It sounds like 2 separate problems to me. Teeth grinding can cause damage to the temporomandibular joint (TMJ), which is in front of the ear, and can present with ear pain. Pain on descent in the aircraft is usually due to a dysfunction of the eustachian tube (the tube that allows the volme of the middle ear to equalise with changing pressures). I would see an ENT surgeon to define the problem a little better. Did you have a cold or hayfever at the time of the flight?