Adaptación marginal e interna de cofias fabricadas por métodos convencionales, CAD/CAM de fresado y sinterizado por láser / Marginal and internal adaptation of copings manufactured by conventional methods, CAD/CAM milling and laser sintering

Introducción: la adaptación marginal e interna de nuestras restauraciones fabricadas por fundición sistemas de fresado y sinterización láser es uno de los factores clínicos más importantes para el éxito de las prótesis fijas, previniendo el riesgo de microfiltración y enfermedad periodontal. Objetivo: evaluar la adaptación marginal e interna de cofias metálicas en aleación Cr-Co confeccionadas por técnicas convencionales, CAD/ CAM de fresado y sinterizado por láser. Material y métodos: estudio de tipo experimental, comparativo e in vitro. Se imprimió un modelo maestro en Cr-Co, proveniente del escaneo de un premolar preparado para corona completa, sobre el cual se diseñaron 30 cofias divididas en tres grupos: el primero que corresponde al grupo cofias fundidas fresadas en disco de cera A (A = 10), el segundo grupo cofias fresadas en disco de metal presinterizado B (B = 10) y el tercer grupo cofias impresas por sinterización láser C (C = 10). Se empleó la réplica de silicona, colocando silicona al interior de cada cofia, sobre el modelo maestro, simulando al cemento, mediante una máquina de ensayo universal se realizó una compresión de 50 N. Luego de retirar cada cofia se rellenaron con silicona pesada de adición, obteniendo una réplica de silicona. Se efectuaron dos cortes transversales en sentido vestíbulolingual y mesiodistal. Se observó el espesor de silicona VPS (vinil poliéter silicona) mediante un estereomicroscopio (Nikon SMZ745T), obteniendo valores en micrómetros. Para el análisis estadístico se utilizó el software SPSS 25 con el fin de realizar la prueba de normalidad y ANOVA de dos vías bajo un nivel de confianza del 95%. Resultados: el menor gap lo obtuvo el grupo de fresadas, seguido de las impresas y por último las fundidas por métodos convencionales. ANOVA de dos vías reveló diferencias estadísticamente significativas entre los tres grupos (p < 0.0001). Conclusiones: se encontró que el gap varía con cada método de fabricación, la técnica convencional de fundido mostró un mayor gap, ninguna excediendo el rango clínicamente aceptable (AU)

Introduction: the marginal and internal adaptation of our restorations manufactured by casting, milling systems and laser sintering is one of the most important clinical factors for the success of fixed prostheses, preventing the risk of microleakage and periodontal disease. Objective: evaluate the marginal and internal adaptation of metal copings in Cr-Co alloy made by conventional techniques, CAD/CAM milling and laser sintering. Material and methods: an experimental, comparative and in vitro study, a Cr-Co master model was printed from the scan of a premolar prepared for a full crown. An experimental, comparative and in vitro study, a Cr-Co master model was printed from the scan of a premolar prepared for a full crown, on which 30 caps divided into three groups were designed; the first group corresponds to the cast copings milled on a wax disc A (A = 10), the second group milled copings on a presintered metal disc B (B = 10) and the third group printed by laser sintering copings C (C = 10). The silicone replica was used, placing silicone inside each coping, on the master model, simulating cement, using a universal testing machine, a 50 N compression was performed. After removing each coping, they were filled with heavy addition silicone, obtaining a silicone replica. Two cross-sections were made in the buccolingual and mesiodistal direction., observing the thickness of the VPS (vinyl polyeter silicone) silicone using a stereomicroscope (Nikon SMZ745T), obtaining values in micrometers. For the statistical analysis, the SPSS 25 software was used in order to perform the normality and two-way ANOVA tests under a 95% confidence level. Results: the smallest gap was obtained by the milled group, followed by the printed ones and finally those cast by conventional methods. Two-way ANOVA revealed statistically significant differences between the three groups (p < 0.0001). Conclusions: the gap was found to vary with each fabrication method, the conventional casting technique showed a larger gap, none exceeding the clinically acceptable range (AU)

Evaluation of EDM inclusion into the conventional polishing of printed Co-Cr alloy by selective laser melting / Avaliação da inclusão de EDM no polimento convencional da liga de Co-Cr impressa por fusão seletiva a laser

Objective: The selective laser melting (SLM) technique used in manufacturing results in a rougher surface that requires more satisfying processing than conventional hand-finishing operations. The electro discharge machine (EDM) has various possibilities in the adjustment of surfaces. The present study assesses whether the participation of the EDM technique with the conventional finishing and polishing methods enables surface improvement for the Cobalt-Chromium alloy fabricated by SLM. Material and Methods: Twenty discs of cobalt chromium alloy were fabricated by SLM, divided equally into two groups: (TF) control group for finishing and polishing in the conventional method in accordance with the manufacturer's recommendations; and (EF) group for conducting polishing incorporating the EDM method. Results: The EF group recorded the lowest mean value of surface roughness and the highest mean value of micro hardness compared to the TF group. Furthermore, statistically significant differences (P < 0.05) were found for surface roughness as well as micro hardness. Conclusion: Reliance of the electric discharge machine proactively within finishing and polishing procedures promotes competence in the conventional polishing method and improves the surface properties of cobalt chromium alloy printed by SLM technology (AU)

Objetivo: A técnica de fusão a laser seletiva (SLM) usada na fabricação resulta em uma superfície mais rugosa a qual requer um processamento mais satisfatório do que o acabamento manual. A máquina de eletro descarga (EDM) possui várias possibilidades no ajuste de superfícies. O presente estudo avalia se a participação da técnica EDM associada aos métodos convencionais de acabamento e polimento possibilita a melhora da superfície da liga Cobalto-Cromo fabricada através da SLM. Material e Métodos: Vinte discos de liga de cromo-cobalto foram confeccionados por SLM, e divididos igualmente em dois grupos: (TF) grupo controle, realizado acabamento e polimento pelo método convencional de acordo com as recomendações do fabricante; e (EF) grupo do polimento associado ao método EDM. Resultados: O grupo EF registrou o menor valor médio de rugosidade superficial e o maior valor médio de microdureza em relação ao grupo TF. Além disso, diferenças estatisticamente significativas (P < 0,05) foram encontradas para rugosidade superficial, assim como para a microdureza. Conclusão: A confiança na máquina de descarga elétrica proativamente nos procedimentos de acabamento e polimento promove a competência no método de polimento convencional e melhora as propriedades de superfície da liga de cromo-cobalto impressa pela tecnologia SLM(AU)

Resistencia estructural de prótesis dentales acrílicas y de cromo cobalto en cadáveres quemados o carbonizados: a propósito de dos casos / Structural resistance of acrylic and cobalt-chromium dental prostheses in burned or charred corpses: a propos of two cases

La identificación humana genera continuos desafíos técnicos y científicos para los equipos de expertos forenses en sus múltiples contextos de intervención. Uno de los más complejos, está representado por el hallazgo de cadáveres quemados o carbonizados, donde las huellas dactilares resultan inviables. En tales situaciones, los tejidos de la cavidad oral han demostrado elevada tolerancia a la injuria térmica, aportando información decisiva, muchas veces com-plementada por estructuras protésicas recupera-das del occiso. El presente artículo reporta dos ca-sos donde las prótesis dentales acrílicas y de cromo cobalto exhibieron notable indemnidad pese a la gran pérdida orgánica sufrida por los cuerpos de las víc-timas ante la acción vulnerante del fuego, otorgando valor probatorio para contribuir en el establecimien-to de su identidad (AU)

Human identification generates continuous technical and scientific challenges for teams of forensic experts in their multiple contexts of intervention. One of the most complex is represented by the discovery of burned or charred corpses, where fingerprints are unviable. In such situations, the tissues of the oral cavity have shown high tolerance to thermal injury, providing decisive information, often complemented by prosthetic structures recovered from the deceased. This article reports two cases where the acrylic and cobalt chrome dental prostheses presented notable indemnity despite the great organic loss suffered by the bodies of the victims before the damaging action of fire, granting probative value to contribute to the establishment of their identity (AU)

Thermal expansion and corrosion resistance of cobalt-chromium alloys fabricated by contemporary manufacturing processes: an in vitro study / Expansión térmica y resistencia a la corrosión de aleaciones de cobalto-cromo fabricadas mediante procesos de abricación contemporáneos: un estudio in vitro

In Purpose: The fabrication technique can influence the mechanical properties of Cobalt-Chromium (Co-Cr) dental alloys. Hence, the present study aims to determine the corrosion resistance and thermal expansion of alloys manufactured using three contemporary techniques. Material and Methods: A total of nine specimens of Co-Cr alloy were prepared according to ISO 22674 by each one of the three manufacturing processes (three in each process); conventional casting, direct metal laser sintering (DMLS) and milling (MIL). All these specimens were tested for coefficient of thermal expansion and corrosion resistance. The data was tabulated and analyzed statistically. Results: The difference in the thermal expansion of alloys fabricated using three techniques was non-significant at almost all the temperatures from 50 ºC to 950 ºC (p>0.05), except 450 ºC and 600 °C. The polarization resistance of specimens manufactured using the conventional method was more compared to DMLS and MIL at pH 5 (Conventional>MIL>DMLS) (p<0.001). Conclusion: The thermal expansion behavior of alloys manufactured using the three selected techniques were similar, whereas, at acidic pH, the corrosion resistance of conventional and MIL were better than the DMLS.

Antecedentes: La técnica de fabricación puede influir en las propiedades mecánicas de las aleaciones dentales de cobalto-cromo (Co-Cr). Por lo tanto, el presente estudio tiene como objetivo determinar la resistencia a la corrosión y la expansión térmica de aleaciones fabricadas con tres técnicas contemporáneas. Material y Métodos: Se prepararon un total de nueve probetas de aleación de Co-Cr según ISO 22674 por cada uno de los tres procesos de fabricación (tres en cada proceso); fundición convencional, sinterización directa de metal por láser (DMLS) y fresado (MIL). Todos estos especímenes fueron probados para determinar el coeficiente de expansión térmica y la resistencia a la corrosión. Los datos fueron tabulados y analizados estadísticamente. Resultados: La diferencia en la dilatación térmica de las aleaciones fabricadas con las tres técnicas no fue significativa en casi todas las temperaturas desde 50ºC hasta 950ºC (p>0,05), excepto 450ºC y 600ºC. La resistencia a la polarización de las muestras fabricadas con el método convencional fue mayor en comparación con DMLS y MIL a pH 5 (Convencional>MIL>DMLS) (p<0, 0 01). Conclusión: El comportamiento de expansión térmica de las aleaciones fabricadas con las tres técnicas seleccionadas fue similar, mientras que, a pH ácido, la resistencia a la corrosión de la convencional y la MIL fue mejor que la de la DMLS.

Avaliação da formação de biofilme bacteriano em diferentes ligas metálicas ortopédicas / Evaluation of the formation of bacterial biofilm in different orthopedic metallic alloys

Objetivo: Esse trabalho objetiva identificar e caracterizar o desenvolvimento da bactéria Pseudomonas aeruginosa forte produtora de biofilme nos seguintes materiais ortopédicos: hastes de titânio e de cromo-cobalto. Método: A quantidade de biofilme formada nas amostras foi avaliada com base na quantidade de Pseudomonas aeruginosa, compondo o biofilme das amostras. Resultado: A formação de biofilme nas ligas de titânio foi significativamente maior do que o observado nas ligas cromo-cobalto, tanto no período de 17 horas quanto em uma semana. O cromo-cobalto possibilitou a formação de maior número de biofilme em uma semana, enquanto o titânio viabilizou maior geração de biofilme no período de 17 horas. Além disso, observou-se que um período de maior permanência do biomaterial em contato com a bactéria não pode ser considerado como um fator de proteção no processo de formação de biofilme. Desse modo, evidenciamos a necessidade de investimento em pesquisas relacionadas à prevalência e desenvolvimento de biofilme em ligas metálicas largamente utilizadas nos implantes cirúrgicos. Conclusão: O tempo influenciou apenas na formação de bactéria no cromo-cobalto, sendo quanto maior tempo de contato com a bactéria, maior quantidade de biofilme. Entre as ligas metálicas titânio e cromo-cobalto, o cromo-cobalto produziu menor quantidade de biofilme.

Objective: This work aims to identify and characterize the development of the bacterium Pseudomonas aeruginosa forte that produces biofilm in the following orthopedic materials: titanium and chromium-cobalt rods. Method: The amount of biofilm formed in the samples was evaluated based on the amount of Pseudomonas aeruginosa composing the biofilm of the samples. Result: The biofilm formation in titanium alloys was significantly higher than that observed in chromium-cobalt alloys both in 17 hours and in a week. Chromium-cobalt enabled the formation of a greater number of biofilms in one week, while titanium enabled greater generation of biofilms in 17 hours. In addition, it was observed that a period of greater permanence of the biomaterial in contact with the bacteria cannot be considered as a protective factor in the biofilm formation process. Thus, we highlight the need for investment in research related to the prevalence and development of biofilm in metal alloys widely used in surgical implants. Conclusion: Time influenced only the formation of bacteria in chromium-cobalt, the longer the contact with the bacteria, the greater the amount of biofilm. Among the titanium and chromium-cobalt metal alloys, chromium-cobalt produced less biofilm.

In Vitro Microscopic Evaluation of Metal- And Zirconium-Oxide-Based Crowns' Marginal Fit

ABSTRACT Objective To evaluate the marginal adaptation of computer-aided designing and computer-aided machining (CAD/CAM) fabricated cobalt-chromium and zirconium-oxide-based ceramic crowns compared to those produced by a conventional method. Material and Methods The study consists of three groups; 45 crowns fabricated from cobalt-chromium (CAD-CoCr) and 45 crowns manufactured from zirconium CAD/CAM technology (CAD-Z), and 45 control (C) which consists of conventional metal-ceramic crowns. The marginal discrepancies in vertical dimensions were assessed utilizing a microscope in four surfaces (mesial, distal, vestibular, and oral) for each crown. On completion of the microscopic evaluation, multivariate analysis of variance (MANOVA) was used to study the difference in the four surfaces, considered altogether. Two-way ANOVA revealed the effect of three systems used for gap measurements of each landmark. The differences observed were considered significant at p<0.05. Results There were no differences in the four surfaces revealed by АNOVА in the three groups when considered altogether. Two-way ANOVA of each surface discovered no differences among all groups as well. Conclusion The CAD/CAM crowns revealed a comparable and satisfactory marginal adaptation compared to conventional metal-ceramic crowns.

Finite element analyses of retention of removable partial denture circumferential clasps manufactured by selective laser melting / 北京大学学报(医学版)

OBJECTIVE@#To compare the retentions of different designs of cobalt-chromium (Co-Cr), pure titanium (CP Ti), and titanium alloy (Ti-6Al-4V) removable partial denture (RPD) circumferential clasps manufactured by selective laser melting (SLM) and to analyze the stress distribution of these clasps during the removal from abutment teeth.@*METHODS@#Clasps with clasp arm size A (1.9 mm width/1.1 mm thickness at the body and 0.8-taper) or B (1.2 times A) and 0.25 mm or 0.50 mm undercut engagement were modeled on a prepared first premolar die, named as designs A1, A2, A3, and A4, respectively. The density and elastic modulus of SLM-built Co-Cr, CP Ti, and Ti-6Al-4V were measured and given to different groups of clasps. The density, elastic modulus, and Poisson ' s ratio of enamel were given to the die. The control group was the cast Co-Cr clasp with design A1, to which the density and elastic modulus of cast Co-Cr alloy were given. The Poisson's ratio of all metals was 0.33. The initial 5 N dislodging force was applied, and the maximum displacement of the clasp along the insertion path was computed. The load was reapplied with an increment of 5 N than in the last simulation until the clasp was completely dislodged. The retentive force range of different groups of clasps was obtained. The retentive forces of the SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with equivalent computed retentive force range to the control group were validated through the insertion/removal experiment. The von Mises stress distributions of these three groups of SLM-built clasps under 15 N loads were analyzed.@*RESULTS@#SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with designs B1 or B2, and Co-Cr clasps with design A2 had higher retentive forces than those of the control group. SLM-built CP Ti and Ti-6Al-4V clasps with design A1 had lower retentive forces than those of the control group. SLM-built Co-Cr clasp with design A1 and SLM-built CP Ti and Ti-6Al-4V clasps with design A2 had equivalent retentive forces to those of the control group. The insertion/removal experiment showed that the measured retentive forces of these three groups of SLM-built clasps were (21.57±5.41) N, (19.75±4.47) N, and (19.32±2.04) N, respectively. No statistically significant measured retentive force difference was found among these three groups of SLM-built clasps (P>0.05). The maximum von Mises stress of these three groups of SLM-built clasps exceeded their responding yield strength except for the Ti-6Al-4V one.@*CONCLUSION@#SLM-built Co-Cr circumferential clasps had higher retention than CP Ti and Ti-6Al-4V ones with the same clasp arm size and undercut engagement. The retention of SLM-built circumferential clasps could be adjusted by changing the undercut engagement and clasp arm size. If SLM-built circumferential clasps are used in clinical practice, the Ti-6Al-4V clasp with clasp arm size A and 0.50 mm undercut engagement is recommended considering the long-term use of RPD in the patient's mouth.

Tratamiento de la anquilosis temporomandibular en niños con materiales aloplásticos / Treatment of temporomandibular ankilosis in children with alloplastic materials

La anquilosis de la articulación temporomandibular en niños continúa siendo una patología presente a pesar de los avances médicos y sociales. El tratamiento de esta patología en niños tiene como objetivos restablecer la apertura bucal y mejorar la estética facial cuando se presentan hipoplasias o micrognatias asociadas. El uso de materiales aloplásticos para el tratamiento de la anquilosis temporomandibular en niños es evitar la reanquilosis y disminuir riesgos, molestias y costos que ocasionan la toma y aplicación de injertos, siendo utilizados con buenos resultados en niños en otras especialidades como la Traumatología y Ortopedia. Estos procedimientos pueden llevarse a cabo de manera segura y predecible. En este artículo se reportan dos casos de anquilosis temporomandibular en niños, tratados con materiales aloplásticos, llevados a cabo en la Unidad Médica de Alta Especialidad No. 71 del Instituto Mexicano del Seguro Social, Torreón, Coahuila, México, con un seguimiento de 11 y 16 años de postoperatorio, demostrando que se trata de una buena opción de tratamiento sin presentar alteraciones al crecimiento y desarrollo de los pacientes (AU)

Temporomandibular ankilosis in children is pathology still present despite the medical and social advances. The treatment of this pathology in children aims to restore mouth opening and improve facial aesthetics when hypoplasia or micrognatia are present. The use of alloplastic materials to treat temporomandibular ankilosis in children is to prevent the re ankilosis and reduce discomfort, risks, and cost causing by the take and application of graft, alloplastic materials being used with good results in children in other specialties such as Traumatology and Orthopedics. These procedures can be made safely and predictably. This article describes two cases of temporomandibular ankilosis in children, treated with alloplastic materials, carried out in the Medical Unit of High Specialty, number 71, of the Mexican Institute Social Security, Torreon, Coahuila, Mexico, with follow up of cases 11 and 16 years of postoperative, prove that is a good option of treatment, without presenting any alterations in growth and development of patients (AU)

Effects of 3 kinds of processing techniques on the fitness of metal clasp / 中南大学学报(医学版)

OBJECTIVES@#At present, removable partial denture is still one of the main restoration methods for dentition defects. However, the trend for digital partial denture is becoming more and more obvious in the field of oral repair. However, there are relatively few studies on digital removable partial denture. The aim of this study is to investigate the effects of 3 processing technologies (precision casting, digital cutting, and 3D printing) on the fitness for the clasps of cobalt chromium alloy and pure titanium removable partial denture, and to provide a theoretical basis for the clinical application of digital removable partial denture.@*METHODS@#Clasps of Co-Cr alloy and pure titanium were produced by 3 different processing technologies (precision casting, digital cutting, and 3D printing). There are 6 groups, including a casting pure titanium group, a casting cobalt chromium group, a cutting pure titanium group, a cutting cobalt chromium group, a printing pure titanium group, and a printing cobalt chromium group (@*RESULTS@#There was no statistical difference in fitness between the casting pure titanium group and the casting cobalt chromium group (@*CONCLUSIONS@#The cobalt chromium alloy and pure titanium clasps made by precision casting, digital cutting, and 3D printing have good fitness. Under the same process, there is no significant difference between cobalt chromium alloy and pure titanium clasps. The 3D printing pure titanium clasps have better fitness than casting pure titanium and cutting pure titanium clasps, which meet the needs of clinical application.

Effect of Sprue Design in Nickel-Chromium Cast Crown Margin

ABSTRACT Objective: To determine the effect of sprue design on the marginal accuracy of the casting. Material and Methods: It was an experimental in-vitro study. There are forty-four crowns of single sprue group with a forty-four double sprue group that was compared in 6 different locations of the margin. The sections were inspected under a microscope at 50X magnification and took a micrograph. The radius from an actual casting edge to a possibly excellent margin was then documented as marginal discrepancy (d), in µm. The marginal discrepancy was documented for each of the six sections per casting. Thus 264 sections were measured for each group. Data were analysed using (ANOVA) for analysis of variance. For bivariate analyses, Chi-square and Student t test were used. The significance level was set at < 0.05. Results: The marginal discrepancy was greater in the single sprue group of cast crown (43.1 ± 4.74 µm) and in double sprue group of cast crown was less (25.7 ± 4.25 µm). This difference is statistically significant (p<0.05). The correlation between single sprue group of casting with a double sprue group of casting by student's t-test where determination height was 95%. Conclusion: Double sprue design produces a higher accurate margin than single sprue design in the nickel-chromium alloy cast crown.

Design and manufacture of a coronary stent INC-1 and initial tests in experimental animal model / Diseño y fabricación del stent coronario INC-1y pruebas iniciales en animales de experimentación

Abstract In this paper, we describe our coronary stent (INC-1) design and development, the way that we found the specific characteristics needed for our device including biophysics aspects, design, finite element testing, manufacturing, and mechanic trials, we submitted and animal models experiences. The stent platform was cobalt-chromium L605 (Co-Cr), with struts thickness of 80 μm, balloon expandable. We placed the coronary stent INC-1 on a rabbit and dog models so we can evaluate efficacy and security of the device in relationship to its biomechanical properties including navigation capacity, traceability, symmetric expansion, and safety, as well as endothelial attachment, thrombogenicity, and lack of involvement of secondary branches in these models. We succeeded in efficacy and safety of the device after fluoroscopy-guided implant proving excellent capacity of release system, traceability, fluoroscopic visualization, symmetric expansion, and complete endothelial attach. Furthermore, we obtained a good post-implant balloon withdrawal, functional integrity, and no vascular complications. We observed adequate clinical evolution 3 weeks after the stent implantation.

Resumen En esta publicación se describen el diseño y el desarrollo de un stent coronario (INC-1), la forma en que se determinaron las características biofísicas deseadas, el diseño y las pruebas computacionales por elemento finito, su fabricación, así como las pruebas mecánicas a las que se sometió el prototipo y por último las primeras experiencias en modelos animales. La plataforma del stent desarrollado fue de cobalto y cromo L605 (Co-Cr), con struts de 80 μm de grosor, expandido por balón. La colocación del stent coronario INC-1 se realizó en un modelo de conejo y uno canino con el objetivo de evaluar el éxito técnico y de seguridad del stent en relación con las propiedades biomecánicas (capacidad de navegación, maniobrabilidad, expansión simétrica del stent) y de seguridad (fijación a la pared vascular y ausencia de compromiso de ramas secundarias y formación de trombos en el momento de la colocación del stent en el modelo animal). Se obtuvo éxito técnico y de seguridad del stent después del implante guiado por fluoroscopia, lo que demostró adecuada capacidad del sistema liberador, excelente maniobrabilidad, adecuada visualización fluoroscópica, expansión simétrica y fijación completa a la pared vascular, capacidad para retirar el balón desinflado después del implante, e integridad funcional y sin complicaciones vasculares. La evolución clínica fue favorable a tres semanas del seguimiento planeado.

Comparative study of some mechanical properties of cobalt chromium and polyether ether ketone thermoplastic removable partial denture clasps: an In-vitro Study / Estudo comparativo de algumas propriedades mecânicas dos grampos parciais removíveis termoplásticos removíveis termoplásticos de cobalto cromo e éter cetona: um estudo in vitro

Objective: was to evaluate the retentive force, fatigue resistance and deformity of clasps made from two materials cobalt chromium and poly ether ether ketone (PEEK). Material and Methods: sixteen models were fabricated,each one having lower 1st molar. Models were divided into two groups according to materials,group I (GI) for cobalt chromium (Co-Cr) and group II (GII) for PEEK. Each testing models and its clasps were mounted inside universal testing machine, the retention was measured by applying withdrawal force to it by this machine at 5 mm/min. The Fatigue resistance is measured by the reduction in retention through repeated insertion and removal cycles using robota chewing simulator. Removal and insertion cycling of clasps was carried out for 360, 730, 1080, 1,440, 2,116 and 2,880 cycles (corresponding to 3, 6, 9, 12, 18 and 24 months of simulated clinical use of a RPD) to simulate the fatigue resistance test. Deformity was measured before and after each cycling using a digital micrometer. Statistical analysis was done by 2-way-ANOVA test to detect significance effects of each variable. Results: Retention and fatigue resistance, after 360, 730, 1080, 1,440, 2,116 and 2,880 cycles totally the difference between Co-Cr and PEEK groups was statistically non-significant (P = 0.0980> 0.05) where (Co-Cr > PEEK). Deformation results, regardless to evaluation time, Co-Cr group recorded statistically significant higher deformation mean value than PEEK group (P = 0.008 < 0.05).Regardless to material group, deformation mean value changed nonsignificantly by time (P = 0.2882> 0.05). Conclusion: PEEK clasps (1.0 mm in cross section diameter) engage 0.50 mm undercut provide sufficient retention nearly similar that of Co-Cr clasps.(AU)

Objetivo: o objetivo foi avaliar a força de retenção, a resistência à fadiga e a deformidade dos grampos fabricados com dois materiais diferentes: cromo-cobalto (Co-Cr) e poliéter-éter-étercetona (PEEK). Materiais e métodos: dezesseis modelos foram confeccionados, cada um com 1º molar inferior. Os modelos foram divididos em dois grupos de acordo com o material: grupo I Co-Cr e grupo II para PEEK. Cada modelo de teste universal e seus grampos foram montados em uma máquina de teste universal. A retenção foi medida aplicando força de retirada por esta máquina a 5 mm/min. A resistência à fadiga foi medida pela redução na retenção através de ciclos repetidos de inserção e remoção usando um simulador do ciclo de mastigação. O ciclo de remoção e inserção dos grampos foi realizado por 360, 730, 1080, 1.440, 2.116 e 2.880 ciclos (correspondendo a 3, 6, 9, 12, 18 e 24 meses de uso clínico simulado de um RPD) para simular o teste de resistência à fadiga. A deformidade foi medida antes e após cada ciclo, usando um micrômetro digital. A análise estatística foi realizada pelo teste ANOVA de 2 fatores para detectar os efeitos de significância de cada variável. Resultados: A retenção e a resistência à fadiga após 360, 730, 1080, 1.440, 2.116 e 2.880 ciclos entre os grupos Co-Cr e PEEK não mostrou diferença estatisticamente significativa (p = 0,0980> 0,05), onde (Co-Cr> PEEK). Para os resultados da deformação, independentemente do tempo de avaliação, o grupo Co-Cr registrou um valor médio de deformação maior, com diferença estatística significativa, quando comparado com o grupo PEEK (p= 0,008 < 0,05). Independentemente do grupo de material, o valor médio da deformação foi alterado de forma não significativa pelo tempo (p= 0,2882> 0,05). Conclusão: os grampos PEEK (1,0 mm de diâmetro da seção transversal) engatam 0,50 mm retenção quase semelhante à dos grampos Co-Cr (AU)

The effect of heat treatment on sliding mechanics of stainless steel orthodontic wires

Aim: The aim of this study was to evaluate the effect of heat treatment (tempering) on the sliding mechanics of stainless steel Chrome Nickel (CrNi) orthodontic wires. Methods: A universal testing machine EMIC DL 2000 was used at a speed of 10 mm/minute for reading-out the sliding strength and friction between brackets and wires, by simulating the sliding mechanics in a fixed orthodontic appliance. The results were submitted to ANOVA variance test for statistical analysis at the level of 5% (p<0.05). Results: The results indicated that depending on the type of bracket, wire and type of treatment, the groups without heat treatment showed higher mean static friction values, except for groups with CrNi GAC wire and conventional brackets, which showed no significant difference with and without heat treatment; and the group with self-ligated brackets and CrNi GAC wires that showed the lowest mean static friction values with heat treatment. Conclusion: The heat treatment reduced the static friction values on CrNi Morelli wires for any combination of brackets (conventional and self-ligated types) and commercial brands. For the CrNi GAC wires, there was a reduction in friction values only in the combination with In-Ovation R/GAC self-ligated brackets

Evaluation of ceramic flexural strength of a cobalt-chromium alloy subjected to airborne particle abrasion and tungsten inert gas welding

Aim: The aim of this study was to evaluate the influence of tungsten inert gas (TIG) welding and airborne particle abrasion using aluminum oxide particles on the flexural strength of a joint between ceramic and cobalt-chromium alloys. Methods: The specimens were cast and welded using TIG, then divided into 6 groups (n = 10) and subjected to blasting with 250 µm, 100 µm, and 50 µm aluminum oxide particles. Ceramic systems were applied to the central part of all specimens. A three-point bending test using a velocity of 0.5 mm/m was performed on the specimens to measure flexural strength. Data were analyzed using two-way analysis of variance and Tukey's test. Results: TIG welding demonstrated the lowest resistance compared with the non-welded groups. Airborne particle abrasion using 250 µm aluminum oxide particles demonstrated greater resistance in the welded groups (p < 0.05). Mixed faults were found in all specimens. Conclusion: TIG welding decreased the bond strength, and the particle size of aluminum oxide did not affect the metal-ceramic bond in groups without TIG welding

Cobalt chromium-Titanium rods versus Titanium-Titanium rods for treatment of adolescent idiopathic scoliosis; which type of rod has better postoperative outcomes?

SUMMARY OBJECTIVE; Compare the outcome of spinal deformity correction between Ti-Ti and CrCo-Ti rods for the treatment of spinal Adolescent Idiopathic Scoliosis (AIS) using rods mentioned with all pedicle screws and translation technique. METHOD; 59 patients operated for spinal deformity (Lenke 1 or 2) AIS. The patients were divided into two groups by random allocation using Ti-Ti rods (n = 29) and CrCo-Ti rods (n = 30) and the alone difference among them in the surgical procedure was rod material (Ti-Ti or CrCo-Ti rods) and finally, radiological outcomes were compared preoperatively, postoperatively and at last follow-up for 12 months. RESULTS; Patients' main curve correction after surgical procedure regardless type of rod was 48.95±11.04 (13-75) degree. Success rate of spinal deformity correction following surgical procedure regardless of type of administered rod was 86.76 ± 11.30 percent (62.5-100%). Mean of deformity correction rate was 91.49±10.67% using CrCo-Ti rods versus 81.86±9.88% using Ti-Ti rods (P-value=0.01). Angle change was 3.29±6.60 for kyphosis angle and 0.59±7.76 for lordosis angle. Rate of main curve correction was not significantly different considering patients' gender (P-value0.657). Main curve correction success rate was in association with patients' age and type of rod (P-value=0.054, r=-1.863 and P-value=0.001, r=8.865 respectively). CONCLUSION; CrCo-Ti rods have the ability to produce higher correction rates in AIS compared to Ti-Ti rod of the same diameter. CrCo-Ti rods provide significant and stable spinal correction, especially in correction of main curve. This rate was associated with patients' age and type of rod administered but not gender.

RESUMO OBJETIVO: Comparar o resultado da correção da deformidade da coluna vertebral com ligas de Ti-Ti e CrCo-Ti para o tratamento da Escoliose Idiopática do Adolescente (EIA) na coluna usando as ligas mencionadas com todos os parafusos pediculares e técnica de tradução. MÉTODO: 59 pacientes operados por EIA com deformidade da coluna vertebral (Lenke 1 ou 2). Os pacientes foram divididos em dois grupos por alocação aleatória usando ligas de Ti-Ti (n = 29) e ligas de CrCo-Ti (n = 30) e a única diferença entre eles no procedimento cirúrgico foi o material da liga (ligas de Ti-Ti ou CrCo-Ti) e, finalmente, resultados radiológicos foram comparados no pré-operatório, pós-operatório e no último retorno por 12 meses. RESULTADOS: A correção da curva principal do paciente após o procedimento cirúrgico, independentemente do tipo de liga, foi de 48,95±11,04 (13-75) graus. A taxa de sucesso da correção da deformidade da coluna vertebral após o procedimento cirúrgico, independentemente do tipo de liga administrada, foi de 86,76 ± 11,30% (62,5-100%). A média da taxa de correção da deformidade foi de 91,49±10,67% usando ligas de CrCo-Ti e 81,86±9,88% usando ligas de Ti-Ti (valor de P = 0,01). A mudança de ângulo foi de 3,29±6,60 para o ângulo de cifose e de 0,59±7,76 para o ângulo de lordose. A taxa de correção da curva principal não foi significativamente diferente considerando o sexo dos pacientes (Valor de P 0,657). A taxa de sucesso da correção da curva principal foi associada à idade do paciente e ao tipo de liga (valor de P=0,054, r=-1,863 e valor de P=0,001, r=8,865, respectivamente). CONCLUSÃO: As ligas de CrCo-Ti têm a capacidade de produzir taxas de correção mais altas em EIA em comparação com a liga de Ti-Ti do mesmo diâmetro. As ligas de CrCo-Ti fornecem uma correção espinhal significativa e estável, especialmente na correção da curva principal. Essa taxa foi associada à idade e ao tipo de liga administrada, mas não ao sexo.

Tratamiento de anquilosis temporomandibular con materiales aloplásticos en niños: reporte de 3 casos / Treatment of temporomandibular joint ankylosis with alloplastic materials in children: report of 3 cases

La anquilosis de la articulación temporomandibular en niños continúa siendo una patología presente a pesar de los avances médicos y sociales. El tratamiento de esta patología en niños tiene como objetivos restablecer la apertura bucal y mejorar la estética facial, cuando se presentan hipoplasias o micrognatias asociadas. El objetivo del uso de materiales aloplásticos para el tratamiento de esta patología en niños es evitar la morbilidad y los gastos que ocasiona la toma y aplicación de injertos, para esto, durante 15 años, en la Unidad Médica de Alta Especialidad del Instituto Mexicano del Seguro Social, Torreón, Coahuila, México, Departamento de Cirugía Maxilofacial, se ha establecido el protocolo de tratar esta patología en niños con el uso de prótesis metálicas de cavidad glenoidea, en lugar de injertos costales o de otro tipo, además de tratar las hipoplasias o micrognatias en un mismo tiempo quirúrgico con el uso de aparatos distractores óseos, teniendo excelentes resultados a mediano plazo, sin daño a estructuras anatómicas ni a los procesos de crecimiento y desarrollo de los pacientes. Se utilizan prótesis prediseñadas de cromo, cobalto, molibdeno, que se adaptan adecuadamente a las estructuras óseas, siendo un material utilizado ya en otras áreas de la ortopedia en niños, concluyendo que se trata de una buena opción de tratamiento que disminuye el riesgo, frecuencia y costos de cirugías de mayor complejidad y que puede llevarse a cabo de manera segura y predecible. En este artículo se reportan tres casos de niños con anquilosis temporomandibular tratados con este método con buenos resultados (AU)

Temporomandibular joint ankylosis in children is actually a pathology still present despite the medical and social advances. The treatment of this pathology in children has restored the buccal opening and improve the facial aesthetics when hypoplasia and micrognathia are present. The purpose of using alloplastic material for treatment of this disease in children is to prevent morbidity and expenses related to making and implementing grafts, for this, for 15 years in the Medical Unit of High Specialty the Mexican Institute of Social Security, Torreon, Coahuila, Mexico, Department of Maxillofacial Surgery, has been established protocol to treatment this pathology in children with the use of metal glenoid prosthesis instead of rib grafts or otherwise in addition to treating hypoplasias or micrognatias in the same surgical time with the use of distracting devices bone, having excellent results in the medium term without damage to anatomical structures or processes of growth and development of patients. The prosthesis used predesigned chromium, cobalt, molybdenum, which are suitably adapted to the bone structures, with a material already used in other areas of orthopedics in children, concluding that this is a good treatment option that reduces the risk, and surgeries often cost more complex and can be performed safely and predictably. In this paper, three cases of children with temporomandibular ankylosis treated with this method with good results are reported (AU)

Comparative analysis of ceramic flexural strength in co-cr and ni-cr alloys joined by TIG welding and conventional brazing

Aims: The purpose of the present study was to evaluate the flexural strength of specimens made of nickel-chromium(Ni-Cr) and cobalt-chromium (Co-Cr) alloys and joined by tungsten inert gas (TIG) welding and conventional brazing. Ni­Cr and Co­Cr base metal specimens (n = 40, each) were cast and welded by TIG or brazing. The specimens were divided into six groups (2 base metals, four welded specimens). Ceramic systems were applied to the central part of all the specimens. A three-point bending test with a velocity of 0.5 mm/m was performed on the specimens up to the point of the first ceramic bond failure by measuring the flexural strength. Data were analyzed using two-way ANOVA and Bonferroni's tests. Conventional welding showed the lowest flexural strength results for both alloys, while the TIG weld and the control group presented with varying bond strengths for the alloys studied. We concluded that TIG welding was superior to the conventional welding method for both Ni­Cr and Co­Cr alloys with regard to the flexural strength of the ceramic (AU)

Fracture Resistance of Endodontically Treated Teeth Restored with Different Types of Intracanal Posts

Objective: To evaluate the fracture resistance of endodontically treated teeth restored with different types of intracanal posts. Material and Methods: Sixty human upper central incisors (n = 60) were divided according to the performance of different protocols for restoration with intracanal posts. Groups without endodontic treatment (NT) and with endodontic treatment (TR) without placement of intracanal posts, served as controls. The experimental groups received endodontic treatment and were restored with: fiberglass post with composite resin filling core (PFV-NP); carbon fiber post with composite resin filling core (PFC-NP); nickel-chromium metal cast and core posts (NiCr); or copper-aluminum metal cast and core posts (CuAl). The specimens were then tested to determine the maximum fracture resistance and the failure types of fracture (infra-crestal and supra-crestal). Data were analyzed by one-way ANOVA and Tukey test (α<0.05). Results: Increased fracture resistance was observed for NT group (p<0.05). Within endodontically treated teeth groups, NiCr showed higher resistance to fracture, differing statistically from groups FV+NP and FC+NP (p<0.05). Higher frequency of infra-crestal fractures was observed in NT and TR groups. Conclusion: The installation of nickel-chromium intracanal cast and core posts contributed to higher fracture resistance and lower risk of fractures difficult to repair.

Research on bond durability among different core materials and zirconia ceramic cemented by self-adhesive resin cements / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This research estimated shear bond durability of zirconia and different substrates cemented by two self-adhesive resin cements (Clearfil SA Luting and RelyX U100) before and after aging conditioning.</p><p><b>METHODS</b>Machined zirconia ceramic discs were cemented with four kinds of core material (cobalt-chromium alloy, flowable composite resin core material, packable composite resin, and dentin) with two self-adhesive resin cements (Clearfil SA Luting and RelyX U100). All specimens were divided into eight test groups, and each test group was divided into two subgroups. Each subgroup was subjected to shear test before and after 10 000 thermal cycles.</p><p><b>RESULTS</b>All factors (core materials, cements, and thermal cycle) significantly influenced bond durability of zirconia ceramic (P<0.00 1). After 10 000 thermal cycles, significant decrease was not observed in shear bond strength of cobalt-chromium alloy luted with Clearfil SA Luting (P>0.05); observed shear bond strength was significantly higher than those of other substrates (P<0.05). Significantly higher shear bond strength was noted in Clearfil SA Luting luted with cobalt-chromium alloy, flowable composite resin core material, and packable composite resin than that of RelyX U100 (P<0.05). However, significant difference was not observed in shear bond strength of dentin luted with Clearfil SA Luting and RelyX U100 (P>0.05).</p><p><b>CONCLUSIONS</b>Different core materials and self-adhesive resin cements can significantly affect bond durability of zirconia ceramic. 
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Surface change assessment of Co-Cr alloy subjected to immersion in denture cleansers

Choosing the right chemical cleanser for removable partial dentures is a challenge, because they present an acrylic and a metallic portion, which should be cleaned and not damaged. Aim: The aim of this study was to assess surface changes of cobalt chromium alloys immersed in diferente cleaners solutions: 0.05% sodium hypochlorite, 4.2% acetic acid, 0.05% sodium salicylate, sodium perborate (Corega Tabs®) and 0.2% peracetic acid. Material and Methods: One hundred and twenty circular specimens (10 mm in diameter) of two commercial available Co-Cr alloys were tested: GM 800 ® (Dentaurum) and Co-Cr® (DeguDent). The samples were randomly divided into tem experimental groups (n=10), according to the trend mark of alloy and cleaners solutions in which they were immersed, and two control groups, in which the samples of the two alloys were immersed in distilled water. Evaluations were performed through roughness measurement (rugosimeter Surftest 211, Mitutoyo), visual evaluation with stereomicroscope (Stereo Discovery 20, Carl Zeiss) and scanning electron microscope surface (JSM, 6360 SEM, JEOL), at experimental times T0 ­ before immersions, T1 - after one immersion, and T2 - after 90 immersions. Intergroup comparison for the effect of immersion in the different cleanser agents was evaluated through ANOVA/Tukey tests (p≤0.05). The effect of the time in the immersion of each alloy was evaluated by t-pared test (p≤0.05). The two alloys were compared using the t-Student test. Results: The analysis of roughness and microscopy showed that surface changes were significantly greater in groups submitted to 0.05% sodium hypochlorite after 90 immersions (T2). When comparing the two alloys, a similar behavior of roughness was observed for the cleaning agents. However, alloy GM 800® showed significant statistical difference for roughness variations in experimental times (Δ1 and Δ2), when immersed in sodium 0.05% hypochlorite. The number of exposures of the alloys to the cleaning agents showed a negative influence when using sodium hypochlorite solution. Conclusions: It is possible to conclude that 0.05% sodium hypochlorite has caused the greatest apparent damage to alloy surface. (AU)