I'm sorry your dealing with this so painful condition and also extra problems .
Dental issues can be in our case trigger by medications, bone decay, but your dentist is the best friend you have.
Work with your dentist and let the dentist know and understand rsd very well. Root canal is really big process to go through ,nerve can be expose and can be trigger your rsd, and special care is need during dental treatment ,more anesthesia ,antibiotics, often dental cleaning with anesthesia so avoid extra trauma .
Make sure you educate your dentist about rsd,if they are not prepare you might need to get referral to a dental surgeon which will have a long variety of options and will do research about how to help you better.
My dentist recommended a prescription toothpaste and mouth wash to avoid mouth dryness and tooth decay.
Periodex the mouthwash and SF 1.1% the tooth paste or gel to apply on the tooth and gums to protect them from getting more damage .
Mere the dentist take all,the precautions needed and also if they are suggesting root canal of extractions should be under anesthesia and avoid any kind of severe pain after , after ward care is the most essential of all, best wishes and good luck,blessings ,Jesika .