Fracture Resistance of Zirconia Restorations with a Modified Framework Design

  • sakineh Nikzadjamnani Associate Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
  • Abbas Azari Associate Professor, Dental Research Center, Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran; Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
  • Somayeh Niakan Assistant Professor, Department of Prosthodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran
  • Seyedeh Fatemeh Namdar Assistant Professor, Dental Materials Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
Zirconium, Failure, Prosthesis Design, Dental Ceramic


Objectives: Chipping is one of the concerns related to zirconia crowns. The reasons of chipping have not been completely understood. This in-vitro study aimed to assess the effect of coping design on the fracture resistance of all-ceramic single crowns with zirconia frameworks. 

Materials and Methods: Two types of zirconia copings were designed (n=12): (1) a standard coping (SC) with a 0.5mm uniform thickness and (2) a modified coping (MC) consisted of a lingual margin of 1mm thickness and 2mm height connected to a proximal strut of 4mm height and a 0.3mm-wide facial collar. After veneer porcelain firing, the crowns were cemented to metal dies. Afterwards, a static vertical load was applied until failure. The modes of failure were determined. Data were calculated and statistically analyzed by independent samples T-test. P<0.05 was considered statistically significant.

Results: The mean and standard deviation (SD) of the final fracture resistance equaled to 3519.42±1154.96 N and 3570.01±1224.33 N in SC and MC groups, respectively; the difference was not statistically significant (P=0.9). Also, the mean and SD of the initial fracture resistance equaled to 3345.34±1190.93 N and 3471.52±1228.93 N in SC and MC groups, respectively (P=0.8). Most of the specimens in both groups showed the mixed failure mode. 

Conclusions: Based on the results, the modified core design may not significantly improve the fracture resistance.


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How to Cite
Nikzadjamnani sakineh, Azari A, Niakan S, Namdar SF. Fracture Resistance of Zirconia Restorations with a Modified Framework Design. Front Dent. 14(6):321-328.
Original Article

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