I had both a cavity replaced and a wisdom tooth pulled. Before both, I mentioned to the dentist that I had tinnitus and I was going to put an ear plug in - which I did solely as a precaution. Neither event spiked my tinnitus that I can remember.
One very odd thing I noticed when I was getting my wisdom pulled. I was pretty anxious - it was about 1 month after I started experiencing a louder, different form of tinnitus. Things had settled down slightly - and I was really scared that these dental procedures, or the recovery process was going to set that all back. I had never had a wisdom tooth pulled so that only added to my anxiety. During the process - which overall went as smooth as I could have asked - when the dentist was yanking the tooth out, my tinnitus went completely quiet. This lasted maybe a minute or so. My feeling is that because my brain was so focused on what was going on at that moment it sorta blocked out the other activity. This gives me some hope that with some meditation / other calming techniques that I might be able to control the intensity of my tinnitus - I'm exploring that now.