Actually, there are alot of factors that can result in dry socket. There are alot of different ways that a tooth can come out. If it is a simple extraction (i.e. just pulled), you put pressure on the socket and a blood clot will form. IF it is complex, and the tooth has to be split and bone has to be removed (a surgical extraction) a dressing MAY be placed (called Surgicel) and sutures are put in to hold it in place. The theory is that the blood clot will form around the Surgicel.
HOWEVER, there ARE times that the blood clots dislodge.
This can happen if a patient uses a straw, for example, to drink. Or rinses a bit too vigorously, or food gets stuck back there and the clot comes out with the food. In this case, dry socket (or an inflammation where the clot WAS) can happen. It happens around 20% of the time regardless of surgical technique. Like the saying says, "S(*& happens".
I had BOTH wisdom tooth sites with dry socket and I feel for you. I survived on Motrin. Just keep in mind that noone ever died of pain and this too shall pass.
Kira