Bond strength and Raman analysis of the zirconia-feldspathic porcelain interface.

STATEMENT OF PROBLEM: Zirconia has the best mechanical properties of the available ceramic systems. However, the stability of the zirconia-feldspathic porcelain interface may be jeopardized by the presence of the chipping and debonding of the feldspathic porcelain. PURPOSE: The purpose of this study is to evaluate the shear bond strength of 3 cold isostatic pressed zirconia materials and a feldspathic veneer by analyzing their interface with micro-Raman spectroscopy. MATERIAL AND METHODS: The test groups were experimental zirconia, Zirkonzahn zirconia, and Schuetz zirconia. Blocks of partially sintered zirconia were cut into disks (n=20) and then veneered with a feldspathic porcelain. Half of the specimens from each group (n=10) were incubated in 37°C water for 24 hours, and the other half were thermocycled. All the specimens were then subjected to shear testing. The fractured areas were analyzed with optical stereomicroscopy and classified as adhesive, cohesive, or an adhesive-cohesive failure. Spectral patterns were examined to detect bands related to the zirconia and feldspathic porcelain phases. The shear strength data were submitted to 2-way ANOVA. RESULTS: No significant differences in shear bond strength were observed among the 3 groups, regardless of whether or not the specimens were thermocycled. Adhesive failures were the most prevalent types of failure (70%). Raman spectra were clearly distinguished for all the materials, which showed the presence of tetragonal and monoclinic phases. CONCLUSIONS: The controlled production of the experimental zirconia did not influence the results of the bond strength. Raman analysis suggested a process of interdiffusion by the presence of peaks associated with the zirconia and feldspathic ceramics.

Restablecimiento estético y funcional de la guía anterior utilizando la técnica de estratificación con resina compuesta

En Odontología, un problema observado constantemente en pacientes adultos en este inicio de siglo es sin duda, el desgaste dental patológico. Este tipo de desgaste ocurre cuando existe pérdida acentuada de la estructura dentaria, lo que generalmente ocasiona el compromiso estético de los dientes antero superiores. En consecuencia, la sociedad se está concientizando sobre la importancia de la salud y de la estética, de esta manera, la demanda por tratamientos estéticos rehabilitadores en casos de desgaste dental patológico ha aumentado. La rehabilitación estética puede ser realizada tanto por medio de tratamientos directos como indirectos. Debido a las ventajas de las resinas compuestas, el presente trabajo tiene por finalidad describir la técnica operatoria para el restablecimiento de la guía anterior con resina compuesta, mediante la técnica de estratificación, que permite simular las características ópticas de la estructura dental. Así, con la evolución de los sistemas adhesivos, asociado a las mejoras en las propiedades químicas, mecánicas y estéticas de las resinas compuestas, tratamientos restauradores extensos, como la reconstrucción directa de las guías anteriores en los casos de desgaste dental patológico, se tornan viables.

In Dentistry, a common problem observed in this beginning of century is the pathologic tooth wear. This type of wear occurs when there is accentuated loss of tooth structure, which frequently results in aesthetic compromise of the anterior maxillary teeth. As a result of the society’s awareness of the importance of health and aesthetics, the request for reparative aesthetic treatments in cases of pathologic tooth wear has increased. This aesthetic rehabilitation may be achieved either through indirect or direct treatments. Due to the advantages of the resin composites, the aim of the present paper is to show specifically the direct approach throughout the use of a layering technique to simulate the optical characteristics of the tooth structure. Hence with the evolution of the adhesive systems associated with improving in the chemical-mechanical-aesthetical charecterics of the resin composites, extensive restorative treatments as the direct reconstruction of the anterior guidance in cases of pathologic tooth wear are now feasible.

Effect of the cavity configuration factor on the marginal microleakage of esthetic restorative materials.

PURPOSE: To evaluate the effect of the cavity configuration factor (CF) on the marginal microleakage of cervical restorations with four aesthetic restorative materials. MATERIALS AND METHODS: Conventional cavities, 2.9 mm in diameter and 1.5 mm deep, with CF=2.7 and "saucer"-shaped ones with CF=2 were created in 60 extracted premolars. The following groups were established: G1: Z100/Single Bond, G2: Freedom/Stae, G3: Vitremer/Primer and G4: Durafill/Durafill Bond, following each manufacturer's directions. Thermocycling of the specimens was performed in an aqueous solution of 2% buffered methylene blue, with the temperature varying between 5 to 55 degrees C, for a total of cycles of 60 minutes per day, for 7 days. The specimens were then sectioned and evaluated by two observers using photographs acquired from a stereomicroscope. The values were subjected to Kruskal-Wallis analysis and the Dunn and Wilcoxon test. RESULTS: The averages of the microleakage scores observed in the conventional and "saucer"-shaped cavities were respectively: G1: 0.66/0.46; G2: 0.92/0.69; G3: 1.8/1.86; G4: 3.54/2.3.