A periodontist is a dentist who specializes in the prevention, diagnosis, and treatment of periodontal disease, and in the placement of dental implants. Periodontists are also experts in the treatment of oral inflammation.
Ground speed. Ground speed is the horizontal speed of an aircraft relative to the ground. An aircraft heading vertically would have a ground speed of zero. Information displayed to passengers through the entertainment system often gives the aircraft ground speed rather than airspeed.
Epic ground mounts are available at level 40 from the normal mount vendors (they're the more expensive ones). Epic flying mounts are rarer and harder to get. However, the type of mount you get isn't really important; it's the training you have purchased that determines your speed.