The aim of this study was to investigate the effect of the taper and space setting of using Ce-TZP/A on retentive force and secondary crown settling. The taper were 2°, 4°, and 6°, and the space settings were 0 and 10 μm. The applied loads were 50 and 100 N. The taper had a significant effect on retentive force and settling at both loads (p<0.05). The space settings did not have a significant effect on retentive force or settling at either load (p<0.05). The taper of the telescopic crowns and the load affected the retentive force and the settling.
Telescopic crowns made from zirconia/alumina can be manufactured using computer-aided design/computer-aided manufacturing systems. For their successful clinical use, a suitable retentive force must be maintained over an extended period. However, it is unclear how retentive force and secondary crown settling change after repeated crown insertion and removal. The aim of the present study was to investigate the changes in retentive force and secondary crown settling of telescopic crowns made from zirconia/alumina. Primary crowns with tapers of 2° and 4° were used. Repeated insertion and removal tests were performed for 10,000 cycles at a cyclic load of 50 N. The loads applied when measuring retentive force and settling were 50 and 100 N. The number of insertions and removals had a significant effect on retentive force and settling at both loads (p<0.01). Taper also had a significant effect on retentive force and settling at both loads (p<0.01).
Within the limitations of this study, the present findings suggest that in photographs of the mouth with non-esthetic restoration on either side, the non-esthetic restoration is first gazed before the opposite side. In addition, the non-esthetic restoration is gazed longer than the opposite side, and there was no major difference in the fixation time regarding the state of non-esthetic restoration.
The objective of this study was to clarify the influences of zirconia materials, one-half taper angle, and thickness of the secondary crown on the fracture strength of the secondary crown. For the primary and secondary crowns, Y-TZP and Ce-TZP/Al2O3 were used, respectively. Samples were prepared at one-half taper angles of 2° and 4°, and a secondary crown thickness of 0.5 and 1.0 mm (n=8). Regarding the fracture strength, the secondary crown was restored on the primary crown, all specimens were loaded until fracture using a universal testing machine. The load value added at the time of secondary crown fracture was regarded as fracture strength.Based on the analysis of variance, the fracture strength of Ce-TZP/Al2O3 was significantly higher than that of Y-TZP with regard to the material and that at 1.0-mm thickness was significantly higher than that at 0.5-mm thickness, but the taper angle had no influence.
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