Abstract
Purpose: All-ceramic prostheses have virtually replaced metal-ceramic prostheses for replacement of missing teeth without sufficient evidence of reliability. These prostheses have been produced either from monolithic zirconia, veneered zirconia, or other ceramic–ceramic products. Objective: To analyze the effect of load orientation on the fracture probability of implant-supported, three-unit, zirconia/veneer prostheses.
Methods and materials: A core ceramic (ZirCAD, Ivoclar Vivadent) and a veneering ceramic (ZirPress, Ivoclar Vivadent) were selected for bilayer models because of their use in an ongoing clinical study. The ANSYS finite element model design for the prosthesis, implants, and supporting bone consisted of 156,913 elements and 253,989 nodes. Finite element models were prepared for 2.0-mm-thick prostheses with a core/veneer thickness ratio of 0.5 mm/1.5 mm and 10 loading orientations. A 600-N load was applied at each of four locations for each case along a 1 mm2 area including the cusps of molar crowns.
Results: A fracture probability of 100% was predicted for maximum principal failure stresses (σ1) in a cuspal area of the veneer ceramic ranging from 243 MPa (60° orientation relative to the horizontal axis) to 671 MPa (horizontal orientation). A loading angle of 75° will reduce σ1 to 189 MPa and the veneer fracture probability to 49.2%.
Conclusion: The stresses in the veneer for the applied load of 600 N over an area of 1 mm2 area are very high. Reliability analysis predicts a 100% failure probability in the fast fracture mode for all load locations and orientations except for those between 75° and 90°. All failures are likely to initiate in the veneer because of the low strength of the ceramic veneer. Although the stress in the core can reach very high values, this ceramic has a very high reliability because of its high tensile strength. Because the consistently high probabilities of FDP fractures do not match clinical results, the sensitivity of model assumptions must be analyzed with a refined model to provide reliable predictions for the time-dependent probability of fracture.
This study was supported by NIH/NIDCR grants DE06672 and K23DE18414.
Methods and materials: A core ceramic (ZirCAD, Ivoclar Vivadent) and a veneering ceramic (ZirPress, Ivoclar Vivadent) were selected for bilayer models because of their use in an ongoing clinical study. The ANSYS finite element model design for the prosthesis, implants, and supporting bone consisted of 156,913 elements and 253,989 nodes. Finite element models were prepared for 2.0-mm-thick prostheses with a core/veneer thickness ratio of 0.5 mm/1.5 mm and 10 loading orientations. A 600-N load was applied at each of four locations for each case along a 1 mm2 area including the cusps of molar crowns.
Results: A fracture probability of 100% was predicted for maximum principal failure stresses (σ1) in a cuspal area of the veneer ceramic ranging from 243 MPa (60° orientation relative to the horizontal axis) to 671 MPa (horizontal orientation). A loading angle of 75° will reduce σ1 to 189 MPa and the veneer fracture probability to 49.2%.
Conclusion: The stresses in the veneer for the applied load of 600 N over an area of 1 mm2 area are very high. Reliability analysis predicts a 100% failure probability in the fast fracture mode for all load locations and orientations except for those between 75° and 90°. All failures are likely to initiate in the veneer because of the low strength of the ceramic veneer. Although the stress in the core can reach very high values, this ceramic has a very high reliability because of its high tensile strength. Because the consistently high probabilities of FDP fractures do not match clinical results, the sensitivity of model assumptions must be analyzed with a refined model to provide reliable predictions for the time-dependent probability of fracture.
This study was supported by NIH/NIDCR grants DE06672 and K23DE18414.
| Original language | American English |
|---|---|
| Pages (from-to) | e2 |
| Journal | Dental Materials |
| Volume | 29 |
| Issue number | Supplement 1 |
| DOIs | |
| State | Published - 2013 |
| Externally published | Yes |
Keywords
- dental prostheses
- zirconia
Disciplines
- Metallurgy
- Materials Science and Engineering