Mechanical behavior of ceramic materials used for fixed partial dentures / Comportamento mecânico de cerâmicas utilizadas na confecção de próteses parciais fixas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

Objectives: to determine the flexural strength (f), Weibull modulus (m), slow crack growth coefficient (n) and fracture toughness (KIC) of three ceramics used as framework materials for fixed partial dentures (FPDs) (YZ- yttria partially stabilized zirconia tetragonal polycrystals; IZ- alumina-based zirconia-reinforced glass infiltrated ceramic; AL alumina polycrystals) and two veneering porcelains (VM7 and VM9); to evaluate the effect of the specimen design (one, two or three layers) in the f and fracture mode; to evaluate the influence of the framework material, connector size and mechanical cycling (MC) in the fracture load (FL) and stress distribution of FPDs; to relate the mechanical behavior of the ceramic materials tested using bar-shaped specimens and FPDs. Materials and Methods: Bar-shaped specimens (2mm x 4mm x 16mm) were produced in three different designs: monolithic, bilayer and trilayer. FPD frameworks were built using CAD-CAM system and veneered with porcelain. Specimens were tested for three point bending in 37ºC artificial saliva. Weibull analysis and dynamic fatigue testing were used to determine m and n values, respectively. FPDs were tested with a load applied in the middle of the pontic. Eight FPDs of each group were subjected to MC using a frequency of 2Hz and load of 140N for 106 cycles and were subsequently loaded to failure. Stress distribution for FPDs was evaluated using finite element analysis (FEA). Fractography principles were used to determine the fracture mode and KIC values. f and FL data were analyzed using Kruskal-Wallis and Tukey (95%). Results: YZ had the highest f value (860 MPa) followed by IZ (411 MPa) and AL (474 MPa). Lower f values were observed for the porcelains (65 MPa). Except for IZ and VM7, m values were similar among the ceramic materials. Higher n values were found for YZ (76) and AL (72), followed by IZ (54) and the veneering materials (40). YZ presented the highest KIC value. The f values were influenced by the material subjected to tensile stress during testing. YZ FPDs with 16mm2 connector showed higher FL values. There was significant influence of the connector size on the FL values for YZ material. MC had no influence in the FL values for the FPDs. The stress distribution was similar for all FPDs. Considering the framework material, there was a good agreement between the fracture strength values obtained for bar-shaped specimens and FPDs. Different fracture modes were observed for bar-shaped specimens and FPDs. Conclusion: YZ presented the best mechanical performance in both bar-shaped and FPD specimen configuration.

ASSUNTO(S)

crescimento de trinca subcrítico dental ceramics propriedades mecânicas mechanical properties slow crack growth cerâmicas odontológicas

ACESSO AO ARTIGO

Documentos Relacionados