if afer u have a retreatment of root canal do u have to have another crown or can u just have a permanebt filling in that tooth?? is the permant filling just as good if u use the old crown?? Can carbonated drinks cause damage to permanet fillings? If so what damage can it cause. Is a permanet filling the samer and as effective as a crown that had already had a crown before previously in like 14 yrs ago??