hi There is absolutely no connection between root canal treatment and acidic refux, but since you are mentioning loss of taste as well ,i suspect the adverse reaction of the anesthetic agent/technique . Since you have nt mentioned the location of the tooth treated upon, i am presuming it to be a lower one as this can be caused by lower anesthetic block and not possible with upper anesthetic block .therefore in case the tooth treated was an upper one ,there is possibly any other cause than the dental treatment done ,but if it was the lower tooth operated you might as well feel heaviness of tongue ,numbness of lower lip and tingling sensation besides your present syptoms which is either due to nerve lesion caused by injection or the anesthetic agent itself . hope this was helpful .take care .