i started off several years ago with a terrible taste in my mouth, very metallic, sometimes dry, cottony taste in my mouth. had bad tooth and had a crown put on. taste did not cease. then had to have root canal. bad taste. metallic. only on left side. especially that part of my tongue that touches that tooth. gets better. then bad again. stopped for awhile then had problem with molar next to it. it had to have a root canal and crown. first crown metal based. second porcelain. got bad then better. i went for several months with no symptoms. then got sinus infection. three weeks of antibiotics. not better. infection and pain behind those two teeth. ent does sinus surgery three weeks ago. during this process, the taste was horrible. better after surgery, but now its bad again. have follow up appt with ent again next week. could sinus still be involved? what else could it be? i am tired of the taste. dentist thinks it could be tonsils or allergic reaction to what ever metal is in the first crown.