Fatigue Tests after Veneering Porcelains on the Zirconia-based Nanocomposites

Objectives: Besides Y-TZP, zirconia-based nanocomposites (P-NANOZR: Panasonic Dental)are available as a framework material for all ceramic restorations because of higher fracture toughness. The aim of this study is to assess the durability of veneered porcelains on P-NANOZR after suffering fatigue loads. Methods: Plate specimens with 25.0x4.0x0.5mm were prepared from a complete sintered body of P-NANOZR followed by sandblasting (50µm,0.2MPa) and heat-treating (1,000°C,5 minutes)(88th IADR). Three veneering porcelains (Cerabien ZR: NORITAKE, Vintage ZR: SHOHU, Cercon ceram kiss: Degudent) were fused to the whole surface of the unilateral side specimens with 0.7mm in thickness (n=5). Bending strengths of porcelains fused to P-NANOZR plates were determined by ISO6872 (Instron: INSTRON JAPAN). Subsequently, fatigue tests were performed under the load of 60% value of the bending strength at first, followed by continuing while decreasing the load little by little until 100,000cycles (Servopulsar: SHIMADZU). Finally, the bending strengths after the fatigue tests were measured using the survived specimens (n=5). The results were statistically analyzed with a Tukey test. Results: Fatigue limit of Cerabien ZR, Vintage ZR, and Cercon ceram kiss fused to P-NANOZR plates were 8.7N (57% value of the bending strength), 7.2N (48%), and 16.9N (54%), respectively. Although there were no significant differences between the bending strengths before and after the fatigue test of all tested specimens, the bending strengths of Cercon ceram kiss were significantly higher than those of other porcelains (p<0.01). Conclusion: The results suggested bonding of porcelains to P-NANOZR seemed durable after a fatigue test. It could be concluded the selection of veneering porcelains and the mechanical property of framework materials might be the most significant factor for all ceramic restorations.