well there is actually a breed called the Borzoi (also known as the Russian Wolfhound) that was used in Russia for pinning wolves down. They would send the dogs in groups of (I think it was three) and they would pin the wolf down until the hunter got there and the wolf would be released.
There is also a breed called the Irish Wolfhound (its actually the tallest dog breed btw, look at pic below for size reference) that was used to hunt wolves in Ireland.
There are also other breeds of dogs that would be strong enough to take down a wolf, such as mastiff type breeds, however these dogs are very large and bulky and don't have great agility. So in a fight with a wolf, they could actually be quickly wripped to shreds by the simple fact that in terms of agility, the wolf would have the upper hand. Thats why the Borzoi and Irish Wolfhounds are similar (in shape) to a greyhound. Because they had to be fast and agile.
Borzoi:
http://upload.wikimedia.org/wikipedia/commons/8/87/Borzoi_female.jpg
Irish Wolfhound:
http://upload.wikimedia.org/wikipedia/commons/6/6e/Irish_Wolfhound_Sam.jpg
Irish Wolfhound Size Pic:
http://www.dogbreedinfo.com/images15/IrishWolfhoundFrankBrendan.JPG