Have just returned from holiday and my teeth are really sensitive. Could flying have caused this and why

Yes.
Some people get earache and congestion aswell .Its due probably to the change in air pressure in the cabin which can affect your sinuses.It should clear quite quickly and if not could be indicative of blocked or infected sinuses so if it persists see your doctor.He will probably tell you to see your dentist but stress that you think it was caused by the air pressure on the plane.

A quick easy answer would be to take a nasal decongestant which is available over the counter at any chemist. As a previous person stated the changing air pressure in the plane can cause this problem if u have nose & sinus which r a little congested & the pressure cannot equalize. The same thing happens with some people is ears if the eustacian tubes r blocked. A decongestant will cure them both.
The sensitivity in ur teeth is because the roots of the posterior teeth often project into the sinuses & if the sinuses r unhappy ur brain can interpret this as coming from ur teeth so u think ur teeth r hurting but it is really ur sinuses which r unhappy.