IADR Abstract Archives
Cyclic Loading of Layered CAD-CAM Milled Crowns
Purpose: To evaluate the effect of cyclic loading on layered crowns of Vitadur Alpha porcelain (a), 3M MZ 100 (MZ), or Vita Mark II (MK) veneers, bonded to copings of glass infused In-Ceram Alumina (IC), MZ 100 (MZ), and resin infused feldspathic porcelain (P). Methods: Cerec 2 and In-lab machines were used to make veneers and copings. A polyether mold was used to duplicate a positive model, using epoxy. 9 combinations were tested: a glass bond, a, and MZ on IC; a, MZ, and MK on MZ; a, MK, and MZ on P. RelyX ARC resin bonding cement was used to bond the veneers to the copings (except for a glass bond on IC) and the assembled crowns to dies. The crowns were polished and kept wet. Cyclic loading was accomplished with a 450 N “dead” weight load on a 7.9 mm sphere, at 1.6 Hz, in wet environment. At least 6 specimens of each combination were tested at various number of cycles (baseline, 5000, 15000, and 50000). Failure loads were measured using compression loading (7.9mm steel sphere) at 0.5 mm/min.
Results: Failure loads [kN (SD)]
|
Group |
Baseline |
5,000 |
15,000 |
50,000 |
|
MZ/IC |
1.24 (0.12), |
1.01 (0.08) |
1.07 (0.14), |
97 (0.10) |
|
a gb/IC |
0.83 (.09) |
0.73 (.08) |
Failed |
Failed |
|
MZ/MZ |
1.81. (0.39) |
1.93 (0.26) |
2.1 (0.15) |
1.37 (0.32) |
|
a/MZ |
1.08 (.08) |
0.85 (.20) |
0.53 (.17) |
Failed |
|
MK/MZ |
1.29 (.09), |
1.04 (.33), |
1.15 (0.23) |
0.97 (.26); |
|
MZ/P |
1.75 (0.15), |
1.56 (0.39); |
1.84 (0.22) |
1.43 (0.15) |
|
a/P |
0.86 (0.13) |
0.56 (0.11) |
Failed |
Failed |
|
MK/P |
1.03 (0.21) |
0.98 (0.25) |
0.88 (0.19) |
0.74 (0.23) |
Conclusions: All veneer/coping combinations showed deceased failure load after 50000 cycles. MZ/MZ and MZ/P combinations demonstrated the smallest decrease in failure load after cycling.