What is the solution for composite restoration overhanged proximally in rct tooth?do i have to remove old one and replace it or crowning the tooth?

Depends: It really depends on the condition of the tooth, is it otherwise healthy with intact walls? If so then have the filling replaced so you floss there without a problem . If the tooth is heavenly restored with large or multiple filling then crowning the tooth would be best.

RCT ; Crowns: Your tooth most likely needed rct due to a deep restoration, cavity, or a fracture. The middle of the tooth is now hollow, but more importantly, it is brittle. Teeth with rct tend to fracture vertically when they do, rendering the tooth unrestorable. In the end it usually costs more that restoring it correctly in the first place. There are a few instances where a filling will work fine. Ask dds.

Restoring RCT teeth: The tooth needs a new restoration due to the overhang regardless of whether or not it had rct. In general, most rct teeth are better off having a crown (proper contours ; thin well adapted margins) as they are more prone to fracture. In certain instances, a composite restoration (with proper contours ; margins) will suffice. A competent restorative dentist can advise you what is best in your case.