Most, if not all 'fronts' reside in pressure troughs. That doesn't mean that fronts *are* pressure troughs.
It can be derived quite easily from Margules' Frontal Slope Equation that the pressure along a front must be a relative minimum. Thus, a front must *always* be placed in a surface pressure trough. This is why synopticians will instruct students to "kink" isobars when they intersect a front. As you state, however, a surface pressure trough does not necessarily mean you have a surface front. The surface pressure trough could easily be a surface reflection of a front aloft.
How does this all tie into the dryline? Well, to understand the dryline let's think about an idealized scenario...Place an incline wedge into a large pan and then pour water into the pan on the side with the smallest edge of the wedge. Notice how as the water depth increases on the small edge of the wedge, it appears to be "advecting" up the incline plane to the higher edge? (I use scare quotes around advecting, because if we were to look at the water from the frame of reference of the surface of the incline plane, it would appear as if water was being advected to the higher side!) As we pour water into the pan, the top of the water will intersect the wedge at a given point. In the atmosphere, we have a special name for this intersection, which I'll say below.
The geography of the central US can be crudely approximated as that of the incline wedge. For example, AMA would be the high side of the wedge, DFW would be in the middle, and HOU would be on the flat side. If moisture in HOU becomes "deeper" (similar to us pouring water into the pan above), it will spread uphill toward DFW and AMA. On a surface map, we'd call this moisture advection. At some location, the "top of the moisture" will intersect the sloped terrain. We give this intersection a special name: "Dryline".
So, because of this, the dryline is *not* a front and therefore should *not* have isobars kinked when they intersect it. However, with that said, it is possible to have a surface pressure trough associated with a dryline...such as when there might be an 850 front co located with the dryline. In this instance, you *would* kink the isobars...not because of the dryline, but because of the surface pressure trough.
Have you ever notice how a wind shift often precedes a dryline? This is actually the result of the surface pressure trough racing ahead of the dryline - most likely because of a front located just above the surface. Margules' Frontal Slope equation also states that in a "front", the winds should change directions cyclonically as the front passes and the wind speeds should increase -- which is precisely what happens along a "wind shift" that races out ahead of a dryline.
