So nervous for first dentist appointment in a decade

I've had TMJ (jaw pain from night clenching)pain for years so have avoided going to the dentist for quite a long while. I've brushed and flossed and kept teeth clean but I know I probably have a cavity, so made an appointment. I'm so nervous because my jaw is misaligned from night clenching, and I can't keep my mouth open for too long. It can occasionally yield vertigo. Plus the TMJ pain creeps in at any time .

I hope they do give me breaks to close my mouth and ice pack my jaw. I know they said the dentist is very good, but am really on edge for this. Please send positive thoughts 😦🫂