Smear plugs

Another important feature of the pre-treatment of the dentine surface is that the smear layer is removed and so also are the smear plugs. The latter is especially important as it opens to dentinal tubules, which means that liquid bonding agent can flow into the tubules (see Fig. 5.2). When polymerization occurs, this results in the formation of... 

The essential mechanism of action of self-etch adhesives is that they simultaneously etch and prime the freshly cut tooth surface, and in doing so, incorporate the components of the smear layer [58,60]. Because of the presence of the smear layer, and also because of smear plugs blocking the dentinal tubules, self-etch adhesives have been claimed to provoke less post-operative sensitivity in patients than the etch-and-rinse approach [61,62]. However, this has not been confirmed by scientific studies [63,64], but rather any reduction in patient discomfort has been attributed to operator technique [15]. 

Surface treatment which follows cutting may attempt to modify or remove the smear layer, in order to ensure that a uniform and reliable surface is left behind. It may also remove the smear plugs, thus opening the tubules and allowing the bonding agent to penetrate the tooth... 

Conditioning with polyacrylic acid results in removal of the smear layer and of the smear plugs, and opening up of the dentinal tubules (O Pig. 56.2). It does not, however, lead to loss of much, if any, intact tooth mineral from the surface. 

The day of identification of a vaginal plug or sperm in vaginal smear (rodents) or the day of observed or performed insemination (rabbits) is termed GDO. 

The day of mating is confirmed by the presence of a vaginal plug or sperm in a vaginal smear or and is defined as day 0 of gestation. Females are separated from the males once copulation has... 

If the flow rate is increased so that Peclet number Pe l, then there is a timescale at which transversal molecular diffusion smears the contact discontinuity into a plug. In Taylor (1993), Taylor found an effective long-time axial diffusivity proportional to the square of the transversal Peclet number and occurring in addition to the molecular diffusivity. After this pioneering work of Taylor, a vast literature on the subject developed, with over 2000 citations to date. The most notable references are the article (Aris, 1956) by Aris, where Taylor s intuitive approach was explained through moments expansion and the lecture notes (Caflisch and Rubinstein, 1984), where a probabilistic justification of Taylor s dispersion is given. In addition to these results, addressing the tube flow with a dominant Peclet number and in the absence of chemical reactions, there is... 

If the radial diffusion or radial eddy transport mechanisms considered above are insufficient to smear out any radial concentration differences, then the simple dispersed plug-flow model becomes inadequate to describe the system. It is then necessary to develop a mathematical model for simultaneous radial and axial dispersion incorporating both radial and axial dispersion coefficients. This is especially important for fixed bed catalytic reactors and packed beds generally (see Volume 2, Chapter 4). 

The plug for the fuse end is drilled to allow for the fuse. The plugs are smeared with glue before being pressed into the ends of the tube. More jg ue is squeezed in around the fuse after it is put in. 

A bare fuse is stuck straight up in the center of the flare igniter and it is left to dry for a day or two. Then the drilled plug is smeared with glue and pushed over the fuse. Then flare igniter is daubed on the fuse and when dry, the thing is ready to use,... 

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