Wolves do not have hollow teeth, at least not more so than any other animal.
Teeth are hard calcified objects but their inner aspects are not completely solid. Inside every tooth there lies a hollow space which, when a tooth is healthy, contains the tooth's nerve tissue.
There is a space in the center of a tooth that is typically hollow called the Pulp Chamber.
Root canal therapy refers to the process by which a dentist treats the inner aspects of a tooth, specifically that area inside a tooth that is occupied by its "pulp tissue." Most people would probably refer to a tooth's pulp tissue as its "nerve." While a tooth's pulp tissue does contain nerve fibers it is also composed of arteries, veins, lymph vessels, and connective tissue.
