Tooth Ache

Tooth ache is a protective response which range from mild sensitivity to severe pain.
It occurs due to reaction of the nerves to different stimulus on the tooth.

Pain on the teeth
Loose filling, deep cavity ,cracked tooth, abscessed tooth, gum recession, teeth grinding habits, sinusitis can cause pain on the tooth

Try to use de sensitizing tooth paste with soft bristle brush and wait for 2 to 4 weeks, if sensitivity or pain worsen see your dentist.
In all cases of pain and discomfort have your dentist evaluate your tooth for proper treatment.