IADR Abstract Archives

Influence of firing procedures on cohesive failure of all-ceramic crowns

Objectives: Cohesive failure within the veneering ceramics of crowns and fixed partial dentures occurs more often in all-ceramic than in metal-ceramic restorations. One possible explanation for this phenomenon is great differences in thermal parameters, leading to different temperature gradients within the restoration during the cooling phase after firing. Therefore, the influence of different cooling procedures on the initial cohesive failure load as well as on the fatigue behavior of all-ceramic crowns was investigated.

Methods: Two veneering ceramics, i.e.,Cercon ceram kiss (CCK) and Cercon ceram love (CCL) (DeguDent, Hanau, Germany) were used to manufacture identical upper central incisor crowns with a ZrO2 framework (Cercon base, DeguDent). In combination with 1) conventional dentin and finishing firing, and 2) conventional firing + 6min longer cooling phase, a total of 4 groups were involved. Each group consisted of 8 crowns for fatigue testing and 5 crowns to determine the initial failure load. Fatigue testing included thermocycling (10,000 cyles, 6.5°C/60°C) and subsequent chewing simulation (Willytec CS3, Fmax=63N, 1,200,000 cycles) with force applied to the incisor edge at an angle of 90°, i.e., in anterior direction. Ultimate load tests were performed with crowns without fatigue testing as well as those surviving fatigue testing. Loading conditions were the same as during chewing simulation. Additionally, fatigue testing was repeated for 8 conventionally fired metal-ceramic crowns (Starloy C / Duceram kiss, Dentsply/DeguDent).

Results: Crowns without fatigue testing demonstrated initial failure loads of 628±140N for CCK and 654±185N for CCL when an extra cooling interval was used, whereas conventionally firing processes were associated with lower initial failure loads (CCK: 433±213N, CCL: 529±139N). For all-ceramic crowns, extra cooling resulted in a considerable reduction of fatigue failures to the level of metal-ceramic crowns.

Conclusion: Longer cooling times than actually used after firing can reduce cohesive failures in all-ceramic crowns.


Continental European, Israeli, Scandinavian Divisions Meeting
2009 Continental European, Israeli, Scandinavian Divisions Meeting (Munich, Germany)
Munich Germany
2009
24
Scientific Groups
  • Rues, Stefan  ( University of Heidelberg, Heidelberg, N/A, Germany )
  • Kröger, Elke  ( University of Heidelberg, Department of Prosthodontics, Heidelberg, N/A, Germany )
  • Becker, Falk  ( University of Heidelberg, Heidelberg, N/A, Germany )
  • Schmitter, Marc  ( University of Heidelberg, Department of Prosthodontics, Heidelberg, N/A, Germany )
  • Rammelsberg, Peter  ( University of Heidelberg, Department of Prosthodontics, Heidelberg, N/A, Germany )
    • Oral Session
    Dental Materials 1
    09/10/2009