IADR Abstract Archives
Porcelain Hardness and Elastic Modulus in Y-TZP Prostheses by Nanoindentation
Objectives: This study evaluated the use of nanoindentation to measure hardness and modulus of elasticity within the porcelain of fatigued zirconia (Y-TZP) veneered three-unit fixed dental prosthesis (FDP).
Methods: One composite-resin replica of maxillary first premolar and first molar prepared crowns were made to obtain Y-TZP frameworks (Amanngirrbach) of 0,5 mm thickness and 9 mm2 connector area. The porcelain veneer (IPS e.max Ceram Transpaclear) was hand layered and fired according to manufacturer. The FDP was cemented (RelyX-U200) on the composite replicas and cyclic loaded on the marginal ridges as follows: distal of first premolar/mesial of second premolar and after suspension, the distal of second premolar/mesial of first molar marginal ridges in water for 1.000.000 cycles with load range from 30-300 N, at 2Hz, 3.18 mm radius lithium-disilicate indenter at 37oC. After fatigue, the FDP was embedded in epoxy resin and sectioned with a diamond saw in three slices. Only the middle one was ground, polished, inspected in stereomicroscope (Leica Zeiss MZE) for surface flaw analysis and nanoindented (TI-950 TriboIndenter) at 3 porcelain regions of the abutments where region-1 was the nearest from the Y-TZP framework, region-3 the farthest, and 2 in between. Each region received 5 nanoindentations with -10 µm of minimum separation. The specimen was loaded to a peak load 4 µN, without held constant and unloaded. Hardness (H) and modulus of elasticity (E) were computed for each abutment.
Results: E and H at the molar abutment for region-1 was 64.89 and 8.79, 70.49 and 8.93 for region-2, 82.79 and 9.25 for 3, respectively. For the premolar, 63.79 and 8.16 for region-1, 92.06 and 10.45 for region-2, and 74.55 and 8.92 for 3.
Conclusions: The hardness and modulus values tended to increase towards the outer porcelain surface relative to the near Y-TZP/porcelain interface, suggesting decreased residual stresses.
Methods: One composite-resin replica of maxillary first premolar and first molar prepared crowns were made to obtain Y-TZP frameworks (Amanngirrbach) of 0,5 mm thickness and 9 mm2 connector area. The porcelain veneer (IPS e.max Ceram Transpaclear) was hand layered and fired according to manufacturer. The FDP was cemented (RelyX-U200) on the composite replicas and cyclic loaded on the marginal ridges as follows: distal of first premolar/mesial of second premolar and after suspension, the distal of second premolar/mesial of first molar marginal ridges in water for 1.000.000 cycles with load range from 30-300 N, at 2Hz, 3.18 mm radius lithium-disilicate indenter at 37oC. After fatigue, the FDP was embedded in epoxy resin and sectioned with a diamond saw in three slices. Only the middle one was ground, polished, inspected in stereomicroscope (Leica Zeiss MZE) for surface flaw analysis and nanoindented (TI-950 TriboIndenter) at 3 porcelain regions of the abutments where region-1 was the nearest from the Y-TZP framework, region-3 the farthest, and 2 in between. Each region received 5 nanoindentations with -10 µm of minimum separation. The specimen was loaded to a peak load 4 µN, without held constant and unloaded. Hardness (H) and modulus of elasticity (E) were computed for each abutment.
Results: E and H at the molar abutment for region-1 was 64.89 and 8.79, 70.49 and 8.93 for region-2, 82.79 and 9.25 for 3, respectively. For the premolar, 63.79 and 8.16 for region-1, 92.06 and 10.45 for region-2, and 74.55 and 8.92 for 3.
Conclusions: The hardness and modulus values tended to increase towards the outer porcelain surface relative to the near Y-TZP/porcelain interface, suggesting decreased residual stresses.
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