I got crowns on my front three teeth a year ago, few days back i noticed my crown was a little shaky,now i have excruciating pain inside the crown?why

Needs evaluation: Tooth may be fractured, crown may have decay underneath, nerve of the tooth may have gone bad. Your dentist needs to take a look.

See your dentist: Possibly the bite is high, which would cause fremitis,movement. Have the dentist check the bite as the most conservative. Other variables include, possible cement washout or need for root canal therapy.

Many possibles: Most common is occlusal trauma resulting in ligament inflammation and pain.Solution-see Dentist to evaluate bite and adjust as needed. However from the "excruciating" pain aspect,you may have recurrent decay underneath and require root canal treatment if tooth is restorable. You may have fractured the tooth.Less likely is cement washout with looseness and sensitivity. Make appt. Good Luck.

See a dentist ASAP: It sounds like a tooth abscess under your crown. In most cases this type of pain means the tooth will need root canal. Do not delay, you should visit your dentist or an endodontist. Good luck!