RESUMO
OBJECTIVES: To investigate the crystalline phases, morphological features and functional groups on the surface of sintered Y:TZP/TiO2 composite ceramics before and after the application of a biomimetic bone-like apatite layer. The effect of TiO2 content on the composite's characteristics was also evaluated. METHODS: Samples of Y:TZP containing 0-30mol% TiO2 were synthesized by co-precipitation, followed by filtration, drying and calcination. The powders were uniaxially pressed and sintered at 1500°C/1h. To obtain biomimetic coatings the samples were exposed to sodium silicate solution and then to a concentrated simulated body fluid solution. The surfaces, before and after coating, were characterized by diffuse reflectance infrared Fourier transformed spectroscopy, X-ray diffraction analysis and scanning electron microscopy. RESULTS: The surfaces of all Y:TZP/TiO2 samples were covered with a dense and uniform calcium phosphate layer with a globular microstructure. This layer was crystalline for specimens with 30% of TiO2 and amorphous for specimens with 0 and 10% of TiO2. Chemical analysis indicated that this layer was composed of type A carbonate apatite. Among the materials tested, the composite with 10% of TiO2 showed the best overall chemical and physical features, such as higher density and more cohesive amorphous apatite layer. SIGNIFICANCE: Y-TZP-based materials obtained in the present investigation by means of the successful association of a calcium phosphate biomimetic layer with small amounts TiO2 should be further explored as an option for ceramic dental implants with improved bioactivity.
Assuntos
Apatitas/química , Materiais Revestidos Biocompatíveis/química , Implantes Dentários , Materiais Dentários/química , Titânio/química , Ítrio/química , Zircônio/química , Materiais Biomiméticos/química , Fosfatos de Cálcio/química , Fenômenos Químicos , Precipitação Química , Cristalização , Cristalografia , Planejamento de Prótese Dentária , Dessecação , Filtração , Temperatura Alta , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Pressão , Silicatos/química , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Difração de Raios XRESUMO
OBJECTIVES: (1) To synthesize 3mol% yttria-stabilized zirconia (3Y-TZP) powders via coprecipitation route, (2) to obtain zirconia ceramic specimens, analyze surface characteristics, and mechanical properties, and (3) to compare the processed material with three reinforced dental ceramics. METHODS: A coprecipitation route was used to synthesize a 3mol% yttria-stabilized zirconia ceramic processed by uniaxial compaction and pressureless sintering. Commercially available alumina or alumina/zirconia ceramics, namely Procera AllCeram (PA), In-Ceram Zirconia Block (CAZ) and In-Ceram Zirconia (IZ) were chosen for comparison. All specimens (6mmx5mmx5mm) were polished and ultrasonically cleaned. Qualitative phase analysis was performed by XRD and apparent densities were measured on the basis of Archimedes principle. Ceramics were also characterized using SEM, TEM and EDS. The hardness measurements were made employing Vickers hardness test. Fracture toughness (K(IC)) was calculated. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey's test (alpha=0.05). RESULTS: ANOVA revealed that the Vickers hardness (p<0.0001) and fracture toughness (p<0.0001) were affected by the ceramic materials composition. It was confirmed that the PA ceramic was constituted of a rhombohedral alumina matrix, so-called alpha-alumina. Both CAZ and IZ ceramics presented tetragonal zirconia and alpha-alumina mixture of phases. The SEM/EDS analysis confirmed the presence of aluminum in PA ceramic. In the IZ and CAZ ceramics aluminum, zirconium and cerium in grains involved by a second phase containing aluminum, silicon and lanthanum were identified. PA showed significantly higher mean Vickers hardness values (H(V)) (18.4+/-0.5GPa) compared to vitreous CAZ (10.3+/-0.2GPa) and IZ (10.6+/-0.4GPa) ceramics. Experimental Y-TZP showed significantly lower results than that of the other monophased ceramic (PA) (p<0.05) but it showed significantly higher fracture toughness (6.0+/-0.2MPam(1/2)) values when compared to the other tested ceramics (p<0.05). SIGNIFICANCE: The coprecipitation method used to synthesize zirconia powders and the adopted ceramic processing conditions led to ceramics with mechanical properties comparable to commercially available reinforced ceramic materials.