The 2nd molar which has had RC would not have temperature sensitivity, so I assume you are referring to your 3rd molar or wisdom tooth. If you have pain upon chewing with temperature sensitivity then a fractured tooth is likely. If you have temperature sensitivity only, that goes away quickly, the most common problem is cervical hypersensitivity due to root exposure. In that case try a toothpaste like Sensodyne, apply directly to the affected area, and wait a couple weeks for the sensitivity to subside. If you have temperature sensitivity that lingers for 10 minutes or longer then see an endodontist. Cervical hypersensitivity is a very common problem with many people and is treated in a variety of ways.
That's the best advice I can give you without seeing you.