Hi, I had a root canal about 6 months ago and all of a sudden the tooth is sensitive to touch...will a crown help? Thanks,

Retreatment. Tooth needs to be reevaluated and, if necessary, retreated if there are any signs of fracture or unsuccessful root canal seal. Please return to General Dentist or specialist Endodontists who did your treatment for reevaluation. Crowns are usually suggested for root-canal treated teeth, but not until the tooth is asymptomatic.
Tooth Pain. Have your dentist re-evaluate the tooth. There may be another infection or the tooth may have fractured. Cannot tell without an examination and even a radiograph. No crown until the tooth is asymptomatic.