I am sorry, but I don't know much about crystals in urine and even less about crystals for dogs. My cat did have an issue a month or so ago. My vet did change Morgan's food for 4 weeks or so to change his PH and help dissolve the crystals. I've since switched his food to EVO by Innova. Morgan has an issue with diabetes, and goes to the vet in a week or two to see if the new food does ok his sugar and I'm going to see if they can do a crystal check too. I don't know if any of this helps with dogs or not, but here is a thread that is in Cat Health regarding this topic. Perhaps something can help you from here, or perhaps not, but it's all I've got.

http://petoftheday.com/talk/showthread.php?t=151655