I cant say much about your dental issues but working in a hospital I could definitely oppose the CT and question if it was needed.
CT's are exposing you to extreme levels of x-rays in just one hit and if you are young (growing body) the probability of it giving you even more health problems further down the track is highly likely.

If they suggest a CT I would question the necessity of it. 8 x-rays in comparison to one CT is a drop in the ocean. A CT is multiple xrays taken in thin cross sections (slices)

This is a great tool if you want to see your own risk of exposure:
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