New frontiers on choosing materials
Dental veneers are the gold standard in cosmetic dentistry, thanks to its reliable time and your ideal aesthetic income. They are considered the treatment of choice in creating a more natural smile possible. One advantage of the facets is to improve - and sometimes solve - not only problems like dyschromias and dental stains , but also change slightly , the slope of the own teeth . Another important advantage of veneers technique consists in preparing the dental element. Unlike crowns, facets actually enable professionals to " save " the tooth structure to be much more conservative.
Nowadays we faced with a very wide choice of materials for carrying out the aesthetic restoration of the previous sectors. Commitment sought in each artifact is that between aesthetic performance and predictability of the material used.
Pottery is one of the materials most commonly used in oral rehabilitation, especially in earlier sections, the aesthetic characteristics and chameleon effect. So far, numerous studies have analyzed and compared the multiple properties of this material. Choosing the restoration is also evaluated the possibility of using a fully ceramic facet or a metal substructure. In the following study we compared some physical properties of these two possible restorations.
The study´s objective was to evaluate the shear strength of various types of ceramics used in a zirconia core, analyze the microscopic any existing surface fractures and compare the shear strength of ceramic veneers on zirconia with that of metal ceramic veneers. The null hypothesis of this study is that both materials behave in a similar way in relation to shear.
They compared four different types of ceramic with shear strength test and examination under the microscope. The groups were as follows: VM9 , Zirkonzanh , Ceramco and IPS . After the fusion of these four types of ceramic zirconia on cylindrical core (8 mm in diameter and 12 mm height), it was proceeded the analysis of the physical characteristics of them. Then, the same procedures for metallic cylinders (Ni- Cr). Subsequently, it analyzed the surface of the cylinder with scanning electron microscope (SEM).
The test results were analyzed from a statistical point of view - Anova test with significance level of p < 0,05.
The shear strength values of ceramics cast in Ni- Cr alloy resulted in 25.3 ± 7.1 MPa, higher values in relation to those registered for all the various ceramic fused zirconia: Zirkonzanh (18.8 ± 1 MPa) Ceramco (18.2 ± 4.7 MPa) and IPS (16 ± 4.5 MPa), except for the VM9 ceramic zirconia (23.2 ± 5.1 MPa). This last result is not statistically significant.
All types of ceramic showed cohesive type of failure within the porcelain itself and adhesive in relation to porcelain -substrate interface.
This study demonstrated that the ceramic- zirconia system has the same to the ceramic-metal system shearing resistance values. Therefore, unlike the esthetics of restorations "full ceramic" (full ceramic), the adhesion between the ceramic and substructure zirconia is considered, until now, a critical point, taking into account the long-term success of these restorations should ensure.
The results of this study demonstrate that only in VM9 ceramic zirconia there shear strength values similar to porcelain fused alloy; all other ceramic zirconia showed significantly lower shear strength values than the control group. The SEM analysis of surface microcracks revealed a cohesive failure mode in terms of ceramic and adhesive in terms of interface. Considering what was found, the only pottery with characteristics at the time of the molten ceramic is VM9.
Source: Dentista Hoje, written by Claudia Dellavia
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