Condensation silicones: do new materials really presents better dimensional stability?

The aim of this study was evaluate the dimensional stability of some condensation silicones. The following materials were studied: Coltex/Coltoflax - Coltène, Speedex - Coltène, and Optosil Comfort/Xantopren VL Plus - Kulzer. They were evaluated by dimensional analysis and gas chromatography (GC) performed at the following times: T0, T1, T2, T3, T4, and T5 (immediately after setting, thirty minutes, two hours, twenty four hours, seventy two hours, and seven days after setting, respectively). The dimensional changes were measured directly in the molds using a Mitutoyo microscope. The Coltex fine/Coltoflax and Optosil Comfort/Xantopren VL Plus materials presented dimensional stability for up to thirty minutes after molding, while the Speedex material remained stable for up to two hours after molding. The gas chromatography experiment demonstrated that these materials release ethanol even after clinical setting.

Light transmission through porcelain.

OBJECTIVE: This study evaluates the effect of shade and thickness of porcelain in light transmission. METHODS: One hundred and twenty-eight disks of Duceram porcelain were made to combine four different thicknesses (1.5; 2.0; 3.0; 4.0 mm) and eight shades (A(1); A(4); B(1); B(4); C(1); C(4); D(2); D(4)). A digital power meter (Newport Optical Power Meter was used to measure light transmission. The porcelain transmission coefficient was calculated using Lambert-Beer law, t(c)=Ce(-alphad), where t(c) is the transmission coefficient, C the contribution factor of the reflection coefficient, e a constant, alpha the absorption coefficient and d is the sample thickness. RESULTS: The transmission coefficients did not vary statistically in relation to the two visible light-curing units studied. From all the samples, the colors A(1) and D(2), thickness 1.5 mm, presented the highest percentages of transmission (8%) and the shades, A(4), B(4) and C(4), thickness 4 mm, the lowest (0.5%). The relationship between the Naperian logarithm of the transmission coefficient and the samples thickness followed the Lambert-Beer law. The linear adjustment of the experimental points of the two variables, showed the absorption coefficient (alpha) and the constant value related to the reflection (C) of each porcelain shade. The reflection coefficient values of all shades did not vary statistically among themselves. SIGNIFICANCE: For most shades there was a significant decrease in light transmission as the sample porcelain thickness increased. For the same thickness most shades presented statistical difference between the transmission coefficients. However, the larger the thickness, the higher the number of shades which, statistically, showed no difference.

Pinos intraradiculares para núcleos de preenchimento / Intra-root posts for post-and-core techniques

Buscou-se através de revisão da literatura, avaliar o emprego de pinos intraradiculares em dentes com terapia endodôntica que receberão um núcleo de preenchimento.