After using the last unit of a raw restraint material, zero of that material remains in your inventory... which is to say that the icon stays in place, but with a zero number. The zero raw material remaining in your inventory isn't directly usable, but it can be recycled. The recycling yield of doing so is equal to that of recycling one unit normally. This removes the icon... until you acquire another unit of that restraint.
Theoretically, you could exploit this for infinite recyclable materials by repeatedly binding and unbinding a given prisoner, recycling the restraint after each time it's removed. It'd be very silly, especially since the payoff is still limited by the capability of the girls you have working the recycler... but it's still technically an infinite exploit in the economy, especially since the recycled materials could then be laundered into saleable items.