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| Author(s): |
Fernanda Campos
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São José dos Campos. 2016-04-07. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Ciência e Tecnologia. São José dos Campos |
| Defense date: | 2016-01-29 |
| Advisor: | Marco Antonio Bottino; Renata de Melo Marques Marinho; Cornelis Johannes Kleverlaan |
| Abstract | |
The cementation of crowns with zirconia infrastructure can be performed in several ways, using different cements and surface treatments. However, despite the existence of some studies on the subject, there is no consensus in the literature on which cementation method would be more appropriate. The aim of this study was to investigate the effect of different cementation strategies in fatigue strength of monolithic zirconia crowns. 75 pillars were machined in epoxy resin with a molar simplified shape (6 mm height, 12 degree tilt, rounded corners). This standard-pillar was scanned and a coping with 0.7 mm of thickness and 80 µm of cement space was virtually designed on the CAD/CAM system software used. From the virtual design, 75 zirconia copings were milled and sintered according to the manufacturer's recommendations. These copings were divided into five groups according to surface treatment or cement used: FZ - cleaning with isopropyl alcohol + zinc phosphate cement, PN - cleaning with isopropyl alcohol + resin cement (Panavia F), GL - application of a thin layer of glaze + resin cement; AL - sandblasting with Al2O3 particles of 125 µm (distance = 15 mm / pressure = 3 bar) + resin cement; CJ - sandblasting with particles of Al2O3/SiO2 of 30 µm (distance = 15 mm / pressure = 3 bar) + resin cement. After surface treatment, the copings were cemented to the pillars with a load of 50 N for 5 minutes. The resin cement was light activated for 30 seconds on each side. The specimens were tested until the moment of fracture in a fatigue machine for 10,000 cycles at each load increment (600, 800, 1000, 1200, 1400 N) at a frequency of 1.4 Hz. The failure mode was assessed by scanning electron microscope. The "Kaplan-Meier" analysis was held followed by the Mantel-Cox test (Log Rank test) and multiple comparison in pairs, all with a significance level of 5%. Furthermore, it has also used the Weibull analysis. For the load to fracture and for the number of cycles to fracture there was detected a difference among the cementation strategies. The predominant mode of failure was a fracture that initiate in the cement/zirconia layer. The FEA showed different stress distribution for the two models. The adhesive cementation approach lead to a significantly higher survival chance for zirconia crowns. (AU) | |
| FAPESP's process: | 12/05657-5 - New treatment of internal surface of infrastructure: influence on fracture resistance of Y-TZP crowns |
| Grantee: | Fernanda Campos |
| Support Opportunities: | Scholarships in Brazil - Doctorate |