BackgroundIt is necessary to know the in vitro behavior of different attachment systems to be used clinically. The evolution of retention capacity over 10 years (14,600 insertion/de-insertion cycles) was determined in vitro, evaluating two overdenture attachment systems (Locator® and OT Equator®).Material and MethodsThe study used an implant replica compatible with the abutments of both systems. 10 Locator® and 10 OT Equator® attachments were screwed to the abutments. Nylon inserts were attached and tested, subjecting them to 14,600 insertion and de-insertion cycles (representing 10 years functional life) in axial direction. The universal test machine crosshead speed was 50 mm/min with a de-insertion range of 2 mm.ResultsThe initial retention of Locator® was 17.02 N and of Equator® 16.36 N. After 14,600 cycles, Locator® suffered a mean loss of retention of 50.89%, while Equator® lost 69.28%. Both systems showed retention increases up to the first 1,000 cycles, which decreased thereafter up to 14.600 cycles. Statistically significant differences between the systems were found after 7,500 cycles.ConclusionsBoth systems presented acceptable retention capacities after 14,600 cycles. Significant differences in retention force between the systems evolved after 7,500 cycles (5 years in vitro use). These results should be treated with caution and should be verified clinically. Key words:Denture, mandibular prosthesis implantation, attachment, dental implant-abutment connection, denture retention.

To evaluate bond strengths of different resin cements to two aluminum oxide-based ceramics. Methods: One hundred ten ceramic cylinders were produced and given four different surface treatments. Resin cement cylinders were then bonded to the ceramic cylinders using different resin cements and the bond strength was determined by shear testing to the breaking point. We were thus able to obtain results for the different combinations of porcelain, surface treatments and cements. All data was analyzed using the Kruskal-Wallis test for more than two independent samples and the Bonferroni correction applied (a=0.01). An optical microscopy study was carried out to analyze the type of failure, and an electronic microscopy examination was carried out in order to evaluate the changes produced in the ceramic by the different surface treatments. Results: The best values corresponded to the control group, composed of silicate ceramics combined with Variolink II resin cement. In-Ceram Alumina showed no significant differences with respect to the type of cement applied. Procera AllCeram obtained the best values when silica coated using the CoJet System and applying Variolink II, or when sandblasted and applying Clearfil SE Bond + Porcelain Bond Activator and Panavia F cement. Significance: Surface treatment modifies the ceramic surface and influences the bond strength, as does the type of cement used. Silica coating is recommended to improve adhesion to Procera AllCeram, applying Variolink II, or sandblasting plus resin cement containing MDP (Panavia F).

RESUMEN:El envejecimiento de la población junto con el incremento de la esperanza de vida, obligan al desarrollo de prótesis que presenten un periodo de vida útil cada vez mayor. El éxito clínico de los implantes está basado en la consecución de la osteointegración. Por lo tanto, las prótesis metálicas necesitan disponer de una compatibilidad mecánica con el hueso que sustituyen, que se consigue mediante una combinación de bajo módulo elástico, alta resistencia a la rotura y a fatiga. La mejora, a corto y largo plazo, de la osteointegración es función de múltiples factores, de entre los cuales son de gran importancia su diseño macroscópico y dimensional, el material y la topografía superficial del implante. Este artículo se centra en resumir las ventajas que presentan el titanio y sus aleaciones para ser empleadas como biomateriales, y la evolución que han sufrido estas, en las últimas décadas, para mejorar su biocompatibilidad. En consecuencia, se ha recapitulado la evolución que han sufrido los implantes, resumiéndose a través de tres generaciones. En los últimos años se ha incrementado el interés en los tratamientos superficiales de las prótesis metálicas, con el objetivo de alcanzar una integración del tejido óseo duradera y en el menor tiempo posible. En este artículo se exponen varios tratamientos superficiales utilizados actualmente para modificar la rugosidad o para obtener recubrimientos superficiales; cabe destacar la oxidación electroquímica con tratamiento térmico, para modificar la estructura cristalina de los óxidos de titanio. Tras la revisión bibliográfica llevada a cabo para la redacción de este artículo, las aleaciones β de titanio, con una superficie de nanotubos obtenida mediante oxidación electroquímica y una etapa posterior de tratamiento térmico para obtener una estructura cristalina, son la opción de futuro para mejorar la biocompatibilidad a largo plazo de las prótesis de titanio. ABSTRACT: Development of titanium alloys and surface treatments to increase the implants lifetime. The population aging together with increase of life expectancy forces the development of new prosthesis which may present a higher useful life. The clinical success of implants is based on the osseointegration achievement. Therefore, metal implants must have a mechanical compatibility with the substituted bone, which is achieved through a combination of low elastic modulus, high flexural and fatigue strength. The improvement, in the short and long term, of the osseointegration depends on several factors, where the macroscopic design and dimensional, material and implant surface topography are of great importance. This article is focused on summarizing the advantages that present the titanium and its alloys to be used as biomaterials, and the development that they

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Commercial pure titanium offers excellent biocompatibility, but its properties are poor for some biomedical applications where both mechanical properties and biocompatibility are required. The present study attempts to evaluate the possibilities of developing Ti-Zr alloys using conventional powder metallurgical techniques by the elemental powder mixture and mechanical mixing of them depending on zirconium content (6, 15 and 20wt%). Sintering was performed at 1523 K after compaction at 700 MPa for the elemental powder mixture and 900 MPa for the mechanically mixed powders. Sintered parts were tested to obtain maximum flexural strength. Samples were characterised microstructurally by X-ray diffraction to study the present phases. Optical microscopy (OM) and scanning electron microscopy (SEM)were performed to study the distribution of possible phases, porosity, grain size, etc. Flexural strength to Ti CP was greater, but slightly diminished with increasing Zr content. However, the elastic modulus increased slightly compared to Ti. The results obtained show that it is possible to make these alloys by powder metallurgy.

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