Conrado Aparicio

Publications of Conrado Aparicio

• In vivo evaluation of micro-rough and bioactive titanium dental implants using histometry and pull-out tests.

  Authors: Conrado Aparicio, Alejandro Padrós, Francisco-Javier Gil

  Journal of the mechanical behavior of biomedical materials. 11/2011; 4(8):1672-82.

  We report on the in vivo histological and mechanical performance of titanium dental implants with a new surface treatment (2Step) consisting of an initial grit-blasting process to produce aWe report on the in vivo histological and mechanical performance of titanium dental implants with a new surface treatment (2Step) consisting of an initial grit-blasting process to produce a micro-rough surface, followed by a combined chemical and thermal treatment that produces a potentially bioactive surface, i.e., that can form an apatitic layer when exposed to biomimetic conditions in vitro. Our aim was to assess the short- and mid-term bone regenerative potential and mechanical retention of 2Step implants in mandible and maxilla of minipigs and compare them with micro-rough grit-blasted, micro-rough acid-etched, and smooth as-machined titanium implants. The percent of bone-to-implant contact after 2, 4, 6, and 10 weeks of implantation as well as the mechanical retention after 4, and 6 weeks of implantation were evaluated with histometric and pull-out tests, respectively, as a measure of the osseointegration of the implants. We also aimed to assess the bioactive nature of 2Step surfaces in vivo. Our results demonstrated that the 2Step treatment produced micro-rough and bioactive implants that accelerated bone tissue regeneration and increased mechanical retention in the bone bed at short periods of implantation in comparison with all other implants tested. This was mostly attributed to the ability of 2Step implants to form in vivo a layer of apatitic mineral that coated the implant and could rapidly stimulate (a) bone nucleation directly on the implant surface, and (b) bone growing from the implant surface. We also proved that roughness values of Ra≈4.5 μm favoured osseointegration of dental implants at short- and mid-term healing periods, as grit-blasted implants and 2Step implants had higher retention values than as machined and acid-etched implants. The surface quality resulting from the 2Step treatment applied on cpTi provided dental implants with a unique combination of rapid bone regeneration and high mechanical retention.

• Discerning the role of topography and ion exchange in cell response of bioactive tissue engineering scaffolds.

  Authors: Elisabeth Engel, Sergio Del Valle, Conrado Aparicio, George Altankov, Luis Asin, Josep A Planell, Maria-Pau Ginebra

  Tissue engineering. Part A. 09/2008; 14(8):1341-51.

  Surface topography is known to have an influence on osteoblast activity. However, in the case of bioactive materials, topographical changes can affect also ion exchange properties. This makes theSurface topography is known to have an influence on osteoblast activity. However, in the case of bioactive materials, topographical changes can affect also ion exchange properties. This makes the problem more complex, since it is often difficult to separate the strictly topographical effects from the effects of ionic fluctuations in the medium. The scope of this paper is to analyze the simultaneous effect of topography and topography-mediated ion exchange on the initial cellular behavior of osteoblastic-like cells cultured on bioactive tissue engineering substrates. Two apatitic substrates with identical chemical composition but different micro/nanostructural features were obtained by low-temperature setting of a calcium phosphate cement. MG63 osteoblastic-like cells were cultured either in direct contact with the substrates or with their extracts. A strong and permanent decrease of calcium concentration in the culture medium, dependent on substrate topography, was detected. A major effect of the substrate microstructure on cell proliferation was observed, explained in part by the topography-mediated ion exchange, but not specifically by the ionic Ca(2+) fluctuations. Cell differentiation was strongly enhanced when cells were cultured on the finer substrate. This effect was not explained by the chemical modification of the medium, but rather suggested a strictly topographical effect.

• Oxidized nickel-titanium foams for bone reconstructions: chemical and mechanical characterization.

  Authors: Maite Barrabés, Alexandra Michiardi, Conrado Aparicio, Pablo Sevilla, Josep A Planell, Francisco Javier Gil

  Journal of materials science. Materials in medicine. 12/2007; 18(11):2123-9.

  This work examines NiTi foams that have been treated using a new oxidation treatment for obtaining Ni-free surfaces that could allow the ingrowth of living tissue, thereby increasing the mechanicalThis work examines NiTi foams that have been treated using a new oxidation treatment for obtaining Ni-free surfaces that could allow the ingrowth of living tissue, thereby increasing the mechanical anchorage of implants. A significant increase in the real surface area of these materials can decrease corrosion resistance and favour the release of Ni. This chemical degradation can induce allergic reactions or toxicity in the surrounding tissues. This study determines the porosity, surface characteristics, phase transformation, mechanical properties, corrosion behaviour and Ni release into the simulated body fluid medium of foams treated by a new surface oxidation treatment that produces Ni-free surfaces. These foams have pores in an appropriate range of sizes and interconnectivity, and thus their morphology is similar to that of bone. Their mechanical properties are biomechanically compatible with bone. The titanium oxide on the surface significantly improves corrosion resistance and decreases nickel ion release, while barely affecting transformation temperatures.

• The effect of shot blasting and heat treatment on the fatigue behavior of titanium for dental implant applications.

  Authors: F Javier Gil, Josep A Planell, Alejandro Padrós, Conrado Aparicio

  Dental materials : official publication of the Academy of Dental Materials. 05/2007; 23(4):486-91.

  OBJECTIVES: The effect of shot blasting treatment on the cyclic deformation and fracture behavior of a commercial pure titanium with two different microstructures; equiaxed (alpha-phase) and acicularOBJECTIVES: The effect of shot blasting treatment on the cyclic deformation and fracture behavior of a commercial pure titanium with two different microstructures; equiaxed (alpha-phase) and acicular (martensitic alpha'-phase) was investigated. METHODS: Fatigue tests were carried out in artificial saliva at 37 degrees C. Cyclic deformation tests were carried out up to fracture and fatigue crack nucleation and propagation were analysed. Residual stresses were determined by means of X-ray diffraction. RESULTS: The results show that shot blasting treatment improves fatigue life in the different microstructures studied. The equiaxed phase has improved mechanical properties compared to the acicular one. Despite the fact that control of the variables of shot blasting is not precise because of the nature of the treatment, it improves the fatigue life by the fact that the initiation site of the fatigue crack changes from the surface of the specimen to the interior of the shot blasted specimen. This is a consequence of the layer of compressive residual stresses that the treatment generates on titanium surfaces. The acicular morphology of the martensite favors crack propagation along the interface of the alpha' plates. SIGNIFICANCE: Shot blasting, which is widely used on titanium dental implants in order to favour their osseointegration, can also improve their fatigue resistance.

• The influence of surface energy on competitive protein adsorption on oxidized NiTi surfaces.

  Authors: Alexandra Michiardi, Conrado Aparicio, Buddy D Ratner, Josep A Planell, Javier Gil

  Biomaterials. 03/2007; 28(4):586-94.

  NiTi shape memory alloy surfaces, untreated, and oxidized by a new oxidation treatment (OT) in order to obtain a Ni-free surface, have been compared in terms of surface energy and protein adsorptionNiTi shape memory alloy surfaces, untreated, and oxidized by a new oxidation treatment (OT) in order to obtain a Ni-free surface, have been compared in terms of surface energy and protein adsorption behavior. The polar and dispersive components of the surface energy have been determined. A competitive adsorption process between fibronectin and albumin has been carried out by (125)I-radiolabeling. Moreover, the adhesion strength between both proteins and NiTi surfaces has been evaluated by performing an elution test. The results show that the OT treatment enhances the hydrophilic character of NiTi surfaces by significantly increasing the polar component of their surface energy. Moreover, the OT treatment increases the amount of fibronectin and albumin adsorbed. It also increases the fibronectin affinity for NiTi surfaces. The elution test results could suggest a conformational change of fibronectin as a function of chemical composition of NiTi material and of surface treatment. Finally, a linear correlation between the amount of adsorbed albumin and the polar component of the surface energy of NiTi surfaces has been demonstrated. This work indicates that the OT treatment has an influence on the surface energy value of NiTi materials, which in turn influences the protein adsorption process.

• Bioceramics as nanomaterials.

  Authors: Tanya Traykova, Conrado Aparicio, Maria-Pau Ginebra, Josep A Planell

  Nanomedicine (London, England). 07/2006; 1(1):91-106.

  Nanostructured materials possess unique capabilities for specific interactions with biological entities. This article reviews several types of nanostructured ceramics, cements and coatings that areNanostructured materials possess unique capabilities for specific interactions with biological entities. This article reviews several types of nanostructured ceramics, cements and coatings that are being considered for use in medical applications. The processing methods for obtaining ceramics are presented and related to the properties (such as wettability, topography and charge) that directly affect interactions with biological entities (ions, biomacromolecules and cells). The literature reviewed demonstrates that these interactions are directly affected by the nanostructure of the ceramic surfaces. Thus, the understanding and control of the interactions between nanoceramics and biological entities may play one of the leading roles in the development of nanomedicine.

• Static mechanical properties of hydroxyapatite (HA) powder-filled acrylic bone cements: effect of type of HA powder.

  Authors: Lizette Morejón, Alonso Eduardo Mendizábal, José Angel Delgado García-Menocal, María Pau Ginebra, Conrado Aparicio, Francisco Javier Gil Mur, Montserrat Marsal, Natalia Davidenko, María E Ballesteros, Josep Anton Planell

  Journal of biomedical materials research. Part B, Applied biomaterials. 03/2005; 72(2):345-52.

  This work reports on the effect of the amount (0, 10, and 30 wt %) and type of HA powder incorporated into an acrylic bone cement on the tensile properties, compression properties, and fractureThis work reports on the effect of the amount (0, 10, and 30 wt %) and type of HA powder incorporated into an acrylic bone cement on the tensile properties, compression properties, and fracture toughness. The three different types of HA powders used were synthesized in the laboratory and coated with a silane agent prior to incorporation into the cement powder, and differed in particle size, water content, surface area, and crystallinity. It was found that the inclusion of any type of HA powder led to an increase in the tensile modulus (ET), but all the other mechanical properties of the cement decreased (relative to the values of the unfilled cement). The increase in ET is attributed to the good adhesion between the filler and the cement matrix, which is due to the silane coating agent. The decrease in the other mechanical properties may be a consequence of HA powder agglomeration and porosity. Hydroxyapatite morphology and crack-growth mechanisms were analyzed by scanning electronic microscopy (SEM).

• Corrosion behaviour of commercially pure titanium shot blasted with different materials and sizes of shot particles for dental implant applications.

  Authors: Conrado Aparicio, F Javier Gil, Carlos Fonseca, Mario Barbosa, Josep Anton Planell

  Biomaterials. 02/2003; 24(2):263-73.

  It is well known that the osseointegration of the commercially pure titanium (c.p. Ti) dental implant is improved when the metal is shot blasted in order to increase its surface roughness. ThisIt is well known that the osseointegration of the commercially pure titanium (c.p. Ti) dental implant is improved when the metal is shot blasted in order to increase its surface roughness. This roughness is colonised by bone, which improves implant fixation. However, shot blasting also changes the chemical composition of the implant surface because some shot particles remain adhered on the metal. The c.p. Ti surfaces shot blasted with different materials and sizes of shot particles were tested in order to determine their topographical features (surface roughness, real surface area and the percentage of surface covered by the adhered shot particles) and electrochemical behaviour (open circuit potential, electrochemical impedance spectroscopy and cyclic polarisation). The results demonstrate that the increased surface area of the material because of the increasing surface roughness is not the only cause for differences found in the electrochemical behaviour and corrosion resistance of the blasted c.p. Ti. Among other possible causes, those differences may be attributed to the compressive residual surface stresses induced by shot blasting. All the materials tested have an adequate corrosion and electrochemical behaviour in terms of its possible use as dental implant material.

• Influence of the height of the external hexagon and surface treatment on fatigue life of commercially pure titanium dental implants.

  Authors: Francisco Javier Gil, Conrado Aparicio, Jose M Manero, Alejandro Padros

  The International journal of oral & maxillofacial implants. 24(4):583-90.

  PURPOSE: This study evaluated the effect of external hexagon height and commonly applied surface treatments on the fatigue life of titanium dental implants. MATERIALS AND METHODS: ElectropolishedPURPOSE: This study evaluated the effect of external hexagon height and commonly applied surface treatments on the fatigue life of titanium dental implants. MATERIALS AND METHODS: Electropolished commercially pure titanium dental implants (seven implants per group) with three different external hexagon heights (0.6, 1.2, and 1.8 mm) and implants with the highest external hexagon height (1.8 mm) and different surface treatments (electropolishing, grit blasting with aluminium oxide, and acid etching with sulfuric acid) were tested to evaluate their mechanical fatigue life. To do so, 10-Hz triangular flexural load cycles were applied at 37 degrees C in artificial saliva, and the number of load cycles until implant fracture was determined. Tolerances of the hexagon/abutment fit and implant surface roughness were analyzed by scanning electron microscopy and light interferometry. Transmission electron microscopy and electron diffraction analyses of titanium hydrides were performed. RESULTS: First, the fatigue life of implants with the highest hexagon (8,683 +/- 978 load cycles) was more than double that of the implants with the shortest hexagons (3,654 +/- 789 load cycles) (P < .02). Second, the grit-blasted implants had the longest fatigue life of the tested materials (21,393 +/- 2,356 load cycles), which was significantly greater than that of the other surfaces (P < .001). The compressive surface residual stresses induced when blasting titanium are responsible for this superior mechanical response. Third, precipitation of titanium hydrides in grain boundaries of titanium caused by hydrogen adsorption from the acid solution deteriorates the fatigue life of acid-etched titanium dental implants. These implants had the shortest fatigue life (P < .05). CONCLUSIONS: The fatigue life of threaded root-form dental implants varies with the height of the external hexagon and/or the surface treatment of the implant. An external hexagon height of 1.8 mm and/or a blasting treatment appear to significantly increase fatigue life of dental implants.