ABSTRACT
Objective@#To investigate the physical properties of Ti-6Al-4V clasps generated by selective laser melting (SLM) with different construction directions and to compare these clasps with cast clasps, which could provide a basis for fabricating SLM clasps with high precision and excellent mechanical properties. @*Methods@# Ti-6Al-4V clasps were fabricated by SLM at 0 degrees (SLM0 group), 45 degrees (SLM45 group) and 90 degrees (SLM90 group) (n = 12). Twelve clasps were cast by the casting method as the control group. Meanwhile, four metal abutments were cast randomly as the abutments of the four groups. X-ray was used to detect cracks in the clasps of each group. The roughness of the clasps was measured by confocal microscopy, the fitness tests between clasps and abutment were processed by stereomicroscopy, and the microstructure of clasps in each group was observed under a metallographic microscope to evaluate the physical properties.@*Results @# There were 0-8 visible cracks in the casting group but no obvious defects in the SLM groups. The maximum surface roughness was observed in the cast group (18.102 ± 3.762) μm, while the minimum roughness was observed in the SLM90 group (5.942 ± 1.486) μm (P < 0.05). There was no statistically significant difference in surface roughness between the SLM0 group [(8.711 ± 2.378) μm] and the SLM45 group [(8.513 ± 1.161) μm]. Fitness was worst in the casting group [(68.445 ± 14.876) μm] and best in the SLM90 group [(33.417 ± 5.880) μm] (P < 0.05). There was no statistically significant difference in fitness between the SLM0 group [(52.917 ± 12.102) μm] and the SLM45 group [(50.889 ± 7.011) μm]. In addition, the growth direction of the β grains was roughly parallel to the build direction, and acicular α grains were present between β grains. SLM was composed of fine grains, while the cast group had large grains.@* Conclusions@# Specimens generated by SLM had finer grains than cast specimens. In addition, SLM90 clasps had the highest fitness and the lowest surface roughness.
ABSTRACT
Introducción: la dificultad en el manejo de prótesis totales convencionales en pacientes totalmente edéntulos puede ser mejorada con el uso de sistemas de anclaje sobre implantes dentales para sobredentaduras. El objetivo fue caracterizar metalográficamente un sistema de barras para sobredentadura por sobrecolado de una aleación de metal base, sobre pilares prefabricados en aleación de titanio. Métodos: mediante un diseño de barras para sobredentaduras, elaboradas con un aditamento de titanio (Ti-6Al-4V) prefabricado y una aleación de metal base (Ni65%-Cr22,5%-Mo9,5%). Se hace caracterización metalográfica del proceso de sobrecolado, analizando la influencia en la microestructura de las aleaciones dentales comerciales Ti-6Al-4V y Ni65%-Cr22,5%-Mo9,5% (Wiron 99) mediante microscopía electrónica de barrido (SEM), microanálisis por técnica de espectrometría de energías dispersivas de rayos X (EDS), análisis mediante microscopía óptica (MO) y estereomicroscopía (EM). Resultados: se encontró que durante el proceso de sobrecolado, se produce una unión química con presencia de oxígenos entre estas 2 aleaciones; evidenciando estructuras dendríticas heterogéneas a lo largo de las muestras debido a la irregularidad en el espesor de las barras utilizadas y los precipitados en sus fronteras de Mo. Conclusiones: la unión química de las 2 aleaciones de Ni65%-Cr22,5%-Mo9,5%y Ti-6Al-4V después del proceso de sobrecolado, permite considerar desde el punto de vista metalográfico, el sobrecolado entre estas dos aleaciones como una opción viable para la realización de estructuras sobre pilares de implantes.
Introduction: the difficulty in handling conventional dentures in fully edentulous patients may be improved by using anchorage systems on dental implants for overdentures. The goal of this study was to conduct a metallographic characterization of a system of bars for overdentures by overcasting a metal base alloy on prefabricated titanium alloy abutments. Methods: using a design of overdenture bars, made with an addition of prefabricated titanium (Ti-6Al-4V) and a metal base alloy (Ni65-Cr22%,5%-Mo9,5%), a metallographic characterization of the overcasting process was performed by analyzing its influence on the microstructure of two commercial dental alloys: Ti-6Al-4V and Ni65%-Cr22,5%-Mo9,5% (Wiron 99) using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), light microscopy analysis (LM), and stereomicroscopy (EM). Results: the findings suggest that during overcasting a chemical bonding occurs due to the presence of oxygen between these two alloys, showing heterogeneous dendritic structures along the samples due to thickness irregularities on the bars and to precipitations of their molybdenum borders. Conclusions: from a metallographic perspective, the chemical bonding of the two alloys (Ni65-Cr22%, 5%-Mo9, 5% and Ti-6Al-4V) after overcasting suggests that overcasting between these two alloys is a viable option for placing structures on implant abutments.