No, not teeth. Though that may yet come.
For this one I used a dark brown linen bookbinder's thread stitched loosely into some light, white-coated chipboard with a large embroidering needle, then scanned it at 600 dpi. Because of all the little "hairs" coming off the thread, I decided to use the Extraction filter (up in the top portion under Filters).
This filter is pretty tricky, and I find it useful only in some very specific cases, such as when you have fine lines that are burned through with background color, which makes extraction with a selection marquee (either with a pen or the lasso) pretty useless, and very frustrating in its fiddly-ness. The Extraction Filter works by painting over the edges of what you want to retain, then filling the inside. You can even set the opacity in terms of what is retained, and that's where it comes in handy... For this one I used a 1 pixel brush to go over the contour of the thread and the "hairs"! On the image below you'll see the original scan, and the extracted thread used on my "Tangle" layout, which follows:
(click for credits and description)