to our attention for signs of arm ischemia. Two weeks before, the patient was submitted to prosthetic shoulder replacement complicated with prosthetic infection. Considering the mechanism of vascular injury, an open surgical revascularization was planned with a deliberate avoidance of the natural anatomic pathway to reduce the risk of graft infection. Consequently, after the complete removal of infected shoulder prosthesis and placement of antibiotic spacer, an axillarbrachial artery bypass using great saphenous vein was performed using a new braided cobalt chrome kink resistant external vascular support to prevent compression, also considering the extra-anatomical position of the graft. At 12 months' follow-up, patient was in good clinical condition with complete resolution of arm ischemia; computed tomographic angiography and duplex scan revealed patency of the graft with excellent distal perfusion. The new external vascular support seems to be useful and feasible for preventing compression of extra-anatomical venous bypass.


Asunto(s)
Artroplastía de Reemplazo de Hombro/efectos adversos , Artroplastía de Reemplazo de Hombro/instrumentación , Implantación de Prótesis Vascular/instrumentación , Prótesis Vascular , Remoción de Dispositivos , Isquemia/cirugía , Infecciones Relacionadas con Prótesis/cirugía , Vena Safena/trasplante , Prótesis de Hombro/efectos adversos , Extremidad Superior/irrigación sanguínea , Anciano , Aleaciones de Cromo , Humanos , Isquemia/diagnóstico por imagen , Isquemia/etiología , Isquemia/fisiopatología , Masculino , Infecciones Relacionadas con Prótesis/diagnóstico , Infecciones Relacionadas con Prótesis/microbiología , Flujo Sanguíneo Regional , Resultado del Tratamiento , Grado de Desobstrucción Vascular
6.
Shanghai Kou Qiang Yi Xue ; 29(1): 40-45, 2020 Feb.
Artículo en Chino | MEDLINE | ID: mdl-32524119

RESUMEN

PURPOSE: To study the change of ion precipitation and surface roughness of three dental alloys'coexisting in standard electrolyte solution, in order to provide a reference for the selection of clinical alloy materials. METHODS: Standard samples of Ni-Cr alloy, Co-Cr alloy and Au-Ag-Pd alloy were prepared and divided into 5 groups: Ni-Cr alloy(group N), Co-Cr alloy(group C), Au-Ag-Pd alloy(Group A), Ni-Cr alloy contact with Au-Ag-Pd alloy(group NA), Ni-Cr alloy contact with Co-Cr alloy(group NC). All groups of alloys were soaked in standard electrolyte solution (T=37 ℃, pH=2.31) for 7 days. Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure the amount of ions released from each group. The surface morphology of each group was observed and the surface roughness(Ra) was measured using atomic force microscope(AFM). SPSS 18.0 software package was used for statistical analysis. RESULTS: The amount of nickel ions released from group N, NA, NC was (1.32±0.03) µg/cm2, (2.13±0.07) µg/cm2, (1.53±0.08) µg/cm2, respectively. Nickel ions of group NA and NC was significantly more than that of group N(P<0.05), nickel ions of group NA was significantly more than that of group NC(P<0.05). The amount of chromium ions released from group N, NA, NC was (0.06±0.01) µg/cm2, (0.08±0.01) µg/cm2, (0.05±0.01) µg/cm2, respectively, the amount of chromium ions of group NA was significantly more than that of group NC(P<0.05). The surface roughness of Ni-Cr alloy in group N, NA, NC was (4.60±0.16) nm, (5.37±0.08) nm, (5.04±0.15) nm, respectively. The surface roughness of Ni-Cr alloy in group NA and group NC was significantly larger than that in group N (P<0.05). When contact with Au-Ag-Pd alloy or Co-Cr alloy, the amount of nickel ions released and the surface roughness of Ni-Cr alloy both significantly increased. Compared with Co-Cr alloy, Au-Ag-Pd alloy caused Ni-Cr alloy to release more nickel, chromium ions and formed a rougher surface.


Asunto(s)
Aleaciones de Cromo , Aleaciones Dentales , Iones , Ensayo de Materiales , Níquel , Propiedades de Superficie
7.
Spine Deform ; 8(5): 871-877, 2020 10.
Artículo en Inglés | MEDLINE | ID: mdl-32424695

RESUMEN

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.


Asunto(s)
Aleaciones de Cromo , Fijadores Internos , Ensayo de Materiales/métodos , Modelos Anatómicos , Fusión Vertebral/instrumentación , Fenómenos Biomecánicos , Tornillos Pediculares
8.
AJR Am J Roentgenol ; 215(2): 425-432, 2020 08.
Artículo en Inglés | MEDLINE | ID: mdl-32374668

RESUMEN

OBJECTIVE. The purpose of this study was to compare a combined dual-energy CT (DECT) and single-energy CT (SECT) metal artifact reduction technique with a SECT metal artifact reduction technique for detecting lesions near an arthroplasty in a phantom model. MATERIALS AND METHODS. Two CT phantoms with a cobalt chromium sphere attached to a titanium rod, simulating an arthroplasty, within a background of soft-tissue attenuation containing spherical lesions (range, 10-20 mm) around the head and stem of different attenuations from the background (range of attenuation, 10-70 HU) were scanned with a single CT scanner individually (unilateral) and together (bilateral) with the following three dose-equivalent techniques: the currently used clinical protocol (140 kVp, 300 Reference mAs); 100 kVp; and DECT (100 kVp and 150 kVp with a tin filter). Three radiologists reviewed the datasets to identify lesions. Nonparametric AUC was estimated for each reader with each technique. Multireader ANOVA was performed to compare AUCs. Multiple-variable logistic regression analysis was used to identify factors affecting sensitivity and specificity. RESULTS. Accuracy was lower (p < 0.001) for the DECT 130-keV technique than for the 100-, 70-, and 140-kVp techniques. Sensitivity was higher with unilateral arthroplasties (p = 0.037), with greater contrast differences from background (p < 0.001), and with the SECT 100-kVp technique versus other techniques (p < 0.001). The difference in specificities of modalities was not statistically significant (p = 0.148). CONCLUSION. Combining DECT and SECT techniques does not provide additional benefits for lesion detection as opposed to using SECT alone.


Asunto(s)
Artefactos , Aleaciones de Cromo , Prótesis Articulares , Titanio , Tomografía Computarizada por Rayos X/métodos , Artroplastia , Fantasmas de Imagen , Imagen Radiográfica por Emisión de Doble Fotón
9.
Spine Deform ; 8(4): 569-576, 2020 08.
Artículo en Inglés | MEDLINE | ID: mdl-32430793

RESUMEN

STUDY DESIGN: Finite-element analysis. OBJECTIVES: Intraoperative contouring of rods is a common procedure for spine surgeons to match the native curvature of the spine, but it may lead to premature weakening of the rod. This study investigated the effect of different bending methods on rod fatigue performance. Rod failure in the cervical spine is of clinical concern, particularly when spanning the cervicothoracic region and when considering corrective osteotomies for deformity correction and global spinal alignment. METHODS: Finite-element models were developed to simulate rod bending (3.5 mm D, 40 mm L) to achieve a 23° angle with 3 different bending methods: French single, multiple bending, and in situ bending. Simulations were conducted in 4 steps: rod bending, rod spring back, residual stress relaxation, and F1717 mechanical test simulation. RESULTS: French single bending resulted in the highest residual stress concentrations for both titanium (TiAlV) and cobalt chrome (CoCr) at 783 MPa and 507 MPa, respectively. During F1717 test simulation, the French single bent rod had its highest tensile stress in the middle, with 917 MPa and 623 MPa, respectively, for TiAlV and CoCr, compared to in situ (580 MPa and 586 MPa for TiAlV and CoCr) and the French multiple bent rod (765 MPa and 619 MPa for TiAlV and CoCr). The computational model found that CoCr rods made the construct least prone to deformation. CONCLUSIONS: French single bend with TiAlV rods put the construct at highest risk of failure. CoCr rods led to minimal physical changes in microstructure while showing evidence of flattening.


Asunto(s)
Vértebras Cervicales/cirugía , Fijadores Internos , Fusión Vertebral/instrumentación , Fenómenos Biomecánicos , Aleaciones de Cromo , Simulación por Computador , Análisis de Elementos Finitos , Humanos , Microscopía Electrónica de Rastreo , Fusión Vertebral/métodos , Vértebras Torácicas/cirugía , Titanio
10.
Int J Comput Dent ; 23(1): 49-56, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32207461

RESUMEN

AIM: Evaluation of appropriate models for computer-aided design/computer-aided manufacturing (CAD/CAM) in vitro studies by investigation of different model materials regarding suitability for intraoral scanners and dimensional stability. MATERIALS AND METHODS: A typodont model was prepared to accommodate a 10-unit prosthesis. The model was duplicated using six different materials: class IV die stone (DS), cobalt-chrome molybdenum (CoCrMo), epoxy resin (EPOX), polyurethane (PU), titanium (TI), and zirconia (ZI). An intraoral scanner was used to obtain three scans of each model. Reference datasets were generated using micro-computed tomography (micro-CT). The first scan was compared with the corresponding reference micro-CT dataset to assess its trueness. The precision was measured by comparing all scans within one test group. For the evaluation of dimensional stability, micro-CT was used to generate three-dimensional (3D) datasets of the models at different time intervals over a 6-week period. The models were kept under constant conditions during the study. All datasets were analyzed with software that determined the deviation of two datasets by alignment using a best-fit algorithm. RESULTS: The criterion of trueness was fulfilled by CoCrMo, EPOX, PU, and the typodont model. Scans of CoCrMo and ZI showed the best precision. PU and the typodont model did not meet the requirement of dimensional stability, whereas EPOX and gypsum were stable only for a period of 10 days. CONCLUSION: The CoCrMo model was the only one that met all the criteria for an appropriate model for CAD/CAM in vitro studies. The other investigated materials either lacked dimensional stability or could not be scanned accurately and reproducibly.


Asunto(s)
Diseño Asistido por Computadora , Adaptación Marginal Dental , Aleaciones de Cromo , Técnica de Impresión Dental , Modelos Dentales , Humanos , Imagenología Tridimensional , Titanio , Microtomografía por Rayos X
11.
J Prosthet Dent ; 123(6): 874.e1-874.e7, 2020 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-32147253

RESUMEN

STATEMENT OF PROBLEM: Laser sintering has several processing parameters, typically under the control of dental laboratory technicians. Laser scan speed is an important parameter, which has a significant effect on manufacturing time but may also affect the adaptation of restorations. However, limited information is available regarding its impact. PURPOSE: The purpose of this in vitro study was to evaluate the intaglio surface adaptation of laser-sintered cobalt-chromium single-crown frameworks sintered at laser scanning speeds of 1, 3, and 6 m/s. MATERIAL AND METHODS: A master bronze metal die was prepared and scanned by using a laboratory scanner to fabricate the metal frameworks for 4 groups (n=10). In group C, the frameworks were fabricated by using the lost-wax method (control). In group L1, L3, and L6, the frameworks were fabricated by using direct metal laser melting (DMLM) at laser scanning speeds of 1, 3, and 6 m/s. After fabrication, 3 scanning data sets were used to evaluate the intaglio surface adaptation: the master die, the intaglio surface of each metal framework, and each metal framework seated on the master die. The intaglio surface adaptation of the metal frameworks was evaluated by using a metrology software program. The data were statistically analyzed by using a 1-way ANOVA, the Tukey honestly significant difference test, and the Tamhane T2 test (α=.05). RESULTS: The highest mean intaglio surface discrepancy value was obtained from group L6, and this was significantly different from the other 3 groups (P<.001). No significant intaglio surface discrepancy differences were found among the other groups. CONCLUSION: The amount of intaglio surface discrepancy increased when the laser scanning speed reached 6 m/s.


Asunto(s)
Coronas , Adaptación Marginal Dental , Aleaciones de Cromo , Diseño Asistido por Computadora , Diseño de Prótesis Dental , Rayos Láser
12.
Sci Rep ; 10(1): 1682, 2020 02 03.
Artículo en Inglés | MEDLINE | ID: mdl-32015475

RESUMEN

In this study, different surface modifications were performed on a Cobalt-Chrome-Molybdenum (CoCrMo) alloy and the effects on cell viability and cytotoxicity as well as the adhesion potential of human osteoblasts (hFOB) and their inflammation reaction were investigated in vitro. CoCrMo discs were coated with TiN, with polished and porous coated surfaces, or with pure titanum (cpTi) surfaces and examined by Scanning Electron Microscopy to evaluate surface modifications. In vitro cell viability, adhesion behaviour, and expression of inflammation markers of hFOB human osteoblasts were measured via CellTiter-Glo, CytoTox, ELISA, and RT-PCR respectively. All results were compared to CoCrMo without surface modifications. The biocompatibility data showed high compatibility for the TiN hard coatings. Likewise, the porous surface coating increased cell viability significantly, compared to an untreated CoCrMo alloy. None of the investigated materials influenced cytotoxicity. Different surface modifications did not influence expression of fibronectin, although TiN, porous surface coatings and polished surfaces showed highly significant reductions in integrin subunit expression. In addition to the regulation of adhesion potential these three surfaces stimulated an anti-inflammatory response by osteocytes. Improved biocompatibility and adhesion properties may contribute to better osteointegration of prosthetics.


Asunto(s)
Adhesión Celular/efectos de los fármacos , Aleaciones de Cromo/química , Materiales Biocompatibles Revestidos/química , Inflamación/tratamiento farmacológico , Molibdeno/farmacología , Osteoblastos/efectos de los fármacos , Titanio/química , Línea Celular , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Humanos , Ensayo de Materiales/métodos , Molibdeno/química , Propiedades de Superficie/efectos de los fármacos
13.
Spine Deform ; 8(3): 369-379, 2020 06.
Artículo en Inglés | MEDLINE | ID: mdl-32096138

RESUMEN

STUDY DESIGN: Biomechanical analysis of scoliosis instrumentation using superelastic Nickel-titanium shape memory (SNT) rods. OBJECTIVE: To compare SNT with conventional Titanium (Ti) and Cobalt-chrome (Co-Cr) rods. A clinical trial has documented comparable efficacy between two adolescent idiopathic scoliosis (AIS) cohorts instrumented using SNT versus conventional Ti rods. The shape memory and superelasticity of the SNT rod are thought to allow easy rod insertion, progressive curve correction, and correction from spinal tissue relaxation, but study is yet to be done to assess the effects of the shape memory and superelasticity. METHODS: Instrumentations of AIS patients from the clinical trial were computationally simulated using SNT, Ti and Co-Cr rods (5.5 or 6 mm; 30°, 50° or 60° sagittal contouring angles; 0°, 25° or 50° coronal over-contouring angles). Curve correction, its improvement from stress relaxation in the spine, and loads in the instrumentation constructs were computed and compared. RESULTS: The simulated main thoracic Cobb angles (MT) and thoracic kyphosis with the SNT rods were 4°-7° higher and 1°-2° lower than the Ti and Co-Cr rods, respectively. Bone-implant forces with Ti and Co-Cr rods were higher than the SNT rods by 84% and 130% at 18 °C and 35% and 65% at 37 °C, respectively (p < 0.001). Further corrections of the MT from the simulated stress relaxation in the spine were 4°-8° with the SNT rods versus 2°-5° with the Ti and Co-Cr rods (p < 0.001). CONCLUSION: This study concurs with clinical observation that the SNT rods are easier to insert and can result in similar correction to the conventional rods. The SNT rods allow significantly lower bone-implant forces and have the ability to take advantage of post-instrumentation correction as the tissues relax.


Asunto(s)
Aleaciones , Simulación por Computador , Prótesis e Implantes , Escoliosis/cirugía , Fusión Vertebral/instrumentación , Adolescente , Fenómenos Biomecánicos , Niño , Aleaciones de Cromo , Femenino , Humanos , Masculino , Diseño de Prótesis , Titanio , Resultado del Tratamiento , Adulto Joven
14.
J Prosthodont Res ; 64(4): 468-477, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32063534

RESUMEN

PURPOSE: Laboratory and clinical assessment of cast titanium dentures were reported, little is known about additive manufacturing (AM) frameworks. This study evaluated in vitro AM titanium alloy clasps for clinical use. METHODS: After scanning the stainless steel dies to simulate the first molar, an Akers clasp was designed by CAD. AM clasp specimens were manufactured using laser sintering and AM machines from CP titanium grade 2 (CPTi), Ti-6Al-4V (Ti64), and Ti-6Al-7Nb (Ti67) powders. As controls, cast titanium clasps were conventionally made with same three titanium alloys. After nondestructive inspection and surface element analysis, surface roughness, fitness accuracy, initial retentive forces, and changes in retentive forces were measured. RESULTS: Although few porosities and little contamination of AM clasps were confirmed, the AM clasp arm and tip indicated slightly worse fitness accuracy as compared to cast clasps. The initial retentive forces of all titanium clasps showed appropriate retentive forces within the acceptable ranges, AM clasps tended to have lower decreases in retentive forces with up to 10,000 insertion/removal cycles as compared to those of the cast clasps. CONCLUSIONS: AM titanium clasps would be acceptable for clinical use similar to that of cast titanium clasps.


Asunto(s)
Abrazadera Dental , Dentadura Parcial Removible , Aleaciones de Cromo , Retención de Dentadura , Ensayo de Materiales , Propiedades de Superficie , Titanio
15.
J Prosthodont Res ; 64(4): 490-497, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32063537

RESUMEN

PURPOSE: Not all elements with ß-stabilizing properties in titanium alloys are suitable for biomaterial applications, because corrosion and wear processes release the alloying elements to the surrounding tissue. Chromium and molybdenum were selected as the alloying element in this work as to find balance between the strength and modulus of elasticity of ß-titanium alloys. This study aimed to investigate the effect of Titanium-10Molybdenum-10Chromium (Ti-10Mo-10Cr), Titanium-10Chromium (Ti-10Cr) and Titanium-10Molybdenum (Ti-10Mo) on the elemental leachability in tissue culture environment and their effect on the viability of human gingival fibroblasts (HGFs). METHODS: Each alloy was immersed in growth medium for 0-21 days, and the elution was analyzed to detect the released metals. The elution was further used as the treatment medium and exposed to seeded HGFs overnight. The HGFs were also cultured directly to the titanium alloy for 1, 3 and 7 days. Cell viability was then determined. RESULTS: Six metal elements were detected in the immersion of titanium alloys. Among these elements, molybdenum released from Ti-10Mo-10Cr had the highest concentration throughout the immersion period. Significant difference in the viability of fibroblast cells treated with growth medium containing metals and with direct exposure technique was not observed. The duration of immersion did not significantly affect cell viability. Nevertheless, cell viability was significantly affected after 1 and 7 days of exposure, when the cells were grown directly onto the alloy surfaces. CONCLUSIONS: Within the limitation of this study, the newly developed ß-titanium alloys are non-cytotoxic to human gingival fibroblasts.


Asunto(s)
Cromo , Titanio , Aleaciones de Cromo , Corrosión , Ensayo de Materiales , Molibdeno
16.
JACC Cardiovasc Interv ; 13(1): 116-127, 2020 01 13.
Artículo en Inglés | MEDLINE | ID: mdl-31918929

RESUMEN

OBJECTIVES: The aim of this study was to investigate the vascular responses and fates of the scaffold after bioresorbable vascular scaffold (BVS) implantation using multimodality imaging. BACKGROUND: Serial comprehensive image assessments after BVS implantation in the context of a randomized trial have not yet been reported. METHODS: In the ABSORB Japan trial, 400 patients were randomized to a BVS (n = 266) or a cobalt-chromium everolimus-eluting stent (n = 134). Through 3 years, patients underwent serial angiography and intravascular ultrasound or optical coherence tomography (OCT). RESULTS: Luminal dimension at 3 years was consistently smaller with the BVS than with the cobalt-chromium everolimus-eluting stent (mean angiographic minimal luminal diameter 2.04 ± 0.63 mm vs. 2.40 ± 0.56 mm, mean difference -0.37 mm [95% confidence interval: -0.50 to -0.24 mm]; p < 0.001), mainly because of smaller device area (6.13 ± 2.03 mm2 vs. 7.15 ± 2.16 mm2, mean difference -1.04 mm2 [95% confidence interval: -1.66 to -0.42 mm2]; p < 0.001), and larger neointimal area (2.10 ± 0.61 mm2 vs. 1.86 ± 0.64 mm2, mean difference 0.24 mm2 [95% confidence interval: 0.06 to 0.43 mm2]; p = 0.01) by OCT. BVS-treated vessels did not show previously reported favorable vessel responses, such as positive vessel remodeling, late luminal enlargement, and restoration of vasomotion, although the OCT-based healing score was on average zero (interquartile range: 0.00 to 0.00). At 3 years, intraluminal scaffold dismantling (ISD) was observed in 14% of BVS. On serial OCT, ISD was observed in 6 lesions at 2 years, where the struts had been fully apposed at post-procedure, while ISD was observed in 12 lesions at 3 years, where 8 lesions were free from ISD on 2-year OCT. In 5 cases of very late scaffold thrombosis, strut discontinuities were detected in all 4 cases with available OCT immediately before reintervention. CONCLUSIONS: In this multimodality serial imaging study, luminal dimension at 3 years was smaller with the BVS than with the cobalt-chromium everolimus-eluting stent. ISD, suspected to be one of the mechanisms of very late BVS thrombosis, was observed in a substantial proportion of cases at 3 years, which developed between post-procedure and 2 years and even beyond 2 years. (AVJ-301 Clinical Trial: A Clinical Evaluation of AVJ-301 [Absorb™ BVS] in Japanese Population [ABSORB JAPAN]; NCT01844284).


Asunto(s)
Implantes Absorbibles , Fármacos Cardiovasculares/administración & dosificación , Aleaciones de Cromo , Enfermedad de la Arteria Coronaria/terapia , Vasos Coronarios/diagnóstico por imagen , Stents Liberadores de Fármacos , Everolimus/administración & dosificación , Imagen Multimodal , Intervención Coronaria Percutánea/instrumentación , Stents , Fármacos Cardiovasculares/efectos adversos , Angiografía Coronaria , Enfermedad de la Arteria Coronaria/diagnóstico por imagen , Trombosis Coronaria/diagnóstico por imagen , Trombosis Coronaria/etiología , Everolimus/efectos adversos , Humanos , Japón , Intervención Coronaria Percutánea/efectos adversos , Valor Predictivo de las Pruebas , Estudios Prospectivos , Diseño de Prótesis , Método Simple Ciego , Factores de Tiempo , Tomografía de Coherencia Óptica , Resultado del Tratamiento , Ultrasonografía Intervencional
17.
Spine Deform ; 8(1): 25-32, 2020 02.
Artículo en Inglés | MEDLINE | ID: mdl-31960354

RESUMEN

STUDY DESIGN: Biomechanical comparative study. OBJECTIVE: To evaluate pedicle screw gripping capacity from five suppliers, comparing single-diameter (S-D) systems using 5.5-mm-diameter rods to dual-diameter (D-D) systems accepting 5.5- and 6.0-mm-diameter rods with both cobalt chromium (CoCr) and titanium alloy (Ti) rods. D-D systems have become increasingly prevalent; however, these systems theoretically may compromise spinal rod gripping, particularly when a smaller-diameter rod is used within a D-D pedicle screw. METHODS: D-D pedicle screw systems from three suppliers (accepting 5.5- and 6.0-mm-diameter, Ti and CoCr rods), and S-D systems from two suppliers (accepting 5.5-mm-diameter, Ti and CoCr rods) were tested on an MTS MiniBionix machine. Axial load was applied in line with the rod to measure axial gripping capacity (AGC), and torsional load was applied to measure torsional gripping capacity (TGC) for each rod material and diameter. AGC and TGC were compared between D-D and S-D constructs, suppliers, rod diameters, and materials with subsequent classification and regression tree (CART) analysis. RESULTS: 5.5-mm rods within D-D screws were no weaker than 5.5-mm rods in S-D systems for AGC (dual > single, p = 0.043) and TGC (p = 0.066). As a whole, D-D systems had greater AGC than S-D systems (p = 0.01). AGC differed between suppliers (p < 0.001). No rod diameter (p = 0.227) or material (p = 0.131) effect emerged. With CART analysis, Supplier was the most significant predictor for greater AGC. As a whole, D-D systems had greater TGC than S-D systems (p = 0.008). TGC differed between suppliers (p < 0.001). Rod diameter was a significant predictor of higher TGC (6.0 > 5.5 mm, p = 0.002). CoCr rods had greater TGC than Ti (p < 0.001). CART analysis revealed that Supplier and CoCr material were significant predictors for increased TGC. CONCLUSIONS: Despite 30%-70% variability in gripping capacity due to rod supplier and material, overall D-D pedicle screw systems had similar AGC and TGC as S-D systems. LEVEL OF EVIDENCE: N/A.


Asunto(s)
Ensayo de Materiales/métodos , Tornillos Pediculares , Fusión Vertebral/métodos , Titanio , Adolescente , Fenómenos Biomecánicos , Aleaciones de Cromo , Humanos , Escoliosis/cirugía
18.
J Shoulder Elbow Surg ; 29(5): 1019-1029, 2020 May.
Artículo en Inglés | MEDLINE | ID: mdl-31948834

RESUMEN

BACKGROUND: Hemiarthroplasty has clear advantages over alternative procedures and is used in 20% of all shoulder joint replacements. Because of cartilage wear, the clinical outcome of hemiarthroplasty is unreliable and controversial. This paper suggests that the optimal choice of prosthetic material may reduce cartilage degeneration and improve the reliability of the procedure. The specific objectives were to assess 3 materials and assess how the severity of arthritis might affect the choice of prosthetic material. METHODS: A CoCr alloy, an AL2O3 ceramic, and a polycarbonate urethane polymer (PCU) were mechanically tested against 5 levels of human osteoarthritic cartilage (from intact to severely arthritic, n = 45). A high friction coefficient, a decrease in Young's modulus, an increase in permeability, a decrease in relaxation time, an increase in surface roughness, and a disrupted appearance of the cartilage after testing were used as measures of cartilage damage. The biomaterial that caused minimal cartilage damage was defined as superior. RESULTS: The CoCr caused the most damage. This was followed by the AL2O3 ceramic, whereas the PCU caused the least amount of damage. Although the degree of arthritis had an effect on the results, it did not change the trend that CoCr performed worst and PCU the best. DISCUSSION AND CONCLUSION: This study indicates that ceramic implants may be a better choice than metals, and the articulating surface should be as smooth as possible. Although our results indicate that the degree of arthritis should not affect the choice of prosthetic material, this suggestion needs to be further investigated.


Asunto(s)
Cartílago Articular/lesiones , Hemiartroplastia/efectos adversos , Hemiartroplastia/instrumentación , Prótesis de Hombro/efectos adversos , Materiales Biocompatibles/efectos adversos , Cerámica/efectos adversos , Aleaciones de Cromo/efectos adversos , Módulo de Elasticidad , Fricción , Humanos , Ensayo de Materiales , Osteoartritis/diagnóstico por imagen , Poliuretanos/efectos adversos , Reproducibilidad de los Resultados , Índice de Severidad de la Enfermedad
19.
Spine (Phila Pa 1976) ; 45(6): E312-E318, 2020 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-31574057

RESUMEN

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.


Asunto(s)
Ensayo de Materiales/métodos , Prótesis e Implantes , Enfermedades de la Columna Vertebral/cirugía , Fusión Vertebral/métodos , Estrés Mecánico , Aleaciones de Cromo/normas , Humanos , Ensayo de Materiales/instrumentación , Procedimientos Neuroquirúrgicos/instrumentación , Procedimientos Neuroquirúrgicos/métodos , Fusión Vertebral/instrumentación , Titanio/normas
20.
J Prosthodont Res ; 64(2): 120-127, 2020 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-31248826

RESUMEN

PURPOSE: To investigate the adhesion strength and bonding interface of layered porcelain to powdered cobalt-chromium (CoCr) processed by two different computer-aided manufacturing methods. METHODS: Sixteen specimens were manufactured from each of Three-dimensionally -printed/laser-sintered (LS) CoCr and milled pre-sintered (SM) CoCr. The specimens were layered with porcelain and 4-point bending was carried out. Nanoindentation was used to calculate changes in elastic modulus and hardness before and after porcelain firing along with adhesion energy. Fracture surface and microstructural changes were examined before and after porcelain firing observed using scanning electron microscopy. RESULTS: The adhesion energy of the LS specimens bonded porcelain were higher than the SM specimens (P<0.05). Analysis of the fracture surfaces showed a predominantly adhesive mode of failure. Elastic-modulus and hardness of the CoCr specimens increased post porcelain firing. Examination using electron-backscatter diffraction (EBSD) showed a fine grain structure for both manufacturing methods. Significant localized changes in the crystal structure post firing were only observed at the surface of the SM specimens. CONCLUSIONS: Both manufacturing methods showed regular microstructures prior to porcelain firing. Laser-sintered CoCr had stronger bonding to porcelain than milled pre-sintered CoCr and was also more stable microstructurally post-ceramic firing. However, both manufacturing methods were deemed to have satisfactory adhesion strength to porcelain. It was also found that increased hardness of CoCr had an inverse relationship with bonding strength. High strength porcelain bonding and stability following multiple ceramic firings indicate suitability for use of these CoCr materials with implant or tooth supported long-span frameworks.


Asunto(s)
Recubrimiento Dental Adhesivo , Porcelana Dental , Cromo , Aleaciones de Cromo , Cobalto , Ensayo de Materiales , Aleaciones de Cerámica y Metal , Microscopía Electrónica de Rastreo , Impresión Tridimensional , Propiedades de Superficie
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